S. Bira, D. Longuevergne
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
Y. Kalboussi
CEA-IRFU, Gif-sur-Yvette, France
S. Keckert, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
Th. Proslier
CEA-DRF-IRFU, France
Multipacting (MP) is a resonating electron discharge, often plaguing radio-frequency (RF) structures, produced by the synchronization of emitted electrons with the RF fields and the electron multiplication at the impact point with the surface structure. The electron multiplication can take place only if the secondary emission yield (SEY, i.e. the number of electrons emitted due to the impact of one incoming electron), , is higher than 1. The SEY value depends strongly on the material and the surface contamination. Multipacting simulations are crucial in high-frenquency (HF) vacuum structures to localize and potentially improve the geometry. In this work, multipacting simulations were carried out on the geometry of the Quadrupole Resonator (QPR) in operation at HZB using the Spark 3D module in Microwave Studio suite (CST). These simulations helped to understand a particular behavior observed during the QPR tests, and furthermore made it possible to suggest enhancement ways in order to limit this phenomenon and facilitate its operation.
N.A. Stilin, A.T. Holic, M. Liepe, R.D. Porter, J. Sears, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Significant progress in the performance of SRF cavities coated with Nb3Sn films during the last few years has provided an energy efficient alternative to traditional Nb cavities, thereby initiating a fundamental shift in SRF technology. These Nb3Sn cavities can operate at significantly higher temperatures than Nb cavities while simultaneously requiring less cooling power. This allows for the use of new cryogenic cooling schemes based on conduction cooling with robust, commercialized turn-key style cryocoolers. Cornell University has developed and tested a 2.6 GHz Nb3Sn cavity assembly which utilizes such cooling methods. These tests have demonstrated stable RF operation at 10 MV/m with measured thermal dynamics which match numerical simulations. These results also serve as a foundation for designing a new standalone SRF cryomodule which will use a pair of cryocoolers to cool a 1.3 GHz Nb3Sn cavity with an input coupler capable of supporting high beam current operation.
C. Contreras-Martinez
FRIB, East Lansing, Michigan, USA
S.K. Chandrasekaran, S. Cheban, G.V. Eremeev, F. Furuta, T.N. Khabiboulline, Y.M. Pischalnikov, O.V. Prokofiev, A.I. Sukhanov, J.C. Yun
Fermilab, Batavia, Illinois, USA
The PIP-II linac will include thirty-six β=0.61 and twenty-four β=0.92 650 MHz 5 cell elliptical SRF cavities. Each cavity will be equipped with a tuning system consisting of a double lever slow tuner for coarse frequency tuning and a piezoelectric actuator for fine frequency tuning. One dressed cavity equipped with an SRF tuner has been tested in the horizontal test stand at Fermilab. Results of testing the cavity-tuner system will be presented.
C. Contreras-Martinez
FRIB, East Lansing, Michigan, USA
T.T. Arkan, T.N. Khabiboulline, Y.M. Pischalnikov, G.V. Romanov, R.P. Stanek, J.C. Yun
Fermilab, Batavia, Illinois, USA
Fermilab conducted testing of three 3.9 GHz cryomodules for the LCLS-II project that will operate in continuous wave mode. A fast/fine tuning component was added to the LCLS-II 3.9 GHz tuner design due to the cavity bandwidth of 130 Hz which consists of two encapsulated piezos. Several cavities faced problems with fast-tuner operations after cooldown to 2 K and tuning the cavities to 3.9 GHz in cryomodule 2. All the piezo actuators were in working conditions but the slow tuner ranges required to stretch some of the cavities to the operational 3.9 GHz frequency were too small to deliver the required preload on the piezos. This behavior can be attributed to several factors: setting the initial warm cavity frequency during production too high, pressure tests of the warm cryomodule could have changed cavity frequency; and the small bending and twisting of the cavity-tuner system during the cooldown and warmup of the cavities. A decision was made to inelastically retune the warm cavities to decrease the unrestrained frequency by 200-300 kHz, this was done via the slow tuner. The results for this retuning method of three 3.9GHz cryomodules will be discussed.
C. Contreras-Martinez
FRIB, East Lansing, Michigan, USA
Y.M. Pischalnikov, J.C. Yun
Fermilab, Batavia, Illinois, USA
The new generation of low beam intensity superconducting linacs will require high accelerating gradients for new scientific discoveries. The high accelerating gradient cavities in pulsed SRF linacs will experience large (~1000’s of Hz) detuning caused by Lorentz force detuning (LFD). The piezo actuators that will be used to compensate large LFD must operate at a nominal voltage of 120V to 150V to deliver the required stroke to the cavity. In this high voltage range, the piezo is expected to warm up drastically due to its location in an insulating vacuum environment. Overheating of the piezo will significantly decrease the longevity of the actuator. A collaboration between FNAL and Physik Instrumente (PI) developed a novel piezo actuator design that mitigates piezo overheating. The design consists of using a metal foam in contact with the piezoelectric ceramic stack for heat removal. The second solution used lithium niobite as an alternative material. A comparison of the temperature stability will be presented and discussed. This study characterizes the dielectric properties for both materials. The results obtained are in the temperature range of 10 K to 300 K.
