IPAC2021 - List of Keywords (SRF)

Paper	Title	Other Keywords	Page
MOXA01	Commissioning and Restart of ESRF-EBS	injection, lattice, storage-ring, MMI	1
	S.M. White, N. Carmignani, L.R. Carver, J. Chavanne, L. Farvacque, L. Hardy, J. Jacob, G. Le Bec, S.M. Liuzzo, T.P. Perron, Q. Qin, P. Raimondi, J.-L. Revol, K.B. Scheidt ESRF, Grenoble, France
	The ESRF operates a 6 GeV 4th generation light source, the ESRF-EBS. This storage ring is the first to implement the Hybrid Multi-Bend Achromat lattice (HMBA). The HMBA lattice provides a reduction of the horizontal emittance of approximately a factor 30 with respect to the former Double Bend Achromat (DBA) structure, considerably improving the brilliance and transverse coherence of the ESRF accelerator complex while maintaining large horizontal acceptance and excellent lifetime performance. In this report, the characteristics of the HMBA lattice will be reviewed and the beam commissioning results and first operation experience of the new ESRF storage ring will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXA01
About •	paper received ※ 11 May 2021 paper accepted ※ 21 August 2021 issue date ※ 31 August 2021
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MOPAB021	A Dispersive Quadrupole Scan Technique for Transverse Beam Characterization	quadrupole, emittance, optics, booster	107
	J. Kallestrup, M. Aiba PSI, Villigen PSI, Switzerland N. Carmignani, T.P. Perron ESRF, Grenoble, France
	Quadrupole scans are one of the standard techniques to characterize the transverse beam properties in transfer lines or linacs. However, in the presence of dispersion the usage of regular quadrupole scans will lead to erroneous estimates of the beam parameters. The standard solution to this problem is to measure the dispersion and then subtract it in the post-analysis of the quadrupole scan measurements assuming the design energy spread. Here we show that the dispersive contribution to the beam size can be included in the quadrupole scan procedure, forming a linear system of equations that can be solved to obtain both the betatronic and dispersive beam parameters. The method is tested at both the SLS and ESRF booster-to-ring transfer lines leading to reasonable estimates of the beam parameters.
	Poster MOPAB021 [0.447 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB021
About •	paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 02 September 2021
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MOPAB051	Operation of the ESRF Booster with the New EBS Storage Ring	emittance, booster, injection, operation	221
	N. Carmignani, L.R. Carver, S.M. Liuzzo, T.P. Perron, S.M. White ESRF, Grenoble, France
	The Extremely Brilliant Source (EBS) has replaced the old ESRF Storage Ring (SR) during the 2019 one-year shutdown. The injector chain, composed of a Linac, a booster synchrotron, and two transfer lines, was not replaced. Nevertheless, some major hardware upgrades were anticipated prior to the long shutdown to ensure its long-term reliability. The shutdown interventions focused on reducing the machine circumference to cope with the new RF frequency of the SR. The status of the upgraded booster will be presented with a focus on the strategy used to lower horizontal emittance especially via emittance exchange.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB051
About •	paper received ※ 14 May 2021 paper accepted ※ 28 May 2021 issue date ※ 10 August 2021
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MOPAB108	ESRF-EBS 352.37 MHz Radio Frequency System	cavity, operation, MMI, HOM	395
	J. Jacob, P.B. Borowiec, A. D’Elia, G. Gautier, V. Serrière ESRF, Grenoble, France
	The ESRF 352 MHz Radio Frequency (RF) system has been upgraded and tailored to the new 4th Generation Extremely Brilliant Source EBS, that was installed in 2019 and commissioned in 2020. The five former five-cell cavities were replaced with 13 single cell strongly HOM damped cavities that were developed in house, 10 of which are powered from existing 1 MW klystron transmitters. The remaining three cavities are individually fed by three 150 kW solid state amplifiers. All this required a reconstruction in record time of an elaborate WR2300 waveguide network. The low level RF system as well as the cavity and transmitter control system have been rebuilt. The RF design, commissioning and operation experience will be reported, including plans for a 4th harmonic RF system for bunch lengthening to further improve the performance of the new EBS ring.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB108
About •	paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 28 August 2021
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MOPAB112	A Modified Hybrid 6BA Lattice for the HALF Storage Ring	lattice, emittance, damping, storage-ring	407
	Z.H. Bai, G.Y. Feng, T.L. He, W. Li, W.W. Li, G. Liu, Z.L. Ren, L. Wang, P.H. Yang, S.C. Zhang, T. Zhang USTC/NSRL, Hefei, Anhui, People’s Republic of China
	In this paper, we propose a modified hybrid 6BA lattice as the baseline lattice of the Hefei Advanced Light Facility (HALF) storage ring. Similar to the Diamond-II lattice, the proposed lattice cell has one long straight section and one mid-straight section; but the two bend units adjacent to the mid-straight are LGB/RB units (LGB: longitudinal gradient bend, RB: reverse bend), which can give both lower emittance and shorter damping times. The designed HALF storage ring, with an energy of 2.2 GeV and 20 lattice cells, has a natural emittance of about 85 pm·rad.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB112
About •	paper received ※ 15 May 2021 paper accepted ※ 20 May 2021 issue date ※ 28 August 2021
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MOPAB116	A Flexible Injection Scheme for the ESRF-EBS	injection, kicker, septum, storage-ring	421
	S.M. White, N. Carmignani, L.R. Carver, M. Dubrulle, L. Hoummi, S.M. Liuzzo, M. Morati, T.P. Perron ESRF, Grenoble, France
	The ESRF-EBS storage ring light source started commissioning in 2019 and successfully resumed users operation in 2020. Due to the smaller emittance and consequently reduced lifetime frequent injections are required that can potentially disturb beam lines experiments. In addition, operating the machine with low beta straight section and reduced insertion devices (ID) gaps are considered, therefore reducing the vertical aperture of the machine. Alternatives to the standard off-axis injection scheme allowing for efficient injection in reduced apertures with minimized perturbations are explored. A flexible layout for potential integration in the ESRF-EBS lattice is proposed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB116
About •	paper received ※ 11 May 2021 paper accepted ※ 27 May 2021 issue date ※ 12 August 2021
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MOPAB117	Single Bunch Collective Effects in the EBS Storage Ring	impedance, simulation, synchrotron, vacuum	425
	L.R. Carver, E. Buratin, N. Carmignani, F. Ewald, L. Hoummi, S.M. Liuzzo, T.P. Perron, B. Roche, S.M. White ESRF, Grenoble, France
	The ESRF storage ring (SR) has been dismantled and replaced by the Extremely Brilliant Source (EBS) which has now been commissioned. Beam based measurements have been performed to characterise the impedance of the new machine and to make a first comparison with predictions. The results from instability threshold scans and tune shift measurements will be presented, as well as bunch length and position variation with current and microwave threshold measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB117
About •	paper received ※ 11 May 2021 paper accepted ※ 31 May 2021 issue date ※ 25 August 2021
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MOPAB224	Optimization and Error Studies for the USSR HMBA Lattice	lattice, injection, booster, dynamic-aperture	730
	L. Hoummi, N. Carmignani, L.R. Carver, S.M. Liuzzo, T.P. Perron, S.M. White ESRF, Grenoble, France I.A. Ashanin, S.M. Polozov MEPhI, Moscow, Russia T. Kulevoy ITEP, Moscow, Russia T. Kulevoy NRC, Moscow, Russia
	Several new accelerator facilities will be built in Russia in the next few years. One of those facilities is a 6 GeV storage ring (SR) light source, the Ultimate Source of Synchrotron Radiation (USSR) to be built in Protvino, near Moscow. The Cremlin+ project aims to incorporate in this activity the best experience of European Accelerator Laboratories. The optimization of such optics including realistic errors and a commissioning-like sequence of corrections, using Multi-Objective Genetic Algorithms (NSGA-II) is presented. Several corrections schemes are also tested.
	Poster MOPAB224 [1.164 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB224
About •	paper received ※ 12 May 2021 paper accepted ※ 01 June 2021 issue date ※ 17 August 2021
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MOPAB247	Multipacting Studies for the JAEA-ADS Five-Cell Elliptical Superconducting RF Cavities	multipactoring, cavity, electron, 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 ※ 02 September 2021
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MOPAB290	Machine Learning-Based LLRF and Resonance Control of Superconducting Cavities	cavity, controls, LLRF, simulation	920
	J.A. Diaz Cruz, S. Biedron, M. Martínez-Ramón UNM-ECE, Albuquerque, USA J.A. Diaz Cruz SLAC, Menlo Park, California, USA R. Pirayesh UNM-ME, Albuquerque, New Mexico, USA S. Sosa ODU, Norfolk, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under award number DE-SC0019468. Superconducting radio frequency (SRF) cavities with high loaded quality factors that operate in continuous wave (CW) and low beam loading are sensitive to microphonics-induced detuning. Cavity detuning can result in an increase of operational power and/or in a cavity quench. Such SRF cavities have bandwidths on the order of 10 Hz and detuning requirements can be as tight as 10 Hz. Passive methods to mitigate vibration sources and their impact in the cryomodule/cavity environment are widely used. Active resonance control techniques that use stepper motors and piezoelectric actuators to tune the cavity resonance frequency by compensating for microphonics detuning have been investigated. These control techniques could be further improved by applying Machine Learning (ML), which has shown promising results in other particle accelerator control systems. In this paper, we describe a Low-level RF (LLRF) and resonance control system based on ML methods that optimally and adaptively tunes the control parameters. We present simulations and test results obtained using a low power test bench with a cavity emulator.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB290
About •	paper received ※ 03 June 2021 paper accepted ※ 11 June 2021 issue date ※ 27 August 2021
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MOPAB332	Design of 4th Harmonic RF Cavities for ESRF-EBS	HOM, cavity, impedance, coupling	1031
	A. D’Elia, J. Jacob, V. Serrière, X.W. Zhu ESRF, Grenoble, France
	Funding: European Union’s Horizon 2020 research and innovation program under grant #871072 An active 4th harmonic RF system for bunch lengthening is under study at the ESRF to improve the performance of the new EBS storage ring, mainly for few bunch operation with high currents per bunch, by reducing Touschek and intrabeam scattering, thereby increasing the lifetime and limiting the emittance growth. It will also reduce impedance heating of the vacuum chambers. The 4th Harmonic 1.41 GHz normal conducting cavity design takes inspiration from the KEK idea of using a TM020 mode exhibiting a reduced R/Q but a higher unloaded Q with respect to TM010. We propose to use multicell cavities for their compactness, the reduced number of required ancillaries and the ease of control for a reduced number of cavities. The drawback is the complexity of the model and the necessity to damp the lower order TM010 mode (LOM) as well as the higher order modes (HOM). The RF design of a 4th harmonic multicell damped cavity will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB332
About •	paper received ※ 19 May 2021 paper accepted ※ 17 August 2021 issue date ※ 18 August 2021
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MOPAB333	ESRF-EBS 352 MHz HOM Damped RF Cavities	cavity, impedance, HOM, MMI	1034
	A. D’Elia, J. Jacob, V. Serrière ESRF, Grenoble, France
