IPAC2021 - List of Keywords (multipactoring)

Paper	Title	Other Keywords	Page
MOPAB247	Multipacting Studies for the JAEA-ADS Five-Cell Elliptical Superconducting RF Cavities	cavity, electron, SRF, simulation	793
	B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura JAEA/J-PARC, Tokai-mura, Japan E. Cicek KEK, Ibaraki, Japan
	The Five-cell Elliptical Superconducting Radio-Frequency Cavities (SRFC) provide the final acceleration in the JAEA-ADS linac (from 208 MeV to 1.5 GeV); thus, their performance is essential for the success of the JAEA-ADS project. After their optimization of the cavity geometry to achieve a high acceleration gradient with lower electromagnetic peaks, the next step in the R&D strategy is the accurate estimation of beam-cavity effects which can affect the performance of the cavities. To this end, multipacting studies were developed to investigate its effect in the cavity operation regimen and find countermeasures. The results of this study will help in the development of the SRFC models and in the consolidation of the JAEA-ADS project.
	Poster MOPAB247 [0.599 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB247
About •	paper received ※ 10 May 2021 paper accepted ※ 07 June 2021 issue date ※ 28 August 2021
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MOPAB336	Multipacting Analysis of Warm Linac RF Vacuum Windows	simulation, vacuum, GUI, Windows	1044
	G.D. Toby, Y.W. Kang, S.-H. Kim, S.W. Lee, J.S. Moss ORNL, Oak Ridge, Tennessee, USA
	Funding: * This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC05-00OR22725. Multipacting in accelerating structures is a complex phenomenon with which there is much to be understood. While multipacting research efforts have primarily been focused on superconducting radio frequency (SRF) systems, normal conducting accelerating structures that have a higher thermal capacity and a greater vacuum pressure tolerance could benefit from additional investigation. This research details multipacting simulation methods and the results of 3-D electromagnetic simulations of RF vacuum windows used on normal conducting linac (NCL) cavities. Possible techniques for reducing and eliminating multipacting activities in these structures are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB336
About •	paper received ※ 17 May 2021 paper accepted ※ 28 May 2021 issue date ※ 29 August 2021
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MOPAB352	High Power Test of a Dielectric Disk Loaded Accelerator for a Two Beam Wakefield Accelerator	wakefield, acceleration, impedance, linear-collider	1096
	B.T. Freemire, C.-J. Jing, S. Poddar Euclid Beamlabs, Bolingbrook, USA M.E. Conde, D.S. Doran, G. Ha, W. Liu, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA M.M. Peng TUB, Beijing, People’s Republic of China E.E. Wisniewski Illinois Institute of Technology, Chicago, Illinois, USA Y. Zhao Euclid TechLabs, Solon, Ohio, USA
	Funding: Small Business Innovation Research Contract No. DE-SC0019864 U.S. DOE Office of Science Contract No. DE-AC02-06CH11357 As part of the Argonne 500 MeV short pulse Two Beam Wakefield Acceleration Demonstrator, a single cell X-band dielectric disk loaded accelerator (DDA) has been designed, fabricated, and tested at high power at the Argonne Wakefield Accelerator. The DDA should provide a short pulse (~20 ns) high gradient (>300 MV/m) accelerator while maintaining a reasonable r/Q and high group velocity. This will allow a significantly larger RF-to-beam efficiency than is currently possible for conventional accelerating structures. A low loss barium titantate ceramic, µ_r = 50, was selected, and a low temperature brazing alloy chosen to preserve the dielectric properties of the ceramic during brazing. High power testing produced breakdown at the triple junction, resulting from the braze joint design. No evidence of breakdown was observed on the iris of the disk, indicating that the maximum surface electric field on the dielectric was not reached. An improved braze joint has been designed and is in production, with high power testing to follow.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB352
About •	paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 21 August 2021
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MOPAB361	Threshold in Filling Failure of RF Cavity Caused by Beam Loading in Multipactor	cavity, simulation, electron, experiment	1122
	J. Pang USTC/NSRL, Hefei, Anhui, People’s Republic of China Y. Dong Institute of Applied Physics and Computational Mathematics, People’s Republic of China Y. Du Institute of Fluid Physics,, China Academy of Engineering Physics, Mianyang, People’s Republic of China
	Funding: NSFC A pulsed RF cavity would be heavily detuned caused by beam loading of multipactor current in the RF filling process. Multipactor zone would be expended by several times than that in static states with assumptions of fixed voltage and no beam loading. The dynamic of multipactor in the RF filling process was simulated by coupling with parameters of external circuit with the developed simulation code, and test in experiments with a parallel-plate resonator. Threshold of RF voltage, which means the lower boundary of peak voltage of multipactor zone, had been quantified with different cavity parameters. When we increased the gap length, the measured threshold became larger due to the ionization in background gas. Then the secondary emission factor would be increased in simulation for consistence with the experiment results. Additionally, some multipactor phenomenon could not be predicted precisely because the simulation code did not take account of ionization. The hysteresis of phase and energy of ionization electrons would be a new driving factor for the growth of multipactor in certain conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB361
About •	paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 10 August 2021
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TUPAB035	ESS Medium Beta Cavities Status at INFN LASA	cavity, SRF, linac, controls	1420
	D. Sertore, M. Bertucci, M. Bonezzi, A. Bosotti, A. D’Ambros, A.T. Grimaldi, P. Michelato, L. Monaco, R. Paparella INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	INFN Milano contributes in-kind to the ESS ERIC Superconducting Linac supplying 36 cavities for the Medium Beta section of the proton accelerator. The production has reached completion, being all the cavities mechanical fabricated, BCP treated and, for most of them, also qualified with vertical test at cold. In this paper, we report on the results and lessons learnt and the actions taken both for quality control managing and recovery of the few cavities that did not reach the project goal after the first qualification test.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB035
