Academic interests
New technology for particle accelerators -- Active Plasma Lenses and accelerating structures for the Compact Linear Collider; involved in experiments and operation of the CERN Linear Accelerator for Research (CLEAR). Particle therapy. Beam instrumentation.
Project leader for SHARP: Particle accelerator final focus systems for improving precision of dose delivery for medical applications and irradiation test stands
Teaching
Background
- 2017 -> : Researcher at UiO, working on Active Plasma Lenses, CLIC Wake Field Monitors, particle therapy, and instrumentation for ESS. Based at CERN (CLEAR) from 2017 to 2019.
- 2014 - 2017: CERN Fellow, working on HL-LHC crab cavities and SixTrack
- 2010 - 2016: PhD student in accelerator physics at UiO / CERN, working on CLIC accelerating structures and vacuum arc breakdowns
- 2008 - 2010: Master student at UiO, working on 3D pixel tracking detectors for ATLAS.
- 2005 - 2008: Bachelor student in Physics at UiO.
Tags:
CERN,
particle accelerators,
Plasma lenses,
CLIC,
ESS,
Geant4
Publications
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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
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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.
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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
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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.
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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.
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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.
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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.
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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.
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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
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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.
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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
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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.
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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.
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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.
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Morales, Hector Garcia; Bruce, Roderik; Redaelli, Stefano; Belen, Salvachua; Wretborn, Joel & Sjobak, Kyrre Ness
(2021).
Off-momentum cleaning simulations and measurements at the Large Hadron Collider.
Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment.
ISSN 0168-9002.
1010.
doi:
10.1016/j.nima.2021.165494.
Full text in Research Archive
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The Large Hadron Collider is designed to collide proton beams with unprecedented energy in order to extend the frontiers of high-energy physics. Particles that have an energy different from the nominal one follow dispersive orbits and, if the energy offset is large enough, could be lost on the cold aperture and cause quenches of superconducting magnets. Therefore, particles with large energy offsets must be removed from the beam by the collimation system. Although the dynamics of such particles is well understood and the efficiency of the momentum cleaning is evaluated in measurements, in the past, there were not general simulations tools available for predicting the efficiency of the collimation system in scenarios where off-momentum particles are involved. In this paper we present a new set of tools to simulate off-momentum losses, the benchmarking of these tools with measurements and the evaluation of off-momentum losses in the future LHC upgrade, the HL-LHC. These new simulation tools are applied for simulating two of the main scenarios where off-momentum particles play an important role in the LHC: particles lost at the start of the energy ramp and simulations of the momentum cleaning at 6.5 TeV energy. In this study, the collimation process during dynamic changes in the machine is simulated, as opposed to previous studies in static conditions. This is the first time that this sort of comparison between different simulation methods and measurements is performed. The results are used to provide a better understanding the dynamics of such particles and, finally, these tools are used to estimate the influence of off-momentum losses in the future High-Luminosity LHC.
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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.
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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.
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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.
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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.
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Kokurewicz, Karolina; Brunetti, Enrico; Curcio, Alessandro; Gamba, Davide; Garolfi, Luca & Gilardi, Antonio
[Show all 11 contributors for this article]
(2021).
An experimental study of focused very high energy electron beams for radiotherapy.
Communications Physics.
4.
doi:
10.1038/s42005-021-00536-0.
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Abstract Very high energy electron (VHEE) beams have been proposed as an alternative radiotherapy modality to megavoltage photons; they penetrate deeply without significant scattering in inhomogeneous tissue because of their high relativistic inertia. However, the depth dose distribution of a single, collimated VHEE beam is quasi-uniform, which can lead to healthy tissue being overexposed. This can be largely overcome by focusing the VHEE beam to a small spot. Here, we present experiments to demonstrate focusing as a means of concentrating dose into small volumetric elements inside a target. We find good agreement between measured dose distributions and Monte Carlo simulations. Focused radiation beams could be used to precisely target tumours or hypoxic regions of a tumour, which would enhance the efficacy of radiotherapy. The development of new accelerator technologies may provide future compact systems for delivering these focused beams to tumours, a concept that can also be extended to X-rays and hadrons.
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Veske, Mihkel; Kyritsakis, Andreas; Djurabekova, F.; Sjobak, Kyrre Ness; Aabloo, Alvo & Zadin, Vahur
(2020).