A.L. Klebaner, C. Boffo, S.K. Chandrasekaran, D. Passarelli, G. Wu
Fermilab, Batavia, Illinois, USA
Funding:US Department of Energy The Proton Improvement Plan II (PIP-II) project is an essential upgrade to Fermilab’s particle accelerator complex to enable the world’s most intense neutrino beam for LBNF/DUNE and a broad particle physics program for many decades to come. PIP-II will deliver 1.2 MW of proton beam power from the Main Injector, upgradeable to multi-MW capability. The central element of PIP-II is an 800 MeV linac, which comprises a room temperature front end followed by an SRF accelerator. The front end has been constructed and operated with (pulsed & CW) beam in the PIP-II Injector Test facility (PIP2IT). The SRF accelerator consists of five different types of cavities/cryomodules, including Half Wave Resonators (HWR), Single Spoke and elliptical resonators operating at state-of-the-art parameters. The first two PIP-II cryomodules, HWR and Single Spoke Resonator 1 (SSR1) are installed in PIP2IT and have accelerated beam to 17 MeV. PIP-II is the first U.S. accelerator project that will be constructed with significant contributions from international partners, including India, Italy, France, United Kingdom and Poland. The project was recently baselined, and site construction is underway
J. Branlard, S. Choroba, M.K. Grecki, S. Köpke, D. Kostin, D. Nölle, V. Vogel, N. Walker, S. Wiesenberg
DESY, Hamburg, Germany
The European X-Ray Free-Electron Laser (EuXFEL) has been successfully operating for almost 4 years, and routinely delivering 6- to 14-KeV X-rays to users (30 KeV photon energy was demonstrated). At the heart of the machine is the 1.3 km long 1.3 GHz SCRF linac which can reach a maximum electron energy of 17.6 GeV, and is capable of accelerating up to 2700 bunches per RF pulse at a repetition rate of 10 Hz, delivering beam to 6 experiments via 3 SASE undulator sections. In this contribution, we relate on the linac operational experience and highlight some recent developments towards monitoring and improving operations and linac availability.
Y.M. Pischalnikov, T.T. Arkan, C.J. Grimm, B.D. Hartsell, J.A. Kaluzny, T.N. Khabiboulline, Y.M. Orlov, J.C. Yun
Fermilab, Batavia, Illinois, USA
C. Contreras-Martinez
FRIB, East Lansing, Michigan, USA
Funding:This manuscript has been authorized by Fermi Research Alliance LLC under Contract N. DE-AC02-07CH11359 with U.S. Department of Energy. The off-frequency detune method is being considered to be applied in the LCLS-II-HE superconducting linac to produce multi-energy electron beams for supporting multiple undulator lines simultaneously. To deliver off-frequency operation (OFO) requirements for SRF cavity tuner must be changed. Tuner design modifications and results of the testing eight cavity/tuner system, deployed in verification cryomodule (vCM), will be presented.
A. Neumann, W. Anders, A. Frahm, F. Göbel, A. Heugel, S. Klauke, J. Knobloch, M. Schuster, Y. Tamashevich
HZB, Berlin, Germany
Funding:The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB. This year, the commissioning of the 50 MeV, 100 mA bERLinPro Energy Recovery Linac test facility [1] will resume. For the Booster cryo-module of the injector line, operated with three modified 1.3 GHz Cornell style 2-cell SRF cavities, a new type of power coupler was developed, based on KEK’s C-ERL injector coupler. Modifications were made for a stronger coupling and lower emittance diluting coupler tip variant, a so-called "Golf Tee" shape and the cooling concept was redesigned based on KEK’s first experiences. For the final stage, the injector needs to deliver a low emittance beam of 100 mA average beam current at 6.5 MeV. That results in a traveling and continuous wave forward power requirement of up to 120 kW each of the twin setup feeding one Booster cavity. In this contribution we will give a short overview of the RF design and its impact on the beam’s emittance, give an overview of the conditioning teststand and the results achieved with the first pairs of couplers. [1] M. Abo-Bakr et al., in Proc. 9th Int. Particle Accelerator Conf. (IPAC’18), Vancouver, BC, Canada, Apr. 4,, pp. 4127-4130, doi:10.18429/JACoW-IPAC2018-THPMF034
C.E. Reece, S. Castagnola, P. Denny, A.L.A. Mitchell
JLab, Newport News, Virginia, USA
Funding:This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OThR23177. The best performance of niobium SRF accelerating cavities is obtained with surfaces smoothed with electropolishing chemical finishing. Jefferson Lab has recently specified, procured, installed, and commissioned a new versatile production electropolishing (EP) tool. Experience with EP research and operations at JLab as well as vendor interactions and experience guided development of the system specification. Detailed design and fabrication was awarded by contract to Semiconductor Process Equipment Corporation (SPEC). The delivered system was integrated into the JLab chemroom infrastructure and commissioned in 2020. The new EP tool provides much improved heat exchange from the circulating H2SO4/HF electrolyte and also the cavity via variable temperature external cooling water flow, resulting in quite uniform cavity wall temperature control and thus improved removal uniformity. With the JLab infrastructure, stabilized process temperature as low as 5 C is available. We describe the system and illustrate operational modes in this contribution.