	For the new ESRF-EBS Storage Ring (SR), HOM damped RF cavities were needed to cope with the reduced thresholds for Longitudinal Coupled Bunch Instabilities (LCBI). The 352 MHz cavities were designed at the ESRF based on an improved version of the 500 MHz EU/ALBA/BESSY structures. A short description of the cavity design will be presented as well as an overview of the fabrication, the preparation and the performance of 13 such cavities for the ESRF-EBS SR. A study of the impedance of a whole cavity equipped with its ancillaries (HOM absorbers, ion pump and tuner) will be presented. One of the three HOM absorbers, the smaller one on top of the cavity, was finally not installed on the machine. The reasons and a detailed analysis in terms of HOM impedances that justifies this choice will be reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB333
About •	paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 23 August 2021
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MOPAB347	High Power Coupler Conditioning for bERLinPro Energy Recovery Linac Injector	booster, cavity, vacuum, MMI	1080
	A. Neumann, W. Anders, 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. Helmholtz Zentrum Berlin is currently finalizing the construction of the demonstrator Energy Recovery Linac bERLinPro . The first part, which will be commissioned, will be the injector consisting of a superconducting RF (SRF) photo-injector (Gun) and a Booster module made up of three two cell SRF cavities. For the latter the 2.3 MeV beam from the gun needs to be accelerated to 6.5 MeV, whereas one Booster cavity will be operated in zero-crossing mode for bunch-shortening. Thus, for the final stage with a 100 mA beam, the twin power couplers of the Booster cavity need to deliver up to 120 kW in travelling continous wave (CW) mode at 1.3 GHz each. To achieve that, a dedicated coupler conditioning setup was installed and commissioned. Here, we will present the first conditioning results with the bERLinPro Booster fundamental power couplers in pulsed and CW regime. 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
	Poster MOPAB347 [3.256 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB347
About •	paper received ※ 18 May 2021 paper accepted ※ 08 June 2021 issue date ※ 23 August 2021
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MOPAB359	Operational Experience and Redesign of the Tuner without Spring Fingers for the LEReC Warm Cavity	cavity, operation, vacuum, electron	1116
	B.P. Xiao, J.M. Brennan, J.C. Brutus, K. Mernick, S. Polizzo, S.K. Seberg, F. Severino, K.S. Smith, 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. A folded coaxial tuner without spring fingers was designed for the Low Energy RHIC electron Cooler (LEReC) 2.1 GHz warm cavity. During RHIC run 2019, this tuner was found to cause cavity trips via different failure modes. After analyzing these failure modes, a new straight coaxial tuner without spring fingers was proposed and was installed. We show the operational experience of the new tuner in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB359
About •	paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 12 August 2021
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MOPAB376	Design and Fabrication of a Quadrupole Resonator for SRF R&D	cavity, quadrupole, niobium, radio-frequency	1158
	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 R. Monroy-Villa, D. Reschke, J.H. Thie DESY, Hamburg, Germany
	As Nb superconducting radio-frequency (SRF) cavities are now approaching the theoretical limits of the material, a variety of different surface treatments have been developed to further improve their performance; although no fully understood theory is yet available. Small superconducting samples are studied to characterize their material properties and their evolution under different surface treatments. To study the RF properties of such samples under realistic SRF conditions at low temperatures, a test cavity called quadrupole resonator (QPR) is currently being fabricated. In this work 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 under cavity-like conditions, i.e., at temperatures between 2K and 8 K, under magnetic fields up to 120mT 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 a status report on the current manufacturing process, will be presented.
	Poster MOPAB376 [1.119 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB376
About •	paper received ※ 26 May 2021 paper accepted ※ 09 June 2021 issue date ※ 23 August 2021
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MOPAB383	Pressure Test for Large Grain and Fine Grain Niobium Cavities	cavity, niobium, experiment, FEM	1173
	M. Yamanaka, T. Dohmae, H. Inoue, T. Saeki, K. Umemori, Y. Watanabe, K. Yoshida KEK, Ibaraki, Japan K. Enami Tsukuba University, Ibaraki, Japan
	The pressure test was performed using a fine grain (FG) and a large grain (LG) niobium cavities. The cavity is 1.3 GHz 3-cell TESLA-like shape. The cavity was housed in a steel vessel. Water is supplied into the vessel and the cavity outside is pressurized. The applying pressure and the natural frequency of cavity were measured during the pressure test. The FG and LG cavities were deformed greatly and the pressure dropped suddenly at 3.4 MPa and 1.6 MPa, respectively. The frequency shifted up to 3.4 MHz and 1.3 MHz, respectively. There was no leak after the pressure test, so the cavity did not rupture under above pressure. The result of the pressure at LG cavity is less half than that of the FG cavity. We calculated the stress distribution in the structure by applying outer water pressure using a FEM. The maximum stress at cell when above test pressure is applied, are 146 MPa in FG and 73 MPa in LG, respectively. These stresses are similar to tensile strength of niobium specimen measure by ourselves. The result of pressure tests agrees well with the calculation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB383
About •	paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 13 August 2021
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MOPAB384	Nb₃Sn Coating of Twin Axis Cavity for Accelerator Applications	cavity, linac, niobium, dipole	1175
	J.K. Tiskumara, S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA J.R. Delayen, H. Park, U. Pudasaini, C.E. Reece JLab, Newport News, Virginia, USA G.V. Eremeev Fermilab, Batavia, Illinois, USA
	Funding: Research supported by DOE Office of Science Accelerator Stewardship Program Award DE- SC0019399. Partially authored by Jefferson Science Associates under contract no. DEAC0506OR23177 A Superconducting twin axis cavity consisting of two identical beam pipes that can accelerate and decelerate beams within the same structure has been proposed for the Energy Recovery Linac (ERL) applications. There are two niobium twin axis cavities at JLab fabricated with the intention of later Nb₃Sn coating and now we are progressing to coat them using vapor diffusion method. Nb₃Sn is a potential alternate material for replacing Nb in SRF cavities for better performance and reducing operational costs. Because of advanced geometry, larger surface area, increased number of ports and hard to reach areas of the twin axis cavities, the usual coating approach developed for typical elliptical single-axis cavities must be evaluated and requires to be adjusted. In this contribution, we report the first results from the coating of a twin axis cavity and discuss current challenges with an outlook for the future.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB384
About •	paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 20 August 2021
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MOPAB385	An Overview of RF Systems for the EIC	cavity, electron, HOM, luminosity	1179
	R.A. Rimmer, J.P. Preble JLab, Newport News, Virginia, USA K.S. Smith, A. Zaltsman BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under DOE Contract No. DE-SC0012704, by Jefferson Science Associates under contract DE-SC0002769, and by SLAC under Contract No. DE-AC02-76SF00515. The Electron Ion Collider (EIC) to be constructed at Brookhaven National Laboratory in the USA will be a complex system of accelerators providing high luminosity, high polarization, variable center of mass energy collisions between electrons and protons or ions. To achieve this a variety of RF systems are required. They must provide for capture, formation and storage of Ampere-class beams in the electron and hadron storage rings (ESR and HSR), fast acceleration of high-charge polarized electron bunches in the rapid cycling synchrotron (RCS), provision of cold high current electron bunches in the high-energy cooler ERL and precise high-gradient crabbing of electrons and hadrons either side of the interaction point. The challenges include strong HOM damping in the storage ring cavities and cooler ERL, very high fundamental mode power in the ESR and cooler injector, extremely stable low-noise operation of the crab cavities, mitigation of transient beam loading from gaps, and operating over a wide range of energies and beam currents. We describe the high-level system parameters and principal design choices made and progress on the R&D plan to develop these state of the art systems.
	Poster MOPAB385 [1.268 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB385
About •	paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 22 August 2021
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MOPAB386	Development of Nitrogen-Doping Technology for SHINE	cavity, niobium, ECR, linac	1182
	Y. Zong, X. Huang, Z. Wang SINAP, Shanghai, People’s Republic of China J.F. Chen, H.T. Hou, D. Wang, J.N. Wu, Y.X. Zhang SARI-CAS, Pudong, Shanghai, People’s Republic of China P.C. Dong Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China Y.W. Huang ShanghaiTech University, Shanghai, People’s Republic of China J. Rong SSRF, Shanghai, People’s Republic of China
	The Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) is under construction, which needs six hundred 1.3GHz cavities with high quality factor. In this paper, we present the newest studies on single cell cavities with nitrogen doping and cold EP treatment, showing an obvious improvement compared with the previous results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB386
About •	paper received ※ 21 May 2021 paper accepted ※ 08 June 2021 issue date ※ 12 August 2021
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MOPAB388	Status of the High Power Couplers for ESS Elliptical Cavities	cavity, cryomodule, simulation, vacuum	1186
	C. Arcambal, P. Bosland, G. Devanz, T. Hamelin, C. Madec, C. Marchand, M. Oublaid, G. Perreu, C. Servouin, C. Simon CEA-IRFU, Gif-sur-Yvette, France M. Baudrier, C. Mayri, S. Regnaud, T.V. Vacher CEA-DRF-IRFU, France
	In the framework of the European Spallation Source (ESS), CEA Paris-Saclay is responsible for the delivery of 30 cryomodules (9 medium beta (β = 0.67) and 21 high beta (β = 0.86) ones). Each cryomodule contains 4 elliptical cavities equipped with a radio frequency power coupler. The ESS nominal pulse is 1.1 MW maximum peak power over a width of 3.6 ms at a repetition rate of 14 Hz. The design of the couplers for medium beta and for high beta cavities is the same, except a small difference of the antenna penetration to adjust the Q_ext. The mass production of the 120 couplers started and all the medium beta couplers have been conditioned at room temperature. The first cryomodules equipped with the power couplers were successfully tested at high RF power and with cavities at 2K reaching the ESS nominal pulse. The main issue at the start of the series production could be fixed and it was due to bad TiN coatings that caused abnormal dielectric losses in the window. Thus, this paper deals with the TiN coating defect, presents the conditioning procedure and gives a conditioning report of these 36 couplers.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB388
About •	paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 30 August 2021
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MOPAB391	Conduction Cooling Methods for Nb₃Sn SRF Cavities and Cryomodules	cavity, controls, accelerating-gradient, simulation	1192
	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
	Rapid progress in the performance of Nb₃Sn SRF cavities during the last few years has made Nb₃Sn 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 critical property enables the use of new, robust, turn-key style cryogenic cooling schemes based on conduction cooling with commercial 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 and the measured thermal dynamics match what is found in numerical simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB391
About •	paper received ※ 20 May 2021 paper accepted ※ 10 June 2021 issue date ※ 17 August 2021
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MOPAB394	Preliminary BCP Flow Field Investigation by CFD Simulations and PIV in a Transparent Model of a SRF Elliptical Low Beta Cavity	cavity, experiment, simulation, laser	1204