Dynamic coupling between particle-in-cell and atomistic simulations.
Physical Review E (PRE).
ISSN 2470-0045.
101(5).
doi:
10.1103/PhysRevE.101.053307.
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Understanding plasma initiation in vacuum arc discharges can help to bridge the gap between nano-scale
triggering phenomena and the macroscopic surface damage caused by vacuum arcs. We present a new two-
dimensional particle-in-cell tool to simulate plasma initiation in direct-current (DC) copper vacuum arc dis-
charges starting from a single, strong field emitter at the cathode. Our simulations describe in detail how a
sub-micron field emission site can evolve to a macroscopic vacuum arc discharge, and provide a possible ex-
planation for why and how cathode spots can spread on the cathode surface. Furthermore, the model provides
us with a prediction for the current and voltage characteristics, as well as for properties of the plasma like
densities, fluxes and electric potentials in a simple DC discharge case, which are in agreement with the known
experimental values.
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Arpaia, Pasquale; Corsini, Roberto; Gilardi, Antonio; Mostacci, Andrea; Sabato, Luca & Sjobak, Kyrre Ness
(2020).
Enhancing particle bunch-length measurements based on Radio Frequency Deflector by the use of focusing elements.
Scientific Reports.
10.
doi:
10.1038/s41598-020-67997-1.
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A method to monitor the length of a particle bunch, based on the combination of a Radio Frequency Deflector (RFD) with magnetic focusing elements, is presented. With respect to state-of-the-art bunch length measurement, the additional focusing element allows to measure also the correlations between the longitudinal and transverse planes in terms of both position and divergence. Furthermore, the quadrupole-based focusing increases the input dynamic range of the measurement system (i.e. allows for a larger range of beam Twiss parameters at the entrance of the RFD). Thus, measurement resolution and precision are enhanced, by simultaneously preserving the accuracy. In this paper, the method is first introduced analytically, and then validated in simulation, by the reference tool ELEctron Generation ANd Tracking, ELEGANT. Finally, a preliminary experimental validation at CLEAR (CERN Linear Electron Accelerator for Research) is reported.
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Maria, Riccardo De; Andersson, Joel; Olsen, Veronica Kristine Berglyd; Field, Laurence; Giovannozzi, Massimo & Hermes, Pascal
[Show all 20 contributors for this article]
(2019).
SixTrack Version 5: Status and New Developments.
Journal of Physics: Conference Series (JPCS).
ISSN 1742-6588.
1350(1).
doi:
10.1088/1742-6596/1350/1/012129.
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SixTrack Version 5 is a major SixTrack release that introduces new features, with improved integration of the existing ones, and extensive code restructuring. New features include dynamic-memory management, scattering-routine integration, a new initial-condition module, and reviewed post-processing methods. Existing features like on-line aperture checking and Fluka-coupling are now enabled by default. Extensive performance regression tests have been developed and deployed as part of the new-release generation. The new features of the tracking environment developed for the massive numerical simulations will be discussed as well.
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Apsimon, Robert; Burt, Graeme M.; Dexter, Amos; Shipman, Nick; Castilla, Alejandro & Macpherson, Alick
[Show all 11 contributors for this article]
(2019).
Prediction of beam losses during crab cavity quenches at the high luminosity LHC.
Physical Review Accelerators and Beams.
ISSN 2469-9888.
22(6).
doi:
10.1103/PhysRevAccelBeams.22.061001.
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Studies of the crab cavities at KEKB revealed that the rf phase could shift by up to 50° within ∼50 μs during a quench; while the cavity voltage is still at approximately 75% of its nominal amplitude. If such a failure were to occur on the HL-LHC crab cavities, it is likely that the machine would sustain substantial damage to the beam line and surrounding infrastructure due to uncontrolled beam loss before the machine protection system could dump the beam. We have developed a low-level rf system model, including detuning mechanisms and beam loading, and use this to simulate the behavior of a crab cavity during a quench, modeling the low-level rf system, detuning mechanisms and beam loading. We supplement this with measurement data of the actual rf response of the proof of principle double-quarter wave crab cravity during a quench. Extrapolating these measurements to the HL-LHC, we show that Lorentz force detuning is the dominant effect leading to phase shifts in the crab cavity during quenches; rather than pressure detuning which is expected to be dominant for the KEKB crab cavities. The total frequency shift for the HL-LHC crab cavities during quenches is expected to be about 460 Hz, leading to a phase shift of no more than 3°. The results of the quench model are read into a particle tracking simulation, SixTrack, and used to determine the effect of quenches on the HL-LHC beam. The quench model has been benchmarked against the KEKB experimental measurements. In this paper we present the results of the simulations on a crab cavity failure for HL-LHC as well as for the SPS and show that beam loss is negligible when using a realistic low-level rf response.