N. Gandolfo, S. Blivet, P. Duchesne, D. Le Dréan
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
In the framework of the MINERVA construction (MYRRHA Isotopes productioN coupling the linEar acceleRator to the Versatile proton target fAcility), a fully equipped prototype cryomodule is being developed. In order to control the resonance frequency of the cavities during operation, a deformation tuner has been studied. The kinematic model is based on a double lever system coupled with a screw nut linear actuator. The motion is generated by a stepper motor and two piezoelectric actuators working at low temperatures within the thermal insulation vacuum of the cryomodule. Key parameter of this work is the high tuning speed which is required to fulfill the fault tolerance strategy. This paper reports the design study and first tests of the built tuners at room temperature and in vertical cryostat configuration.
J. Steimel, V.M. Grzelak, D.W. Peterson
Fermilab, Batavia, Illinois, USA
V.R. Bala, S.K. Bharade, G. Joshi, R. Keshwani, J.K. Mishra, M.M. Pande, S. Shrotriya, H. Shukla, S. Singh, C.I. Sujo
BARC, Mumbai, India
D. Balakrishna, N. Chikte, S. Dubey, C. G, V. Gollapalli, J. K Chandra, V. Kumar, M. M, A. Maheshwari, S.N. Nagaratnam, G. Poornima, T.V.S. Thalluri
ECIL, Hyderabad, India
Funding:1Fermilab, U.S.Department of Energy 2 Bhabha Atomic Research Centre, Department of Atomic Energy, Government of India 3 Electronic Corporation of India, Department of Atomic Energy, Government of India The PIP-II Injector Test (PIP2IT) has successfully accelerated ionized hydrogen up to 17MeV through a superconducting, single spoke resonator (SSR1) cryomodule at Fermi National Accelerator Laboratory (FNAL). Each of the SSR1 cavities is tuned to 325MHz and requires up to 6 kW of RF power to accelerate 2mA of ionized hydrogen at the design gradients. RF power amplifiers, specialized for SRF cavity beam operations, were designed by Bhabha Atomic Research Center (BARC) and constructed in a collaboration between the BARC in Mumbai, India and the Electronics Corporation of India Limited (ECIL) in Hyderabad, India. The RF amplifiers meet the specifications and requirements mutually approved between BARC and FNAL. They operate at 325 MHz with a linear power output of 7 kW in both CW and pulse mode. The amplifiers are compatible with the FNAL accelerator personnel safety system and the cavity protection interlocks. Access to controls and internal diagnostic instrumentation are compatible with EPICS control standards. This paper gives details about RF power amplifier development within the Department of Atomic Energy (DAE), India and the operational details with PIP2IT at FNAL.
G. Ciovati, G. Cheng, E. Daly, G.K. Davis, M.A. Drury, J.F. Fischer, D. Forehand, K. Macha, F. Marhauser, E.A. McEwen, A.L.A. Mitchell, A.V. Reilly, R.A. Rimmer, S. Wang
JLab, Newport News, Virginia, USA
Funding:U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. The CEBAF cryomodule rework program was updated over the last few years to increase the energy gain of refurbished cryomodules to 75 MeV. The concept recycles the waveguide end-groups from original CEBAF cavities fabricated in the 1990s and replaces the five elliptical cells in each with a new optimized cell shape fabricated from large-grain, ingot Nb material. Eight cavities were fabricated at Research Instruments, Germany, and two cavities were built at Jefferson Lab. Each cavity was processed by electropolishing and tested at 2.07 K. The best eight cavities were assembled into ’cavity pairs’ and re-tested at 2.07 K, before assembly into the cryomodule. All but one cavity in the cryomodule were within 10% of the target accelerating gradient of 19 MV/m with a quality factor of 8·109. The performance limitations were field emission and multipacting.
T.C. Jiang, F. Bai, Y. He, Z.Q. Lin, Y.Q. Wan, R.X. Wang, Z.J. Wang, M. Xu, S.H. Zhang
IMP/CAS, Lanzhou, People’s Republic of China
More than 100 Half-wave resonators (HWR) will be adopted for China Initiative Accelerator Driven Sys-tem (CiADS) and High Intensity heavy-ion Accelerator Facility (HIAF) at IMP. Each HWR cavity equips with one variable coupling, dual-warm-ceramic fundamen-tal power coupler (FPC). The FPC should be able to transmit up to 30 kW in CW mode. This paper will give an overview of the RF design of the 162.5 MHz CW power coupler. The coupler employs two warm ceram-ics in a 50 Ω coaxial line to ensure operation relia-bility. The results of thermal and thermomechanical will also be reported. Two prototype couplers have been fabricated and the RF measurements with low RF power were carried out.