	A. D’Ambros, M. Bertucci, A. Bosotti, A.T. Grimaldi, P. Michelato, L. Monaco, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy F. Cozzi, G. Pianello Politecnico di Milano, Milano, Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	Standard vertical Buffered Chemical Polishing (BCP) is one of the main surface treatment for Superconducting Radiofrequency (SRF) cavities. A finite element Computational Fluid Dynamic (CFD) model has been developed. Uncertainties in the solution of fluid simulations are not negligible due to the complex geometry of a SRF cavity; thus without an experimental validation, results from this type of simulations cannot be confidently used to improve the process. To this aim, an experimental study was started to investigate the fluid dynamics of the BCP process by means of Particle Image Velocimetry (PIV) technique. Similitude on Reynolds number and Refractive Index Matching (RIM) technique were also implemented to replace the dangerous BCP mixture with a glycerine-water mixture. The paper describes the preliminary results from simulations and experiment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB394
About •	paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 14 August 2021
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MOPAB396	Measurements of Magnetic Field Penetration in Superconducting Materials for SRF Cavities	cavity, experiment, solenoid, accelerating-gradient	1208
	I.H. Senevirathne, J.R. Delayen, A.V. Gurevich ODU, Norfolk, Virginia, USA J.R. Delayen, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	Funding: This work is supported by NSF Grants PHY-1734075 and PHY-1416051, and DOE Award DE-SC0010081 and DE-SC0019399 Superconducting radiofrequency (SRF) cavities used in particle accelerators operate in the Meissner state. To achieve high accelerating gradients, the cavity material should stay in the Meissner state under high RF magnetic field without penetration of vortices through the cavity wall. The field onset of flux penetration into a superconductor is an important parameter of merit of alternative superconducting materials other than Nb which can enhance the performance of SRF cavities. There is a need for a simple and efficient technique to measure the onset of field penetration into a superconductor directly. We have developed a Hall probe experimental setup for the measurement of the flux penetration field through a superconducting sample placed under a small superconducting solenoid magnet which can generate magnetic fields up to 500 mT. The system has been calibrated and used to measure different bulk and thin film superconducting materials. This system can also be used to study SIS multilayer coatings that have been proposed to enhance the vortex penetration field in Nb cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB396
About •	paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 11 August 2021
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TUXC03	Ferro-Electric Fast Reactive Tuner Applications for SRF Cavities	cavity, beam-loading, operation, controls	1305
	N.C. Shipman, A. Castilla, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley, H. Timko CERN, Geneva, Switzerland I. Ben-Zvi BNL, Upton, New York, USA G. Burt, A. Castilla Cockcroft Institute, Lancaster University, Lancaster, United Kingdom C.-J. Jing, A. Kanareykin Euclid TechLabs, Solon, Ohio, USA
	A Ferro-Electric fast Reactive Tuner (FE-FRT) is a novel type of RF cavity tuner containing a low loss ferroelectric material. FE-FRTs have no moving parts and allow cavity frequencies to be changed extremely quickly (on the timescale of 100s of ns or less). They are of particular interest for SRF cavities as they can be placed outside the liquid helium environment and without an FE-FRT it’s typically very difficult to tune SRF cavities quickly. FE-FRTs can be used for a wide variety of use cases including microphonics suppression, RF switching, and transient beam loading compensation. This promises entirely new operational capabilities, increased performance and cost savings for a variety of existing and proposed accelerators. An overview of the theory and potential applications will be discussed in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXC03
About •	paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 01 September 2021
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TUPAB017	Study of Conduction-Cooled Superconducting Quadrupole Magnets Combined with Dipole Correctors for the ILC Main Linac	quadrupole, dipole, linac, cavity	1375
	Y. Arimoto, S. Michizono, Y. Morikawa, N. Ohuchi, T. Oki, H. Shimizu, K. Umemori, X. Wang, A. Yamamoto, Y. Yamamoto, Z.G. Zong KEK, Ibaraki, Japan V.S. Kashikhin Fermilab, Batavia, Illinois, USA
	A superconducting rf (SRF) cryomodule for International Linear Collider(ILC) Main Linac equips focus/steering magnets. The magnets are "superferric" magnets with four superconducting (SC) race track coils conductively cooled from the cryomodule LHe supply pipe. The quadrupole field gradient and dipole field are 40 T/m and 0.1 T, respectively. The magnet length and iron-pole radius are 1 m and 0.045 m, respectively. It is known that dark current is generated at SRF cavities and accelerated through the following linac string. The dark current reaches and heats the SC magnets. It is estimated that the power deposition in the magnet may reach more than a few watts and temperature of the SC coils may locally reach to critical temperature of NbTi. It is important to make the magnet not reach quench with sufficient conduction cooling. We aim to realize the SC magnet which can stably operate under such condition. We plan to develop test coils made of three types of SC materials, NbTi, Nb₃Sn, and MgB₂ and study thermal characteristics and stability . We will develop a short model magnet, based on the test coil results. Here, we will present the magnet design study and the R&D plan.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB017
About •	paper received ※ 19 May 2021 paper accepted ※ 16 June 2021 issue date ※ 20 August 2021
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TUPAB035	ESS Medium Beta Cavities Status at INFN LASA	cavity, linac, multipactoring, 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 ※ 15 August 2021
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TUPAB048	HMBA Optics Correction Experience at ESRF	optics, lattice, MMI, closed-orbit	1462
	S.M. Liuzzo, N. Carmignani, L.R. Carver, L. Farvacque, T.P. Perron, P. Raimondi, S.M. White ESRF, Grenoble, France
	The ESRF-EBS storage ring, successfully commissioned in 2020, operates the HMBA lattice, first proposed in * and then adopted in several recent upgrade programs. The successful and timely commissioning of the storage is in large part due to the excellent optics control achieved over that period. Design performance were obtained with lower than predicted correction strengths, localized for the most part in the vicinity of sextupoles. This remarkable behavior is not only the result of the corrective actions taken during the commissioning but also of the extremely accurate conception and alignment of the machine. This report summarizes the steps that lead to the present performances and discusses their stability over time. * J.Biasci et al. Synchrotron Radiation News27, 8 (2014), https://doi.org/10.1080/08940886.2014.970931.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB048
About •	paper received ※ 10 May 2021 paper accepted ※ 11 June 2021 issue date ※ 21 August 2021
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TUPAB049	USSR HMBA Storage Ring Lattice Options	injection, emittance, lattice, optics	1466
	S.M. Liuzzo, N. Carmignani, L.R. Carver, J. Chavanne, L. Hoummi, J. Jacob, T.P. Perron, R. Versteegen, S.M. White ESRF, Grenoble, France I.A. Ashanin, V.S. Dyubkov, S.M. Polozov MEPhI, Moscow, Russia I.A. Ashanin, V.S. Dyubkov, T. Kulevoy, S.M. Polozov NRC, Moscow, Russia T. Kulevoy ITEP, Moscow, Russia
	Funding: European Union’s Horizon 2020 research and innovation program under grant #871072 Russian federation resolution #287 Several new accelerator facilities will be built in Russia in a few years from now. One of those facilities is a 6GeV storage ring (SR) light source (USSR - Ultimate Source of Synchrotron Radiation) to be built in Protvino, near Moscow. The Cremlin+ project aims to incorporate in this activity the best experience of European Accelerator Laboratories. The design of the optics for this SR is presented here in two declinations leading to 70 pm-rad equilibrium horizontal emittance. The first is a 40 cells lattice, the second is the same but includes high field Short Bending magnet sources in each cell. Optics and high order multipole optimizations are performed to obtain sufficient lifetime and dynamic aperture for a conservative off-axis injection.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB049
About •	paper received ※ 12 May 2021 paper accepted ※ 11 June 2021 issue date ※ 01 September 2021
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TUPAB098	Recent Progress Toward a Conduction-Cooled Superconducting Radiofrequency Electron Gun	cavity, simulation, electron, accelerating-gradient	1604
	O. Mohsen, N. Adams, V. Korampally, A. McKeown, D. Mihalcea, P. Piot, I. Salehinia, N. Tom Northern Illinois University, DeKalb, Illinois, USA R. Dhuley, M.G. Geelhoed, D. Mihalcea, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA P. Piot ANL, Lemont, Illinois, USA
	Funding: This work was supported by the US Department of Energy (DOE) under contract DE-SC0018367 High-repetition-rate electron sources have widespread applications. This contribution discusses the progress toward a proof-of-principle demonstration for a conduction-cooled electron source. The source consists of a simple modification of an elliptical cavity that enhances the field electric field at the photocathode surface. The source was cooled to cryogenic temperatures and preliminary measurements for the quality factor and accelerating field were performed. Additionally, we present future plans to improve the source along with simulated beam-dynamics performances.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB098
About •	paper received ※ 29 May 2021 paper accepted ※ 17 June 2021 issue date ※ 14 August 2021
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TUPAB166	A New Design of a Dressed Balloon Cavity with Superior Mechanical Properties	cavity, multipactoring, 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 ※ 12 August 2021
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TUPAB167	Status of Conduction Cooled SRF Photogun for UEM/UED	gun, cavity, cryomodule, shielding	1773
	R.A. Kostin, C. Jing Euclid Beamlabs, Bolingbrook, USA P.V. Avrakhov, A. Liu, Y. Zhao Euclid TechLabs, Solon, Ohio, USA
	Funding: DOE #DE-SC0018621 Benefiting from the rapid progress on RF photogun technologies in the past two decades, the development of MeV range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation. UEM or UED use low power electron beams with modest energies of a few MeV to study ultrafast phenomena in a variety of novel and exotic materials. SRF photoguns become a promising candidate to produce highly stable electrons for UEM/UED applications because of the ultrahigh shot-to-shot stability compared to room temperature RF photoguns. SRF technology was prohibitively expensive for industrial use until two recent advancements: Nb₃Sn and conduction cooling. The use of Nb₃Sn allows to operate SRF cavities at higher temperatures (4K) with low power dissipation which is within the reach of commercially available closed-cycle cryocoolers. Euclid is developing a continuous wave (CW), 1.5-cell, MeV-scale SRF conduction cooled photogun operating at 1.3 GHz. In this paper, the technical details of the design and first experimental data are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB167
About •	paper received ※ 29 May 2021 paper accepted ※ 21 June 2021 issue date ※ 31 August 2021
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TUPAB211	The Accelerator System of IFMIF-DONES Multi-MW Facility	linac, cavity, rfq, cryomodule	1910
	I. Podadera, A. Ibarra, D. Jimenez-Rey, J. Mollá, C. Oliver, D. Regidor, R. Varela, C. de la Morena CIEMAT, Madrid, Spain F. Arbeiter, V. Hauer KIT, Eggenstein-Leopoldshafen, Germany N. Bazin, J. Dumas, L. Seguí CEA-IRFU, Gif-sur-Yvette, France L. Bellan, E. Fagotti, A. Palmieri, A. Pisent INFN/LNL, Legnaro (PD), Italy N. Chauvin, S. Chel, J. Plouin CEA-DRF-IRFU, France G. Duglue, H. Dzitko F4E, Germany W.C. Grabowski, A. Wysocka-Rabin NCBJ, Świerk/Otwock, Poland M. Jaksic, T. Tadic RBI, Zagreb, Croatia W. Królas IFJ-PAN, Kraków, Poland R. López, A. Muñoz, C. Prieto Empresarios Agrupados, Madrid, Spain O. Nomen, M. Sanmartí, F.J. Saura Esteban, B.K. Singh, D. Sánchez-Herranz IREC, Sant Adria del Besos, Spain