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Maria, Riccardo De; Andersson, Joel; Olsen, Veronica Kristine Berglyd; Field, Laurence; Giovannozzi, Massimo & Hermes, Pascal
[Show all 19 contributors for this article]
(2019).
SixTrack V and runtime environment.
International Journal of Modern Physics A.
ISSN 0217-751X.
34:36,
p. 1–17.
doi:
10.1142/S0217751X19420351.
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SixTrack is a single-particle tracking code for high-energy circular accelerators routinely
used at CERN for the Large Hadron Collider (LHC), its luminosity upgrade (HL-LHC),
the Future Circular Collider (FCC) and the Super Proton Synchrotron (SPS) simula-
tions. The code is based on a 6D symplectic tracking engine, which is optimized for
long-term tracking simulations and delivers fully reproducible results on several plat-
forms. It also includes multiple scattering engines for beam–matter interaction studies,
as well as facilities to run the integrated simulations with external particle matter inter-
action codes. These features differentiate SixTrack from general-purpose, optics-design
software. The code recently underwent a major restructuring to merge the advanced
features into a single branch, such as multiple ion species, interface with external codes
and high-performance input/output. This restructuring also removed a large number
of compilation flags, instead enabling/disabling the functionality with runtime options.
In the process, the code was moved from Fortran 77 to Fortran 2018 standard, also
allowing and achieving a better modularization. Physics models (beam–beam effects,
Radio-Frequency (RF) multipoles, current carrying wires, solenoid and electron lenses)
and methods (symplecticity check) have also been reviewed and refined to offer more
accurate results. The SixDesk runtime environment allows the user to manage the large
batches of simulations required for accurate predictions of the dynamic aperture. SixDesk
supports several cluster environments available at CERN as well as submitting jobs to
the LHC@Home volunteering computing project, which enables volunteers contributing
with their hardware to CERN simulation. SixTrackLib is a new library aimed at provid-
ing a portable and flexible tracking engine for single- and multi-particle problems using
the models and formalism of SixTrack. The library is able to run in CPUs as well as
graphical processing units (GPUs). This contribution presents the status of the code,
summarizes the main existing features and provides details about the main development
lines SixTrack, SixDesk and SixTrackLib.
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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.
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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.
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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.
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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.
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Grenier, Philippe; Alimonti, G; Barbero, M; Bates, R; Bolle, Erlend & Borri, M
[Show all 92 contributors for this article]
(2011).
Test beam results of 3D silicon pixel sensors for the ATLAS upgrade.
Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment.
ISSN 0168-9002.
638(1),
p. 33–40.
doi:
10.1016/j.nima.2011.01.181.
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Results on beam tests of 3D silicon pixel sensors aimed at the ATLAS Insertable B-Layer and High Luminosity LHC (HL-LHC) upgrades are presented. Measurements include charge collection, tracking efficiency and charge sharing between pixel cells, as a function of track incident angle, and were performed with and without a 1.6 T magnetic field oriented as the ATLAS inner detector solenoid field. Sensors were bump-bonded to the front-end chip currently used in the ATLAS pixel detector. Full 3D sensors, with electrodes penetrating through the entire wafer thickness and active edge, and double-sided 3D sensors with partially overlapping bias and read-out electrodes were tested and showed comparable performance.
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Micelli, A.; Helle, Kristine Indahl; Sandaker, Heidi; Stugu, Bjarne; Barbero, M & Hugging, F
[Show all 92 contributors for this article]
(2011).
3D-FBK pixel sensors: Recent beam tests results with irradiated devices.
Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment.
ISSN 0168-9002.
650(1),
p. 150–157.
doi:
10.1016/j.nima.2010.12.209.