S. Barrière, S. Atieh, B. Bulat, R. Calaga, S.J. Calvo, O. Capatina, T. Demazière, G. Favre, A. Gallifa Terricabras, M. Garlasché, J.-M. Geisser, J.A. Mitchell, E. Montesinos, F. Motschmann, P. Naisson, R. Ninet, L. Prever-Loiri, L.R.A. Renaglia, K. Scibor, N. Villanti
CERN, Meyrin, Switzerland
Superconducting RF crab cavities are being manufactured as part of the HL-LHC upgrade at CERN. Amongst its related ancillaries, radiofrequency HOM (High Order Modes) suppressors and field antennas are essential for reaching nominal performance during operation with high energy beams, as they monitor and control the electromagnetic fields in the cavities. Several concepts of such equipment have been engineered and manufactured, for both design validation and RF performance assessment. The following paper highlights manufacturing process definition, its challenges and the assembly strategies focusing on the ongoing RFD prototypes for the SPS beam tests. Specific tooling development and test campaigns are also described.
A.J. May, A.E.T. Akintola, A.R. Bainbridge, R.K. Buckley, G. Collier, P.A. Corlett, K.D. Dumbell, M.J. Ellis, S. Hitchen, P.C. Hornickel, G. Hughes, C.R. Jenkins, P.A. McIntosh, K.J. Middleman, A.J. Moss, N. Pattalwar, S.M. Pattalwar, M.D. Pendleton, P.A. Smith, A.E. Wheelhouse, AAJ. White, S. Wilde
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
M.D. Hancock, J. Hathaway, C. Hodgkinson, G. Jones, M. Lowe, D.A. Mason, G. Miller, J. Mutch, A. Oates, P. Sollars, J.T.G. Wilson
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
A novel vertical test facility has been developed at the STFC Daresbury Laboratory. The VTF is designed to test 3 jacketed SRF cavities in a horizontal configuration in a single cool-down run at 2 K. Cavities were tested at low power levels for HOMs and passband modes, and Q vs E field measurements at high power levels. The specification requires an unloaded Q of 5·109 at a field gradient of 19.9 MV/m. The cavities are cooled with superfluid helium filled into their individual helium jackets. This reduces the liquid helium consumption by more than 70% in comparison with the conventional facilities operational elsewhere. The facility will be used to conduct a 2-year program to qualify 84 high-beta SRF cavities for the European Spallation Source as part of the UK’s in-kind contribution. This paper reports on the commissioning program, along with a detailed discussion of the RF and cryogenic operations and performance of the facility.
N. Sakamoto, H. Imao, O. Kamigaito, T. Nagatomo, T. Nishi, K. Ozeki, K. Suda, A. Uchiyama, K. Yamada
RIKEN Nishina Center, Wako, Japan
After commissioning of the RIKEN superconducting linac (SRILAC) in the end of FY2019, heavy ion beams were provided to the nuclear physics experiments. In this paper operation history and evolution of field emission levels through the year will be presented.
T.E. Oseroff, M. Liepe, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
With the increasing worldwide focus on the development of new surfaces for SRF cavities, exploring alternative materials and multilayer structures, test systems that allow measuring the RF performance of simple sample geometries (e.g., flat samples) become increasingly essential. These systems provide RF performance results that are needed to guide the development of these surfaces. This contribution gives an overview of sample test systems currently available, including the improved Cornell sample host cavity. Recent advances in this important technology, performance specifications, and current limitations are discussed. In addition, an overview is given of interesting recent RF performance results on samples coated with non-niobium bulk and multilayer films.
B. Yee-Rendón, Y. Kondo, F. Maekawa, S.I. Meigo, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan
To overcome the nuclear waste problem, the Japan Atomic Energy Agency (JAEA) has been developing an accelerator-driven subcritical system (ADS) since the late 1980s. In the JAEA-ADS proposal, an 800 MWth subcritical reactor is driven by a 30 MW cw proton linear accelerator (linac). The biggest challenges for the ADS machines are the high reliability and availability required for their operations. To this end, the present JAEA-ADS linac was redesigned by adopting the current developments in Superconducting Radio-Frequency (SRF) technology. Additionally, we developed a robust lattice to control the beam loss and implemented a fault-tolerance scheme for the fast recovery of SRF cavity failures. This work presents the latest results of the R&D of the JAEA-ADS superconducting linac.
M. Nishiwaki, K. Akai, T. Furuya, T. Kobayashi, S. Mitsunobu, Y. Morita, T. Okada
KEK, Ibaraki, Japan
Eight SRF cavity modules, which have been operated in KEKB for more than ten years, are stably operating also in SuperKEKB. As for calibration of the cavity voltage Vc, non-negligible discrepancy was observed between the results obtained from two different methods: one is using external Q value (Qext) of pickup ports, and the other is using loaded Q value (QL) of the cavities. The discrepancy comes from inaccuracy of power measurement in high power RF system and uncertainty of the Qext or QL values. In order to solve the discrepancy by improving the accuracy of the calibration for each individual cavity, we investigated a method by measuring synchrotron frequency fs of stored beam. With this method, Vc calibration can be performed without affected by inaccuracy of high-power measurement or uncertainty of the Qext or QL values. The fs measurement studies were carried out in SuperKEKB. With these studies, Vc calibration was obtained with a high accuracy of about 1%. The results are applied to the SuperKEKB operation.
