Erik Adli

• Finnerud, Ole Gunnar; Adli, Erik; Ariniello, R; Corde, S; Dalichaouch, T N & Emma, C [Show all 21 contributors for this article] (2026). First results from the E302 efficiency–instability experiment at the FACET-II facility. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 3266(1). doi: 10.1088/1742-6596/3266/1/012001. Full text in Research Archive Show summary

  Abstract The beam-breakup (BBU) instability in plasma accelerators is seeded by a transverse offset between the driver and a trailing bunch. The BBU instability induces oscillations in the trailing bunch, which are detrimental to its beam quality. When the instability is large, assuming little mitigation from ion motion and energy spread, the beam suffers emittance growth, and charge can be kicked transversely out of the plasma channel. The detrimental effect on beam quality is substantially worse at high efficiencies, which places constraints on the achievable power efficiency in applications such as linear colliders, where maintaining the beam quality is required. In this paper, we present the first experimental signatures of the BBU instability in data taken in the E302 experiment at the FACET-II facility at SLAC National Accelerator Laboratory. We use a specific beam-optical setup and a novel method to probe for transverse instabilities on diagnostic screens downstream of a magnetic dipole spectrometer. We complement the analysis with full 3D particle-in-cell (PIC) simulations of the plasma interaction using similar driver and trailing bunch parameters on a simulated FACET-II spectrometer.

• Sjobak, Kyrre Ness; Rød-Lindberg, E; Ellingsen, Abélia; Drobniak, Pierre; Rieker, Vilde Flognfeldt & Reaz, F [Show all 8 contributors for this article] (2026). SHARP: A compact focusing system for medical applications using a diverging plasma lens. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 3266(1), p. 012014–012014. doi: 10.1088/1742-6596/3266/1/012014. Full text in Research Archive Show summary

  Abstract Cancer therapy for deep-seated tumors requires precise irradiation of a small target deep within the patient while minimizing radiation exposure to surrounding tissues. This can be accomplished with a round beam sharply converging towards a single spot, requiring a large beam size in both planes at the exit of the focusing system. Achieving this over a short distance using only quadrupole lenses is challenging; but by using a linear active plasma lens (APL) in defocusing mode, the beam can be quickly and non-destructively enlarged before focusing using quadrupoles. The position of the irradiation spot can also be scanned in three dimensions by changing magnet settings. The SHARP project will develop and test this concept. Such a system can be used with very high energy electrons (hundreds of MeV), creating a Bragg-peak-like spot using novel accelerator technology. This could lead to more compact radiotherapy facilities, not requiring a bulky infrastructure typically associated with proton radiotherapy machines. If successful, SHARP will enable precision conformal radiotherapy, spatial fractionation, and potentially be useful for FLASH radiotherapy.

• Adli, Erik; Lindstrøm, Carl A.; Kalvik, Daniel; Sjobak, Kyrre Ness; Finnerud, Ole Gunnar & Chen, Jian Bin Ben [Show all 7 contributors for this article] (2025). Transverse tolerances in the plasma-wakefield acceleration blow-out regime. Proceedings of the International Particle Accelerator Conference. ISSN 2673-5490. p. 1434–1437. doi: 10.18429/JACOW-IPAC2025-TUPS011. Full text in Research Archive Show summary

  We report on recent progress in transverse instabilities and transverse tolerances for plasma-wakefield accelerators in the blow-out regime. In this regime, the transverse fields provide both strong focusing and strong deflection via transverse wakefields. The deflection effect of the wakefields on the main beam leads to limitations on the acceleration efficiency, if not mitigated. Based on comprehensive particle-in-cell simulations we summarize recent findings of the instability--efficiency relation for the blow-out regime. Ion motion and energy spread may mitigate the instability; with linac start-to-end simulations, using the recently developed ABEL framework, we demonstrate that the instability and emittance growth may be sufficiently mitigated for the colliding beams in the HALHF concept. Independent of wakefield effects, the strong focusing fields lead to very tight tolerances for the drive-beam jitter. We quantify these tolerances, using examples from HALHF start-to-end simulations. We show that the tolerances are greatly loosened by applying external magnetic fields to guide the drive-beam propagation in the plasma.

• Adli, Erik; D’Auria, Gerardo; Catalan Lasheras, Nuria; Cilento, Vera; Corsini, Roberto & Doebert, Steffen [Show all 474 contributors for this article] (2025). CLIC readiness report. The European Physical Journal Special Topics (EPJ - Special Topics (EPJ ST)). ISSN 1951-6355. 234(22), p. 6473–6652. doi: 10.1140/epjs/s11734-025-02016-w. Full text in Research Archive
• Finnerud, Ole Gunnar; Lindstrøm, Carl Andreas; Chen, Jian Bin Ben & Adli, Erik (2025). The E302 instability-versus-efficiency experiment at FACET-II. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 3124(1). doi: 10.1088/1742-6596/3124/1/012005. Full text in Research Archive Show summary

  We discuss plans for the E302 instability-efficiency experiment, starting in 2024 at the recently upgraded FACET-II facility at SLAC National Accelerator Laboratory. The beam-breakup instability will be the main area of study for the E302 experiment. With the imaging spectrometer at FACET-II, we introduce a novel technique for observing and quantifying the amplitude growth of the trailing bunch due to the transverse instability. Using the transverse position on the spectrometer screen and the transfer matrix of the magnetic lattice used for the spectrometer, we aim to extract a x′–E charge distribution that can be used to quantify the amplitude of the beam. By varying the trailing bunch’s charge and, hence, the beam loading of the accelerating field, we aim to adjust the wake-to-beam power transfer efficiency in the E302 experiment. We plan to quantify the amplitude for different configurations of the beam charge and, hence, investigate the relationship between the beam-breakup instability and efficiency. We use a combination of particle-in-cell (PIC) codes to simulate a beam-driven plasma wakefield accelerator from start-to-end with a FACET-II-like spectrometer and demonstrate the methodology that will be used for the instability studies at the E302 experiment.

• Chen, Jian Bin Ben; Lindstrøm, Carl Andreas; Finnerud, Ole Gunnar & Adli, Erik (2025). Modelling transverse instability in HALHF plasma stages. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 3124(1). doi: 10.1088/1742-6596/3124/1/012015. Full text in Research Archive Show summary

  We present first results for a parameter study of the plasma linac of HALHF, a novel electron-positron collider concept combining plasma wakefield acceleration and mature RF acceleration to reach a centre of mass energy of 250 GeV. This study is a preliminary extension of the previous studies that indicated promising performance, by including transverse instability. Transverse instability was simulated using start-to-end simulations, where PIC simulations were combined with a simplified model to efficiently model transverse instability in the plasma-acceleration stages. No interstage optics were included. With a small initial transverse offset, the currently proposed parameter set will result in emittance growth and charge losses. If additional transverse misalignments are introduced between stages in the form of drive beam transverse jitter, the emittance growth is even more severe. Mitigation mechanisms to reduce the instability to an acceptable level are suggested.

• Finnerud, O. G.; Lindstrøm, Carl A. & Adli, Erik (2025). Parametric mapping of the efficiency–instability relation in plasma-wakefield accelerators. Physical Review Accelerators and Beams. ISSN 2469-9888. 28(7). doi: 10.1103/72qb-517d. Full text in Research Archive Show summary

  High efficiency is essential for plasma-wakefield accelerators to be a cost-effective alternative in high-power applications, such as a linear collider. However, in a plasma-wakefield accelerator, the beam-breakup instability can be seeded by a transverse offset between the driver and trailing bunch. This instability, which rapidly increases the oscillation amplitude of the trailing bunch, grows with higher power-transfer efficiency from the driver to the trailing bunch [V. Lebedev et al., Phys. Rev. Accel. Beams 20, 121301 (2017)]. In this paper, we use particle-in-cell simulations to investigate the efficiency–instability relation that constrains the driver-to-trailing-bunch power-transfer efficiency in beam-driven plasma accelerators. We test the relation using a grid of simulations across all parameters that affect the beam-breakup instability, assuming a uniform accelerating field (optimal beam loading) and no ion motion. We find that the previously proposed efficiency–instability relation represents a lower limit on the strength of the instability for a given efficiency. For each normalized wake radius, only a certain accelerating field reaches this lowest value of the transverse instability; deviating from this point can increase the growth rate by several orders of magnitude. Finally, we highlight how the oscillation-amplitude growth of the trailing bunch can be reduced or damped with an initial uncorrelated energy spread and the presence of ion motion.

• Foster, Brian; Adli, Erik; Barklow, Timothy L.; Berggren, Mikael; Boogert, Stewart & Chen, Jian Bin Ben [Show all 24 contributors for this article] (2025). Proceedings of the Erice workshop: A new baseline for the hybrid, asymmetric, linear Higgs factory HALHF. Physics Open. 23. doi: 10.1016/j.physo.2025.100261. Full text in Research Archive Show summary

  The HALHF collaboration has discussed a new baseline for the project, taking into account comments from the accelerator community on various aspects of the original design. In particular, these concerned the practicality of the dual-purpose linac to accelerate both colliding positron bunches and the drive beams required for the plasma linac. In addition, many other aspects of the project were also considered; the discussion and conclusions are documented in this paper. Finally, a new baseline is outlined that has been optimised and addresses several weaknesses in the original design, has higher luminosity, reduced centre-of-mass energy boost and additional features such as two interaction points and positron polarisation as well as electron polarisation. Although HALHF has become longer and more expensive, it remains significantly smaller and cheaper than other mature Higgs factory designs currently under discussion.

• Drobniak, Pierre Bony Henri; Adli, Erik; Anderson, Hektor Bergravf; Dyson, Anthony E; Mewes, S. M. & Sjobak, Kyrre Ness [Show all 8 contributors for this article] (2025). Development of a nonlinear plasma lens for achromatic beam transport. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 1072. doi: 10.1016/j.nima.2025.170223. Full text in Research Archive Show summary

  We introduce the new idea of a nonlinear active plasma lens, as part of a larger transport lattice for achromatic electron beam transport. The proposed implementation uses an external dipole magnet acting on a plasma and is motivated by 1D-hydrodynamic simulations. The manufactured design is presented, including its undergoing experimental characterisation on the CLEAR beam-line at CERN.

• Cao, Jiawei; Lindstrøm, Carl A.; Adli, Erik; Corde, Sébastien & Gessner, Spencer (2024). Positron acceleration in plasma wakefields. Physical Review Accelerators and Beams. ISSN 2469-9888. 27(3). doi: 10.1103/PhysRevAccelBeams.27.034801. Full text in Research Archive Show summary

  Plasma acceleration has emerged as a promising technology for future particle accelerators, particularly linear colliders. Significant progress has been made in recent decades toward high-efficiency and high-quality acceleration of electrons in plasmas. However, this progress does not generalize to the acceleration of positrons, as plasmas are inherently charge asymmetric. Here, we present a comprehensive review of historical and current efforts to accelerate positrons using plasma wakefields. Proposed schemes that aim to increase energy efficiency and beam quality are summarized and quantitatively compared. A dimensionless metric that scales with the luminosity-per-beam power is introduced, indicating that positron-acceleration schemes are currently below the ultimate requirement for colliders. The primary issue is electron motion; the high mobility of plasma electrons compared to plasma ions, which leads to nonuniform accelerating and focusing fields that degrade the beam quality of the positron bunch, particularly for high efficiency acceleration. Finally, we discuss possible mitigation strategies and directions for future research.

• Rieker, Vilde Flognfeldt; Corsini, Roberto; Stapnes, Steinar; Adli, Erik; Farabolini, Wilfrid & Grilj, Veljko [Show all 15 contributors for this article] (2024). Active dosimetry for VHEE FLASH radiotherapy using beam profile monitors and charge measurements. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 1069. doi: 10.1016/j.nima.2024.169845. Full text in Research Archive Show summary

  The discovery of the FLASH effect has revealed a high potential for treating cancer more efficiently by sparing healthy tissue. The surge in related medical research activities over the last couple of years has triggered a demand for technology with the capability of generating and measuring ionizing radiation at ultra-high dose-rates (UHDR). A reliable dosimetry system is an integral part of a radiotherapy machine. Because existing active dosimetry methods are unable to handle the dose-rates required for FLASH, UHDR dosimetry has emerged as an important area of research. In this paper we present an active dosimetry method based on a scintillating screen and an integrating current transformer. This method provides a simultaneous measurement of the absolute dose delivery as well as the 2D dose distribution. The measurements have been correlated with corresponding readings from radiochromic films (RCFs), and a procedure for image processing has been established. Moreover, different methods of calibrating the active dosimetry system against RCFs have been introduced and evaluated. Lastly, we present results which demonstrate that an agreement with RCFs of better than 5% can be realistically expected if camera parameters are carefully optimized.