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The Pixel Detector is the innermost part of the ATLAS experiment tracking device at the Large Hadron Collider, and plays a key role in the reconstruction of the primary vertices from the collisions and secondary vertices produced by short-lived particles. To cope with the high level of radiation produced during the collider operation, it is planned to add to the present three layers of silicon pixel sensors which constitute the Pixel Detector, an additional layer (Insertable B-Layer, or IBL) of sensors. 3D silicon sensors are one of the technologies which are under study for the IBL. 3D silicon technology is an innovative combination of very-large-scale integration and Micro-Electro-Mechanical-Systems where electrodes are fabricated inside the silicon bulk instead of being implanted on the wafer surfaces. 3D sensors, with electrodes fully or partially penetrating the silicon substrate, are currently fabricated at different processing facilities in Europe and USA. This paper reports on the 2010 June beam test results for irradiated 3D devices produced at FBK (Trento, Italy). The performance of these devices, all bump-bonded with the ATLAS pixel FE-I3 read-out chip, is compared to that observed before irradiation in a previous beam test.
View all works in NVA
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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/.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Korysko, Pierre; Dosanjh, Manjit; Bateman, Joseph John; Robertson, Cameron Stewart; Corsini, Roberto & Farabolini, Wilfrid
[Show all 10 contributors for this article]
(2023).
THE CLEAR USER FACILITY: A REVIEW OF THE EXPERIMENTAL METHODS AND FUTURE PLANS.
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The CERN Linear Electron Accelerator for Research (CLEAR), operating since 2017, is a user facility providing electron beams for a large and varied range of experiments.The electron beam is produced from a Cs2 Te photocathode and is accelerated between 30 MeV and 220 MeV in a 20 m long linear accelerator. In 2022, several hardware and software tools were upgraded and novel procedures and methods were developed to address specific user requirements, including a further extension of the beam parameter ranges. In the paper, these improvements are described and the experimental activities during 2022/2023 are outlined. An outlook on future potential upgrades and on the planned experimental activities in the next years is also given.
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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.
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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.
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Corsini, Roberto; Farabolini, Wilfrid; Malyzhenkov, Alexander; Rieker, Vilde; Korysko, Pierre & Sjobak, Kyrre Ness
(2022).
Status of the CLEAR User Facility at CERN and its Experiments.
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The CERN Linear Accelerator for Research (CLEAR) at CERN is a versatile user facility providing a 200 MeV electron beam for accelerator R&D, irradiation studies for space, and medical applications. After successful operation in 2017-2020, CLEAR running was extended in 2021 for another 5-year period. In the paper we give a status of the facility, outlining recent progress in beam performance and hardware improvements. We report on beam operation over the last years and review the main results of experimental activities. Finally, we discuss the planned upgrades together with the proposed future experimental program.
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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.
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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.
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Corsini, Roberto; Farabolini, Wilfrid; Gilardi, Antonio; Dyks, Luke; Koryśko, Pierre & Sjobak, Kyrre Ness
(2021).
STATUS OF VHEE RADIOTHERAPY RELATED STUDIES AT THE CLEAR USER FACILITY AT CERN.
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Despite the increase in interest in using Very High Energy Electron (VHEE) beams for cancer radiotherapy many unanswered questions in its development remain. The use of test facilities will be an essential tool used to solve these issues. The 200 MeV electron beam from the CERN Linear Accelerator for Research (CLEAR) has been used extensively, in collaboration with several research institutes, to perform dosimetry studies and explore potential applications of VHEE beams to radiotherapy, including the exploitation of the so called FLASH effect. In this paper, we present an overview of past studies with emphasis on the more recent results. We describe methods, techniques and equipment developed at CERN in this framework, and give an outlook on future activities.
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Maria, Riccardo De; Andersson, Joel; Dalena, Barbara; Field, Laurence; Giovannozzi, Massimo & Hermes, Pascal
[Show all 17 contributors for this article]
(2019).
SixTrack Version 5: Status and new developments.
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SixTrack Version 5 is a major SixTrack release that introduces new features, with improved integration of the existing ones, and extensive code restructuring. New features include dynamic-memory management, scattering-routine integration, a new initial-condition module, and reviewed post-processing methods. Existing features like on-line aperture checking and Fluka-coupling are now enabled by default. Extensive performance regression tests have been developed and deployed as part of the new-release generation. The new features of the tracking environment developed for the massive numerical simulations will be discussed as well.
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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.
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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.