About •	paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 18 August 2021
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TUPAB166	A New Design of a Dressed Balloon Cavity with Superior Mechanical Properties	cavity, SRF, linac, software	1769
	R.A. Kostin, C. Jing, S. Ross Euclid Beamlabs, Bolingbrook, USA I.V. Gonin, T.N. Khabiboulline, G.V. Romanov, V.P. Yakovlev Fermilab, Batavia, Illinois, USA M.P. Kelly ANL, Lemont, Illinois, USA R.E. Laxdal TRIUMF, Vancouver, Canada
	Funding: Work supported by the SBIR program of the U.S. Department of Energy, under grant DE-SC0020781 Superconducting spoke cavities are prone to multipactor - resonant raise of a number of electrons due to secondary emission. Recently proposed and tested by TRIUMF balloon-type spoke cavity showed an outstanding multipactor (MP) suppression property but unfortunately serious Q degradation at high fields. A new fully developed design of a dressed balloon cavity which can be used for any proton linac SSR2 section is developed. The design incorporates additional EP ports for high Q-factor demonstration. Superior properties are demonstrated, such as effective multipactor suppression, 40% lower Lorentz force coefficient, zero sensitivity to external pressure. This paper presents the results of coupled structural Multiphysics analysis, and engineering design of the dressed balloon cavity with EP ports.
	Poster TUPAB166 [1.394 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB166
About •	paper received ※ 15 May 2021 paper accepted ※ 21 June 2021 issue date ※ 01 September 2021
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TUPAB339	High Power Test of the Antenna Adjustable Power Coupler for 325 MHz Superconducting Cavities	cavity, vacuum, electron, pick-up	2286
	J.Y. Yoon, E.-S. Kim, C.S. Park, S.H. Park KUS, Sejong, Republic of Korea J. Bahng Korea University Sejong Campus, Sejong, Republic of Korea E. Kako KEK, Ibaraki, Japan K.R. Kim PAL, Pohang, Republic of Korea
	Funding: The Ministry of Education (South Korea) The power coupler is development at Korea University for a Single Spoke Resonator (SSR) of heavy ion accelerator. Our power coupler is a coaxial capacitive type based on a conventional 3-1/8 inch electronic industries alliance (EIA) 50 Ω coaxial transmission line with a titanium nitride (TiN) coated single ceramic window. A high power test is rectangular test cavity with high vacuum and various measuring equipment, such as an arc detector, a power meter, and an electron pick-up probe. The interlock system under vacuum and arc instrumentations prevent the RF window from breaking the power coupler window during the high power test. We conduct high power tests for more than 12 hrs at 12 kW in a 325 MHz continous wave (CW) mode to verify the performance of the designed power coupler. Superconducting, Power Coupler
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB339
About •	paper received ※ 12 May 2021 paper accepted ※ 21 June 2021 issue date ※ 24 August 2021
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TUPAB342	Preliminary Cryogenic Cold Test Results of the First 9-Cell LSF Shape Cavity	cavity, niobium, SRF, laser	2296
	R.L. Geng, W.A. Clemens, R.S. Williams JLab, Newport News, Virginia, USA S.A. Belomestnykh Fermilab, Batavia, Illinois, USA Y. Fuwa JAEA/J-PARC, Tokai-mura, Japan H. Hayano KEK, Ibaraki, Japan Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan Z. Li SLAC, Menlo Park, California, USA V.D. Shemelin Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Supplemental support by US-Japan Collaboration on HEP. Following successful prototyping and testing of single- & 5-cell LSF shape cavities , , the first 9-cell LSF shape cavity LSF9-1 was successfully constructed using an innovative process at JLab with the in-house facilities. The cavity was then shipped to KEK for post-fabrication mechanical adjustment and ILC TDR style treatment and surface processing. Cold testing was carried out at the JLab VTA facility, instrumented with a suite of Kyoto instruments. Favorable values for the bath pressure detuning sensitivity and Lorentz force detuning coefficient were experimentally measured, validating the design improvement in cell stiffeners. Pass-band measurements indicate 4 out of 9 cells reaching gradient capability of > 45 MV/m, including 2 cells reaching 51 MV/m. Cornell OST detectors identified the cell and location responsible for the current hard quench limit. Multipacting-like barriers observed in end cells are investigated both analytically and numerically. The cavity was shipped to FNAL and received a light EP at the joint ANL/FNAL facility for further cold testing at Jlab. Two new 9-cell LSF cavities are being constructed including one made of large-grain niobium material. R. L. Geng et al.,WEPWI013, IPAC15. ** R. L. Geng et al., MOP064, SRF’19.
	Poster TUPAB342 [1.600 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB342
About •	paper received ※ 09 May 2021 paper accepted ※ 14 June 2021 issue date ※ 20 August 2021
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TUPAB343	Final Design Studies for the VSR DEMO 1.5 GHz Coupler	SRF, operation, cavity, electron	2300
	E. Sharples-Milne, V. Dürr, P. Echevarria, J. Knobloch, A. Neumann, A.V. Vélez HZB, Berlin, Germany
	With the 1.5 GHz couplers for the Variable pulse length Storage Ring (VSR) DEMO now in the manufacturing stages, the studies that led to the final coupler design will be presented. The system specific constraints and design modifications that combat the challenges of thermomechanical stresses, higher order mode (HOM) propagation and dimensional constraints are explored. This includes S-Parameter analysis, an in-depth study of the coupling factor, and multipacting studies for the average (1.5 kW) and peak (16 kW) power.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB343
About •	paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 14 August 2021
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TUPAB355	Design and Implementation of a Production Model Bias Tee	high-voltage, MMI, cavity, linac	2339