• Storey, D.; Zhang, C.; Claveria, Miguel San Miguel; Cao, Jiawei; Adli, Erik & Alsberg, L. [Show all 32 contributors for this article] (2024). Wakefield generation in hydrogen and lithium plasmas at FACET-II: Diagnostics and first beam-plasma interaction results. Physical Review Accelerators and Beams. ISSN 2469-9888. 27(5). doi: 10.1103/PhysRevAccelBeams.27.051302. Full text in Research Archive Show summary

  Plasma wakefield acceleration provides ultrahigh acceleration gradients of tens of GeV/m, providing a novel path toward efficient, compact, TeV-scale linear colliders, and high brightness free electron lasers. Critical to the success of these applications is demonstrating simultaneously high gradient acceleration, high energy transfer efficiency, and preservation of emittance, charge, and energy spread. Experiments at the FACET-II National User Facility at SLAC National Accelerator Laboratory aim to achieve all of these milestones in a single-stage plasma wakefield accelerator, providing a 10 GeV energy gain in a <1  m plasma with high energy transfer efficiency. Such a demonstration depends critically on diagnostics able to measure emittance with mm mrad accuracy, energy spectra to determine both percent level energy spread, and broadband energy gain and loss, incoming longitudinal phase space, and matching dynamics. This paper discusses the experimental setup at FACET-II, including the incoming beam parameters from the FACET-II linac, plasma sources, and diagnostics developed to meet this challenge. Initial progress on the generation of beam ionized wakes in meter-scale hydrogen gas is discussed as well as commissioning of the plasma sources and diagnostics.

• D’Auria, G.; Adli, Erik; Aicheler, M.; Aksoy, A.; Alesini, D. & Apsimon, R. [Show all 143 contributors for this article] (2024). The CompactLight Design Study. The European Physical Journal Special Topics (EPJ - Special Topics (EPJ ST)). ISSN 1951-6355. 233, p. 1–208. doi: 10.1140/epjs/s11734-023-01076-0. Full text in Research Archive Show summary

  CompactLight is a Design Study funded by the European Union under the Horizon 2020 research and innovation funding programme, with Grant Agreement No. 777431. CompactLight was conducted by an International Collaboration of 23 international laboratories and academic institutions, three private companies, and five third parties. The project, which started in January 2018 with a duration of 48 months, aimed to design an innovative, compact, and cost-effective hard X-ray FEL facility complemented by a soft X-ray source to pave the road for future compact accelerator-based facilities. The result is an accelerator that can be operated at up to 1 kHz pulse repetition rate, beyond today’s state of the art, using the latest concepts for high brightness electron photoinjectors, very high gradient accelerating structures in X-band, and novel short-period undulators. In this report, we summarize the main deliverable of the project: the CompactLight Conceptual Design Report, which overviews the current status of the design and addresses the main technological challenges.

• Zhang, Chaojie; Storey, Doug; Claveria, Pablo San Miguel; Nie, Zan; Marsh, Ken A. & Mori, Warren B. [Show all 29 contributors for this article] (2024). Correlations between X-rays, visible light and drive-beam energy loss observed in plasma wakefield acceleration experiments at FACET-II. Journal of Plasma Physics. ISSN 0022-3778. 90(4). doi: 10.1017/S0022377824000734. Full text in Research Archive Show summary

  This study documents several correlations observed during the first run of the plasma wakefield acceleration experiment E300 conducted at FACET-II, using a single drive electron bunch. The established correlations include those between the measured maximum energy loss of the drive electron beam and the integrated betatron X-ray signal, the calculated total beam energy deposited in the plasma and the integrated X-ray signal, among three visible light emission measuring cameras and between the visible plasma light and X-ray signal. The integrated X-ray signal correlates almost linearly with both the maximum energy loss of the drive beam and the energy deposited into the plasma, demonstrating its usability as a measure of energy transfer from the drive beam to the plasma. Visible plasma light is found to be a useful indicator of the presence of a wake at three locations that overall are two metres apart. Despite the complex dynamics and vastly different time scales, the X-ray radiation from the drive bunch and visible light emission from the plasma may prove to be effective non-invasive diagnostics for monitoring the energy transfer from the beam to the plasma in future high-repetition-rate experiments.

• Zhang, C.; Storey, D.; Claveria, Miguel San Miguel; Nie, Z.; Marsh, K.A. & Hogan, M. [Show all 29 contributors for this article] (2024). Generation of meter-scale hydrogen plasmas and efficient, pump-depletion-limited wakefield excitation using 10 GeV electron bunches. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 66(2). doi: 10.1088/1361-6587/ad1ae4. Full text in Research Archive Show summary

  High repetition rates and efficient energy transfer to the accelerating beam are important for a future linear collider based on the beam-driven plasma wakefield acceleration scheme (PWFA-LC). This paper reports the first results from the Plasma Wakefield Acceleration Collaboration (E300) that are beginning to address both of these issues using the recently commissioned FACET-II facility at SLAC national accelerator laboratory. We have generated meter-scale hydrogen plasmas using time-structured 10 GeV electron bunches from FACET-II, which hold the promise of dramatically increasing the repetition rate of PWFA by rapidly replenishing the gas between each shot compared to the hitherto used lithium plasmas that operate at 1–10 Hz. Furthermore, we have excited wakes in such plasmas that are suitable for high gradient particle acceleration with high drive-bunch to wake energy transfer efficiency- a first step in achieving a high overall energy transfer efficiency. We have done this by using time-structured electron drive bunches that typically have one or more ultra-high current (>30 kA) femtosecond spike(s) superimposed on a longer (∼0.4 ps) lower current (<10 kA) bunch structure. The first spike effectively field-ionizes the gas and produces a meter-scale (30–160 cm) plasma, whereas the subsequent beam charge creates a wake. The length and amplitude of the wake depends on the longitudinal current profile of the bunch and plasma density. We find that the onset of pump depletion, when some of the drive beam electrons are nearly fully depleted of their energy, occurs for hydrogen pressure ≥1.5 Torr. We also show that some electrons in the rear of the bunch can gain several GeV energies from the wake. These results are reproduced by particle-in-cell simulations using the QPAD code. At a pressure of ∼2 Torr, simulation results and experimental data show that the beam transfers about 60% of its energy to the wake.

• Knetsch, A.; Andriyash, I.A.; Gilljohann, M.; Kononenko, O.; Matheron, A. & Mankovska, Y. [Show all 10 contributors for this article] (2023). High Average Gradient in a Laser-Gated Multistage Plasma Wakefield Accelerator. Physical Review Letters. ISSN 0031-9007. 131(13). doi: 10.1103/PhysRevLett.131.135001. Full text in Research Archive Show summary

  Plasma wakefield accelerators driven by particle beams are capable of providing accelerating gradient several orders of magnitude higher than currently used radio-frequency technology, which could reduce the length of particle accelerators, with drastic influence on the development of future colliders at TeV energies and the minimization of x-ray free-electron lasers. Since interplasma components and distances are among the biggest contributors to the total accelerator length, the design of staged plasma accelerators is one of the most important outstanding questions in order to render this technology instrumental. Here, we present a novel concept to optimize interplasma distances in a staged beam-driven plasma accelerator by drive-beam coupling in the temporal domain and gating the accelerator via a femtosecond ionization laser.

• Barklow, Tim; Gessner, Spencer; Hogan, Mark; Ng, Cho-Kuen; Peskin, Michael & Raubenheimer, Tor [Show all 30 contributors for this article] (2023). Beam delivery and beamstrahlung considerations for ultra-high energy linear colliders. Journal of Instrumentation (JINST). 18(9). doi: 10.1088/1748-0221/18/09/P09022. Full text in Research Archive
• Reaz, Fardous; Sjobak, Kyrre Ness; Malinen, Eirik; Edin, Nina Frederike Jeppesen & Adli, Erik (2022). Sharp dose profiles for high precision proton therapy using strongly focused proton beams. Scientific Reports. 12(1). doi: 10.1038/s41598-022-22677-0. Full text in Research Archive Show summary

  The main objective of radiotherapy is to exploit the curative potential of ionizing radiation while inflicting minimal radiation-induced damage to healthy tissue and sensitive organs. Proton beam therapy has been developed to irradiate the tumor with higher precision and dose conformity compared to conventional X-ray irradiation. The dose conformity of this treatment modality may be further improved if narrower proton beams are used. Still, this is limited by multiple Coulomb scattering of protons through tissue. The primary aim of this work was to develop techniques to produce narrow proton beams and investigate the resulting dose profiles. We introduced and assessed three different proton beam shaping techniques: (1) metal collimators (100/150 MeV), (2) focusing of conventional- (100/150 MeV), and (3) focusing of high-energy (350 MeV, shoot-through) proton beams. Focusing was governed by the initial value of the Twiss parameter 𝛼 (𝛼0), and can be implemented with magnetic particle accelerator optics. The dose distributions in water were calculated by Monte Carlo simulations using Geant4, and evaluated by target to surface dose ratio (TSDR) in addition to the transverse beam size (σ𝑇) at the target. The target was defined as the location of the Bragg peak or the focal point. The different techniques showed greatly differing dose profiles, where focusing gave pronouncedly higher relative target dose and efficient use of primary protons. Metal collimators with radii <2 mm gave low TSDRs (< 0.7) and large σ𝑇(> 3.6 mm). In contrast, a focused beam of conventional (150 MeV) energy produced a very high TSDR (> 80) with similar σ𝑇 as a collimated beam. High-energy focused beams were able to produce TSDRs > 100 and σ𝑇 around 1.5 mm. From this study, it appears very attractive to implement magnetically focused proton beams in radiotherapy of small lesions or tumors in close vicinity to healthy organs at risk. This can also lead to a paradigm change in spatially fractionated radiotherapy. Magnetic focusing would facilitate FLASH irradiation due to low losses of primary protons.

• White, G.; Gessner, S.; Adli, Erik; Cao, Jiawei; Sjobak, Kyrre Ness & Barber, S. [Show all 15 contributors for this article] (2022). Beam delivery and final focus systems for multi-TeV advanced linear colliders. Journal of Instrumentation (JINST). 17(5). doi: 10.1088/1748-0221/17/05/P05042. Full text in Research Archive Show summary

  The Beam Delivery System (BDS) is a critical component of a high-energy linear collider. It transports the beam from the accelerator and brings it to a focus at the Interaction Point. The BDS system includes diagnostic sections for measuring the beam energy, emittance, and polarization, as well as collimators for machine protection. The length of the BDS increases with collision energy. Higher collision energies also require higher luminosities, and this is a significant constraint on the design for energy-frontier machines. Here, we review BDS designs based on traditional quadrupole magnets and examine the challenges involved in extending these to the Multi-TeV regime consistent with requirements for advanced accelerator concepts.

• Adli, Erik (2022). Towards a PWFA linear collider-opportunities and challenges. Journal of Instrumentation (JINST). 17(5). doi: 10.1088/1748-0221/17/05/T05006. Full text in Research Archive Show summary

  I discuss some key opportunities and challenges of a PWFA collider, and outline some objectives which I consider important to be able to assess the machine performance, assuming that numerous technical challenges can be solved. The highlighted topics are purely the choices of this author. Several other articles in this issue are relevant for a collider design, and discuss challenges for different sub-systems of a collider, including the articles on the beam delivery system [1], drive-beam generation [2], and emittance preservation [3]. A more complete overview of agreed challenges and objectives can be found in international research roadmaps [4,5]. Here, we highlight in particular the option of a PWFA γγ collider.