	Funding: Work carried out within EUROfusion Consortium and DONES-PreP and received funding from the Euratom research and training programme 2014-2018 & 2019-2020 under grants agreement No. 633053 & 870186 The IFMIF-DONES (DEMO-Oriented Neutron Early Source) facility has passed the preliminary design phase and the detailed design phase is very much advanced. Next step will be the preparation phase for the construction of the facility. The DONES facility aims at developing a database of fusion-like radiation effects on materials to be used in future fusion reactors up to damage levels expected in the EU DEMO. It will be based on an intense neutron source created by an accelerated deuteron beam (125 mA CW, 40 MeV) impinging on a liquid lithium curtain. The DONES Accelerator Systems (AS) will be responsible of delivering this 5 MW D⁺ beam with very high availability. The beam acceleration will be performed by several stages: an ion source and LEBT, an RFQ, a MEBT, an SRF Linac and a HEBT transporting and delivering an optimized profile down to the target. A high power RF system and several ancillaries will ensure the equipment is properly operated. This contribution will report the present status of the AS design, the main challenges faced, the R&D programme to overcome them, and the prospects for the construction and commissioning of the DONES accelerator in Granada (Spain).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB211
About •	paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 13 August 2021
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TUPAB302	Arrival Time Stabilization at Flash Using the Bunch Arrival Corrector Cavity (BACCA)	cavity, electron, feedback, laser	2194
	B. Lautenschlager, L. Butkowski, M.K. Czwalinna, B. Dursun, M. Hierholzer, S. Pfeiffer, H. Schlarb, Ch. Schmidt DESY, Hamburg, Germany
	For pump-probe and seeding experiments at free electron lasers, a femtosecond precise bunch arrival time stability is mandatory. To stabilize the arrival times a fast longitudinal intra bunch-train feedback (L-IBFB) using bunch arrival time monitors is applied. The electron bunch energy prior to a bunch compression chicane is modulated by superconducting radio frequency (SRF) cavities to compensate fast arrival time fluctuations of the subsequent bunches. A broadband normal conducting RF cavity was installed in front of the first bunch compression chicane at FLASH. The L-IBFB uses the normal conducting cavity for small but fast energy corrections together with the SRF cavities for larger and slower corrections. Current measurements show arrival time stabilities of the electron bunches towards 5 fs (rms) at the end of the linac, if the normal conducting cavity acts together with the SRF cavities in the L-IBFB system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB302
About •	paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 12 August 2021
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TUPAB328	Machine Learning for Time Series Prediction of an Accelerator Beam to Recognize Equipment Malfunction	cavity, linac, ion-source, neutron	2272
	C.C. Peters ORNL RAD, Oak Ridge, Tennessee, USA W. Blokland, D.L. Brown, F. Liu, C.D. Long, D. Lu, P. Ramuhalli, D.E. Womble, J. Zhang, A.P. Zhukov ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05- 00OR22725 for the U.S. Department of Energy. The Spallation Neutron Source (SNS) is an accelerator based pulsed neutron source based on a 1 GeV pulsed proton Superconducting Radio Frequency (SRF) linear accelerator (linac). Since beginning high power beam operation in 2006 correlations have been found linking abrupt beam loss events to SRF cavity instabilities. With the planned upgrades to double the beam power we expect increased rates of degradation and the importance of minimizing these beam loss events will become ever more important. To further limit degradation, we are developing machine learning approaches to monitor the beam and to detect, predict and prevent beam loss events. Initial research has shown that precursors to beam loss events are detectable. The initial steps are to use ML-based classification to recognize anomalies and to use Long Short-Term Memory (LSTM) autoencoders to predict beam loss. In this paper, we describe recent progress in applying machine learning for recognizing anomalies and predicting beam loss and present initial results of our research using acquired data from different diagnostics and the Machine Protection System (MPS).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB328
About •	paper received ※ 23 May 2021 paper accepted ※ 28 May 2021 issue date ※ 23 August 2021
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TUPAB333	Status of PIP-II 650 MHz Prototype Dressed Cavity Qualification	cavity, cryomodule, status, superconductivity	2279
	G.V. Eremeev, D.J. Bice, C. Boffo, S.K. Chandrasekaran, S. Cheban, F. Furuta, I.V. Gonin, C.J. Grimm, S. Kazakov, T.N. Khabiboulline, A. Lunin, M. Martinello, N. Nigam, J.P. Ozelis, Y.M. Pischalnikov, K.S. Premo, O.V. Prokofiev, O.V. Pronitchev, G.V. Romanov, N. Solyak, A.I. Sukhanov, G. Wu Fermilab, Batavia, Illinois, USA M. Bagre, V. Jain, A. Puntambekar, S. Raghvendra, P. Shrivastava RRCAT, Indore (M.P.), India P. Bhattacharyya, S. Ghosh, S. Seth VECC, Kolkata, India R. Kumar BARC, Mumbai, India J. Lewis, P.A. McIntosh, A.E. Wheelhouse STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom C. Pagani, R. Paparella INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy T. Reid ANL, Lemont, Illinois, USA A.D. Shabalina STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	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. Low-beta and high-beta sections of PIP-II linac will use nine low-beta cryomodules with four cavities each and four high-beta cryomodules with six cavities each. These cavities will be produced and qualified in collaboration between Fermilab and the international partner labs. Prior to their installation into prototype cryomodules, several dressed cavities, which include jacketed cavities, high power couplers, and tuners, will be qualified in STC horizontal test bed at Fermilab. After qualification of bare β = 0.9 cavities at Fermilab, several pre-production β = 0.92 and β = 0.61 cavities have been and are being fabricated and qualified. Procurements have also been started for high power couplers and tuners. In this contribution we present the current status of prototype dressed cavity qualification for PIP-II.
	Poster TUPAB333 [6.247 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB333
About •	paper received ※ 23 May 2021 paper accepted ※ 19 July 2021 issue date ※ 25 August 2021
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TUPAB338	Surface Roughness Reduction of Nb₃Sn Thin Films via Laser Annealing for Superconducting Radio-Frequency Cavities	laser, cavity, superconductivity, HOM	2283
	Z. Sun, M. Ge, M. Liepe, T.E. Oseroff, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A.B. Connolly, M.O. Thompson Cornell University, Ithaca, USA
	Superconducting radio frequency (SRF) cavities, a key component of particle accelerators, await new SRF materials beyond the state-of-the-art niobium. Nb₃Sn is one of the most competitive candidates, since it increases the superheating field, allows the operation temperature up to 4K, and improves cavity efficiency. Surface roughness and grain boundaries, however, significantly affect the RF performance of current Nb₃Sn cavities. Here, we explore a post laser annealing technique to reduce the surface roughness. In doing so, we deposited a TiN laser-absorber on Nb₃Sn and Nb surfaces, and then annealed the samples by laser scanning via different laser systems. The Nb₃Sn surface roughness was minimized to 101 nm (Ra) by laser annealing via 308 nm, 35 ns pulses. Surface imaging and Fourier analysis revealed laser annealing is able to remove sharp edges and <1 um wavelength features.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB338
About •	paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 19 August 2021
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TUPAB342	Preliminary Cryogenic Cold Test Results of the First 9-Cell LSF Shape Cavity	cavity, niobium, multipactoring, 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 ※ 30 August 2021
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TUPAB343	Final Design Studies for the VSR DEMO 1.5 GHz Coupler	multipactoring, 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 ※ 01 September 2021
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TUPAB344	Evaluation of Anisotropic Magnetoresistive (AMR) Sensors for a Magnetic Field Scanning System for SRF Cavities	cavity, experiment, niobium, MMI	2304
	I.P. Parajuli, G. Ciovati, J.R. Delayen, A.V. Gurevich ODU, Norfolk, Virginia, USA G. Ciovati, J.R. Delayen JLab, Newport News, Virginia, USA
	Funding: Work supported by NSF Grant 100614-010. G. C. is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. One of the significant causes of residual losses in superconducting radio-frequency (SRF) cavities is trapped magnetic flux. The flux trapping mechanism depends on many factors that include cool-down conditions, surface preparation techniques, and ambient magnetic field orientation. Suitable diagnostic tools are not yet available to quantitatively correlate such factors’ effect on the flux trapping mechanism. A magnetic field scanning system (MFSS) consisting of AMR sensors, fluxgate magnetometers, or Hall probes is recently commissioned to scan the local magnetic field of trapped vortices around 1.3 GHz single-cell SRF cavities. In this contribution, we will present results from sensitivity calibration and the first tests of AMR sensors in the MFSS.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB344
About •	paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 25 August 2021
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TUPAB345	Availability Modeling of the Solid-State Power Amplifiers for the CERN SPS RF Upgrade	operation, cavity, simulation, MMI	2308
	L. Felsberger, A. Apollonio, T. Cartier-Michaud, E. Montesinos, J.C. Oliveira, J.A. Uythoven CERN, Geneva, Switzerland
	Funding: This project has received funding from the Euratom research and training programme 2019-2020 under grant agreement No 945077. As part of the LHC Injector Upgrade program a complete overhaul of the Super Proton Synchrotron Radio-Frequency (RF) system took place. New cavities have been installed for which the solid-state technology was chosen to deliver a combined RF power of 2 MW from 2560 RF amplifiers. This strategy promises high availability as the system continues operation when some of the amplifiers fail. This study quantifies the operational availability that can be achieved with this new installation. The evaluation is based on a Monte Carlo simulation of the system using the novel AvailSim4 simulation software. A model based on lifetime estimations of the RF modules is compared against data from early operational experience. Sensitivity analyses have been made, that give insight to the chosen operational scenario. With the increasing use of solid-state RF power amplifiers, the findings of this study provide a useful reference for future application of this technology in particle accelerators.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB345
About •	paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 02 September 2021
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TUPAB350	Design of 71 MHz Power Amplifier in a Single-ended Architecture for IRANCYC-10 Cyclotron	cyclotron, simulation, impedance, factory	2325
	F. Babagoli Moziraji, H. Afarideh AUT, Tehran, Iran M. Dehghan Shahid Beheshti University, Tehran, Iran F. Ghasemi NSTRI, Tehran, Iran
	In this paper, the design and simulation of a high power amplifier to provide the required power of a cyclotron accelerator (IRANCYC-10) is presented step-by-step. By combining four modules of this amplifier, a power of 2.5 kW can be achieved to start the main power amplifier. The single ended designs amplifier can generate 1 kW the operating frequency of 71MHz continuous wave (CW). The purpose of choosing this type of design is simplicity to build without the need for a balun, low weight to build high power, as well as cost-effectiveness. The gain and PAE of the SSPA are 21.21 and 71%, respectively. There are also ways to reduce the size of the amplifier.