Y. Yamamoto, M. Akemoto, D.A. Arakawa, A. Araki, S. Araki, A. Aryshev, T. Dohmae, M. Egi, M.K. Fukuda, K. Hara, H. Hayano, Y. Honda, T. Honma, H. Ito, E. Kako, H. Katagiri, R. Katayama, M. Kawamura, N. Kimura, Y. Kojima, Y. Kondou, T. Konomi, M. Masuzawa, T. Matsumoto, S. Michizono, Y. Morikawa, H. Nakai, H. Nakajima, K. Nakanishi, M. Omet, T. Oyama, T. Saeki, H. Sakai, H. Shimizu, S.I. Takahara, R. Ueki, K. Umemori, A. Yamamoto
KEK, Ibaraki, Japan
S. Aramoto
Hiroshima University, Higashi-Hiroshima, Japan
M. Kuriki
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
Z.J. Liptak
HU/AdSM, Higashi-Hiroshima, Japan
K. Sakaue
The University of Tokyo, The School of Engineering, Tokyo, Japan
A. Yamamoto
CERN, Meyrin, Switzerland
In STF at KEK, as the operational demonstration of the SRF accelerator for ILC, the STF-2 cryomodules (CM1+CM2a: one and half size CM with 12 cavities) have achieved 33 MV/m as average accelerating gradient with 7 cavities in Mar/2019. After that, one cavity with the lowest performance installed in CM2a was replaced with one N-infused cavity developed for High-Q/High-G R&D between Japan and US. From this April, the beam operation started again and those CMs achieved 33 MV/m as average accelerating gradient with 9 cavities including one N-infused cavity again. This is the very important milestone for ILC. In this report, the detailed results will be presented.
A. Arnold, P.N. Lu, S. Ma, P. Murcek, A.A. Ryzhov, J. Schaber, J. Teichert, H. Vennekate, R. Xiang
HZDR, Dresden, Germany
G. Ciovati, P. Kneisel
JLab, Newport News, Virginia, USA
At the electron accelerator for beams with high brilliance and low emittance (ELBE), the second version of a superconducting radio-frequency (SRF) photoinjector was brought into operation in 2014. After a period of commissioning, a gradual transfer to routine operation took place in 2017 and 2018, so that more than 3000h of user beam have already been generated since 2019. During this time, a total of 20 cathodes (2 Cu, 12 Mg, 6 Cs2Te) were used, but no serious cavity degradation was observed. In this paper, we summarize the operational experience of the last 6 years of SRF gun operation, with special emphasis on the main RF properties of the cavity. This includes the evolution of QvsE, dark current, multipacting, but also mechanical properties such as Lorentz force detuning, helium pressure sensitivity as well as microphonics. The latter is closely connected to an active compensation by a so-called low-level RF feedback loop, which is also briefly presented.
D. Kostin, J. Eschke, K. Jensch, N. Krupka, L. Lilje, A. Muhs, D. Reschke, S. Saegebarth, J. Schaffran, M. Schalwat, P. Schilling, M. Schmökel, S. Sievers, N. Steinhau-Kühl, E. Vogel, H. Weise, M. Wiencek, B. van der Horst
DESY, Hamburg, Germany
Eight SRF cavities assembled in an accelerating module represent a building block of the particle linear accelerator based on TESLA SRF technology. DESY has two machines, European XFEL and FLASH. Both use almost same module and cavity types. During the module assembly many factors can deteriorate the cavity performance and cause a need for a repair action. Currently two European XFEL modules and two FLASH ones underwent reassembly procedures. The repair was not immediately successful on every of these modules and re-iterations did follow. The degradation causes were investigated. SRF modules were tested on both test-stands at DESY: AMTF and CMTB. The results of the described actions are presented and discussed.
Z.A. Conway, R. Anderson, D. Holmes, K. Mernick, S. Polizzo, S.K. Seberg, F. Severino, K.S. Smith, Q. Wu, B.P. Xiao, W. Xu, A. Zaltsman
BNL, Upton, New York, USA
Funding:Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. In preparation for the 2023 RHIC sPHENIX experi-mental program the superconducting 56 MHz quarter-wave resonator cryomodule, used operationally for longitudinal bunch compression with up to 1 MV RF voltage, is being refit to accommodate an expected beam current of 418 mA per ring, an increase of ~1.5 relative to previous operation. The upgrades to the system include an improved fundamental mode damp-er, and dual function fundamental power and higher-order mode damper couplers. This paper will describe the preliminary testing, select subsystem changes and plans for testing the cryomodule prior to installation in the RHIC beam line in 2022.