• Sjobak, Kyrre Ness; Adli, Erik; Corsini, Roberto; Farabolini, Wilfrid; Boyle, Gregory & Lindstrøm, Carl A. [Show all 11 contributors for this article] (2021). Strong focusing gradient in a linear active plasma lens. Physical Review Accelerators and Beams. ISSN 2469-9888. 24(12). doi: 10.1103/PhysRevAccelBeams.24.121306. Full text in Research Archive Show summary

  Active plasma lenses are compact devices developed as a promising beam-focusing alternative for charged particle beams, capable of short focal lengths for high-energy beams. We have previously shown that linear magnetic fields with gradients of around 0.3 kT/m can be achieved in argon-filled plasma lenses that preserve beam emittance [C.A. Lindstrøm et al., Phys. Rev. Lett. 121, 194801 (2018)]. Here we show that with argon in a 500  μm diameter capillary, the fields are still linear with a focusing gradient of 3.6 kT/m, which is an order of magnitude higher than the gradients of quadrupole magnets. The current pulses that generate the magnetic field are provided by compact Marx banks, and are highly repeatable. The demonstrated operation with simultaneously high-gradient, linear fields and good repeatability establish active plasma lenses as an ideal device for pulsed particle beam applications requiring very high focusing gradients that are uniform throughout the lens aperture.

• Chappell, J.; Adli, Erik; Agnello, R.; Aladi, M.; Andrebe, Y. & Apsimon, O. [Show all 99 contributors for this article] (2021). Experimental study of extended timescale dynamics of a plasma wakefield driven by a self-modulated proton bunch. Physical Review Accelerators and Beams. ISSN 2469-9888. 24(1), p. 011301-1–011301-13. doi: 10.1103/PhysRevAccelBeams.24.011301. Full text in Research Archive Show summary

  Plasma wakefield dynamics over timescales up to 800 ps, approximately 100 plasma periods, are studied experimentally at the Advanced Wakefield Experiment (AWAKE). The development of the longitudinal wakefield amplitude driven by a self-modulated proton bunch is measured using the external injection of witness electrons that sample the fields. In simulation, resonant excitation of the wakefield causes plasma electron trajectory crossing, resulting in the development of a potential outside the plasma boundary as electrons are transversely ejected. Trends consistent with the presence of this potential are experimentally measured and their dependence on wakefield amplitude are studied via seed laser timing scans and electron injection delay scans.

• Görgen, Andreas; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Siem, Sunniva; Adli, Erik & Edin, Nina Frederike J [Show all 14 contributors for this article] (2021). The Oslo Cyclotron Laboratory. The European Physical Journal Plus. 136, p. 1–13. doi: 10.1140/epjp/s13360-021-01150-3. Full text in Research Archive Show summary

  Research at the Oslo Cyclotron Laboratory at the University of Oslo is focused on spectroscopy experiments for nuclear structure and nuclear astrophysics using the Oslo Scintillator Array OSCAR. Light-ion beams from the K=35 cyclotron are furthermore used for studies in radiation biology and medical physics, for research and development related to medical isotope production, and for irradiation of materials and electronics components. Here we present an overview of the laboratory and its research infrastructure, give a brief discussion of the respective research programs and methods, and present recent highlights.

• Kim, Seong-Yeol; Chung, M.; Sjobak, Kyrre Ness; Adli, Erik; Doebert, Steffen & Dayyani, M. [Show all 9 contributors for this article] (2021). Witness electron beam injection using an active plasma lens for a proton beam-driven plasma wakefield accelerator. Physical Review Accelerators and Beams. ISSN 2469-9888. 24. doi: 10.1103/PhysRevAccelBeams.24.121304. Full text in Research Archive Show summary

  An active plasma lens (APL) focuses the beam in both the horizontal and vertical planes simultaneously using a magnetic field generated by a discharge current through the plasma. A beam size of 5–10  μm can be achieved within a short distance using a focusing gradient on the order of 100  T/m. The APL is therefore an attractive element for plasma wakefield acceleration, because an ultrasmall size of the witness electron beam is required for injection into the plasma wakefield to minimize emittance growth and to enhance the capturing efficiency. When the drive beam and witness electron beam copropagate through the APL, interactions between the drive and witness beams, and the plasma must be considered. In this paper, through particle-in-cell simulations, we discuss the possibility of using an APL for the final focusing of the electron beam for the AWAKE RUN 2 experiments. It is confirmed that the amplitude of the plasma wakefield excited by proton bunches remains the same even after propagation through the APL. The emittance of the witness electron beam increases rapidly in the plasma density ramp regions of the lens. Nevertheless, when the witness electron beam has a charge of 100 pC, emittance of 10 mm mrad, and bunch length of 60  μm, its emittance growth is not significant along the active plasma lens. For small emittance, such as 2 mm mrad, the emittance growth is found to be strongly dependent on the rms beam size, plasma density, and multiple Coulomb scattering.

• Hue, C.S.; Cao, Jiawei; Andriyash, I.A.; Knetsch, A.; Hogan, M.J. & Adli, Erik [Show all 8 contributors for this article] (2021). Efficiency and beam quality for positron acceleration in loaded plasma wakefields. Physical Review Research (PRResearch). 3(4). doi: 10.1103/PhysRevResearch.3.043063. Full text in Research Archive Show summary

  Accelerating particles to high energies in plasma wakefields is considered to be a promising technique with good energy efficiency and high gradient. While important progress has been made in plasma-based electron acceleration, positron acceleration in plasma has been scarcely studied and a fully self-consistent and optimal scenario has not yet been identified. For high energy physics applications where an electron-positron collider would be desired, the ability to accelerate positrons in plasma wakefields is, however, paramount. Here we show that the preservation of beam quality can be compromised in a plasma wakefield loaded with a positron beam, and a tradeoff between energy efficiency and beam quality needs to be found. For electron beams driving linear plasma wakefields, we have found that despite the transversely nonlinear focusing force induced by positron beam loading, the bunch quickly evolves toward an equilibrium distribution with limited emittance growth. Particle-in-cell simulations show that for μm-scale normalized emittance, the growth of uncorrelated energy spread sets an important limit. Our results demonstrate that the linear or moderately nonlinear regimes with Gaussian drivers provide a good tradeoff, achieving simultaneously energy-transfer efficiencies exceeding 30% and uncorrelated energy spread below 1%, while donut-shaped drivers in the nonlinear regime are more appropriate to accelerate high-charge bunches at higher gradients, at the cost of a degraded tradeoff between efficiency and beam quality.

• Turner, M; Muggli, P; Adli, Erik; Agnello, R; Aladi, M & Andrebe, Y [Show all 50 contributors for this article] (2020). Experimental study of wakefields driven by a self-modulating proton bunch in plasma. Physical Review Accelerators and Beams. ISSN 2469-9888. 28(8), p. 1–8. doi: 10.1103/PhysRevAccelBeams.23.081302. Full text in Research Archive
• Braunmüller, F; Nechaeva, T.; Adli, Erik; Agnello, R; Aladi, M & Andrebe, Y [Show all 50 contributors for this article] (2020). Proton Bunch Self-Modulation in Plasma with Density Gradient. Physical Review Letters. ISSN 0031-9007. 125. doi: 10.1103/PhysRevLett.125.264801. Full text in Research Archive
• Gorn, A.A.; Turner, M.; Adli, Erik; Agnello, R.; Aladi, M. & Andrebe, Y. [Show all 99 contributors for this article] (2020). Proton beam defocusing in AWAKE: comparison of simulations and measurements. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 62(12). doi: 10.1088/1361-6587/abc298. Full text in Research Archive
• Chen, J.B.B.; Schulte, D. & Adli, Erik (2020). Modeling and simulation of transverse wakefields in PWFA. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 1596(1). doi: 10.1088/1742-6596/1596/1/012057. Full text in Research Archive
• Ibison, M.G.; Welsch, C.P.; Adli, Erik; Gjersdal, Håvard; Christoforo, Mark Greyson & Shea, T. [Show all 8 contributors for this article] (2020). Development of a beam imaging system for the European spallation source tuning dump. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 950. doi: 10.1016/j.nima.2019.162790. Full text in Research Archive Show summary

  To provide essential beam diagnostics for the spallation target and for the tuning dump of the European Spallation Source (ESS) with its high-power, low-emittance proton beam, optical imaging systems have been developed allowing remote viewing of the beam profiles, using scintillation light from coatings on the proton beam window (PBW) at the accelerator exit and the target entry window (TW), and insertable interceptive screens at the tuning dump (TD). In this paper, we present the techniques used and the main parameters in the design of the TD system, including the optical configurations modelled in the software Zemax OpticStudio (ZOS). We also present the design principles for reflective optics which can transmit high-quality images, showing the performance of the imaging systems as predicted by ZOS and by prototyping. We take account of the requirements for initial alignment and ongoing maintenance of the optical system. Studies of the radiation and thermal environments, which impact on sensitive optical components such as cameras and mirrors, are also described, as are mechanical considerations for the vacuum vessels and screen actuators. Finally, comments are made on the applicability of similar optics to diagnostic systems at other neutron sources and accelerators.

• Doss, Christopher E; Adli, Erik; Ariniello, Robert; Cary, John; Corde, Sébastien & Hidding, Bernhard [Show all 14 contributors for this article] (2019). Laser-ionized, beam-driven, underdense, passive thin plasma lens. Physical Review Accelerators and Beams. ISSN 2469-9888. 22(11). doi: 10.1103/PhysRevAccelBeams.22.111001. Full text in Research Archive Show summary

  We present a laser-ionized, beam-driven, passive thin plasma lens that operates in the nonlinear blowout regime. This thin plasma lens provides axisymmetric focusing for relativistic electron beams at strengths unobtainable by magnetic devices. It is tunable, compact, and it imparts little to no spherical aberrations. The combination of these features make it more attractive than other types of plasma lenses for highly divergent beams. A case study is built on beam matching into a plasma wakefield accelerator at SLAC National Accelerator Laboratory’s FACET-II facility. Detailed simulations show that a thin plasma lens formed by laser ionization of a gas jet reduces the electron beam’s waist beta function to half of the minimum value achievable by the FACET-II final focus magnets alone.

• Claveria, Pablo San Miguel; Adli, Erik; Amorim, Lígia Diana; An, Weiming; Clayton, Christopher E. & Corde, Sébastien [Show all 21 contributors for this article] (2019). Betatron radiation and emittance growth in plasma wakefield accelerators. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. ISSN 1364-503X. 377(2151), p. 1–9. doi: 10.1098/rsta.2018.0173. Full text in Research Archive
• Gschwendtner, Edda M.; Turner, M; Adli, Erik; Ahuja, A; Apsimon, O & Apsimon, R [Show all 78 contributors for this article] (2019). Proton-driven plasma wakefield acceleration in AWAKE. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. ISSN 1364-503X. 377:20180418(2151), p. 1–9. doi: 10.1098/rsta.2018.0418. Full text in Research Archive
• Vafaei-Najafabadi, N.; Amorim, L. D.; Adli, Erik; An, W; Clarke, C. I. & Clayton, C. E. [Show all 24 contributors for this article] (2019). Producing multi-coloured bunches through beam-induced ionization injection in plasma wakefield accelerator. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. ISSN 1364-503X. 377(2151), p. 1–13. doi: 10.1098/rsta.2018.0184. Full text in Research Archive
• Amorim, Lígia Diana; Vafaei-Najafabadi, Navid; Emma, Claudio; Clarke, Christine I.; Green, Selina Z. & Storey, Doug [Show all 22 contributors for this article] (2019). Shaping trailing beams for beam loading via beam-induced-ionization injection at FACET. Physical Review Accelerators and Beams. ISSN 2469-9888. 22(11), p. 1–10. doi: 10.1103/PhysRevAccelBeams.22.111303. Full text in Research Archive
• Adli, Erik (2019). Plasma wakefield linear colliders—opportunities and challenges. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. ISSN 1364-503X. 377(2151), p. 1–11. doi: 10.1098/rsta.2018.0419. Full text in Research Archive Show summary

  A linear electron-positron collider operating at TeV-scale energies will provide high precision measurements and allow, for example, precision studies of the Higgs boson as well as searches for physics beyond the standard model. A future linear collider should produce collisions at high energy, with high luminosity and with a good wall plug to beam power transfer efficiency. The luminosity per power consumed is a key metric that can be used to compare linear collider concepts. The plasma wakefield accelerator has demonstrated high-gradient, high-efficiency acceleration of an electron beam and is therefore a promising technology for a future linear collider. We will go through the opportunities of using plasma wakefield acceleration technology for a collider, as well as a few of the collider-specific challenges that must be addressed in order for a high-energy, high luminosity-per-power plasma wakefield collider to become a reality.