	T.L. Larter, E. Gutierrez, S.H. Kim, D.G. Morris, J.T. Popielarski, T. Xu, S. Zhao FRIB, East Lansing, Michigan, USA
	Funding: This work is supported by the US Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University. The Facility for Rare Isotope Beams (FRIB) includes two types of half wave SC resonators (HWR) operating at 322MHz. The fundamental power couplers used to transmit RF power into the HWRs commonly suffer from multipacting which can result in long conditioning times. A bias tee can be used to apply a high voltage to the couplers to help alleviate multipacting. A production version of the bias tee was commissioned for use at FRIB. The bias tee went through several design revisions to diagnose and correct thermal dissipation issues. This paper will discuss details of design and challenges faced during production validation of the bias tee.
	Poster TUPAB355 [0.630 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB355
About •	paper received ※ 19 May 2021 paper accepted ※ 28 May 2021 issue date ※ 12 August 2021
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WEPAB148	RF Design of an X-Band TM02 Mode Cavity for Field Emitter Testing	cavity, electron, coupling, insertion	2961
	Z. Li, S.G. Tantawi SLAC, Menlo Park, California, USA S.V. Baryshev, T. Posos, M.E. Schneider Michigan State University, East Lansing, Michigan, USA
	Funding: Work at SLAC was supported by DOE under contract No. DE-AC02-76SF00515. Work at MSU was supported by DOE under Award No. DE-SC0020429 and under Cooperative Agreement Award No. DE-SC0018362. Planar polycrystalline synthetic diamond with nitrogen-doping/incorporation was found to be a remarkable field emitter. It is capable of generating a high charge beam and handling moderate vacuum conditions. Integrating it with an efficient RF cavity could therefore provide a compact electron source for RF injectors. Understanding the performance metrics of the emitter in RF fields is essential toward developing such a device. We investigated a test setup of the field emitter at the X-band frequency. The setup included an X-band cavity operating at the TM02 mode. The field emitter material will be plated on the tip of a insertion rod on the cavity back plate. Part of the back plate and the emitter rod are demountable, allowing for exchange of the field emitters. The TM02 mode was chosen such that the design of the demountable back plate does not induce field enhancement at the installation gap. The cavity were optimized to achieve a high surface field at the emitter tip and a maximum energy gain of the emitted electrons at a given input power. We will present the RF and mechanical design of such a TM02 X-band cavity for field emitter testing.
	Poster WEPAB148 [1.642 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB148
About •	paper received ※ 14 May 2021 paper accepted ※ 12 July 2021 issue date ※ 12 August 2021
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WEPAB195	Design and Optimization of a Low Frequency RF-Input Coupler for the IsoDAR RFQ	rfq, coupling, simulation, cyclotron	3081
	M.P. Sangroula, J.M. Conrad, D. Winklehner MIT, Cambridge, Massachusetts, USA M. Schuett BEVATECH, Frankfurt, Germany
	Funding: The RFQ-DIP project is supported by National Science Foundation grant \# PHY-1626069 and the Heising-Simons Foundation. The Isotope Decay-At-Rest experiment (IsoDAR) is a proposed underground experiment which is expected to be a definitive search for sterile neutrinos. IsoDAR uses an especially designed low-frequency spilt-coaxial radio frequency quadrupole (RFQ) to accelerate H²⁺ ions directly from the ion source into the main cyclotron accelerator. This paper mainly focuses on the design and optimization of a low frequency (32.8 MHz) RF-input coupler for the IsoDAR RFQ. Starting with a basic design, we determine its appropriate position for this coupler in the RFQ. Finally, we optimized the design to lower the input power without compromising the coupling efficiency.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB195
About •	paper received ※ 21 May 2021 paper accepted ※ 30 June 2021 issue date ※ 29 August 2021
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WEPAB338	Amorphous Carbon Coating in SPS	vacuum, electron, target, operation	3475
	W. Vollenberg, P. Chiggiato, P. Costa Pinto, P. Cruikshank, H. Moreno, C. Pasquino, J. Perez Espinos, M. Taborelli CERN, Meyrin, Switzerland
	Within the LHC Injector Upgrade (LIU) project, the Super Proton Synchrotron (SPS) needs to be upgraded to inject into the LHC higher intensity and brighter 25-ns bunch spaced beams. To mitigate the Electron Multipacting (E.M.) phenomenon, a well-known limiting factor for high-intensity positively charged beams, CERN developed carbon coatings with a low Secondary Electron Yield (SEY). During the 2016 & 2017 year-end technical stops, such coatings were deposited on the inner wall of the vacuum chambers of some SPS quadrupole and dipole magnets by a dedicated in-situ setup. A much larger scale deployment was implemented during the Long Shutdown 2 (2019-2020) to coat all beam pipes of focussing quadrupoles (QF) and their adjacent short straight sections. In this contribution, we remind the motivation of the project, and present the results and the quality control of the carbon coating campaign during the latter phase of implementation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB338
About •	paper received ※ 19 May 2021 paper accepted ※ 16 June 2021 issue date ※ 13 August 2021
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WEPAB381	Multipactor Simulations for MYRRHA Spoke Cavity: Comparison Between SPARK3D, MUSICC3D, CST PIC and Measurement	electron, simulation, cavity, niobium	3606
	N. Hu, M. Chabot, J.-L. Coacolo, D. Longuevergne, G. Olry Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France M.B. Belhaj ONERA, Toulouse, France
	The multipactor effect can lead to thermal breakdown (quench), high field emission and limited accelerating gradient in superconducting accelerator devices. To determine the multipactor breakdown power level, multipactor simulations can be performed. The objective of this study is to compare the results given by different simulation codes with the results of vertical testing of SRF cavities. In this paper, Spark3D, MUSICC3D and CST Studio PIC solver have been used to simulate the multipactor effect in Spoke cavity developed within the framework of MYRRHA project. Then, a benchmark of these three simulation codes has been made. The breakdown power level, the multipactor order and the most prominent location of multipactor are presented. Finally, the simulation results are compared with the measurements done during the vertical tests.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB381