T. Stengler, K. Aulenbacher, F. Hug, D. Simon
KPH, Mainz, Germany
Funding:supported by the German Research Foundation (DFG): EXC 2118/2019 The Institute of Nuclear Physics at the Johannes Gutenberg University Mainz, Germany is currently constructing the Mainz Energy-recovering Superconducting Accelerator (MESA). The centerpiece of the MESA consists of two superconducting cryomodules of the ELBE/Rossendorf type, which are operated at 1.8 K. Furthermore, accelerator elements for polarimetry, a 10 T solenoid, and the external SRF test facility of the Helmholtz Institute Mainz have to be supplied with 4 K helium. One challenge here is to supply the components located throughout the accelerator according to their requirements and to establish a 16mbar system for 1.8 K operation. To ensure the required supply of helium at the different temperature levels, the existing helium liquefier has to be upgraded. The cryogenic infrastructure has to be adapted to the accelerator. The concept of the future cryogenic distribution network is presented in this paper and the design of the cryogenic facilities including the modifications is described in detail.
S. Weih, M. Arnold, M. Dutine, J. Enders, R. Grewe, L.E. Jürgensen, N. Pietralla, F. Schließmann, M. Steinhorst
TU Darmstadt, Darmstadt, Germany
Funding:work supported by German research council (DFG) through GRK 2128 ’AccelencE’ and the state of Hesse through the LOEWE research project Nuclear Photonics and the Collaborative Research Cluster ELEMENTS The superconducting part of the injector section of the superconducting Darmstadt electron linear accelerator (S-DALINAC) [1] consisted of one five-cell capture cavity and two 20-cell cavities at 3 GHz resonance frequency. All of them were geometrically adapted to electron velocities with a beta of 1, while the thermionic gun provides electrons with a beta of 0.74. This mismatch resulted in an insufficient capture process for optimum beam quality. For this reason, a new six-cell capture cavity with a beta of 0.86 has been designed and built. Field flatness tuning, a test in the vertical bath cryostat, and a UHV furnace treatment have been carried out in-house to finalize the cavity processing. The cryostat module was adapted to house the new cavity, which has been recently installed. Following the module assembly, a first RF test run was conducted at the S-DALINAC. We report on these latest advancements towards the implementation of the injector upgrade. * N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018).
Y.M. Pischalnikov
Fermilab, Batavia, Illinois, USA
Funding:This manuscript has been authorized by Fermi Research Alliance LLC under Contract N. DE-AC02-07CH11359 with U.S. Department of Energy Large SRF Linacs and HEP experiments require accurate frequency control, which is achieved using cavity tuners typically actuated by the piezoelectric ceramic stacks. The piezoelectric ceramic stacks became ’standard’ components of the SRF cavity tuner and, depending on the application, could be operated in the different environment: in air, at cryogenic temperature, in vacuum, and submerged in liquid helium. Different applications place different requirements on the piezo actuators, but the important parameters, common to all applications, are the lifetime and reliability of the actuators. Several R&D programs targeting the development of reliable piezo actuators are reviewed in this contribution.
N. Wunderer, V. Dürr, A. Frahm, H.-W. Glock, F. Glöckner, J. Knobloch, E. Sharples-Milne, A.V. Tsakanian, A. Veléz
HZB, Berlin, Germany
M. Bonezzi, A. D’Ambros, R. Paparella
INFN/LASA, Segrate (MI), Italy
J. Guo, J. Henry, R.A. Rimmer
JLab, Newport News, Virginia, USA
J. Knobloch
University of Siegen, Siegen, Germany
A. Veléz
Technical University Dortmund, Dortmund, Germany
The BESSY VSR project aims to demonstrate the possibility to simultaneously run both long (15ps) and short bunches (1.7ps) within BESSY II storage ring. To achieve this, a new SRF cavity system with higher harmonic cavities (3 and 3.5 harm.) needs to be installed. The combined cavity SRF beating allows for stable bunch shortening for half of the buckets while standard lengths remaining for the other half. These SRF cavities will be equipped with waveguide-connected HOM absorbers and will be controlled with a blade tuner plus piezos. To demonstrate the feasibility of this complex system the VSR DEMO cold string consists of two 1.5 GHz cavities, each featuring five waveguides and a higher power coupler, plus all interconnecting elements coupled to the beam vacuum. For most of these components the fundamental development work is completed and has been reported in the past. This paper summarizes recent enhancements, component detailing and manufacturing status. The key cold string components such as cavities, higher power couplers and blade tuners have already entered the manufacturing phase. All other cold string components will be ready for purchase at the latest beginning of 2022.
