| 1. |
- Ruber, Roger, et al.
(författare)
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Accelerator development at the FREIA Laboratory
- 2021
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Ingår i: Journal of Instrumentation. - : Institute of Physics Publishing (IOPP). - 1748-0221. ; 16:7
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Tidskriftsartikel (refereegranskat)abstract
- The FREIA Laboratory at Uppsala University focuses on superconducting technology and accelerator development. It actively supports the development of the European Spallation Source, CERN, and MAX IV, among others. FREIA has developed test facilities for superconducting accelerator technology such as a double-cavity horizontal test cryostat, a vertical cryostat with a novel magnetic field compensation scheme, and a test stand for short cryomodules. Accelerating cavities have been tested in the horizontal cryostat, crab-cavities cavities in the vertical cryostat, and cryomodules for ESS on the cryomodule test stand. High power radio-frequency amplifier prototypes based on vacuum tube technology were developed for driving spoke cavities. Solid-state amplifiers and power combiners are under development for future projects. We present the status of the FREIA Laboratory complemented with results of recent projects and future prospects.
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| 2. |
- Bagni, Tommaso, et al.
(författare)
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Modeling Results of the Quench Behavior of a Nb-Ti Canted-Cosine-Theta Corrector Magnet for LHC
- 2024
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Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 34:5, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- A newly designed superconducting magnet of the Canted-Cosine-Theta (CCT) type was developed as a result of a collaboration between Swedish universities (Uppsala and Linneaus) and Swedish industries. This magnet was designed to function as a replacement of the present LHC orbit corrector magnets, which are approaching their end of life due to the radiation load. As a result, the new CCT magnet was developed to be more radiation tolerant and to constitute a one-to-one replacement to the currently installed version, which is a 1 m long 70 mm double aperture dipole magnet. The final magnet, which is currently under construction, will be tested at FREIA laboratory at Uppsala University and generate a magnetic field of 3.3 T and an integrated field of 2.8 Tm at about 85 A. To examine the magnet quench behavior and to identify a suitable quench protection system, the 3D electro-magnetic and thermal behavior of the coil was modeled using the RAT-Raccoon software. Based on the simulation results, a Metrosil varistor was selected to protect the magnet during the test. In this article, we report the results of the numerical analysis. The magnet model is equipped with a spot heater to initialize the quench and the temperature and voltages are monitored during the avalanche effect. The simulated current decay and the hot-spot temperature are analyzed with a focus on the impact of quench-back on the magnet protection.
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| 3. |
- Barna, D., et al.
(författare)
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Test Results of the First Wax-Impregnated Nb-Ti Canted Cosine Theta Septum Magnet “SuShi”
- 2024
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Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 34:5, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- In the framework of the future circular collider study, a new septum magnet concept (“SuShi”) has been developed, and a prototype was built at Wigner RCP, and tested at the FREIA facility of Uppsala University. The concept uses a canted cosine theta (CCT)-like superconducting magnet and a passive superconducting shield to create a zero-field and high-field region within its aperture. SuShi is the first CCT magnet with both of its winding layers simultaneously impregnated with wax. Details of the construction will be presented, with special emphasis on the wax impregnation procedure which deals with the ∼ 15% contraction of wax upon solidification. The empty magnet (no shield in its aperture) was powered without training to 450 A with a peak field of 3.64 T, corresponding to 80% of the short sample limit of the conductor along the load line. No quench or other anomaly was observed during the entire testing period. A clear onset of quench-back was observed above about 200 A.
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| 4. |
- Barna, D., et al.
(författare)
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Training-free performance of the wax-impregnated SuShi septum magnet
- 2024
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Ingår i: Superconductors Science and Technology. - : Institute of Physics (IOP). - 0953-2048 .- 1361-6668. ; 37:4
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Tidskriftsartikel (refereegranskat)abstract
- In the framework of the Future Circular Collider Study a new septum magnet concept, nicknamed 'SuShi' has been developed, and a prototype was built at Wigner Research Center for Physics, and tested at the FREIA facility of Uppsala University in April 2023. The concept uses a canted cosine theta (CCT)-like superconducting magnet and a passive superconducting shield to create a zero-field and high-field region within its aperture. SuShi is the first CCT magnet with both of its winding layers simultaneously impregnated with wax. This paper describes the first powering test of the empty magnet at 4.2 K, without the shield being inserted in its aperture. The performance of the magnet, including the observation of quench-back, estimation of hot-spot temperatures and the fraction of energy dissipated in the magnet are presented, and most interestingly the absence of any quench during the entire testing period is reported. Sushi reached its nominal +5% peak field of 3.64 T at 450 A, which corresponds to 80% of the calculated short sample limit along the load line, without training.