About •	paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 25 August 2021
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WEPAB396	First Measurements on Multipactor Study	electron, vacuum, simulation, ECR	3633
	Y. Gómez Martínez, J. Angot, M.A. Baylac, T. Cabanel, P.-O. Dumont, N. Emeriaud, O. Zimmermann LPSC, Grenoble Cedex, France D. Longuevergne FLUO, Orsay, France G. Sattonnay Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
	Multipactor (MP) is an undesired phenomenon of resonant electron build up encountered on particle accelerators. It can induce anomalous thermal losses, higher than the Joule losses, inducing a decrease of the superconducting cavities quality factor, it can even lead to a cavity quench. On couplers, it can produce irreversible damages or generate a breakdown of their vacuum window. Multipactor may lead to Electron Cloud build up as well. The accelerator group at LPSC has developed a test bench dedicated to the multipactor studies. This paper presents the experimental set-up and its first measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB396
About •	paper received ※ 18 May 2021 paper accepted ※ 14 July 2021 issue date ※ 17 August 2021
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THPAB210	Extrapolated Range for Low Energy Electrons (< 1 keV)	electron, simulation, experiment, GUI	4201
	C. Inguimbert, M.B. Belhaj, Q. Gibaru ONERA, Toulouse, France Q. Gibaru, D. Lambert, M. Raine CEA, Arpajon, France Q. Gibaru CNES, PARIS, France
	Funding: ONERA- DPHY, 2 avenue E. Belin, 31055 Toulouse, France CEA, DAM, DIF, 91297 Arpajon, France CNES, 18 av. E. Belin, 31055 Toulouse, France The Secondary Electron Emission (SEE) process plays an important role in the performance of various devices. Mitigating the multipactor phenomenon that may occur in radio-frequency components is a concern in many fields such as space technologies or electron microscopy. SEE is also a concern in the accelerator physics community, where the beam lines stability can strongly be affected by this phenomenon,. In that scope, the escaped depth and thus the range of emitted electrons is of great interest. Our goal, by means of simulations is to provide a better knowledge of SEE. We have developed a Monte Carlo electron transport code for low energy electrons [~eV, ~10keV], that is part of the Dec. 2020 release of GEANT4*. It has been used to study the practical range of low energy electrons. Our goal is to formulate, below ~10 keV, an analytic range vs. energy expression, and to relate it to fundamental physcial parameters such as the mean free paths of electrons in matter. The goal is to provide simple practical extrapolated range formula that can help to understand SEE phenomenon. M. Mostajeran et al. J. of Instr. 5 (2010) C. Y. Vallgren et al. Phys. Rev. Accel. Beam 14 (2011) * Q. Gibaru et al. Nuc. Inst. And Met. 487 (2021)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB210
About •	paper received ※ 10 May 2021 paper accepted ※ 23 June 2021 issue date ※ 27 August 2021
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THPAB211	Monte Carlo Simulation of 3D Surface Morphologies for Secondary Electron Emission Reduction	electron, simulation, GUI, experiment	4204
	Q. Gibaru, M.B. Belhaj, C. Inguimbert ONERA, Toulouse, France Q. Gibaru, D. Lambert, M. Raine CEA, Arpajon, France Q. Gibaru CNES, PARIS, France
	Low energy electrons of few tens of eV may cause Multipactor breakdowns in waveguides driven by the Secondary Electron Emission Yield (SEY) of the walls. This risk is lowered by using low emissive surfaces and this topic has been studied experimentally and with numerical simulations. The dependence of the SEY on surface properties is well known. Surface morphology has been widely used to reduce the SEY by forming roughness patterns on the surface. All patterns do not have the same efficiency so their analysis in terms of SEY is relevant. Monte-Carlo simulation codes can be used to study the processes behind the SEY. The MicroElec module of GEANT4 has recently been extended with more materials and processes and validated with experimental data for SEY calculations. In this work, simulation results are shown for a bulk sample capped with different roughness patterns. The effects of the shape parameters on the SEY are studied for typical dimensions between 20 µm and 100 µm. The results are checked with experimental SEY measurements on samples with similar roughness patterns. :T Gineste et al, Appl Surf Sci 359 (2015) 398-404 :J Pierron et al, J Appl Phys 124 (2018) 095101 *:Q. Gibaru, C. Inguimbert, P. Caron, M. Raine, D. Lambert, J. Puech, NIM B. 487 (2021) 66-77
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB211
About •	paper received ※ 12 May 2021 paper accepted ※ 23 June 2021 issue date ※ 17 August 2021
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THPAB341	TiN Metalizing and Coating for Multi-Megawatt RF Vacuum Windows	Windows, electron, vacuum, high-voltage	4457
	M.L. Neubauer, A. Dudas, R.P. Johnson Muons, Inc, Illinois, USA
	Coatings on microwave windows and high-voltage ceramics are required to eliminate secondary electron emission (SEE), which initiates multipactoring discharge causing local heating and ceramic failures due to cracking and loss of vacuum. The region surrounding the triple junction (ceramic+metal+vacuum) is the primary source of free electrons and in microwave windows and high-voltage ceramics. This region is located at the metalizing and braze joint of the ceramic support structure making the vacuum seal. On very large microwave windows typically at low frequencies, this critical region is difficult to coat by the traditional techniques of sputter coating anti-multipactoring titanium nitride or other materials. The novel processes proposed here include a means for applying and controlling the thickness of titanium nitride both in the metallizing (controlling the source) and on the surface of the window, eliminating SEE and the multipactoring discharge.
	Poster THPAB341 [0.845 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB341
About •	paper received ※ 23 May 2021 paper accepted ※ 21 July 2021 issue date ※ 01 September 2021
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Paper