	Poster TUPAB350 [1.008 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB350
About •	paper received ※ 19 May 2021 paper accepted ※ 15 August 2021 issue date ※ 25 August 2021
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TUPAB369	A Fast Non-Linear Model for the EBS Combined Sextupole-Corrector Magnets	sextupole, dipole, multipole, quadrupole	2381
	G. Le Bec ESRF, Grenoble, France
	Corrector are often integrated in higher order accelerator magnets. In the new ESRF-EBS storage ring, the sextupoles include additional windings allowing for dipole and skew quadrupole corrections. The accurate modelization of such magnets is not as trivial as it may appear, due to their non-linearities and to the crosstalk between their channels. Changing any corrector current induce non-linear errors in the other corrector channels and in the main sextupole strength, making difficult the trimming of the magnets. A model based on a non-linear excitation curve and quadratic contributions from corrector currents was developed. This model is very fast and was included in the accelerator control system to compute the corrector currents in real-time. It was tested against 3D magnetic simulations and magnetic measurements and compared to a simpler matrix-based model.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB369
About •	paper received ※ 17 May 2021 paper accepted ※ 15 August 2021 issue date ※ 31 August 2021
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WEXC03	Review of Superconducting Radio Frequency Gun	cathode, gun, cavity, operation	2556
	R. Xiang HZDR, Dresden, Germany
	The success of proposed high power free-electron lasers (FELs) and energy recovery linac (ERL) largely depends on the development of the electron source, which requires the best beam quality and CW operation. An elegant way to realize this average brilliance is to combine the high beam quality of mature normal conducting radio frequency photoinjector with the quick developing superconducting radio frequency technology, to build superconducting rf photoinjectors (SRF guns). In last decade, several SRF gun programs based on different approaches have achieved promising progress, even succeeded in routine operation at BNL and HZDR [,]. In the near future SRF guns are expected to play an important role for hard X-ray FEL facilities. In this contribution, we will review the design concepts, parameters, and the status of the major SRF gun projects. I. Petrushina et al., Phys. Rev. Lett. 124, 244801 **J. Teichert at al., Phys. Rev. Accel. Beams 24, 033401
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXC03
About •	paper received ※ 19 May 2021 paper accepted ※ 28 June 2021 issue date ※ 11 August 2021
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WEPAB020	The Relation Between Field Flatness and the Passband Frequency in the Elliptical Cavities	cavity, simulation, gun, accelerating-gradient	2636
	G.-T. Park, R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA
	A technique that predicts the field flatness of the operating pi-mode based on the passband frequency is highly desirable when the direct measurement of the field is not available. Such a technique was developed for the SNS-PPU cavity, a 6-cell SRF cavity whose field flatness is important for cold operation. In this paper, we will present the theory on the relations between field profile and passband frequencies of the arbitrary deformed cavities, the simulation studies, and comparison with the experimental measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB020
About •	paper received ※ 17 May 2021 paper accepted ※ 24 June 2021 issue date ※ 31 August 2021
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WEPAB138	Superconducting RF Gun with High Current and the Capability to Generate Polarized Electron Beams	gun, electron, cathode, cavity	2936
	I. Petrushina SUNY SB, Stony Brook, New York, USA S.A. Belomestnykh, S. Kazakov, T.N. Khabiboulline, M. Martinello, Y.M. Pischalnikov, V.P. Yakovlev Fermilab, Batavia, Illinois, USA J.C. Brutus, P. Inacker, Y.C. Jing, V. Litvinenko, J. Skaritka, E. Wang BNL, Upton, New York, USA J.M. Grames, M. Poelker, R. Suleiman, E.J-M. Voutier JLab, Newport News, Virginia, USA
	High-current low-emittance CW electron beams are indispensable for nuclear and high-energy physics fixed target and collider experiments, cooling high energy hadron beams, generating CW beams of monoenergetic X-rays (in FELs) and gamma-rays (in Compton sources). Polarization of electrons in these beams provides extra value by opening a new set of observables and frequently improving the data quality. We report on the upgrade of the unique and fully functional CW SRF 1.25 MeV SRF gun, built as part of the Coherent electron Cooling (CeC) project, which has demonstrated sustained CW operation with CsK2Sb photocathodes generating electron bunches with record-low transverse emittances and record-high bunch charge exceeding 10 nC. We propose to extend the capabilities of this system to high average current of 100 milliampere in two steps: increasing the current 30-fold at each step with the goal to demonstrate reliable long-term operation of the high-current low-emittance CW SRF guns. We also propose to test polarized GaAs photocathodes in the ultra-high vacuum (UHV) environment of the SRF gun, which has never been successfully demonstrated in RF accelerators.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB138
About •	paper received ※ 25 May 2021 paper accepted ※ 29 July 2021 issue date ※ 23 August 2021
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WEPAB165	Metamaterial Waveguide HOM Loads for SRF Accelerating Cavities	HOM, GUI, vacuum, cavity	2994
	S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA
	Suppression of beam induced HOMs is necessary for most SRF accelerating cavities driven with high currents. One of the problems in design of a HOM load is that vacuum compatible materials with high enough imaginary part of the dielectric permittivity, which provides absorption, have also a high real part of the permittivity. This does not allow absorbing RF radiation at short distance and in broad frequency band. We propose considering artificial metamaterials where besides lossy dielectric pieces, an absorber with high magnetic permeability is included. In our proposal, we suggest composing a waveguide HOM load of a metamaterial consisted of well-known ceramic and ferrite plates placed periodically in a stack. Such a design provides low return losses, compactness and broad frequency range of the operation.
	Poster WEPAB165 [1.844 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB165
About •	paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 15 August 2021
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WEPAB360	Future Prospective for Bent Crystals in Accelerators	lattice, collimation, scattering, experiment	3545
	M. Romagnoni INFN-Ferrara, Ferrara, Italy M. Romagnoni Universita’ degli Studi di Milano, Milano, Italy
	Super magnet dipoles employed to steer high energy particle beams are massive instruments requiring cryogenic cooling and featuring large energy consumption. A bent crystal has the potential in a few millimeters to deflect 100-1000 GeV particle beams as much as an hundreds-tesla magnetic dipole. Indeed, within the lattice of a crystal, large electric fields up to several GeV/cm are present. Positive charged particles can be efficiently channeled between two adjacent lattice planes, thus following their curvature. These features and the possibility to selectively affect only the portion of the beam intercepting the crystal led to the proposal of exploiting bent crystals for several purposes, such as the collimation of ions at LHC. In this scheme, the particles on the beam halo instead of being scattered by tens-centimeters long collimators are directly separated from the beam using a 4 mm long silicon crystal. The production of a bent crystal suitable for installation in the LHC beamline requires strict control over lattice features and bending apparatus. The results obtained by the years long research of the INFN research team in Ferrara are presented in this work.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB360
About •	paper received ※ 14 May 2021 paper accepted ※ 28 July 2021 issue date ※ 29 August 2021
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THPAB007	Technology Spinoff and Lessons Learned from the 4-Turn ERL CBETA	permanent-magnet, cavity, radiation, linac	3762
	K.E. Deitrick, N. Banerjee, A.C. Bartnik, D.C. Burke, J.A. Crittenden, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter, Y. Li, W. Lou, P. Quigley, D. Sagan, K.W. Smolenski Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA J.S. Berg, S.J. Brooks, R.L. Hulsart, G.J. Mahler, F. Méot, R.J. Michnoff, S. Peggs, T. Roser, D. Trbojevic, N. Tsoupas BNL, Upton, New York, USA T. Miyajima KEK, Ibaraki, Japan
	The Cornell-BNL ERL Test Accelerator (CBETA) developed several energy-saving measures: multi-turn energy recovery, low-loss superconducting radiofrequency (SRF) cavities, and permanent magnets. With green technology becoming imperative for new high-power accelerators, the lessons learned will be important for projects like the FCC-ee or new light sources, where spinoffs and lessons learned from CBETA are already considered for modern designs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB007
About •	paper received ※ 20 May 2021 paper accepted ※ 05 July 2021 issue date ※ 28 August 2021
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THPAB074	ESRF-EBS: Implementation, Performance and Restart of User Operation	MMI, operation, storage-ring, emittance	3929
	J.-L. Revol, P. Berkvens, J.-F. Bouteille, N. Carmignani, L.R. Carver, J.M. Chaize, J. Chavanne, F. Ewald, A. Franchi, L. Hardy, J. Jacob, L. Jolly, G. Le Bec, I. Leconte, S.M. Liuzzo, D. Martin, J. Pasquaud, T.P. Perron, Q. Qin, P. Raimondi, B. Roche, K.B. Scheidt, R. Versteegen, S.M. White ESRF, Grenoble, France
	The European Synchrotron Radiation Facility - Extremely Brilliant Source (ESRF-EBS) is a facility upgrade allowing its scientific users to take advantage of the first high-energy 4th generation light source. In December 2018, after 30 years of operation, the beam stopped for a 12-month shutdown to dismantle the old storage ring and to install the new X-ray source. In December 2019, the first beam was stored and accumulated in the storage ring, allowing the vacuum conditioning and tuning to be started. The beam was delivered to beamlines in March 2020 for their commissioning. On 25 August, the user programme was restarted with beam parameters very close to nominal values. In this report, the milestones and key aspects of the return to user-mode operation are presented and discussed.
	Poster THPAB074 [2.864 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB074
About •	paper received ※ 19 May 2021 paper accepted ※ 26 July 2021 issue date ※ 01 September 2021
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THPAB120	Beam on Demand for High-Repetition-Rate X-Ray Free-Electron Lasers	electron, laser, FEL, linac	3995
	Z. Zhang, Y. Ding, Z. Huang SLAC, Menlo Park, California, USA
	High-repetition-rate (HRR) free-electron lasers (FELs) with multiple undulator beamlines will advance the frontiers of X-ray science significantly from the remarkable success of existing X-ray FEL facilities. The wide-ranging requirements for the photon properties from multiple beamlines are extremely challenging to satisfy by the same electron beam from a single superconducting radio-frequency (SRF) accelerator. To realize the full potential of an HRR FEL facility, a new emerging concept of "beam on demand" is proposed here. The concept is based on advanced beam dynamics and radio-frequency (RF) techniques to provide beam properties tailored to each undulator line at the desired repetition rate. The beam properties that will be pursued in this proposal include, but are not limited to, beam energy, bunch charge, bunch length, beam current, and its profile. The realization of "beam on demand" will allow optimization of photon properties of individual beamlines to maximize their performance and drastically improve the multiplexing capabilities of Linac Coherent Light Source II and its high-energy upgrade.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB120
About •	paper received ※ 17 May 2021 paper accepted ※ 23 July 2021 issue date ※ 26 August 2021
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THPAB153	Design, Construction and Tests of the Cooling System with a Cryocooler for Cavity Testing	cavity, cryogenics, vacuum, simulation	4056