• Adli, Erik; Ahuja, A.; Apsimon, O.; Apsimon, R.; Bachmann, A. M & Barrientos, D. [Show all 112 contributors for this article] (2019). Experimental Observation of Proton Bunch Modulation in a Plasma at Varying Plasma Densities. Physical Review Letters. ISSN 0031-9007. 122(5). doi: 10.1103/PhysRevLett.122.054802. Full text in Research Archive
• Turner, M.; Adli, Erik; Ahuja, A.; Apsimon, O.; Apsimon, R. & Bachmann, A. M [Show all 112 contributors for this article] (2019). Experimental Observation of Plasma Wakefield Growth Driven by the Seeded Self-Modulation of a Proton Bunch. Physical Review Letters. ISSN 0031-9007. 122(5). doi: 10.1103/PhysRevLett.122.054801. Full text in Research Archive
• Adli, Erik; Ahuja, A.; Apsimon, O.; Apsimon, R; Bachmann, AM & Barrientos, D [Show all 93 contributors for this article] (2018). Acceleration of electrons in the plasma wakefield of a proton bunch. Nature. ISSN 0028-0836. 561(7723), p. 363–367. doi: 10.1038/s41586-018-0485-4. Full text in Research Archive Show summary

  High-energy particle accelerators have been crucial in providing a deeper understanding of fundamental particles and the forces that govern their interactions. To increase the energy of the particles or to reduce the size of the accelerator, new acceleration schemes need to be developed. Plasma wakefield acceleration, in which the electrons in a plasma are excited, leading to strong electric fields (so called ‘wakefields’), is one such promising acceleration technique. Experiments have shown that an intense laser pulse or electron bunch10,11 traversing a plasma can drive electric fields of tens of gigavolts per metre and above—well beyond those achieved in conventional radio-frequency accelerators (about 0.1 gigavolt per metre). However, the low stored energy of laser pulses and electron bunches means that multiple acceleration stages are needed to reach very high particle energies. The use of proton bunches is compelling because they have the potential to drive wakefields and to accelerate electrons to high energy in a single acceleration stage. Long, thin proton bunches can be used because they undergo a process called self-modulation, a particle–plasma interaction that splits the bunch longitudinally into a series of high-density microbunches, which then act resonantly to create large wakefields. The Advanced Wakefield (AWAKE) experiment at CERN uses high-intensity proton bunches—in which each proton has an energy of 400 gigaelectronvolts, resulting in a total bunch energy of 19 kilojoules—to drive a wakefield in a ten-metre-long plasma. Electron bunches are then injected into this wakefield. Here we present measurements of electrons accelerated up to two gigaelectronvolts at the AWAKE experiment, in a demonstration of proton-driven plasma wakefield acceleration. Measurements were conducted under various plasma conditions and the acceleration was found to be consistent and reliable. The potential for this scheme to produce very high-energy electron bunches in a single accelerating stage means that our results are an important step towards the development of future high-energy particle accelerators.

• Olsen, Veronica Kristine Berglyd; Adli, Erik & Muggli, Patric (2018). Emittance preservation of an electron beam in a loaded quasilinear plasma wakefield. Physical Review Accelerators and Beams. ISSN 2469-9888. 21(1), p. 1–8. doi: 10.1103/PhysRevAccelBeams.21.011301. Full text in Research Archive Show summary

  We investigate beam loading and emittance preservation for a high-charge electron beam being accelerated in quasilinear plasma wakefields driven by a short proton beam. The structure of the studied wakefields are similar to those of a long, modulated proton beam, such as the AWAKE proton driver. We show that by properly choosing the electron beam parameters and exploiting two well known effects, beam loading of the wakefield and full blow out of plasma electrons by the accelerated beam, the electron beam can gain large amounts of energy with a narrow final energy spread (%-level) and without significant emittance growth.

• Joshi, C.; Adli, Erik; An, W.; Clayton, C. E.; Corde, S. & Gessner, S. [Show all 16 contributors for this article] (2018). Plasma wakefield acceleration experiments at FACET II. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 60(3). doi: 10.1088/1361-6587/aaa2e3. Full text in Research Archive Show summary

  During the past two decades of research, the ultra-relativistic beam-driven plasma wakefield accelerator (PWFA) concept has achieved many significant milestones. These include the demonstration of ultra-high gradient acceleration of electrons over meter-scale plasma accelerator structures, efficient acceleration of a narrow energy spread electron bunch at high-gradients, positron acceleration using wakes in uniform plasmas and in hollow plasma channels, and demonstrating that highly nonlinear wakes in the 'blow-out regime' have the electric field structure necessary for preserving the emittance of the accelerating bunch. A new 10 GeV electron beam facility, Facilities for Accelerator Science and Experimental Test (FACET) II, is currently under construction at SLAC National Accelerator Laboratory for the next generation of PWFA research and development. The FACET II beams will enable the simultaneous demonstration of substantial energy gain of a small emittance electron bunch while demonstrating an efficient transfer of energy from the drive to the trailing bunch. In this paper we first describe the capabilities of the FACET II facility. We then describe a series of PWFA experiments supported by numerical and particle-in-cell simulations designed to demonstrate plasma wake generation where the drive beam is nearly depleted of its energy, high efficiency acceleration of the trailing bunch while doubling its energy and ultimately, quantifying the emittance growth in a single stage of a PWFA that has optimally designed matching sections. We then briefly discuss other FACET II plasma-based experiments including in situ positron generation and acceleration, and several schemes that are promising for generating sub-micron emittance bunches that will ultimately be needed for both an early application of a PWFA and for a plasma-based future linear collider.

• Cour, Naja De La; Wilborgsson, Mattias; Shea, Thomas; Thomas, Cyrille; Rey, Fabien & Ghatnekar, Sara [Show all 12 contributors for this article] (2018). Implementation of the proton beam instrumentation into the proton beam instrumentation plug. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 1021(1), p. 1–5. doi: 10.1088/1742-6596/1021/1/012082. Full text in Research Archive Show summary

  The 5 MW proton beam to be delivered to the ESS spallation target must be tuned to its nominal value and controlled at all times. To achieve this, a suite of beam diagnostics has been proposed and is currently been designed. It is located in two plugs, the Proton Beam Window (PBW) plug and the Proton Beam Instrumentation Plug (PBIP). Here we present the design concept for the PBIP imposed by the beam physics requirements as well as by the high power target environment, i.e. material lifetime, remote handling and waste management.

• Lindstrøm, Carl A.; Adli, Erik; Boyle, Gregory; Corsini, Roberto; Dyson, Anthony E & Farabolini, Wilfrid [Show all 12 contributors for this article] (2018). Emittance Preservation in an Aberration-Free Active Plasma Lens. Physical Review Letters. ISSN 0031-9007. 121(19), p. 194801-1–194801-6. doi: 10.1103/PhysRevLett.121.194801. Full text in Research Archive Show summary

  Active plasma lensing is a compact technology for strong focusing of charged particle beams, which has gained considerable interest for use in novel accelerator schemes. While providing kT=m focusing gradients, active plasma lenses can have aberrations caused by a radially nonuniform plasma temperature profile, leading to degradation of the beam quality. We present the first direct measurement of this aberration, consistent with theory, and show that it can be fully suppressed by changing from a light gas species (helium) to a heavier gas species (argon). Based on this result, we demonstrate emittance preservation for an electron beam focused by an argon-filled active plasma lens.

• Malina, Lukas; Corsini, R; Persson, T.; Skowronski, Piotr Krzysztof & Adli, Erik (2018). Drive beam stabilisation in the CLIC Test Facility 3. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 894, p. 25–32. doi: 10.1016/j.nima.2018.03.057. Full text in Research Archive Show summary

  The proposed Compact Linear Collider (CLIC) uses a high intensity, low energy drive beam to produce the RF power needed to accelerate a lower intensity main beam with 100 MV/m gradient. This scheme puts stringent requirements on drive beam stability in terms of phase, energy and current. The consequent experimental work was carried out in CLIC Test Facility CTF3. In this paper, we present a novel analysis technique in accelerator physics to find beam drifts and their sources in the vast amount of the continuously gathered signals. The instability sources are identified and adequately mitigated either by hardware improvements or by implementation and commissioning of various feedbacks, mostly beam-based. The resulting drive beam stability is of 0.2°@ 3 GHz in phase, 0.08% in relative beam energy and about 0.2% beam current. Finally, we propose a stabilisation concept for CLIC to guarantee the main beam stability.

• Muggli, Patrick; Adli, Erik; Apsimon, R; Asmus, F; Baartman, R & Bachmann, AM [Show all 109 contributors for this article] (2018). AWAKE readiness for the study of the seeded self-modulation of a 400 GeV proton bunch. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 60, p. 1–12. doi: 10.1088/1361-6587/aa941c. Full text in Research Archive
• Lindstrøm, Carl A.; Sjøbæk, Kyrre Ness; Adli, Erik; Röckemann, J.-H.; Schaper, L. & Osterhoff, J. [Show all 11 contributors for this article] (2018). Overview of the CLEAR plasma lens experiment. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 909, p. 379–382. doi: 10.1016/j.nima.2018.01.063. Full text in Research Archive Show summary

  Discharge capillary-based active plasma lenses are a promising new technology for strongly focusing charged particle beams, especially when combined with novel high gradient acceleration methods. Still, many questions remain concerning such lenses, including their transverse field uniformity, limitations due to plasma wakefields and whether they can be combined in multi-lens lattices in a way to cancel chromaticity. These questions will be addressed in a new plasma lens experiment at the CLEAR User Facility at CERN. All the subsystems have been constructed, tested and integrated into the CLEAR beam line, and are ready for experiments starting late 2017.

• Lindstrøm, Carl A.; Adli, Erik; Allen, James M.; An, Weiming; Beekman, C. & Clarke, Christine I. [Show all 21 contributors for this article] (2018). Measurement of Transverse Wakefields Induced by a Misaligned Positron Bunch in a Hollow Channel Plasma Accelerator. Physical Review Letters. ISSN 0031-9007. 120:124802(12), p. 1–5. doi: 10.1103/PhysRevLett.120.124802. Full text in Research Archive Show summary

  Hollow channel plasma wakefield acceleration is a proposed method to provide high acceleration gradients for electrons and positrons alike: a key to future lepton colliders. However, beams which are misaligned from the channel axis induce strong transverse wakefields, deflecting beams and reducing the collider luminosity. This undesirable consequence sets a tight constraint on the alignment accuracy of the beam propagating through the channel. Direct measurements of beam misalignment-induced transverse wakefields are therefore essential for designing mitigation strategies. We present the first quantitative measurements of transverse wakefields in a hollow plasma channel, induced by an off-axis 20 GeV positron bunch, and measured with another 20 GeV lower charge trailing positron probe bunch. The measurements are largely consistent with theory.

• Doche, A.; Beekman, C.; Corde, S.; Allen, J. M.; Clarke, C. I. & Frederico, J. [Show all 21 contributors for this article] (2017). Acceleration of a trailing positron bunch in a plasma wakefield accelerator. Scientific Reports. 7(1). doi: 10.1038/s41598-017-14524-4. Full text in Research Archive Show summary

  High gradients of energy gain and high energy efficiency are necessary parameters for compact, cost-efficient and high-energy particle colliders. Plasma Wakefield Accelerators (PWFA) offer both, making them attractive candidates for next-generation colliders. In these devices, a charge-density plasma wave is excited by an ultra-relativistic bunch of charged particles (the drive bunch). The energy in the wave can be extracted by a second bunch (the trailing bunch), as this bunch propagates in the wake of the drive bunch. While a trailing electron bunch was accelerated in a plasma with more than a gigaelectronvolt of energy gain, accelerating a trailing positron bunch in a plasma is much more challenging as the plasma response can be asymmetric for positrons and electrons. We report the demonstration of the energy gain by a distinct trailing positron bunch in a plasma wakefield accelerator, spanning nonlinear to quasi-linear regimes, and unveil the beam loading process underlying the accelerator energy efficiency. A positron bunch is used to drive the plasma wake in the experiment, though the quasi-linear wake structure could as easily be formed by an electron bunch or a laser driver. The results thus mark the first acceleration of a distinct positron bunch in plasma-based particle accelerators.

