Kyrre Ness Sjøbæk

• 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). ISSN 1748-0221. 18(9). doi: 10.1088/1748-0221/18/09/P09022.
• 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. ISSN 2045-2322. 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). ISSN 1748-0221. 17(5). doi: 10.1088/1748-0221/17/05/P05042. Full text in Research Archive
• 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.

• 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.

• Garcia Morales, Hector; 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
• 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. ISSN 2399-3650. 4. doi: 10.1038/s42005-021-00536-0. Full text in Research Archive
• 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. ISSN 2045-2322. 10. doi: 10.1038/s41598-020-67997-1. Full text in Research Archive Show summary

  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.

• 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. Full text in Research Archive Show summary

  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.

• De Maria, Riccardo; Andersson, Joel; Berglyd Olsen, Veronica Kristine; 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. Show summary

  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.

• De Maria, Riccardo; Andersson, Joel; Berglyd Olsen, Veronica Kristine; 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. Full text in Research Archive
• 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. Show summary

  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.

• 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.

• 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.

• Timko, H; Sjøbæk, Kyrre Ness; Mether, L.; Calatroni, S.; Djurabekova, F. & Matyash, K. [Show all 9 contributors for this article] (2015). From field emission to vacuum arc ignition: A new tool for simulating copper vacuum arcs. Contributions to Plasma Physics. ISSN 0863-1042. 55(4), p. 299–314. doi: 10.1002/ctpp.201400069.
• 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. Show summary

  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.

• 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. Show summary

  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.

• Gjersdal, Håvard; Bolle, Erlend; Borri, M; Da Via, C; Dorholt, Ole & Fazio, S [Show all 27 contributors for this article] (2011). Tracking efficiency and charge sharing of 3D silicon sensors at different angles in a 1.4T magnetic field. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 636, p. S42–S49. doi: 10.1016/j.nima.2010.04.083.
• Hansson, P; Balbuena, J; Barrera, C; Bolle, Erlend; Borri, M & Boscardin, M [Show all 45 contributors for this article] (2011). 3D silicon pixel sensors: Recent test beam results. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 628(1), p. 216–220. doi: 10.1016/j.nima.2010.06.321.

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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. 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.

• 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. Show summary

  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.

• 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. 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.

• 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. 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.

• Korysko, Pierre; Dosanjh, Manjit; Dyks, Luke; Bateman, Joseph John; Robertson, Cameron & Corsini, Roberto [Show all 10 contributors for this article] (2022). STATUS OF VHEE RADIOTHERAPY RELATED STUDIES AT THE CLEAR USER FACILITY AT CERN.
• 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. Show summary

  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.

• Dyks, Luke; Burrows, Philip Nicholas; Koryśko, Pierre; Corsini, Roberto; Curt, Stephane & Farabolini, Wilfrid [Show all 12 contributors for this article] (2021). CONSOLIDATION AND FUTURE UPGRADES TO THE CLEAR USER FACILITY AT CERN.
• 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. Show summary

  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.

• 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. Show summary

  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.

• 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. 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.

• Sjobak, Kyrre Ness; Burkhardt, Helmut; De Maria, Riccardo & Berglyd Olsen, Veronica Kristine (2019). Generalised scattering module in SixTrack 5. Show summary

  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.

• Sjobak, Kyrre Ness & Holmestad, Helga Margrete (2019). MiniScatter, a Simple Geant4 Wrapper. Show summary

  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.

• De Maria, Riccardo; 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. Show summary

  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.

• De Maria, Riccardo; 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. Show summary

  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

• Corsini, Roberto; Gamba, Davide; Farabolini, Wilfrid; Curcio, Alessandro; Doebert, Steffen & García Alía, Rubén [Show all 16 contributors for this article] (2018). FIRST EXPERIMENTS AT THE CLEAR USER FACILITY.
• Lindström, B.; Berglyd Olsen, Veronica Kristine; Burkhardt, Helmut; Sjobak, Kyrre Ness; Santamaria Garcia, Andrea & Valette, Mathieu [Show all 7 contributors for this article] (2018). CRAB CAVITY FAILURES COMBINED WITH A LOSS OF THE BEAM-BEAM KICK IN THE HIGH LUMINOSITY LHC .
• Sjøbæk, Kyrre Ness; Grudiev, A & Adli, Erik (2014). New Criterion for Shape Optimization of Normal-Conducting Accelerator Cells for High-Gradient Applications.
• Sjøbæk, Kyrre Ness; Adli, Erik & Grudiev, A (2013). Surface Field Optimization of Accelerating Structures for CLIC using ACE3P on Remote Computing Facility.
• Sjøbæk, Kyrre Ness; Adli, Erik; Grudiev, A & Wuensch, W (2012). Design of an Accelerating Structure for a 500 GeV CLIC using Ace3P.
• Pajchel, Katarina; Samset, Bjørn Hallvard; Pedersen, Maiken; Gramstad, Eirik; Lynnebakken, Hilde & Henriksen, Ellen Karoline [Show all 13 contributors for this article] (2008). Hva er du laget av? Forskningstorget 2008, institutt bod. Show summary

  LHC/CERN - temabod for Fysisk instititt i forbindelse med oppstarten av LHC

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