	P. Pizzol, J.W. Lewellen, E.R. Olivas, E.I. Simakov, T. Tajima LANL, Los Alamos, New Mexico, USA
	Cryogenically cooled normal-conducting cavities have shown higher gradients than those operated at room temperature. We are constructing a compact cooling system with a cryocooler to test C-band normal-conducting cavities and 1.3 GHz superconducting cavities. This paper describes the design, construction, and cooling test results as well as some low-power cavity Q measurement results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB153
About •	paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 12 August 2021
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THPAB156	Built-in Thermionic Electron Source for an SRF Linacs	cathode, cavity, electron, gun	4062
	I.V. Gonin, S. Kazakov, R.D. Kephart, T.N. Khabiboulline, T.H. Nicol, N. Solyak, J.C.T. Thangaraj, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	The design of a thermionic electron source connected directly to a superconducting cavity, the key part of an SRF gun, is described. The results of beam dynamics optimization are presented which allow lack of beam current intercepting in the superconducting cavity. The electron source concept is presented including the cathode-grid assembly, thermal insulation of the cathode from the cavity, and the gun resonator design. The cavity thermal load caused by the gun is analyzed including the static heat load, black body radiation, backward electron heating, etc.
	Poster THPAB156 [0.670 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB156
About •	paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 28 August 2021
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THPAB173	Fundamental Study on Electromagnetic Characteristics of Half-Wave Resonator for 200 MeV Energy Upgrade of KOMAC Proton Linac	cavity, simulation, linac, proton	4098
	J.J. Dang, Y.-S. Cho, H.S. Kim, H.-J. Kwon, S. Lee Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea
	Funding: This work has been supported through KOMAC operation fund of KAERI by the Korea government (MSIT). A superconducting linac has been developed at KOrea Multi-purpose Accelerator Complex (KOMAC). A goal of the SRF linac is to increase proton beam energy from 100 MeV to 200 MeV. 350 MHz medium beta half-wave resonator (HWR) should provide 3.6 MV accelerating voltage to achieve the energy upgrade. An electromagnetic (EM) analysis on the parametrically designed HWR cavity was conducted. The cavity design was optimized to reduce a peak electric field and a peak magnetic field while satisfying the required acerating voltage. In addition, a mechanical-EM coupled simulation was conducted to estimate a helium pressure sensitivity. Also, Lorentz force detuning was simulated. The design is being optimized to minimize the frequency detuning due to the helium pressure and Lorentz force.
	Poster THPAB173 [0.800 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB173
About •	paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 22 August 2021
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THPAB320	ALD-Based NbTiN Studies for SIS R&D	site, cavity, plasma, niobium	4420
	I. González Díaz-Palacio, R.H. Blick, R. Zierold University of Hamburg, Hamburg, Germany W. Hillert, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Superconductor-Insulator-Superconductor multilayers improve the performance of SRF cavities providing magnetic screening of the bulk cavity and lower surface resistance. In this framework NbTiN mixtures stand as a potential material of interest. Atomic layer deposition (ALD) allows for uniform coating of complex geometries and enables tuning of the stoichiometry and precise thickness control in sub-nm range. In this talk, we report about NbTiN thin films deposited by plasma-enhanced ALD on insulating AlN buffer layer. The deposition process has been optimized by studying the superconducting electrical properties of the films. Post-deposition thermal annealing studies with varying temperatures, annealing times, and gas atmospheres have been performed to further improve the thin film quality and the superconducting properties. Our experimental studies show an increase in Tc by 87.5% after thermal annealing and a maximum Tc of 13.9 K has been achieved for NbTiN of 23 nm thickness. Future steps include lattice characterization, using XRR/XRD/EBSD/PALS, and SRF measurements to obtain Hc1 and the superconducting gap.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB320
About •	paper received ※ 24 May 2021 paper accepted ※ 23 July 2021 issue date ※ 26 August 2021
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THPAB322	Transient Beam Loading in the CBETA Multi-Turn ERL	cavity, linac, beam-loading, operation	4422
	N. Banerjee Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA G.H. Hoffstaetter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was supported by NSF Grant No. DMR0807731, DOE Award No. DE-SC0012704, and NYSERDA Agreement No. 102192. The Cornell-BNL ERL Test Accelerator (CBETA) is the first superconducting multi-turn ERL that has been commissioned at Cornell University in a low current mode. In this paper, we first discuss a new model of beam loading which is valid for the low injection energies used in CBETA. Using this model, we explore the effect of bunch patterns, beam turn-on, and turn-off transients on the fundamental mode of the 7-cell SRF cavities used in the main linac. In particular, we examine the operational constraints on the rf system at the design current of 40 mA.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB322
About •	paper received ※ 20 May 2021 paper accepted ※ 29 July 2021 issue date ※ 26 August 2021
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THPAB336	Novel Magnetron Operation and Control Methods for Superconducting RF Accelerators	controls, injection, operation, cavity	4442
	G.M. Kazakevich, R.P. Johnson Muons, Inc, Illinois, USA T.N. Khabiboulline, G.V. Romanov, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	High power magnetrons designed and optimized for industrial heating, being injection-locked, have been suggested to power superconducting RF cavities for accelerators due to lower cost and higher efficiency. However, standard operation methods do not provide high efficiency with wideband control suppressing microphonics. We have developed and experimentally verified novel methods of operating and controlling the magnetron that provide stable RF generation with higher efficiency and lower noise than other RF sources. By our method the magnetrons operate with the anode voltage notably lower than the self-excitation threshold improving its performance. This is also a promising way to increase tube reliability and longevity. A magnetron operating with the anode voltage lower than the self-excitation threshold, in so-called stimulated coherent generation mode has special advantage for pulse operation with a gated injection-locking signal. This eliminates the need for expensive pulsed HV modulators and additionally increases the magnetron RF source efficiency due to absence of losses in HV modulators.
	Poster THPAB336 [0.960 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB336
About •	paper received ※ 15 May 2021 paper accepted ※ 08 July 2021 issue date ※ 18 August 2021
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THPAB343	Test Results of the Prototype SSR1 Cryomodule for PIP-II at Fermilab	cavity, cryomodule, vacuum, focusing	4461
	D. Passarelli, J. Bernardini, C. Boffo, B.M. Hanna, S. Kazakov, T.N. Khabiboulline, A. Lunin, J.P. Ozelis, M. Parise, Y.M. Pischalnikov, V. Roger, B. Squires, A.I. Sukhanov, G. Wu, V.P. Yakovlev, S. Zorzetti Fermilab, Batavia, Illinois, USA C. Contreras-Martinez FRIB, East Lansing, Michigan, USA
	Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DEAC02- 07CH11359 with the United States Department of Energy A prototype cryomodule containing eight Single Spoke Resonators type-1 (SSR1) operating at 325 MHz and four superconducting focusing lenses has been successfully assembled and cold tested in the framework of PIP-II project at Fermilab. The performance of cavities and focusing lenses along with test results of other cryomodule’s key parameters are presented in this contribution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB343
About •	paper received ※ 20 May 2021 paper accepted ※ 08 August 2021 issue date ※ 26 August 2021
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THPAB348	INFN-LASA for the PIP-II LB650 Linac	cavity, linac, experiment, cryogenics	4474
	R. Paparella, M. Bertucci, M. Bonezzi, A. Bosotti, A. D’Ambros, A.T. Grimaldi, P. Michelato, L. Monaco, D. Sertore INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	INFN joined the international effort for the PIP-II project at Fermilab and it’s going to contribute to the low-beta section of the PIP-II proton linac. In particular, INFN-LASA is finalizing its commitment to deliver in kind the full set of the LB650 cavities, namely 36 plus spares 5-cell cavities at 650 MHz and geometrical beta 0.61. All cavities, designed by INFN-LASA, will be produced and surface treated in industry, qualified through vertical cold test, and delivered as ready for string installation. This paper reports the status of INFN’s contribution to PIP-II and of ongoing activities toward the experimental qualifications of infrastructures and prototypes.
	Poster THPAB348 [4.076 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB348
About •	paper received ※ 16 May 2021 paper accepted ※ 01 July 2021 issue date ※ 01 September 2021
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THPAB351	INFN-LASA Experimental Activities on PIP-II Low-Beta Cavity Prototypes	cavity, target, experiment, superconductivity	4481
	M. Bertucci, A. Bosotti, A. D’Ambros, A.T. Grimaldi, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy A. Gresele, A. Torri Ettore Zanon S.p.A., Nuclear Division, Schio, Italy M. Rizzi Ettore Zanon S.p.A., Schio, Italy
	This paper reports on the first results obtained by INFN-LASA on PIP-II low-beta cavity prototypes. The goal of this activity was to validate the reference surface treatment based on Electropolishing as a bulk removal step. The cavity treatment procedures are here presented together with the strategy used for their optimization. The experimental results of cavity cold tests for a single cell prototype are presented and discussed. Having this cavity achieved the requested performance, the baseline procedure is considered as validated and a plan for a future high-Q cavity surface treatment is proposed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB351
About •	paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 22 August 2021
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FRXC01	Superconducting Radio-Frequency Cavity Fault Classification Using Machine Learning at Jefferson Laboratory	cavity, cryomodule, network, radio-frequency	4535
	C. Tennant, A. Carpenter, T. Powers, L.S. Vidyaratne JLab, Newport News, Virginia, USA K.M. Iftekharuddin, M. Rahman ODU, Norfolk, Virginia, USA A.D. Shabalina STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: This work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC05-06OR23177. We report on the development of machine learning models for classifying C100 superconducting radiofrequency (SRF) cavity faults in the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. Of the 418 SRF cavities in CEBAF, 96 are designed with a digital low-level RF system configured such that a cavity fault triggers recordings of RF signals for each of eight cavities in the cryomodule. Subject matter experts analyze the collected time-series data and identify which of the eight cavities faulted first and classify the type of fault. This information is used to find trends and strategically deploy mitigations to problematic cryomodules. However, manually labeling the data is laborious and time-consuming. By leveraging machine learning, near real-time - rather than postmortem - identification of the offending cavity and classification of the fault type has been implemented. We discuss the performance of the machine learning models during a recent physics run. We also discuss efforts for further insights into fault types through unsupervised learning techniques and present preliminary work on cavity and fault prediction using data collected prior to a failure event.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXC01
About •	paper received ※ 16 May 2021 paper accepted ※ 01 July 2021 issue date ※ 11 August 2021
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Paper