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| 5. |
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| 6. |
- Galvin, Tom, et al.
(författare)
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Characterisation of SiC Varistor Quench Protection Operating at 4 Kelvin for Use With Superconducting Magnets
- 2023
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Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 33:5
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Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide (SiC) composite high-energy varistors have been demonstrated as a viable alternative to linear resistors as energy extraction devices during an abrupt loss of superconductivity in a magnet, called a quench. These have typically been installed external to the cryostat at ambient temperatures, but for some superconducting magnets it may be beneficial to mount the varistors within the cryostat in vacuum, a gaseous environment, or submerged in liquid cryogens. Varistors are semiconductors and therefore exhibit a temperature-dependent voltage-current relationship, so characterising their behaviour at low temperatures is important to predict their energy extraction behaviour. In this paper we present characterisation data of SiC varistor devices from 4-300 K: voltage-current characteristics, thermal conductivity, specific heat capacity, thermal expansion, and flexural strength. These varistors are a candidate for protection at 1.9 K of the MCBY magnets, currently being built at Uppsala University for CERN.
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| 7. |
- Gschwendtner, Dda, et al.
(författare)
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The AWAKE Run 2 Programme and Beyond
- 2022
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 14:8
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Tidskriftsartikel (refereegranskat)abstract
- Plasma wakefield acceleration is a promising technology to reduce the size of particle accelerators. The use of high energy protons to drive wakefields in plasma has been demonstrated during Run 1 of the AWAKE programme at CERN. Protons of energy 400 GeV drove wakefields that accelerated electrons to 2 GeV in under 10 m of plasma. The AWAKE collaboration is now embarking on Run 2 with the main aims to demonstrate stable accelerating gradients of 0.5-1 GV/m, preserve emittance of the electron bunches during acceleration and develop plasma sources scalable to 100s of metres and beyond. By the end of Run 2, the AWAKE scheme should be able to provide electron beams for particle physics experiments and several possible experiments have already been evaluated. This article summarises the programme of AWAKE Run 2 and how it will be achieved as well as the possible application of the AWAKE scheme to novel particle physics experiments.
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| 8. |
- Nechaeva, T., et al.
(författare)
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Hosing of a Long Relativistic Particle Bunch in Plasma
- 2024
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 132:7
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Tidskriftsartikel (refereegranskat)abstract
- Experimental results show that hosing of a long particle bunch in plasma can be induced by wakefields driven by a short, misaligned preceding bunch. Hosing develops in the plane of misalignment, selfmodulation in the perpendicular plane, at frequencies close to the plasma electron frequency, and are reproducible. Development of hosing depends on misalignment direction, its growth on misalignment extent and on proton bunch charge. Results have the main characteristics of a theoretical model, are relevant to other plasma -based accelerators and represent the first characterization of hosing.
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| 9. |
- Pepitone, Kevin, Dr, 1988-, et al.
(författare)
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Design and Fabrication of a Canted-Cosine-Theta Double Aperture Orbit Corrector Dipole for the LHC
- 2023
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Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 33:5
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Tidskriftsartikel (refereegranskat)abstract
- A prototype CCT dipole magnet developed by a collaboration between Swedish universities, Swedish industry and CERN will be tested at Uppsala University. This 1 m long double-aperture magnet can provide a field strength of 3.3 T at 85 A in a 70 mm aperture with an integrated field of 2.8 Tm. It is intended to replace the current LHC orbit corrector magnets which are reaching the end of their expected life due to the radiation load. The new magnet is designed to handle the radiation dose of the upgrade to the high-luminosity LHC, which will deliver about ten times the current radiation dose. It must therefore be more resistant to radiation and meet strict requirements in terms of electrical insulation while matching the original field quality and self-protective capability, mechanical volume, and maximum excitation current. This paper will present the latest of the design and manufacturing work, including the results of simulations of the mechanical field and the mechanical stress. Details of the various tests performed before machining the parts are also presented.