• Pfingstner, Juergen; Adli, Erik & Schulte, Daniel (2017). On-line dispersion estimation and correction scheme for the Compact Linear Collider. Physical Review Accelerators and Beams. ISSN 2469-9888. 20. doi: 10.1103/PhysRevAccelBeams.20.011006. Full text in Research Archive Show summary

  The Compact Linear Collider (CLIC) has stringent component alignment tolerances in order to preserve the ultralow emittance of the utilized particle beams. Beam-based alignment techniques have been designed to relax these tolerances to realizable values. In this paper, a scheme is presented that is capable of mitigating besides the effects of static misalignments also dynamic misalignments caused by ground motion. It is based on the well-known dispersion-free steering (DFS) algorithm, with the peculiarity that it can perform its correction during the usual operation (on-line). This is enabled by performing the necessary dispersion measurements by introducing only negligibly small beam energy changes (per mille level). It has been found that this on-line correction becomes sensitive to the imperfections of transverse wakefields and structure tilts. These sensitivities have been studied via analytical models and in simulations and appropriate countermeasures to improve the robustness of the method have been proposed. The correction performance and robustness properties of the improved algorithm have been studied in detail with respect to all relevant static and dynamic imperfections in a realistic scenario. The presented scheme is not only a potentially important operational tool for CLIC, but the findings with respect to robustness properties for different imperfections are of general interest for the application of the dispersion-free steering algorithm.

• Gamba, D.; Corsini, Roberto; Curt, S.; Doebert, Steffen; Farabolini, W. & McMonagle, G. [Show all 13 contributors for this article] (2017). The CLEAR user facility at CERN. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 909, p. 480–483. doi: 10.1016/j.nima.2017.11.080. Full text in Research Archive Show summary

  The conversion of the CALIFES beamline of CTF3 into the ‘‘CERN Linear Electron Accelerator for Research’’ (CLEAR) facility was approved in December 2016. The primary focus for CLEAR is general accelerator R&D and component studies for existing and possible future accelerator applications. This includes studies for high gradient acceleration methods, e.g. for CLIC and plasma technology, and prototyping and validation of accelerator components, e.g. for the HL-LHC upgrade. The facility also provides irradiation test capabilities for characterisation of electronic components and for medical applications. A description of the facility with details on the achievable beam parameters, and the status and plans are presented.

• Hidding, B.; Manahan, G. G.; Heinemann, T.; Scherkl, P.; Habib, F. & Ullmann, D. [Show all 28 contributors for this article] (2017). FIRST MEASUREMENTS OF TROJAN HORSE INJECTION IN A PLASMA WAKEFIELD ACCELERATOR, Proceedings of the 8th International Particle Accelerator Conference. JACoW. ISSN 9783954501823. p. 1252–1257. Full text in Research Archive Show summary

  Plasma accelerators support accelerating fields of 10-100’s of GV/m over meter-scale distances and routinely produce femtosecond-scale, multi-kA electron bunches. The so called Trojan Horse underdense photocathode plasma wakefield acceleration scheme combines state of-the-art accelerator technology with laser and plasma methods and paves the way to improve beam quality as regards emittance and energy spread by many orders of magnitude. Electron beam brightness levels exceeding 10^20 A m^-2 rad^-2 may be reached, and the tunability allows for multi-GeV energies, designer bunches and energy spreads <0.05% in a single plasma accelerator stage. The talk will present results of the international E210 multiyear experimental program at SLAC FACET, which culminated in successful first demonstration of the Trojan Horse method during FACET’s final experimental run in 2016. Enabling implications for applications, including high performance plasma-based 5th generation light sources such as hard x-ray FEL’s, for which preliminary start-to-end simulations are presented, and for high energy physics are discussed.

• Lillestol, Reidar; Adli, Erik; Aftab, N.; Corsini, Roberto; Döbert, S. & Farabolini, W. [Show all 10 contributors for this article] (2016). Status of Wakefield Monitor Experiments at the CLIC Test Facility. In Petit-Jean-Genaz, Christine; Kim, Dong Eon; Kim, Kyung Sook; Ko, In Soo; Kim, Kyung Ryul & Schaa, Volker RW (Ed.), Proceedings of the 7th International Particle Accelerator Conference. JACoW. ISSN 9783954501472. Full text in Research Archive
• Clayton, C.E.; Adli, Erik; Allen, J.; An, W.; Clarke, C.I. & Corde, Sebastien [Show all 18 contributors for this article] (2016). Self-mapping the longitudinal field structure of a nonlinear plasma accelerator cavity. Nature Communications. 7. doi: 10.1038/ncomms12483. Full text in Research Archive
• Lindstrøm, Carl Andreas; Adli, Erik; Allen, James; Delahaye, Jean-Pierre; Hogan, Mark J. & Joshi, Chan [Show all 9 contributors for this article] (2016). Staging Optics Considerations for a Plasma Wakefield Acceleration Linear Collider. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 829, p. 224–228. doi: 10.1016/j.nima.2015.12.065. Full text in Research Archive Show summary

  Plasma wakefield acceleration offers acceleration gradients of several GeV/m, ideal for a next-generation linear collider. The beam optics requirements between plasma cells include injection and extraction of drive beams, matching the main beam beta functions into the next cell, canceling dispersion as well as constraining bunch lengthening and chromaticity. To maintain a high effective acceleration gradient, this must be accomplished in the shortest distance possible. A working example is presented, using novel methods to correct chromaticity, as well as scaling laws for a high energy regime.

• Adli, Erik; Lindstrøm, Carl Andreas; Allen, J.; Clarke, C. I.; Frederico, J. & Gessner, S.J. [Show all 19 contributors for this article] (2016). Long-range attraction of an ultrarelativistic electron beam by a column of neutral plasma. New Journal of Physics. 18(103013). doi: 10.1088/1367-2630/18/10/103013. Full text in Research Archive Show summary

  We report on the experimental observation of the attraction of a beam of ultrarelativistic electrons towards a column of neutral plasma. In experiments performed at the FACET test facility at SLAC we observe that an electron beam moving parallel to a neutral plasma column, at an initial distance of many plasma column radii, is attracted into the column. Once the beam enters the plasma it drives a plasma wake similar to that of an electron beam entering the plasma column head-on. A simple analytical model is developed in order to capture the essential physics of the attractive force. The attraction is further studied by 3D particle-in-cell numerical simulations. The results are an important step towards better understanding of particle beam–plasma interactions in general and plasma wakefield accelerator technology in particular.

• Adli, Erik; Olsen, Veronica Kristine Berglyd; Lindstrøm, Carl Andreas; Muggli, Patric; Reimann, O. & Vieira, Jorge [Show all 20 contributors for this article] (2016). Progress of plasma wakefield self-modulation experiments at FACET. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 829, p. 334–338. doi: 10.1016/j.nima.2016.02.075. Full text in Research Archive Show summary

  Simulations and theory predict that long electron and positron beams may under favorable conditions self-modulate in plasmas. We report on the progress of experiments studying the self-modulation instability in plasma wakefield experiments at FACET. The experimental results obtained so far, while not being fully conclusive, appear to be consistent with the presence of the self-modulation instability.

• Gessner, Spencer; Adli, Erik; Allen, James; An, Weiming; Clarke, Christine & Clayton, Christopher E. [Show all 24 contributors for this article] (2016). Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator. Nature Communications. 7:11785. doi: 10.1038/ncomms11785. Full text in Research Archive Show summary

  Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV/m is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.

• Adli, Erik; Lindstrøm, Carl Andreas; Allen, James; Clarke, Christine; Frederico, Joel & Gessner, Spencer [Show all 19 contributors for this article] (2016). Transverse oscillations in plasma wakefield experiments at FACET. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 829, p. 94–98. doi: 10.1016/j.nima.2016.02.054. Full text in Research Archive Show summary

  We study transverse effects in a plasma wakefield accelerator. Experimental data from FACET with asymmetry in the beam-plasma system is presented. Energy dependent centroid oscillations are observed on the accelerated part of the charge. The experimental results are compared to PIC simulations and theoretical estimates.

• Lindstrøm, Carl Andreas & Adli, Erik (2016). Design of general apochromatic drift-quadrupole beam lines. Physical Review Special Topics. Accelerators and Beams. 19:071002(7). doi: 10.1103/PhysRevAccelBeams.19.071002. Full text in Research Archive Show summary

  Chromatic errors are normally corrected using sextupoles in regions of large dispersion. In low emittance linear accelerators, use of sextupoles can be challenging. Apochromatic focusing is a lesser-known alternative approach, whereby chromatic errors of Twiss parameters are corrected without the use of sextupoles, and has consequently been subject to renewed interest in advanced linear accelerator research. Proof of principle designs were first established by Montague and Ruggiero and developed more recently by Balandin et al. We describe a general method for designing drift-quadrupole beam lines of arbitrary order in apochromatic correction, including analytic expressions for emittance growth and other merit functions. Worked examples are shown for plasma wakefield accelerator staging optics and for a simple final focus system.

• Litos, M.; Adli, Erik; Allen, J. M.; An, W.; Clarke, C.I. & Corde, S. [Show all 18 contributors for this article] (2016). 9 GeV energy gain in a beam-driven plasma wakefield accelerator. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 58(3). doi: 10.1088/0741-3335/58/3/034017. Full text in Research Archive
• Gschwendtner, Edda; Adli, Erik; Amorim, L; Apsimon, R; Assmann, R & Bachmann, AM [Show all 91 contributors for this article] (2016). AWAKE, The Advanced Proton Driven Plasma Wakefield Acceleration Experiment at CERN. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 829, p. 76–82. doi: 10.1016/j.nima.2016.02.026. Full text in Research Archive
• Vafaei-Najafabadi, Navid; Marsh, Kenneth A.; Clayton, Christopher E.; An, Weiming; Mori, Warren B. & Joshi, Chan [Show all 18 contributors for this article] (2016). Limitation on the accelerating gradient of a wakefield excited by an ultrarelativistic electron beam in rubidium plasma. Physical Review Special Topics. Accelerators and Beams. 19:101303, p. 1–15. doi: 10.1103/PhysRevAccelBeams.19.101303. Full text in Research Archive
• Vafaei-Najafabadi, Navid; Clayton, Christopher E.; Marsh, Kenneth A.; An, Weiming; Lu, Wei & Mori, Warren B. [Show all 19 contributors for this article] (2016). Ionization injection and acceleration of electrons in a plasma wakefield accelerator at FACET. AIP Conference Proceedings. ISSN 0094-243X. 1777:070011, p. 1–6. doi: 10.1063/1.4965654. Full text in Research Archive
• Gessner, Spencer; Allen, James; Clarke, Christine; Delahaye, Jean-Pierre; Frederico, Joel & Green, Selina [Show all 25 contributors for this article] (2016). Demonstration of the hollow channel plasma wakefield accelerator. In Petit-Jean-Genaz, Christine; Kim, Dong Eon; Kim, Kyung Sook; Ko, In Soo; Kim, Kyung Ryul & Schaa, Volker RW (Ed.), Proceedings of the 7th International Particle Accelerator Conference. JACoW. ISSN 9783954501472. p. 3202–3206. Full text in Research Archive Show summary

  Over the past decade, there has been enormous progress in the field of beam and laser-driven plasma acceleration of electron beams. However, in order for plasma wakefield acceleration to be useful for a high-energy e+e−collider, we need a technique for accelerating positrons in plasma as well. This is a unique challenge, because the plasma responds differently to electron and positron beams, with plasma electrons being pulled through the positron beam and creating a non-linear focusing force that is disruptive to the beam. Here, we demonstrate a technique called hollow channel acceleration that symmetrizes the wakefield response to beams of either charge. Using a transversely shaped laser pulse, we create an annular plasma with a fixed radius of 200 μIm. We observe the acceleration of a positron bunch with energies up to 33.4 MeV in a 25 cm long channel, indicating an effective gradient greater than 100 MeV/m. This is the first demonstration of a technique that way be used for staged acceleration of positron beams in plasma.