Title

Other Keywords

Page

MOPAB247

Multipacting Studies for the JAEA-ADS Five-Cell Elliptical Superconducting RF Cavities

cavity, electron, SRF, simulation

793

B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan
E. Cicek
KEK, Ibaraki, Japan

The Five-cell Elliptical Superconducting Radio-Frequency Cavities (SRFC) provide the final acceleration in the JAEA-ADS linac (from 208 MeV to 1.5 GeV); thus, their performance is essential for the success of the JAEA-ADS project. After their optimization of the cavity geometry to achieve a high acceleration gradient with lower electromagnetic peaks, the next step in the R&D strategy is the accurate estimation of beam-cavity effects which can affect the performance of the cavities. To this end, multipacting studies were developed to investigate its effect in the cavity operation regimen and find countermeasures. The results of this study will help in the development of the SRFC models and in the consolidation of the JAEA-ADS project.

Poster MOPAB247 [0.599 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB247

About •

paper received ※ 10 May 2021 paper accepted ※ 07 June 2021 issue date ※ 28 August 2021

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MOPAB336

Multipacting Analysis of Warm Linac RF Vacuum Windows

simulation, vacuum, GUI, Windows

1044

G.D. Toby, Y.W. Kang, S.-H. Kim, S.W. Lee, J.S. Moss
ORNL, Oak Ridge, Tennessee, USA

Funding: * This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC05-00OR22725.
Multipacting in accelerating structures is a complex phenomenon with which there is much to be understood. While multipacting research efforts have primarily been focused on superconducting radio frequency (SRF) systems, normal conducting accelerating structures that have a higher thermal capacity and a greater vacuum pressure tolerance could benefit from additional investigation. This research details multipacting simulation methods and the results of 3-D electromagnetic simulations of RF vacuum windows used on normal conducting linac (NCL) cavities. Possible techniques for reducing and eliminating multipacting activities in these structures are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB336

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paper received ※ 17 May 2021 paper accepted ※ 28 May 2021 issue date ※ 29 August 2021

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MOPAB352

High Power Test of a Dielectric Disk Loaded Accelerator for a Two Beam Wakefield Accelerator

wakefield, acceleration, impedance, linear-collider

1096

B.T. Freemire, C.-J. Jing, S. Poddar
Euclid Beamlabs, Bolingbrook, USA
M.E. Conde, D.S. Doran, G. Ha, W. Liu, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
M.M. Peng
TUB, Beijing, People’s Republic of China
E.E. Wisniewski
Illinois Institute of Technology, Chicago, Illinois, USA
Y. Zhao
Euclid TechLabs, Solon, Ohio, USA

Funding: Small Business Innovation Research Contract No. DE-SC0019864 U.S. DOE Office of Science Contract No. DE-AC02-06CH11357
As part of the Argonne 500 MeV short pulse Two Beam Wakefield Acceleration Demonstrator, a single cell X-band dielectric disk loaded accelerator (DDA) has been designed, fabricated, and tested at high power at the Argonne Wakefield Accelerator. The DDA should provide a short pulse (~20 ns) high gradient (>300 MV/m) accelerator while maintaining a reasonable r/Q and high group velocity. This will allow a significantly larger RF-to-beam efficiency than is currently possible for conventional accelerating structures. A low loss barium titantate ceramic, µ_r = 50, was selected, and a low temperature brazing alloy chosen to preserve the dielectric properties of the ceramic during brazing. High power testing produced breakdown at the triple junction, resulting from the braze joint design. No evidence of breakdown was observed on the iris of the disk, indicating that the maximum surface electric field on the dielectric was not reached. An improved braze joint has been designed and is in production, with high power testing to follow.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB352

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paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 21 August 2021

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MOPAB361

Threshold in Filling Failure of RF Cavity Caused by Beam Loading in Multipactor

cavity, simulation, electron, experiment

1122

J. Pang
USTC/NSRL, Hefei, Anhui, People’s Republic of China
Y. Dong
Institute of Applied Physics and Computational Mathematics, People’s Republic of China
Y. Du
Institute of Fluid Physics,, China Academy of Engineering Physics, Mianyang, People’s Republic of China

Funding: NSFC
A pulsed RF cavity would be heavily detuned caused by beam loading of multipactor current in the RF filling process. Multipactor zone would be expended by several times than that in static states with assumptions of fixed voltage and no beam loading. The dynamic of multipactor in the RF filling process was simulated by coupling with parameters of external circuit with the developed simulation code, and test in experiments with a parallel-plate resonator. Threshold of RF voltage, which means the lower boundary of peak voltage of multipactor zone, had been quantified with different cavity parameters. When we increased the gap length, the measured threshold became larger due to the ionization in background gas. Then the secondary emission factor would be increased in simulation for consistence with the experiment results. Additionally, some multipactor phenomenon could not be predicted precisely because the simulation code did not take account of ionization. The hysteresis of phase and energy of ionization electrons would be a new driving factor for the growth of multipactor in certain conditions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB361

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paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 10 August 2021

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TUPAB035

ESS Medium Beta Cavities Status at INFN LASA

cavity, SRF, linac, controls

1420

D. Sertore, M. Bertucci, M. Bonezzi, A. Bosotti, A. D’Ambros, A.T. Grimaldi, P. Michelato, L. Monaco, R. Paparella
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

INFN Milano contributes in-kind to the ESS ERIC Superconducting Linac supplying 36 cavities for the Medium Beta section of the proton accelerator. The production has reached completion, being all the cavities mechanical fabricated, BCP treated and, for most of them, also qualified with vertical test at cold. In this paper, we report on the results and lessons learnt and the actions taken both for quality control managing and recovery of the few cavities that did not reach the project goal after the first qualification test.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB035