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MOXA01

Commissioning and Restart of ESRF-EBS

injection, lattice, storage-ring, MMI

1

S.M. White, N. Carmignani, L.R. Carver, J. Chavanne, L. Farvacque, L. Hardy, J. Jacob, G. Le Bec, S.M. Liuzzo, T.P. Perron, Q. Qin, P. Raimondi, J.-L. Revol, K.B. Scheidt
ESRF, Grenoble, France

The ESRF operates a 6 GeV 4th generation light source, the ESRF-EBS. This storage ring is the first to implement the Hybrid Multi-Bend Achromat lattice (HMBA). The HMBA lattice provides a reduction of the horizontal emittance of approximately a factor 30 with respect to the former Double Bend Achromat (DBA) structure, considerably improving the brilliance and transverse coherence of the ESRF accelerator complex while maintaining large horizontal acceptance and excellent lifetime performance. In this report, the characteristics of the HMBA lattice will be reviewed and the beam commissioning results and first operation experience of the new ESRF storage ring will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOXA01

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paper received ※ 11 May 2021 paper accepted ※ 21 August 2021 issue date ※ 31 August 2021

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MOPAB021

A Dispersive Quadrupole Scan Technique for Transverse Beam Characterization

quadrupole, emittance, optics, booster

107

J. Kallestrup, M. Aiba
PSI, Villigen PSI, Switzerland
N. Carmignani, T.P. Perron
ESRF, Grenoble, France

Quadrupole scans are one of the standard techniques to characterize the transverse beam properties in transfer lines or linacs. However, in the presence of dispersion the usage of regular quadrupole scans will lead to erroneous estimates of the beam parameters. The standard solution to this problem is to measure the dispersion and then subtract it in the post-analysis of the quadrupole scan measurements assuming the design energy spread. Here we show that the dispersive contribution to the beam size can be included in the quadrupole scan procedure, forming a linear system of equations that can be solved to obtain both the betatronic and dispersive beam parameters. The method is tested at both the SLS and ESRF booster-to-ring transfer lines leading to reasonable estimates of the beam parameters.