• Lindstrøm, Carl Andreas; Adli, Erik; Pfingstner, Juergen; Marin, E. & Schulte, D (2016). Transverse tolerances of a multi-stage plasma wakefield accelerator. In Petit-Jean-Genaz, Christine; Kim, Dong Eon; Kim, Kyung Sook; Ko, In Soo; Kim, Kyung Ryul & Schaa, Volker RW (Ed.), Proceedings of the 7th International Particle Accelerator Conference. JACoW. ISSN 9783954501472. p. 2561–2564. Full text in Research Archive Show summary

  Plasma wakefield acceleration (PWFA) provides GeV/m-scale accelerating fields, ideal for applications such as a future linear collider. However, strong focusing fields imply that a transversely offset beam with an energy spread will experience emittance growth from the energy depen- dent betatron oscillation. We develop an analytic model for estimating tolerances from this effect, as well as an effective simplified simulation tool in Elegant. Estimations for a proposed 1 TeV PWFA linear collider scheme indicate tight tolerances of order 40 nm and 1 μrad in position and angle respectively.

• Pfingstner, Juergen; Adli, Erik; Lindstrøm, Carl Andreas; Marin, E. & Schulte, D (2016). Considerations for a drive beam scheme for a plasma wakefield linear collider. In Petit-Jean-Genaz, Christine; Kim, Dong Eon; Kim, Kyung Sook; Ko, In Soo; Kim, Kyung Ryul & Schaa, Volker RW (Ed.), Proceedings of the 7th International Particle Accelerator Conference. JACoW. ISSN 9783954501472. p. 2565–2568. Full text in Research Archive Show summary

  The potential for high average gradients makes plasma wakefield acceleration (PWFA) an attracting option for future linear colliders. For a beam-driven PWFA collider a sequence of cells has to be supplied with synchronised drive beam bunches. This paper is concerned with the generation, transport and distribution of these drive beam bunches in a so-called drive beam complex for a 3 TeV collider. Based on earlier concepts, several modifications are suggested. The new design includes a superconducting linac and an optimised bunch delay system with a tree structure. To verify the feasibility for the overall complex, a lattice design and tracking studies for the critical bending arc subsystem are presented. Also the feasibility of a compact bunch separation system is shown. The result of these efforts is a drive beam complex that is optimised for construction cost and power efficiency that favours unified lattice solutions.

• Caldwell, Allen C.; Adli, Erik; Amorim, L; Apsimon, R; Argyropoulos, T & Assmann, R [Show all 121 contributors for this article] (2016). Path to AWAKE: Evolution of the concept. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 829, p. 3–16. doi: 10.1016/j.nima.2015.12.050. Full text in Research Archive
• Adli, Erik & Muggli, Patric (2016). Proton-Beam-Driven Plasma Acceleration. Reviews of Accelerator Science and Technology. ISSN 1793-6268. 9, p. 85–104. doi: 10.1142/S1793626816300048. Full text in Research Archive
• Corde, S.; Adli, Erik; Allen, J. M.; An, W.; Clarke, C.I. & Clausse, B. [Show all 20 contributors for this article] (2016). High-field plasma acceleration in a high-ionization-potential gas. Nature Communications. 7(11898). doi: 10.1038/ncomms11898. Full text in Research Archive
• Vafaei-najafabadi, Navid; An, W.; Clayton, C.E.; Joshi, Chan; Marsh, K.A. & Mori, W.B. [Show all 17 contributors for this article] (2016). Evidence for high-energy and low-emittance electron beams using ionization injection of charge in a plasma wakefield accelerator. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 58(3). doi: 10.1088/0741-3335/58/3/034009. Full text in Research Archive
• Zha, Hao; Latina, Andrea; Grudiev, Alexej; Michele, Giovanni De; Solodko, Anastasiya & Wuensch, Walter [Show all 10 contributors for this article] (2016). Beam-based measurements of long-range transverse wakefields in the Compact Linear Collider main-linac accelerating structure. Physical Review Special Topics. Accelerators and Beams. 19:01100. doi: 10.1103/PhysRevAccelBeams.19.011001. Full text in Research Archive
• Adli, Erik; Gessner, S.J.; Corde, S.; Hogan, M.J. & Bjerke, Henrik Hemmestad (2015). Cherenkov light-based beam profiling for ultrarelativistic electron beams. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 783, p. 35–42. doi: 10.1016/j.nima.2015.02.003. Full text in Research Archive Show summary

  We describe a beam profile monitor design based on Cherenkov light emitted from a charged particle beam in an air gap. The main components of the profile monitor are silicon wafers used to reflect Cherenkov light onto a camera lens system. The design allows for measuring large beam sizes, with large photon yield per beam charge and excellent signal linearity with beam charge. The profile monitor signal is independent of the particle energy for ultrarelativistic particles. Different design and parameter considerations are discussed. A Cherenkov light-based profile monitor has been installed at the FACET User Facility at SLAC. We report on the measured performance of this profile monitor.

• Corde, Sébastien; Adli, Erik; Allen, Jim M.; An, Weiming; Clarke, Clyde I. & Clayton, Christopher E. [Show all 22 contributors for this article] (2015). Multi-gigaelectronvolt acceleration of positrons in a self-loaded plasma wakefield. Nature. ISSN 0028-0836. 524(7566), p. 442–445. doi: 10.1038/nature14890. Full text in Research Archive
• Pfingstner, Juergen; Adli, Erik & Schulte, D (2015). Effect of accelerating structures on on-line DFS in the main linac of CLIC, Proceedings of the 6th International Particle Accelerator Conference. Jefferson Lab, Newport News. ISSN 9783954501687. Full text in Research Archive
• Pfingstner, Juergen & Adli, Erik (2015). Performance and tolerance studies of the X-ray production for the X-band FEL collaboration, Proceedings of the 37th International Free Electron Laser Conference. Creative Commons Attribution 3.0 license. ISSN 9783954501335. Full text in Research Archive
• Latina, Andrea; Pfingstner, Juergen; Schulte, D; Adli, Erik; Snuverink, J & Fuster-Martinez, Nuria (2015). Tests of wakefield-free steering at ATF2, Proceedings of the 6th International Particle Accelerator Conference. Jefferson Lab, Newport News. ISSN 9783954501687. Full text in Research Archive
• Lillestol, Reidar; Adli, Erik; Pfingstner, Juergen; Corsini, Roberto; Doebert, Steffen & Farabolini, Wilfrid [Show all 8 contributors for this article] (2015). Wakefield monitor development for X-band accelerating structures, Proceedings of the 6th International Particle Accelerator Conference. Jefferson Lab, Newport News. ISSN 9783954501687. Full text in Research Archive
• Lillestøl, Reidar Lunde; Döbert, S.; Adli, Erik & Olvegård, M. (2014). Electron beam deceleration measurements using the decelerator test beam line in the Compact Linear Collider test facility. Physical Review Special Topics. Accelerators and Beams. 17(3). doi: 10.1103/PhysRevSTAB.17.031003. Full text in Research Archive
• Green, Sarah Z.; Adli, Erik; Clarke, Clyde I.; Corde, Sébastien; Edstrom, Steve A. & Fisher, Alan S. [Show all 22 contributors for this article] (2014). Laser ionized preformed plasma at FACET. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 56(8). doi: 10.1088/0741-3335/56/8/084011. Full text in Research Archive
• Vafaei-Najafabadi, Navid; Marsh, Kenneth A.; Clayton, Christopher E.; An, Weiming; Mori, Warren B. & Joshi, Chan [Show all 21 contributors for this article] (2014). Beam loading by distributed injection of electrons in a Plasma Wakefield Accelerator. Physical Review Letters. ISSN 0031-9007. 112(025001). doi: 10.1103/PhysRevLett.112.025001. Full text in Research Archive Show summary

  We show through experiments and supporting simulations that propagation of a highly relativistic and dense electron bunch through a plasma can lead to distributed injection of electrons, which depletes the accelerating field, i.e., beam loads the wake. The source of the injected electrons is ionization of the second electron of rubidium (Rb II) within the wake. This injection of excess charge is large enough to severely beam load the wake, and thereby reduce the transformer ratio T. The reduction of the average T with increasing beam loading is quantified for the first time by measuring the ratio of peak energy gain and loss of electrons while changing the beam emittance. Simulations show that beam loading by Rb II electrons contributes to the reduction of the peak accelerating field from its weakly loaded value of 43  GV/m to a strongly loaded value of 26  GV/m. © 2014 American Physical Society

• Litos, Michael dennis; Adli, Erik; An, Weiming; Clarke, Christine; Clayton, C.E. & Corde, Sebastien [Show all 24 contributors for this article] (2014). High-efficiency acceleration of an electron beam in a plasma wakefield accelerator. Nature. ISSN 0028-0836. 515(7525), p. 92–95. doi: 10.1038/nature13882. Full text in Research Archive Show summary

  High-efficiency acceleration of an electron beam in a plasma wakefield accelerator

• Latina, Andrea; Pfingstner, Juergen; Pellegrini, Dario; Adli, Erik & Schulte, D (2014). Toolbox for applying beam-based alignment to linacs, Proceedings of the 27th Linear Accelerator Conference. Creative Commons Attribution 3.0. ISSN 9783954501427. Full text in Research Archive
• Latina, A; Pfingstner, J.; Schulte, D; Adli, Erik; Decker, F.J. & Lipkowitz, N (2014). Experimental demonstration of a global dispersion-free steering correction at the new linac test facility at SLAC. Physical Review Special Topics. Accelerators and Beams. 17(4). doi: 10.1103/PhysRevSTAB.17.042803. Full text in Research Archive
• An, W.; Zhou, M.; Vafaei-Najafabadi, N.; Marsh, K.A.; Clayton, C.E. & Joshi, C. [Show all 19 contributors for this article] (2013). Strategies for mitigating the ionization-induced beam head erosion problem in an electron-beam-driven plasma wakefield accelerator. Physical Review Special Topics. Accelerators and Beams. 16(10). doi: 10.1103/PhysRevSTAB.16.101301. Full text in Research Archive
• Olvegård, Maja; Adli, Erik; Andreazza, William; Bolzon, Benoit; Bravin, Enrico & Chritin, Nicolas [Show all 12 contributors for this article] (2013). Beam profile monitoring at the test beam line at the Compact Linear Collider test facility. Physical Review Special Topics. Accelerators and Beams. 16(8). doi: 10.1103/PhysRevSTAB.16.082802. Full text in Research Archive
• Adli, Erik; Hogan, M; Frederico, J; Litos, M. D.; An, W. & Mori, W. (2012). Transverse effects in plasma wakefield acceleration at FACET - simulation studies. AIP Conference Proceedings. ISSN 0094-243X. 1507, p. 541–546. doi: 10.1063/1.4773755. Full text in Research Archive
• Olvegård, Maja; Adli, Erik; Braun, Hans H.; Bravin, Enrico; Chritin, Nicolas & Corsini, Roberto [Show all 14 contributors for this article] (2012). High intensity profile monitor for time resolved spectrometry at the CLIC Test Facility 3. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 683, p. 29–39. doi: 10.1016/j.nima.2012.04.065. Full text in Research Archive
• Adli, Erik; Ruber, Roger; Ziemann, Volker; Corsini, Roberto; Dubrovskiy, A. & Syratchev, I. (2011). X-band rf power production and deceleration in the two-beam test stand of the Compact Linear Collider test facility. Physical Review Special Topics. Accelerators and Beams. 14(8). doi: 10.1103/PhysRevSTAB.14.081001. Full text in Research Archive
• Berriaud, C; Adli, Erik; Dudarev, A; Rabbers, J.J.; Broggi, F & Junker, S [Show all 26 contributors for this article] (2006). On-Surface Tests of the ATLAS Barrel Toroid Coils: Acceptance Criteria and Results. IEEE Transactions on Applied Superconductivity (TAS). ISSN 1051-8223. 16(2), p. 557–560. doi: 10.1109/TASC.2006.870839. Full text in Research Archive
• Dudarev, A; Adli, Erik; Berriaud, C; Rabbers, J.J; Broggi, F & Pengo, R [Show all 17 contributors for this article] (2006). On-Surface Test of the ATLAS Barrel Toroid Coils: Overview. IEEE Transactions on Applied Superconductivity (TAS). ISSN 1051-8223. 16(2), p. 508–511. doi: 10.1109/TASC.2005.869549. Full text in Research Archive