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Sjobak, Kyrre Ness & Holmestad, Helga Margrete
(2019).
MiniScatter, a Simple Geant4 Wrapper.
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In order to estimate what happens to particle beams when they hit windows, gas, and various other targets, a simple tool has been developed based on Geant4. This tool wraps geometry setup, primary beam generation from Twiss parameters, visualization, and automatic analysis and plots in a simple-to-use command-line tool. Furthermore, a Jupyter-friendly Python interface for running simulations and parallelized parameter scans is included. The code, its interface, and a few selected examples will be presented.
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Arpaia, Pasquale; Corsini, Roberto; Gilardi, Antonio & Sjobak, Kyrre Ness
(2019).
Beam–based alignment of the CLIC high-gradient X-Band accelerating structure using beam-screen.
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An experimental campaign has been carried out at the European Organization for Nuclear Research (CERN) in order to estimate the wakefield kick in the X-Band accelerating structure of the future Compact LInear Collider (CLIC). The CLIC Project, currently under study, is an electron-positron collider with centre of mass energy of 3 TeV and an instantaneous luminosity of 2 × 10 34 cm -2 s -1 . The X-Band accelerating structures are able to sustain an accelerating gradient of 100 MV/m. The wakefield kick is an electromagnetic field perturbing the particle bunch. This campaign is carried out at the CERN Linear Electron Accelerator for Research (CLEAR). A beam-based method to align the accelerating structure to the beam trajectory with the use of a beam-screen is proposed in order to estimate the transverse wakefield kick. Aligning such a structure to the beam trajectory, with an accuracy of 3.5 μm, is a key point to achieve the above luminosity.
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Sjobak, Kyrre Ness; Burkhardt, Helmut; Maria, Riccardo De & Olsen, Veronica Kristine Berglyd
(2019).
Generalised scattering module in SixTrack 5.
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A generalised scattering module has recently been added to SixTrack. This module enables the use of arbitrary generators and target profiles. Presently, a simple model of elastic scattering and a coupling to Pythia8 have been implemented. This makes it possible to use SixTrack for studies of aperture losses and beam lifetime as a result of beam–beam scattering.
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Maria, Riccardo De; Andersson, Joel; Field, Laurence; Giovannozzi, Massimo; Hermes, Pascal & Høimyr, Nils Kristian
[Show all 19 contributors for this article]
(2018).
SixTrack Project: Status, Runtime Environment, and New Developments.
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SixTrack is a single-particle tracking code for high-energy circular accelerators routinely used at CERN for the Large Hadron Collider (LHC), its luminosity upgrade (HL-LHC), the Future Circular Collider (FCC), and the Super Proton Synchrotron (SPS) simulations. The code is based on a 6D symplectic tracking engine, which is optimised for long-term tracking simulations and delivers fully reproducible results on several platforms. It also includes multiple scattering engines for beam-matter interaction studies, as well as facilities to run integrated simulations with FLUKA and GEANT4. These features differentiate SixTrack from general-purpose, optics-design software like MAD-X. The code recently underwent a major restructuring to merge advanced features into a single branch, such as multiple ion species, interface with external codes, and high-performance input/output (XRootD, HDF5). This restructuring also removed a large number of build flags, instead enabling/disabling the functionality at run-time. In the process, the code was moved from Fortran 77 to Fortran 2018 standard, also allowing and achieving a better modularization. Physics models (beam-beam effects, RF-multipoles, current carrying wires, solenoid, and electron lenses) and methods (symplecticity check) have also been reviewed and refined to offer more accurate results. The SixDesk runtime environment allows the user to manage the large batches of simulations required for accurate predictions of the dynamic aperture. SixDesk supports CERN LSF and HTCondor batch systems, as well as the BOINC infrastructure in the framework of the LHC@Home volunteering computing project. SixTrackLib is a new library aimed at providing a portable and flexible tracking engine for single- and multi-particle problems using the models and formalism of SixTrack. The tracking routines are implemented in a parametrized C code that is specialised to run vectorized in CPUs and GPUs, by using SIMD intrinsics, OpenCL 1.2, and CUDA tech
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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
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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
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Sjøbæk, Kyrre Ness; Adli, Erik; Grudiev, A & Wuensch, W
(2012).
Design of an Accelerating Structure for a 500 GeV CLIC using Ace3P.
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