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 18 August 2021

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TUPAB166

A New Design of a Dressed Balloon Cavity with Superior Mechanical Properties

cavity, SRF, linac, software

1769

R.A. Kostin, C. Jing, S. Ross
Euclid Beamlabs, Bolingbrook, USA
I.V. Gonin, T.N. Khabiboulline, G.V. Romanov, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
M.P. Kelly
ANL, Lemont, Illinois, USA
R.E. Laxdal
TRIUMF, Vancouver, Canada

Funding: Work supported by the SBIR program of the U.S. Department of Energy, under grant DE-SC0020781
Superconducting spoke cavities are prone to multipactor - resonant raise of a number of electrons due to secondary emission. Recently proposed and tested by TRIUMF balloon-type spoke cavity showed an outstanding multipactor (MP) suppression property but unfortunately serious Q degradation at high fields. A new fully developed design of a dressed balloon cavity which can be used for any proton linac SSR2 section is developed. The design incorporates additional EP ports for high Q-factor demonstration. Superior properties are demonstrated, such as effective multipactor suppression, 40% lower Lorentz force coefficient, zero sensitivity to external pressure. This paper presents the results of coupled structural Multiphysics analysis, and engineering design of the dressed balloon cavity with EP ports.

Poster TUPAB166 [1.394 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB166

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paper received ※ 15 May 2021 paper accepted ※ 21 June 2021 issue date ※ 01 September 2021

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TUPAB339

High Power Test of the Antenna Adjustable Power Coupler for 325 MHz Superconducting Cavities

cavity, vacuum, electron, pick-up

2286

J.Y. Yoon, E.-S. Kim, C.S. Park, S.H. Park
KUS, Sejong, Republic of Korea
J. Bahng
Korea University Sejong Campus, Sejong, Republic of Korea
E. Kako
KEK, Ibaraki, Japan
K.R. Kim
PAL, Pohang, Republic of Korea

Funding: The Ministry of Education (South Korea)
The power coupler is development at Korea University for a Single Spoke Resonator (SSR) of heavy ion accelerator. Our power coupler is a coaxial capacitive type based on a conventional 3-1/8 inch electronic industries alliance (EIA) 50 Ω coaxial transmission line with a titanium nitride (TiN) coated single ceramic window. A high power test is rectangular test cavity with high vacuum and various measuring equipment, such as an arc detector, a power meter, and an electron pick-up probe. The interlock system under vacuum and arc instrumentations prevent the RF window from breaking the power coupler window during the high power test. We conduct high power tests for more than 12 hrs at 12 kW in a 325 MHz continous wave (CW) mode to verify the performance of the designed power coupler.
*Superconducting, *Power Coupler

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB339

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paper received ※ 12 May 2021 paper accepted ※ 21 June 2021 issue date ※ 24 August 2021

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TUPAB342

Preliminary Cryogenic Cold Test Results of the First 9-Cell LSF Shape Cavity

cavity, niobium, SRF, laser

2296

R.L. Geng, W.A. Clemens, R.S. Williams
JLab, Newport News, Virginia, USA
S.A. Belomestnykh
Fermilab, Batavia, Illinois, USA
Y. Fuwa
JAEA/J-PARC, Tokai-mura, Japan
H. Hayano
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
Z. Li
SLAC, Menlo Park, California, USA
V.D. Shemelin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Supplemental support by US-Japan Collaboration on HEP.
Following successful prototyping and testing of single- & 5-cell LSF shape cavities *, **, the first 9-cell LSF shape cavity LSF9-1 was successfully constructed using an innovative process at JLab with the in-house facilities. The cavity was then shipped to KEK for post-fabrication mechanical adjustment and ILC TDR style treatment and surface processing. Cold testing was carried out at the JLab VTA facility, instrumented with a suite of Kyoto instruments. Favorable values for the bath pressure detuning sensitivity and Lorentz force detuning coefficient were experimentally measured, validating the design improvement in cell stiffeners. Pass-band measurements indicate 4 out of 9 cells reaching gradient capability of > 45 MV/m, including 2 cells reaching 51 MV/m. Cornell OST detectors identified the cell and location responsible for the current hard quench limit. Multipacting-like barriers observed in end cells are investigated both analytically and numerically. The cavity was shipped to FNAL and received a light EP at the joint ANL/FNAL facility for further cold testing at Jlab. Two new 9-cell LSF cavities are being constructed including one made of large-grain niobium material.
* R. L. Geng et al.,WEPWI013, IPAC15.
** R. L. Geng et al., MOP064, SRF’19.

Poster TUPAB342 [1.600 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB342

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paper received ※ 09 May 2021 paper accepted ※ 14 June 2021 issue date ※ 20 August 2021

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TUPAB343

Final Design Studies for the VSR DEMO 1.5 GHz Coupler

SRF, operation, cavity, electron

2300

E. Sharples-Milne, V. Dürr, P. Echevarria, J. Knobloch, A. Neumann, A.V. Vélez
HZB, Berlin, Germany

With the 1.5 GHz couplers for the Variable pulse length Storage Ring (VSR) DEMO now in the manufacturing stages, the studies that led to the final coupler design will be presented. The system specific constraints and design modifications that combat the challenges of thermomechanical stresses, higher order mode (HOM) propagation and dimensional constraints are explored. This includes S-Parameter analysis, an in-depth study of the coupling factor, and multipacting studies for the average (1.5 kW) and peak (16 kW) power.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB343

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 14 August 2021

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TUPAB355

Design and Implementation of a Production Model Bias Tee

high-voltage, MMI, cavity, linac

2339

T.L. Larter, E. Gutierrez, S.H. Kim, D.G. Morris, J.T. Popielarski, T. Xu, S. Zhao
FRIB, East Lansing, Michigan, USA

Funding: This work is supported by the US Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.
The Facility for Rare Isotope Beams (FRIB) includes two types of half wave SC resonators (HWR) operating at 322MHz. The fundamental power couplers used to transmit RF power into the HWRs commonly suffer from multipacting which can result in long conditioning times. A bias tee can be used to apply a high voltage to the couplers to help alleviate multipacting. A production version of the bias tee was commissioned for use at FRIB. The bias tee went through several design revisions to diagnose and correct thermal dissipation issues. This paper will discuss details of design and challenges faced during production validation of the bias tee.