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| 10. |
- Pepitone, Kevin, Dr, 1988-, et al.
(författare)
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Design of a Canted-Cosine-Theta Orbit Corrector for the High Luminosity LHC
- 2022
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Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 32:6
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Tidskriftsartikel (refereegranskat)abstract
- The High Luminosity LHC requires dipole orbit correctors grouped in double aperture magnet assemblies. They provide a field of 3.1 T at 100 A in an aperture of 70 mm. The current standard design is a classical cosine-theta layout made with ribbon cable. However, the electric insulation of this cable is not radiation-resistant enough to withstand the radiation load expected in the coming years of LHC operation. A new design, based on a cable with polyimide insulator, that can replace the existing orbit correctors, is needed. The challenge is to design a magnet that fits directly into the existing positions and that can operate with the same busbars, passive quench protection, and power supplies. The new orbit corrector design meets high requirements on the field quality while keeping within the same mechanical volume and maximum excitation current. A collaboration of Swedish universities and Swedish industry has been formed for the development and production of a prototype magnet following a concurrent engineering methodology to reduce the time needed to produce a CCT magnet. The magnet has a 1 m long CCT dipole layout consisting of two coils. The superconductor is a commercially available 0.33 mm wire with polyimide insulation in a 6-around-1 cable. The channels in the coil formers, that determine the CCT layout, allow for 2 x 5 cable layers. A total of 70 windings makes that the coil current can be kept below 100 A. We will present the detailed design and preliminary quench simulations.
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| 11. |
- Pepitone, Kevin, Dr, 1988-, et al.
(författare)
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First magnet operation on the cryogenic test stand Gersemi at FREIA
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Gersemi cryogenic test bench, installed at FREIA laboratory at Uppsala University, was used for the first time in 2021 to power a superconducting magnet. As part of the HL-LHC program, this cryostat offers an operating temperature between 4.2K and 1.9K. Its satellite equipment such as power converters and the acquisition system allow two superconducting magnet coils to be powered up to 2 kA and provide magnet protection through a robust quench detection and two energy extraction units. This report describes Gersemi's first cryogenic operational experiment and the safety strategy to ensure magnet integrity during operation.
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| 12. |
- Pepitone, Kevin, Dr, 1988-, et al.
(författare)
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Operation of a high-current drive beam electron gun prototype for the Compact Linear Collider
- 2020
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Ingår i: Review of Scientific Instruments. - : AMER INST PHYSICS. - 0034-6748 .- 1089-7623. ; 91:9
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Tidskriftsartikel (refereegranskat)abstract
- The high-average current electron gun low energy electrons from a thermionic cathode at high intensity is the prototype of the drive beam source for the Compact Linear Collider project. The electromagnetic design of the gun was done originally with 2D simulations to minimize the beam emittance for high-current operation (of the order of 8 A) at 140 keV. This paper reports on the first experimental measurements of beam extraction and transport. For the first time, 3D tracking simulations, which take into account precisely the cathode-grid geometry, have been compared with experimental optical transition radiation images of the beam, and we obtained impressive agreement. In addition, we have confirmed that the details of the cathode-grid assembly can impact significantly the beam emittance.
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| 13. |
- Rossi, L., et al.
(författare)
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A European Collaboration to Investigate Superconducting Magnets for Next Generation Heavy Ion Therapy
- 2022
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Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 32:4
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Tidskriftsartikel (refereegranskat)abstract
- Next generation ion therapy magnets both for gantry and for accelerator (synchrotron) are under investigation in a recently launched European collaboration that, in the frame of the European H2020 HITRIplus and I.FAST programmes, has obtained some funding for work packages on superconducting magnets. Design and technology of superconducting magnets will be developed for ion therapy synchrotron and -especially- gantry, taking as reference beams of 430 MeV/nucleon ions (C-ions) with 10(10) ions/pulse. The magnets are about 60-90 mm diameter, 4 to 5 T peak field with a field change of about 0.3 T/s and good field quality. The paper will illustrate the organization of the collaboration and the technical program. Various superconductor options (LTS, MgB2 or HTS) and different magnet shapes, like classical CosTheta or innovative Canted CosTheta (CCT), with curved multifunction (dipole and quadrupole), are under evaluation, CCT being the baseline. These studies should provide design inputs for a new superconducting gantry design for existing facilities and, on a longer time scale, for a brand-new hadron therapy centre to be placed in the South East Europe (SEEIIST project).