C. Zhang, W. Chang, K. Elliott, W. Hartung, S.H. Kim, J.T. Popielarski, K. Saito, T. Xu
FRIB, East Lansing, Michigan, USA
Development of techniques for in-situ plasma cleaning of quarter-wave and half-wave resonator cryomodules is underway at the Facility for Rare Isotope Beams (FRIB) at Michigan State University. If SRF cavity performance degradation is seen during future FRIB linac operation, in-situ plasma cleaning may help to restore performance without disassembly of the cavities from the cryomodules for off-line cleaning. A plasma cleaning feasibility study for FRIB cryomodules indicates that plasma cleaning can be done on-line without modifications to the RF couplers or cryomodules. Initial bench measurements have been performed on a FRIB half-wave resonator using noble gases (Ne, Ar), with and without added oxygen gas. The plasma ignition threshold has been measured as a function of gas pressure and composition. Studies of plasma cleaning efficacy are underway. Results will be presented.
H. Sakai, M. Adachi, D.A. Arakawa, S. Eguchi, M.K. Fukuda, K. Haga, M. Hagiwara, K. Hara, K. Harada, N. Higashi, T. Honda, Y. Honda, T. Honma, M. Hosumi, E. Kako, Y. Kamiya, R. Kato, H. Kawata, Y. Kobayashi, Y. Kojima, T. Konomi, H. Matsumura, S. Michizono, C. Mitsuda, T. Miura, T. Miura, T. Miyajima, Y. Morikawa, S. Nagahashi, H. Nakai, N. Nakamura, K. Nakanishi, K.N. Nigorikawa, T. Nogami, T. Obina, F. Qiu, H. Sagehashi, M. Shimada, H. Shimizu, T. Shioya, M. Tadano, T. Takahashi, R. Takai, H. Takaki, O.A. Tanaka, Y. Tanimoto, A. Toyoda, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, M. Yamamoto
KEK, Ibaraki, Japan
R. Hajima, K. Kawase
QST, Tokai, Japan
N.P. Norvell
SLAC, Menlo Park, California, USA
F. Sakamoto
Akita National College of Technology, Akita, Japan
M. Shimada
HSRC, Higashi-Hiroshima, Japan
Funding:Supported by Accelerator Inc. and a New Energy and Industrial Technology Development Organization (NEDO) project and JSPS Grant-in-Aid for Scientific Research (KAKENHI) Grant Number JP18H03473. A superconducting Compact Energy Recovery Linac (cERL) for electrons was constructed in 2013 at KEK to demonstrate energy recovery concept with low emittance, high-current CW beams of more than 10 mA for future multi-GeV ERL. Recently this cERL was operated not only to demonstrate energy recovery linac high current beam operation but also to promote and conduct a variety of industrial applications such as FEL, THz operation and Rare Isotope Production and irradiation for some materials. In this talk, I will present the status of the studies to realize the stable high-current low emittance CW beam and some applications with this beam.
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E.R. Harms, B.E. Chase, E. Cullerton, B.D. Hartsell, J. Hurd, M.J. Kucera, F.L. Lewis, A. Lunin, J.N. Makara, D.L. Newhart, D.J. Nicklaus, P.S. Prieto, J. Reid, R.P. Stanek, R. Wang
Fermilab, Batavia, Illinois, USA
A.L. Benwell
SLAC, Menlo Park, California, USA
C. Contreras-Martinez
FRIB, East Lansing, Michigan, USA
C.M. Ginsburg
JLab, Newport News, Virginia, USA
Funding:This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Cold powered testing of all LCLS-II production cryomodules at Fermilab is complete as of February 2021. A total of twenty-five tests on both 1.3 GHz and 3.9 GHz cryomodules were conducted over a nearly five year time span beginning in the summer of 2016. During the course of this campaign cutting-edge results for cavity Q0 and gradient in continuous wave operation were achieved. A summary of all test results will be presented, with a comparison to established acceptance criteria, as well as overall test stand statistics and lessons learned.
K. Turaj, O. Brunner, A.C. Butterworth, F. Gerigk, P. Maesen, E. Montesinos, F. Peauger, M. Therasse, W. Venturini Delsolaro
CERN, Meyrin, Switzerland
The LHC RF cryomodule "Asia" suffered an accidental influx of about 0.5 l of tunnel air during the leak checks of the pumping manifolds. The resulting risk of particle contamination was difficult to assess, and could not be excluded with certainty. If one or more cavities were contaminated, a severe impact on beam operations in the LHC machine was to be expected. In order to minimize the risks, the Asia cryomodule has been replaced with a spare unit. Subsequently, the cryomodule was tested in the SM18 test facility without intermediate venting, and showed high levels of radiation due to field emission above 1.8 MV in one of the cavities. The other cavities were less strongly affected, but clear signs of contamination were observed. The helium processing technique was used to improve the performance of the SRF cavity with respect to field emission. This paper will discuss the results of the above-mentioned test.
R. Monroy-Villa, W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Gorgi Zadeh, P. Putek
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
M. Lemke, R. Monroy-Villa, D. Reschke, M. Röhling, J.H. Thie
DESY, Hamburg, Germany
A basic understanding of the properties of SRF samples under surface treatments would aid in the development of consistent theories. To study the RF properties of such samples under realistic superconducting-cavity-like conditions, a test device called Quadrupole Resonator (QPR) was fabricated. In this publication we report the status of the QPR at Universität Hamburg in collaboration with DESY. Our device is based on the QPRs operated at CERN and at HZB, and its design will allow for testing samples at temperatures between 2 K and 8 K, under magnetic fields up to 120 mT and with operating frequencies of 433 MHz, 866 MHz and 1300 MHz. Fabrication tolerance studies on the electromagnetic field distributions and simulations of the static detuning of the device, together with the commissioning report and the ongoing surface treatment, will be presented.