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• Ellingsen, Abélia; Adli, Erik; Drobniak, Pierre; Lindstrøm, Carl A.; Rød-Lindbergh, Elisabeth & Rieker, Vilde Flognfeldt [Show all 14 contributors for this article] (2026). SHARP: A Compact Focusing System for Emerging Particle Therapies using an Active Plasma Lens. doi: https:/indico.desy.de/event/51069/contributions/205605/. Full text in Research Archive Show summary

  Background: Improved control of the beam envelope in particle radiotherapy could enhance the precision of dose delivery. A novel approach is to incorporate an active plasma lens (APL) into the beamline. This compact device is used for strong and radially symmetric defocusing, giving rapid and controlled beam expansion. Such an expanded beam is of interest in itself, as it is generated by beam optics rather than through scattering, enabling large high intensity fields that may be relevant for FLASH applications. Beam expansion can also be followed by downstream refocusing to produce a sharp waist at the target. This may reduce entrance dose to healthy tissue while enhancing dose deposition at depth. Such beam geometries from a compact system could benefit precision conformal radiotherapy and spatial fractionation. The SHARP project is in the process of demonstrating these ideas experimentally with 200 MeV very high-energy electrons (VHEE), supported by simulations of beam optics and dose distributions. Materials and Methods: Experiments are being conducted at the CLEAR facility at CERN. The system combines a defocusing APL with quadrupole magnets for final focusing onto the target. Beam enlargement, without focusing, is evaluated on a downstream profile monitoring screen. The refocused beam is subsequently characterized with screens downstream of the quadrupoles. Radiation transport simulations in Geant4 are used to model dose deposition at the target and outside the focal region. Simulations with ImpactX are used for designing beam optics and assessing the influence of e.g. energy spread. Results: Beam enlargement from the APL is experimentally observed to be linear and symmetric in both transverse planes. Simulations show that quadrupoles can modify these beams into large, quasi-parallel fields for broad irradiation of higher intensity than passive scattering, which could be useful to investigate further for certain FLASH applications. For small deep targets, simulations show that increasing the APL current coupled with refocusing quadrupoles reduces focal beam size while increasing divergence, producing a sharp Bragg-like peak. Larger opening angles upstream and downstream of the target have also been confirmed experimentally. Conclusions: SHARP investigates a compact hybrid APL-quadrupole system to achieve precise focal spots and controlled dose distributions. The technique could serve as a versatile research platform for SFRT and FLASH applications. The project’s first experimental results represent a promising step towards improved dose delivery by demonstrating both controlled beam enlargement and refocusing. Ongoing work to refine the concept includes simulations and experiments of scattering in water phantoms, nonlinear APL defocusing for generating enlarged flat fields, spot scanning, and extension of the concept to protons.

• Drobniak, Pierre; Adli, Erik; Anderson, H. B.; Sjobak, Kyrre Ness; Lindstrøm, Carl A. & Dyson, A. [Show all 8 contributors for this article] (2025). Preliminary results from the CLEAR nonlinear plasma lens experiment. doi: 10.18429/JACOW-IPAC2025-MOPS027. Full text in Research Archive Show summary

  Plasma lensing provides compact focusing of electron beams, since they offer strong focusing fields (kT/m) in both planes simultaneously. This becomes particularly important for highly diverging beams with a large energy spread such as those typically originating from plasma accelerators. The lens presented here is a nonlinear active plasma lens, with a controlled focusing-strength variation purposely introduced in one transverse direction. This lens is a key element of a larger transport lattice, core of the ERC project SPARTA, which aims to provide a solution for achromatic transport between plasma-accelerator stages. We report on preliminary experimental results from the CLEAR facility at CERN, which aims to probe the magnetic field structure of the lens using an electron beam, in search of the desired nonlinearity, together with 2D plasma simulation results.

• Lindstrøm, Carl A.; Adli, Erik; Anderson, Hektor B.; Drobniak, Pierre; Kalvik, Daniel & Peña, Felipe [Show all 7 contributors for this article] (2025). The SPARTA project: toward a demonstrator facility for multistage plasma acceleration. doi: 10.18429/JACOW-IPAC2025-TUPS120. Full text in Research Archive Show summary

  Plasma acceleration is a rapidly maturing technology, but is not yet ready for large-scale applications such as linear colliders. The SPARTA project aims to develop a near-term, medium-scale plasma-accelerator facility to enable new experiments in strong-field quantum electrodynamics (SFQED)—an application that requires solving two of the most important remaining challenges in plasma acceleration: reaching high energy by using multiple accelerating stages; and achieving high beam stability. We report on progress toward the three main objectives: demonstrating a nonlinear plasma lens for achromatic beam transport between stages; developing self-stabilization and instability suppression mechanisms; and developing a conceptual design for a multistage SFQED facility.

• Chen, Jian Bin Ben; Adli, Erik; Drobniak, Pierre; Finnerud, Ole Gunnar; Hørlyk, Eir Eline & Kalvik, Daniel [Show all 9 contributors for this article] (2025). ABEL: The adaptable beginning-to-end linac simulation framework. doi: 10.18429/JACOW-IPAC2025-TUPS012. Full text in Research Archive Show summary

  We introduce ABEL, the Adaptable Beginning-to-End Linac simulation framework developed for agile design studies of plasma-based accelerators and colliders. ABEL’s modular architecture allows users to simulate particle acceleration across various beamline components. The framework supports specialised codes such as HiPACE++, Wake-T, ELEGANT, GUINEA-PIG and CLICopti, which facilitate precise modelling of complex machine components. Key features include simplified models for addressing transverse instabilities, radiation reactions, and ion motion, alongside comprehensive diagnostics and optimisation capabilities. Our simulation studies focus on the HALHF plasma linac, examining tolerances for drive beam jitter, including effects of self-correction mechanisms. Simulation results demonstrate ABEL's ability to model emittance growth under transverse instability and ion motion, highlighting the framework’s adaptability in balancing simulation fidelity with computational efficiency. The findings point towards ABEL’s potential for advancing compact accelerator designs and contribute to the broader goals of enhancing control and precision in plasma-based acceleration.

• Peña, Felipe; Adli, Erik; Drobniak, Pierre; Kalvik, Daniel; Sjobak, Kyrre Ness & Lindstrøm, Carl A. (2025). Development of an achromatic spectrometer for a laser-wakefield-accelerator experiment. doi: 10.18429/JACOW-IPAC2025-TUPM096. Full text in Research Archive Show summary

  The large gradients of plasma-wakefield accelerators promise to shorten accelerators and reduce their financial and environmental costs. For such accelerators, a key challenge is the transport of beams with high divergence and energy spread. Achromatic optics is a potential solution that would allow staging of plasma accelerators without beam-quality degradation. For this, a nonlinear plasma lens is being developped within the SPARTA project. As a first application of this lens, we aim to implement an achromatic spectrometer for electron bunches produced by a laser-wakefield accelerator. We report on progress in designing such an experiment.

• Lindstrøm, Carl A.; Adli, Erik; Chen, Jian Bin Ben; Drobniak, Pierre; Hørlyk, Eir Eline & Kalvik, Daniel [Show all 28 contributors for this article] (2025). Updated baseline design for HALHF: the hybrid, asymmetric, linear Higgs factory. doi: 10.18429/JACOW-IPAC2025-MOCD1. Full text in Research Archive Show summary

  Particle physicists aim to construct a electron–positron Higgs factory as the next major particle collider. However, the high associated costs motivate the development of more affordable collider designs. Plasma-wakefield acceleration is a promising technology to this end. HALHF is a proposal for a Higgs factory that utilizes beam-driven plasma-wakefield acceleration to accelerate electrons to high energy with high gradient, while using radio-frequency acceleration to accelerate positrons to a lower energy. This asymmetry sidesteps a major difficulty in plasma acceleration: that of accelerating positrons with high efficiency and quality. Since publication, several challenges were identified in the original baseline design. We summarize the updated baseline design, which addresses these challenges, and describe the parameter- and cost-optimization process used to arrive at this design.

• Rieker, Vilde Flognfeldt; Aksoy, Avni; Malyzhenkov, Alexander; Wroe, Laurence Matthew; Corsini, Roberto & Farabolini, Wilfrid [Show all 11 contributors for this article] (2023). BEAM INSTRUMENTATION FOR REAL TIME FLASH DOSIMETRY: EXPERIMENTAL STUDIES IN THE CLEAR FACILITY. Full text in Research Archive Show summary

  Real-time dosimetry for ultra-high dose-rates (UHDR) and very high energy electrons (VHEE) is a challenge which is currently being studied using the electron beam at CERN Linear Accelerator for Research (CLEAR). These studies are motivated by the demand for reliable dosimetry for FLASH radiotherapy. This mode of irradiation relies on UHDR, a dose rate regime where conventional dosimetry monitors such as ionization chambers saturate. One potential approach is the use of a calibrated beam-based dosimetry method. The existing beam instrumentation provides real-time information on charge and both transverse and longitudinal profiles of the pulses, and makes possible a measurement of the beam Twiss parameters. In the context of achieving a real-time prediction of the dose deposition, this paper presents experimental studies of the correlation of these parameters with the read-out of passive and dose-rate independent methods such as radiochromic films, and compares them with simulation results.

• Fackelman, Eric Daniel; Sjobak, Kyrre Ness; Gjersdal, Håvard; Adli, Erik; Thomas, Cyrille & Levinsen, Yngve Inntjore [Show all 7 contributors for this article] (2023). SIMULATION OF THE ESS PROTON BEAM WINDOW SCATTERING. Full text in Research Archive Show summary

  The European Spallation Source produces neutrons used for science by delivering a 5 MW proton beam to a tungsten target. The proton beam parameters must remain within a well-defined range during all phases of facility exploitation. The proton beam parameters are measured and monitored by an instrumentation suite, among which are two beam imaging systems. Parameters such as position and beam current density can be calculated from the images, supporting beam tuning and operation. However, one of the two systems may be affected by beam scattering. In this paper, we will focus on modelling the impact of the scattering on the beam on target distribution. The modelling process, involving simulation codes such as Geant4 and two-dimensional convolution in Matlab, is described. Initially, Geant4 simulates a scattered pencil beam. The resulting distribution is fitted and can be used similarly to an instrument response in image processing to model any possible beam distribution. Finally, we discuss the results of the scattered beam imaging model, showing the range of applications of the model and the impact of scattering on the beam parameters.

• Adli, Erik; Gjersdal, Håvard; Sjobak, Kyrre Ness; Christoforo, Mark Greyson; Fackelman, Eric Daniel & Røhne, Ole Myren [Show all 17 contributors for this article] (2022). PROGRESS OF THE ESS PROTON BEAM IMAGING SYSTEMS. Full text in Research Archive Show summary

  The ESS Target Proton Beam Imaging Systems has the objective to image the 5 MW ESS proton beam as it enters the spallation target. The imaging systems has to operate in a harsh radiation environment, leading to a number of challenges : development of radiation hard photon sources, long and aperture-restricted optical paths and fast electronics required to provide rapid information in case of beam anoma- lies. This paper outlines how main challenges of the imaging systems have been addressed, and the status of deployment as ESS gets closer to beam.