Poster TUPAB355 [0.630 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB355

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paper received ※ 19 May 2021 paper accepted ※ 28 May 2021 issue date ※ 12 August 2021

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WEPAB148

RF Design of an X-Band TM02 Mode Cavity for Field Emitter Testing

cavity, electron, coupling, insertion

2961

Z. Li, S.G. Tantawi
SLAC, Menlo Park, California, USA
S.V. Baryshev, T. Posos, M.E. Schneider
Michigan State University, East Lansing, Michigan, USA

Funding: Work at SLAC was supported by DOE under contract No. DE-AC02-76SF00515. Work at MSU was supported by DOE under Award No. DE-SC0020429 and under Cooperative Agreement Award No. DE-SC0018362.
Planar polycrystalline synthetic diamond with nitrogen-doping/incorporation was found to be a remarkable field emitter. It is capable of generating a high charge beam and handling moderate vacuum conditions. Integrating it with an efficient RF cavity could therefore provide a compact electron source for RF injectors. Understanding the performance metrics of the emitter in RF fields is essential toward developing such a device. We investigated a test setup of the field emitter at the X-band frequency. The setup included an X-band cavity operating at the TM02 mode. The field emitter material will be plated on the tip of a insertion rod on the cavity back plate. Part of the back plate and the emitter rod are demountable, allowing for exchange of the field emitters. The TM02 mode was chosen such that the design of the demountable back plate does not induce field enhancement at the installation gap. The cavity were optimized to achieve a high surface field at the emitter tip and a maximum energy gain of the emitted electrons at a given input power. We will present the RF and mechanical design of such a TM02 X-band cavity for field emitter testing.

Poster WEPAB148 [1.642 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB148

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paper received ※ 14 May 2021 paper accepted ※ 12 July 2021 issue date ※ 12 August 2021

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WEPAB195

Design and Optimization of a Low Frequency RF-Input Coupler for the IsoDAR RFQ

rfq, coupling, simulation, cyclotron

3081

M.P. Sangroula, J.M. Conrad, D. Winklehner
MIT, Cambridge, Massachusetts, USA
M. Schuett
BEVATECH, Frankfurt, Germany

Funding: The RFQ-DIP project is supported by National Science Foundation grant \# PHY-1626069 and the Heising-Simons Foundation.
The Isotope Decay-At-Rest experiment (IsoDAR) is a proposed underground experiment which is expected to be a definitive search for sterile neutrinos. IsoDAR uses an especially designed low-frequency spilt-coaxial radio frequency quadrupole (RFQ) to accelerate H²⁺ ions directly from the ion source into the main cyclotron accelerator. This paper mainly focuses on the design and optimization of a low frequency (32.8 MHz) RF-input coupler for the IsoDAR RFQ. Starting with a basic design, we determine its appropriate position for this coupler in the RFQ. Finally, we optimized the design to lower the input power without compromising the coupling efficiency.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB195

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paper received ※ 21 May 2021 paper accepted ※ 30 June 2021 issue date ※ 29 August 2021

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WEPAB338

Amorphous Carbon Coating in SPS

vacuum, electron, target, operation

3475

W. Vollenberg, P. Chiggiato, P. Costa Pinto, P. Cruikshank, H. Moreno, C. Pasquino, J. Perez Espinos, M. Taborelli
CERN, Meyrin, Switzerland

Within the LHC Injector Upgrade (LIU) project, the Super Proton Synchrotron (SPS) needs to be upgraded to inject into the LHC higher intensity and brighter 25-ns bunch spaced beams. To mitigate the Electron Multipacting (E.M.) phenomenon, a well-known limiting factor for high-intensity positively charged beams, CERN developed carbon coatings with a low Secondary Electron Yield (SEY). During the 2016 & 2017 year-end technical stops, such coatings were deposited on the inner wall of the vacuum chambers of some SPS quadrupole and dipole magnets by a dedicated in-situ setup. A much larger scale deployment was implemented during the Long Shutdown 2 (2019-2020) to coat all beam pipes of focussing quadrupoles (QF) and their adjacent short straight sections. In this contribution, we remind the motivation of the project, and present the results and the quality control of the carbon coating campaign during the latter phase of implementation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB338

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paper received ※ 19 May 2021 paper accepted ※ 16 June 2021 issue date ※ 13 August 2021

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WEPAB381

Multipactor Simulations for MYRRHA Spoke Cavity: Comparison Between SPARK3D, MUSICC3D, CST PIC and Measurement

electron, simulation, cavity, niobium

3606

N. Hu, M. Chabot, J.-L. Coacolo, D. Longuevergne, G. Olry
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
M.B. Belhaj
ONERA, Toulouse, France

The multipactor effect can lead to thermal breakdown (quench), high field emission and limited accelerating gradient in superconducting accelerator devices. To determine the multipactor breakdown power level, multipactor simulations can be performed. The objective of this study is to compare the results given by different simulation codes with the results of vertical testing of SRF cavities. In this paper, Spark3D, MUSICC3D and CST Studio PIC solver have been used to simulate the multipactor effect in Spoke cavity developed within the framework of MYRRHA project. Then, a benchmark of these three simulation codes has been made. The breakdown power level, the multipactor order and the most prominent location of multipactor are presented. Finally, the simulation results are compared with the measurements done during the vertical tests.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB381