A. Pandey, R. Ahuja, G.K. Chaudhari, B.B. Chaudhary, R.N. Dutt, S. Ghosh, B. Karmakar, J. Karmakar, R. Kumar, D.S. Mathuria, P. Patra, P.N. Potukuchi, A. Rai, B.K. Sahu, S.K. Saini, A. Sharma, S.K. Sonti, S.K. Suman
IUAC, New Delhi, India
The phase locking of the QWRs by dynamic phase control method in the superconducting linac at IUAC is done in a faster time scale. The slow frequency drifts (few hundreds of ms) are corrected using a niobium bellows tuner attached at the open end of the cavity. Initially, the tuners in the cavities were operated using helium gas. This system had the limitation of non-linearity, hysteresis and slow response due to which the cavities could not be phase locked at higher fields. To address this, piezo based tuning system was implemented in the cavities of the 2nd and 3rd linac modules. But due to space constraints, the same could not be used in the 1st linac module and the buncher modules. For them, the helium gas based system was continued, albeit with suitable modifications. The old flow control valves which operated with DC voltages were replaced with valves operating in pulsed mode and controlled by varying the duty cycle of the input pulses. The above mentioned limitations were overcome by using this PWM based technique and this enabled phase locking at higher gradients. This paper presents our operational experience with all the different tuning systems and their comparison.
D. Sertore, M. Bertucci, M. Bonezzi, A. Bosotti, D. Cardelli, A. D’Ambros, A.T. Grimaldi, L. Monaco, R. Paparella, G.M. Zaggia
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
INFN Milano - LASA contributes in-kind to the ESS ERIC Superconducting Linac supplying 36 cavities for the Medium Beta section of the proton accelerator. All the cavities have been mechanical fabricated, BCP treated and, for most of them, also qualified with vertical test at cold at DESY. We present the result of the cavities already qualified and delivered to CEA, discussing the lessons learnt so far. For remaining cavities, we discuss the actions taken and the plans foreseen to recover them to full specifications.
H. Jenhani, P. Carbonnier
CEA-IRFU, Gif-sur-Yvette, France
The Proton Improvement Plan - II (PIP-II) project is underway at Fermilab with an international collaboration involving CEA in the development and testing of 650 MHz cryomodules. The risk analysis related to cryomodule operation proposed to add a vacuum gauge on the power coupler to prevent the untimely rupture of its ceramic. Due to the advanced design of the cryomodules, the gauge needs to be integrated inside the insulation vacuum to reduce the impact of this new modification. The lack of experience feedback on a similar operating condition requires an experimental validation before the implementation. This article details the experimental tests carried out before the approval of this solution.
N.A. Huque, E. Daly, J.P. Preble, K.M. Wilson
JLab, Newport News, Virginia, USA
Cryomodules for the Linear Coherent Light Source II (LCLS-II) at SLAC National Accelerator Laboratory were jointly fabricated at Thomas Jefferson National Accelerator Facility (JLab) and Fermi National Accelerator Facility (FNAL). Procurements, cavity testing, cryomodule assembly, and cryomodule testing were carried out at the two labs. Twenty-one 1.3 GHz cryomodules were fabricated at JLab. The LCLS-II cryomodules are based on the design used in the European X-Ray Free Electron Laser (XFEL) but modified for continuous wave operation. The higher performance requirements lead to challenges in cavity processing, microphonics, magnetic hygiene and cryomodule transportation. This paper outlines the cryomodule production experience at JLab, as well as improvements to procedures and infrastructure to overcome the performance challenges of the LCLS-II design.
K.M. Wilson, G. Cheng, E. Daly, N.A. Huque, T. Huratiak, M. Laney, K. Macha, D.J. Maddox, M. Marchlik, P.D. Owen, T. Peshehonoff, M. Torres, M. Wiseman
JLab, Newport News, Virginia, USA
Funding:Supported by the Dept of Energy, Office of Nuclear Physics under contract DE-AC05-06OR23177 (JSA); and by UT-B which manages Oak Ridge National Laboratory under contract DE-AC05-00OR22725. In early 2020, COVID-19 swept across the world. The accelerator industry, like many others, was impacted by disease, delays, shortages, and new working conditions. All Thomas Jefferson National Accelerator Facility (JLab) employees were sent home in mid-March 2020, with many still working remotely now. At the time, JLab was working on the Proton Power Upgrade (PPU) to the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). Procurements had been placed and were being managed, parts were being received and inspected. This paper details the JLab procurement plan for the SNS PPU project, and the mitigations that were developed to continue to support this project smoothly under the limitations imposed by COVID-19.