• Deng, A.; Karger, O.S.; Heinemann, T.; Knetsch, A.; Scherkl, P. & Manahan, G.G. [Show all 28 contributors for this article] (2019). Generation and acceleration of electron bunches from a plasma photocathode. Nature Physics. ISSN 1745-2473. 15(11), p. 1156–1160. doi: 10.1038/s41567-019-0610-9. Full text in Research Archive
• Sjobak, Kyrre Ness; Adli, Erik; Bergamaschi, Michele; Burger, Stephane; Corsini, Roberto & Curcio, Alessandro [Show all 30 contributors for this article] (2019). Status of the CLEAR electron beam user facility at CERN. Full text in Research Archive Show summary

  The CERN Linear Electron Accelerator for Research (CLEAR) has now finished its second year of operation, providing a testbed for new accelerator technologies and a versatile radiation source. Hosting a varied experimental program, this beamline provides a flexible test facility for users both internal and external to CERN, as well as being an excellent accelerator physics training ground. The energy can be varied between 60 and 220 MeV, bunch length between 1 and 4 ps, bunch charge in the range 10 pC to 2 nC, and number of bunches in the range 1 to 200, at a repetition rate of 0.8 to 10 Hz. The status of the facility with an overview of the recent experimental results is presented.

• Adli, Erik (2019). Particle Physics at the Energy Frontier. Full text in Research Archive
• Corsini, Roberto; Gamba, Davide; Farabolini, Wilfrid; Curcio, Alessandro; Doebert, Steffen & Alía, Rubén García [Show all 16 contributors for this article] (2018). FIRST EXPERIMENTS AT THE CLEAR USER FACILITY. Full text in Research Archive
• Adli, Erik; Karsch, Stefan & Pompili, Riccardo (2018). Summary of working group 1: Electron beams from plasmas. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 909, p. 38–40. doi: 10.1016/j.nima.2017.12.018. Full text in Research Archive
• Adli, Erik (2017). Recent progress in beam-driven plasma wakefield acceleration research. Full text in Research Archive
• Adli, Erik (2017). AWAKE: the proton-driven plasma wakefield accelerator experiment at CERN. Full text in Research Archive Show summary

  AWAKE: the proton-driven plasma wakefield accelerator experiment at CERN In order to achieve affordable and compact high-energy particle accelerators, machines with high accelerating gradients and high efficiency is necessary. The beam-driven plasma wakefield accelerator is a novel accelerator technique being developed for this purpose. The field has recently seen a rapid experimental progress. The AWAKE experiment at CERN is the first proton-driven plasma wakefield accelerator experiment. It uses the self-modulation instability (SMI) to transform the 12 cm long, 400 GeV proton bunch from the SPS into a train of bunches spaced by the plasma wavelength (~ 1mm). The train can then resonantly drive GV/m fields that can be used to accelerate electrons over 10s to 100s of meters. The first experiments started in December 2016 aiming at measuring the parameters of the p+ bunch after it has experienced the SMI in a 10 m long rubidium plasma with an electron density in the 1-10e14/cm3 range. The principle of SMI physics, the experimental goals and first experimental results will be presented. We also briefly discuss future plans for AWAKE, as well as ideas for high-energy physics applications.

• Adli, Erik & Sorheim, Aashild (2016). Fysikktirsdag: Partikkelakseleratorer "Det begynte med Rolf Widerøe. Hvor skal det ende?". Full text in Research Archive
• Adli, Erik (2016). Oslo ESS in-kind contribution: Target Proton Beam Imaging Systems. Full text in Research Archive
• Adli, Erik & Lindstrøm, Carl Andreas (2016). Long-range attraction of an ultrarelativistic electron beam by a column of neutral plasma. Full text in Research Archive
• Adli, Erik (2016). Som å bygge et Hubble-teleskop inne i en kjernereaktor. [Internet]. https://titan.uio.no/node/1441. Full text in Research Archive
• Adli, Erik (2015). Big Bang in a Box - The Interplay between High Energy Physics and the Society. Full text in Research Archive
• Adli, Erik (2015). PLASMABØLGEAKSELERASJON: Ny teknologi gir elektroner enorm energi. [Journal]. Teknisk Ukeblad. Full text in Research Archive
• Adli, Erik (2015). Recent results from beam-driven plasma acceleration experiments at FACET. Full text in Research Archive
• Adli, Erik (2015). Particle Driven Plasma Acceleration. Full text in Research Archive
• Adli, Erik (2015). Noreg med på den kraftigaste nøytronkanon i verda. [Journal]. Avisa Hordaland. Full text in Research Archive
• Adli, Erik (2015). Consideration for a plasma stage in a PWFA linear collider. Full text in Research Archive
• Adli, Erik (2015). Plasma wakefield accelerators - the particle colliders of the future? Full text in Research Archive
• Adli, Erik (2015). Knuser atomer for å designe fremtidens legemidler og solceller. [Journal]. Apollon. Full text in Research Archive
• Adli, Erik (2015). Big Bang in a Box. [Internet]. YouTube. Full text in Research Archive
• Adli, Erik (2015). CERN jakter på høyere fart i plasma. Full text in Research Archive
• Olsen, Veronica Kristine Berglyd; Adli, Erik; Muggli, P.; Amorim, L. D. & Vieira, J. M. (2015). LOADING OF A PLASMA-WAKEFIELD ACCELERATOR SECTION DRIVEN BY A SELF-MODULATED PROTON BUNCH, Proceedings of the 6th International Particle Accelerator Conference. Jefferson Lab, Newport News. ISSN 9783954501687. Full text in Research Archive
• Muggli, Patric; Reimann, O.; Amorim, L. D.; Lopes, N. C.; Silva, L. O. & Vieira, J. M. [Show all 22 contributors for this article] (2015). Measuring the Self-modulation Instability of Electron and Positron Bunches in Plasmas, Proceedings of the 6th International Particle Accelerator Conference. Jefferson Lab, Newport News. ISSN 9783954501687. p. 2506–2508. Full text in Research Archive Show summary

  We briefly describe some of the features of the E209 experiment at SLAC-FACET. The experiment aims at studying the physics of the self-modulation instability of long electron and positron bunches in dense plasmas. Encouraging initial results were obtained so far. Further experiments will take place soon.

• Lindstrøm, Carl Andreas; Adli, Erik & Olsen, Veronica Kristine Berglyd (2015). Nå tar også positronene bølgen. [Internet]. Fysisk Institutt: Forskning. Full text in Research Archive
• Sjøbæk, Kyrre Ness; Grudiev, A & Adli, Erik (2014). New Criterion for Shape Optimization of Normal-Conducting Accelerator Cells for High-Gradient Applications. Full text in Research Archive
• Adli, Erik (2014). Transverse effects in plasma wakefield acceleration at FACET. Full text in Research Archive
• Adli, Erik (2014). The CLIC Project - Status and Prospects. ICFA Beam Dynamics Newsletter. 62, p. 15–24. Full text in Research Archive Show summary

  Invited summary article about the CLIC Project, in the 62th edition of the ICFA Beam Dynamics newsletter, focusing on CLIC.

• Sjøbæk, Kyrre Ness; Adli, Erik & Grudiev, A (2013). Surface Field Optimization of Accelerating Structures for CLIC using ACE3P on Remote Computing Facility. Full text in Research Archive
• Adli, Erik; Delahaye, J.P.; Hogan, M.J.; Gessner, S.J.; Raubenheimer, T & An, W [Show all 9 contributors for this article] (2013). Design of a TeV Beam Driven Plasma-wakefield Linear Collider. Full text in Research Archive
• Adli, Erik (2013). The CLIC Project - Status and Prospects. Full text in Research Archive
• Sjøbæk, Kyrre Ness; Adli, Erik; Grudiev, A & Wuensch, W (2012). Design of an Accelerating Structure for a 500 GeV CLIC using Ace3P. Full text in Research Archive
• Adli, Erik (2009). Next Generation Particle Accelerators – CLIC. Nordic space activities. ISSN 0805-7397. 17. Full text in Research Archive
• Adli, Erik (2009). Mens kjempebabyen. [Internet]. forskning.no. Full text in Research Archive
• Adli, Erik (2009). CERN søker. [Internet]. forskning.no. Full text in Research Archive
• Adli, Erik; Ruber, Roger; Syratchev, I; Schulte, D; Corsini, Roberto & Ziemann, Volker (2009). First Beam Tests of the CLIC Power Extraction Structure in the Two-beam Test Stand. Full text in Research Archive
• Adli, Erik & Nordahl, Marianne (2009). CERN søker rekrutter. [Internet]. http://www.forskning.no/artikler/2009/februar/210902. Full text in Research Archive
• Adli, Erik & Nordahl, Marianne (2009). Mens kjempebabyen sover. [Internet]. http://www.forskning.no/artikler/2009/februar/211327 . Full text in Research Archive
• Adli, Erik (2008). Beam Dynamics of the CLIC Decelerator. Full text in Research Archive
• Adli, Erik (2008). Drive Beam Decelerator and TBL. Full text in Research Archive
• Adli, Erik; Corsini, Roberto; Anne, Dabrowski; Schulte, D; Shaker, S.H. & Skowronski, Piotr Krzysztof [Show all 8 contributors for this article] (2008). Status of an Automatic Beam Steering for the CLIC Test Facility 3. Full text in Research Archive
• Kvittingen, Ida & Adli, Erik (2008). Undergrunnsforskning. [Internet]. forskerforum.no. Full text in Research Archive
• Adli, Erik & Andersen, P. A. Flodin (2008). Verdens største samarbeid om å finne verdens minste ting (i "Get Real" / UiO). [Internet]. http://www.realfag.uio.no/sporsmaalene.shtml. Full text in Research Archive
• Adli, Erik & Eggen, Espen (2008). Verdens lengste skalpell. [Internet]. http://www.forskning.no/artikler/2007/desember/1198079322.03. Full text in Research Archive
• Adli, Erik; Schulte, D & Syratchev, I (2008). A Study of Failure Modes in the CLIC Decelerator. Full text in Research Archive
• Adli, Erik & Schulte, D (2008). Beam-Based Alignment for the CLIC Decelerator. Full text in Research Archive
• Adli, Erik (2008). Drive Beam Dynamics for CLIC. Full text in Research Archive
• Adli, Erik (2007). Particle Accelerators - the Next Generation. Full text in Research Archive
• Adli, Erik (2007). Neste generasjons partikkelakseleratorer - LHC i perspektiv. Full text in Research Archive
• Adli, Erik (2007). Test Beam Line (TBL) Beam Dynamics studies. Full text in Research Archive
• Adli, Erik (2007). Beam Dynamic Studies for the CLIC Decelerator. Full text in Research Archive
• Syratchev, I; Schulte, D & Adli, Erik (2007). HIGH RF POWER PRODUCTION FOR CLIC. Full text in Research Archive
• Adli, Erik (2007). Particle Accelerators - the Next Generation. Full text in Research Archive
• Adli, Erik (2006). Forskning ved CERN i kulturtidsskriftet LILLIT (lillit.web). [Journal]. Kulturtidsskriftet LILLIT. Full text in Research Archive
• Finnerud, Ole Gunnar; Adli, Erik & Lindstrøm, Carl A. (2026). Beam-breakup instability and efficiency in plasma accelerators. Universitetet i Oslo. Full text in Research Archive Show summary

  Particle colliders have been important tools in particle physics since the early 20th century. However, the growing demand for larger and higher-energy particle accelerators is driving up their cost. Plasma-based colliders have emerged as a candidate for reducing their size and cost thanks to their higher accelerating gradients. A major obstacle for this emerging technology is the efficiency—instability relation, which states that at higher efficiencies, the beam becomes more unstable, eventually breaking apart. This thesis tackles this issue through numerical simulations and experimental studies. The efficiency—instability relation is shown to be a lower bound on the strength of the instability, which varies by a large amount depending on the accelerator parameters, indicating the importance of choosing an optimal operating point. The effect of mitigation strategies is shown to be significant while also dependent on the parameters chosen. An experiment is carried out to probe the instability using novel measurement techniques. The results show indications of the instability, its correlation with efficiency, and mitigating effects. The efficiency—instability relation is complicated to measure and not fully understood in theory, but studies like the ones outlined in this thesis are important milestones towards a better understanding of it.

• Adli, Erik (2009). A Study of the Beam Phyiscs in the CLIC Drive Beam Decelerator. Det matematisk naturvitenskapelige fakultet. Full text in Research Archive

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