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 25 August 2021

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WEPAB396

First Measurements on Multipactor Study

electron, vacuum, simulation, ECR

3633

Y. Gómez Martínez, J. Angot, M.A. Baylac, T. Cabanel, P.-O. Dumont, N. Emeriaud, O. Zimmermann
LPSC, Grenoble Cedex, France
D. Longuevergne
FLUO, Orsay, France
G. Sattonnay
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

Multipactor (MP) is an undesired phenomenon of resonant electron build up encountered on particle accelerators. It can induce anomalous thermal losses, higher than the Joule losses, inducing a decrease of the superconducting cavities quality factor, it can even lead to a cavity quench. On couplers, it can produce irreversible damages or generate a breakdown of their vacuum window. Multipactor may lead to Electron Cloud build up as well. The accelerator group at LPSC has developed a test bench dedicated to the multipactor studies. This paper presents the experimental set-up and its first measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB396

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paper received ※ 18 May 2021 paper accepted ※ 14 July 2021 issue date ※ 17 August 2021

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THPAB210

Extrapolated Range for Low Energy Electrons (< 1 keV)

electron, simulation, experiment, GUI

4201

C. Inguimbert, M.B. Belhaj, Q. Gibaru
ONERA, Toulouse, France
Q. Gibaru, D. Lambert, M. Raine
CEA, Arpajon, France
Q. Gibaru
CNES, PARIS, France

Funding: ONERA- DPHY, 2 avenue E. Belin, 31055 Toulouse, France CEA, DAM, DIF, 91297 Arpajon, France CNES, 18 av. E. Belin, 31055 Toulouse, France
The Secondary Electron Emission (SEE) process plays an important role in the performance of various devices. Mitigating the multipactor phenomenon that may occur in radio-frequency components is a concern in many fields such as space technologies or electron microscopy. SEE is also a concern in the accelerator physics community, where the beam lines stability can strongly be affected by this phenomenon*,**. In that scope, the escaped depth and thus the range of emitted electrons is of great interest. Our goal, by means of simulations is to provide a better knowledge of SEE. We have developed a Monte Carlo electron transport code for low energy electrons [~eV, ~10keV], that is part of the Dec. 2020 release of GEANT4***. It has been used to study the practical range of low energy electrons. Our goal is to formulate, below ~10 keV, an analytic range vs. energy expression, and to relate it to fundamental physcial parameters such as the mean free paths of electrons in matter. The goal is to provide simple practical extrapolated range formula that can help to understand SEE phenomenon.
* M. Mostajeran et al. J. of Instr. 5 (2010)
** C. Y. Vallgren et al. Phys. Rev. Accel. Beam 14 (2011)
*** Q. Gibaru et al. Nuc. Inst. And Met. 487 (2021)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB210

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paper received ※ 10 May 2021 paper accepted ※ 23 June 2021 issue date ※ 27 August 2021

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THPAB211

Monte Carlo Simulation of 3D Surface Morphologies for Secondary Electron Emission Reduction

electron, simulation, GUI, experiment

4204

Q. Gibaru, M.B. Belhaj, C. Inguimbert
ONERA, Toulouse, France
Q. Gibaru, D. Lambert, M. Raine
CEA, Arpajon, France
Q. Gibaru
CNES, PARIS, France

Low energy electrons of few tens of eV may cause Multipactor breakdowns in waveguides driven by the Secondary Electron Emission Yield (SEY) of the walls. This risk is lowered by using low emissive surfaces and this topic has been studied experimentally and with numerical simulations. The dependence of the SEY on surface properties is well known*. Surface morphology has been widely used to reduce the SEY by forming roughness patterns on the surface**. All patterns do not have the same efficiency so their analysis in terms of SEY is relevant. Monte-Carlo simulation codes can be used to study the processes behind the SEY. The MicroElec module of GEANT4 has recently been extended with more materials and processes and validated with experimental data for SEY calculations**. In this work, simulation results are shown for a bulk sample capped with different roughness patterns. The effects of the shape parameters on the SEY are studied for typical dimensions between 20 µm and 100 µm. The results are checked with experimental SEY measurements on samples with similar roughness patterns.
*:T Gineste et al, Appl Surf Sci 359 (2015) 398-404
**:J Pierron et al, J Appl Phys 124 (2018) 095101
***:Q. Gibaru, C. Inguimbert, P. Caron, M. Raine, D. Lambert, J. Puech, NIM B. 487 (2021) 66-77

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB211

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paper received ※ 12 May 2021 paper accepted ※ 23 June 2021 issue date ※ 17 August 2021

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THPAB341

TiN Metalizing and Coating for Multi-Megawatt RF Vacuum Windows

Windows, electron, vacuum, high-voltage

4457

M.L. Neubauer, A. Dudas, R.P. Johnson
Muons, Inc, Illinois, USA

Coatings on microwave windows and high-voltage ceramics are required to eliminate secondary electron emission (SEE), which initiates multipactoring discharge causing local heating and ceramic failures due to cracking and loss of vacuum. The region surrounding the triple junction (ceramic+metal+vacuum) is the primary source of free electrons and in microwave windows and high-voltage ceramics. This region is located at the metalizing and braze joint of the ceramic support structure making the vacuum seal. On very large microwave windows typically at low frequencies, this critical region is difficult to coat by the traditional techniques of sputter coating anti-multipactoring titanium nitride or other materials. The novel processes proposed here include a means for applying and controlling the thickness of titanium nitride both in the metallizing (controlling the source) and on the surface of the window, eliminating SEE and the multipactoring discharge.

Poster THPAB341 [0.845 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB341

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paper received ※ 23 May 2021 paper accepted ※ 21 July 2021 issue date ※ 01 September 2021

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