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| 14. |
- Shamuilov, Georgii, et al.
(författare)
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Emittance self-compensation in blow-out mode
- 2022
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Ingår i: New Journal of Physics. - : Institute of Physics (IOP). - 1367-2630. ; 24
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Tidskriftsartikel (refereegranskat)abstract
- We report an unusual regime of emittance self-compensation in an electron bunch generated in the blow-out mode by a radio-frequency photocathode gun. This regime is observed for a strong space-charge field on the cathode reaching around 30%-35% of the accelerating field. Simulations clearly show an initial growth and a subsequent self-compensation of projected emittance in a divergent electron bunch originating from the effects of: (a) strong space-charge forces of mirror charges on the cathode, (b) an energy chirp in the bunch and (c) substantial re-shaping of the electron bunch. Furthermore, we show analytically and numerically how a complex interplay between these effects leads to emittance self-compensation at the gun exit-the effect that is normally observed only in the presence of focusing fields.
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| 15. |
- Shamuilov, Georgii, et al.
(författare)
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Nanometre-scale emittance beams from a continuous-wave RF gun
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The operation of Ultrafast Electron Diffractometers (UEDs) and Free-Electron Lasers (FELs) relies on high-brightness electron beams produced by radio-frequency (RF) photocathode guns. The next generation of high-repetition rate UEDs and FELs requires electron beams with a high average brightness. To this end, we introduce a continuous wave RF photocathode gun at 325 MHz with an APEX-like geometry. The gun allows for the production of electron beams with very high both peak and average 5D brightness while having moderate RF power consumption. The gun is operated in blowout regime with an energy gain of 0.4 MeV and a peak cathode field of 35 MV/m. Via massive numerical simulations, we exemplify three regimes of the gun operation: (i) 160 fC electron beams with a 5-nm-scale emittance for UEDs, (ii) 1.6 pC beams with a 20-nm-scale emittance for table-top FELs and dielectric-based accelerators, and (iii) 16 pC beams with a 50-nm-scale emittance for inverse Compton sources and other accelerator-based photon sources. We introduce a simple analytical model for the formation of the virtual cathode - the onset of the suppression of photoemission current due to space-charge forces. The model accounts for the laser pulse duration. Furthermore, our extensive numerical simulations indicate a well-pronounced maximum in the 5D beam brightness for the laser spot radius approximately 150% of that corresponding to the onset of the virtual cathode. The finding does not support the common approach in the literature that in the blowout regime the laser spot radius must be much larger than the critical radius corresponding to the virtual cathode onset.
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| 16. |
- Verra, L., et al.
(författare)
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Controlled Growth of the Self-Modulation of a Relativistic Proton Bunch in Plasma
- 2022
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Ingår i: Physical Review Accelerators and Beams. - : American Physical Society. - 2469-9888. ; 25:7
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Tidskriftsartikel (refereegranskat)abstract
- A long, narrow, relativistic charged particle bunch propagating in plasma is subject to the self -modulation (SM) instability. We show that SM of a proton bunch can be seeded by the wakefields driven by a preceding electron bunch. SM timing reproducibility and control are at the level of a small fraction of the modulation period. With this seeding method, we independently control the amplitude of the seed wakefields with the charge of the electron bunch and the growth rate of SM with the charge of the proton bunch. Seeding leads to larger growth of the wakefields than in the instability case.
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| 17. |
- Verra, L., et al.
(författare)
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Development of the self-modulation instability of a relativistic proton bunch in plasma
- 2023
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Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 30:8
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Tidskriftsartikel (refereegranskat)abstract
- Self-modulation is a beam-plasma instability that is useful to drive large-amplitude wakefields with bunches much longer than the plasma skin depth. We present experimental results showing that, when increasing the ratio between the initial transverse size of the bunch and the plasma skin depth, the instability occurs later along the bunch, or not at all, over a fixed plasma length because the amplitude of the initial wakefields decreases. We show cases for which self-modulation does not develop, and we introduce a simple model discussing the conditions for which it would not occur after any plasma length. Changing bunch size and plasma electron density also changes the growth rate of the instability. We discuss the impact of these results on the design of a particle accelerator based on the self-modulation instability seeded by a relativistic ionization front, such as the future upgrade of the Advanced WAKefield Experiment.
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