Poster MOPAB021 [0.447 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB021

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 02 September 2021

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MOPAB051

Operation of the ESRF Booster with the New EBS Storage Ring

emittance, booster, injection, operation

221

N. Carmignani, L.R. Carver, S.M. Liuzzo, T.P. Perron, S.M. White
ESRF, Grenoble, France

The Extremely Brilliant Source (EBS) has replaced the old ESRF Storage Ring (SR) during the 2019 one-year shutdown. The injector chain, composed of a Linac, a booster synchrotron, and two transfer lines, was not replaced. Nevertheless, some major hardware upgrades were anticipated prior to the long shutdown to ensure its long-term reliability. The shutdown interventions focused on reducing the machine circumference to cope with the new RF frequency of the SR. The status of the upgraded booster will be presented with a focus on the strategy used to lower horizontal emittance especially via emittance exchange.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB051

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paper received ※ 14 May 2021 paper accepted ※ 28 May 2021 issue date ※ 10 August 2021

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MOPAB108

ESRF-EBS 352.37 MHz Radio Frequency System

cavity, operation, MMI, HOM

395

J. Jacob, P.B. Borowiec, A. D’Elia, G. Gautier, V. Serrière
ESRF, Grenoble, France

The ESRF 352 MHz Radio Frequency (RF) system has been upgraded and tailored to the new 4th Generation Extremely Brilliant Source EBS, that was installed in 2019 and commissioned in 2020. The five former five-cell cavities were replaced with 13 single cell strongly HOM damped cavities that were developed in house, 10 of which are powered from existing 1 MW klystron transmitters. The remaining three cavities are individually fed by three 150 kW solid state amplifiers. All this required a reconstruction in record time of an elaborate WR2300 waveguide network. The low level RF system as well as the cavity and transmitter control system have been rebuilt. The RF design, commissioning and operation experience will be reported, including plans for a 4th harmonic RF system for bunch lengthening to further improve the performance of the new EBS ring.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB108

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paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 28 August 2021

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MOPAB112

A Modified Hybrid 6BA Lattice for the HALF Storage Ring

lattice, emittance, damping, storage-ring

407

Z.H. Bai, G.Y. Feng, T.L. He, W. Li, W.W. Li, G. Liu, Z.L. Ren, L. Wang, P.H. Yang, S.C. Zhang, T. Zhang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

In this paper, we propose a modified hybrid 6BA lattice as the baseline lattice of the Hefei Advanced Light Facility (HALF) storage ring. Similar to the Diamond-II lattice, the proposed lattice cell has one long straight section and one mid-straight section; but the two bend units adjacent to the mid-straight are LGB/RB units (LGB: longitudinal gradient bend, RB: reverse bend), which can give both lower emittance and shorter damping times. The designed HALF storage ring, with an energy of 2.2 GeV and 20 lattice cells, has a natural emittance of about 85 pm·rad.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB112

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paper received ※ 15 May 2021 paper accepted ※ 20 May 2021 issue date ※ 28 August 2021

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MOPAB116

A Flexible Injection Scheme for the ESRF-EBS

injection, kicker, septum, storage-ring

421

S.M. White, N. Carmignani, L.R. Carver, M. Dubrulle, L. Hoummi, S.M. Liuzzo, M. Morati, T.P. Perron
ESRF, Grenoble, France

The ESRF-EBS storage ring light source started commissioning in 2019 and successfully resumed users operation in 2020. Due to the smaller emittance and consequently reduced lifetime frequent injections are required that can potentially disturb beam lines experiments. In addition, operating the machine with low beta straight section and reduced insertion devices (ID) gaps are considered, therefore reducing the vertical aperture of the machine. Alternatives to the standard off-axis injection scheme allowing for efficient injection in reduced apertures with minimized perturbations are explored. A flexible layout for potential integration in the ESRF-EBS lattice is proposed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB116

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paper received ※ 11 May 2021 paper accepted ※ 27 May 2021 issue date ※ 12 August 2021

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MOPAB117

Single Bunch Collective Effects in the EBS Storage Ring

impedance, simulation, synchrotron, vacuum

425

L.R. Carver, E. Buratin, N. Carmignani, F. Ewald, L. Hoummi, S.M. Liuzzo, T.P. Perron, B. Roche, S.M. White
ESRF, Grenoble, France

The ESRF storage ring (SR) has been dismantled and replaced by the Extremely Brilliant Source (EBS) which has now been commissioned. Beam based measurements have been performed to characterise the impedance of the new machine and to make a first comparison with predictions. The results from instability threshold scans and tune shift measurements will be presented, as well as bunch length and position variation with current and microwave threshold measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB117

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paper received ※ 11 May 2021 paper accepted ※ 31 May 2021 issue date ※ 25 August 2021

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MOPAB224

Optimization and Error Studies for the USSR HMBA Lattice

lattice, injection, booster, dynamic-aperture

730

L. Hoummi, N. Carmignani, L.R. Carver, S.M. Liuzzo, T.P. Perron, S.M. White
ESRF, Grenoble, France
I.A. Ashanin, S.M. Polozov
MEPhI, Moscow, Russia
T. Kulevoy
ITEP, Moscow, Russia
T. Kulevoy
NRC, Moscow, Russia

Several new accelerator facilities will be built in Russia in the next few years. One of those facilities is a 6 GeV storage ring (SR) light source, the Ultimate Source of Synchrotron Radiation (USSR) to be built in Protvino, near Moscow. The Cremlin+ project aims to incorporate in this activity the best experience of European Accelerator Laboratories. The optimization of such optics including realistic errors and a commissioning-like sequence of corrections, using Multi-Objective Genetic Algorithms (NSGA-II) is presented. Several corrections schemes are also tested.

Poster MOPAB224 [1.164 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB224

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paper received ※ 12 May 2021 paper accepted ※ 01 June 2021 issue date ※ 17 August 2021

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MOPAB247

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

multipactoring, cavity, electron, 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]

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

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paper received ※ 10 May 2021 paper accepted ※ 07 June 2021 issue date ※ 02 September 2021

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MOPAB290

Machine Learning-Based LLRF and Resonance Control of Superconducting Cavities

cavity, controls, LLRF, simulation

920

J.A. Diaz Cruz, S. Biedron, M. Martínez-Ramón
UNM-ECE, Albuquerque, USA
J.A. Diaz Cruz
SLAC, Menlo Park, California, USA
R. Pirayesh
UNM-ME, Albuquerque, New Mexico, USA
S. Sosa
ODU, Norfolk, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under award number DE-SC0019468.
Superconducting radio frequency (SRF) cavities with high loaded quality factors that operate in continuous wave (CW) and low beam loading are sensitive to microphonics-induced detuning. Cavity detuning can result in an increase of operational power and/or in a cavity quench. Such SRF cavities have bandwidths on the order of 10 Hz and detuning requirements can be as tight as 10 Hz. Passive methods to mitigate vibration sources and their impact in the cryomodule/cavity environment are widely used. Active resonance control techniques that use stepper motors and piezoelectric actuators to tune the cavity resonance frequency by compensating for microphonics detuning have been investigated. These control techniques could be further improved by applying Machine Learning (ML), which has shown promising results in other particle accelerator control systems. In this paper, we describe a Low-level RF (LLRF) and resonance control system based on ML methods that optimally and adaptively tunes the control parameters. We present simulations and test results obtained using a low power test bench with a cavity emulator.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB290

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paper received ※ 03 June 2021 paper accepted ※ 11 June 2021 issue date ※ 27 August 2021

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MOPAB332

Design of 4th Harmonic RF Cavities for ESRF-EBS

HOM, cavity, impedance, coupling

1031

A. D’Elia, J. Jacob, V. Serrière, X.W. Zhu
ESRF, Grenoble, France

Funding: European Union’s Horizon 2020 research and innovation program under grant #871072
An active 4th harmonic RF system for bunch lengthening is under study at the ESRF to improve the performance of the new EBS storage ring, mainly for few bunch operation with high currents per bunch, by reducing Touschek and intrabeam scattering, thereby increasing the lifetime and limiting the emittance growth. It will also reduce impedance heating of the vacuum chambers. The 4th Harmonic 1.41 GHz normal conducting cavity design takes inspiration from the KEK idea of using a TM020 mode exhibiting a reduced R/Q but a higher unloaded Q with respect to TM010. We propose to use multicell cavities for their compactness, the reduced number of required ancillaries and the ease of control for a reduced number of cavities. The drawback is the complexity of the model and the necessity to damp the lower order TM010 mode (LOM) as well as the higher order modes (HOM). The RF design of a 4th harmonic multicell damped cavity will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB332

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paper received ※ 19 May 2021 paper accepted ※ 17 August 2021 issue date ※ 18 August 2021

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MOPAB333

ESRF-EBS 352 MHz HOM Damped RF Cavities

cavity, impedance, HOM, MMI

1034

A. D’Elia, J. Jacob, V. Serrière
ESRF, Grenoble, France

For the new ESRF-EBS Storage Ring (SR), HOM damped RF cavities were needed to cope with the reduced thresholds for Longitudinal Coupled Bunch Instabilities (LCBI). The 352 MHz cavities were designed at the ESRF based on an improved version of the 500 MHz EU/ALBA/BESSY structures. A short description of the cavity design will be presented as well as an overview of the fabrication, the preparation and the performance of 13 such cavities for the ESRF-EBS SR. A study of the impedance of a whole cavity equipped with its ancillaries (HOM absorbers, ion pump and tuner) will be presented. One of the three HOM absorbers, the smaller one on top of the cavity, was finally not installed on the machine. The reasons and a detailed analysis in terms of HOM impedances that justifies this choice will be reported.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB333

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paper received ※ 19 May 2021 paper accepted ※ 07 June 2021 issue date ※ 23 August 2021

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MOPAB347

High Power Coupler Conditioning for bERLinPro Energy Recovery Linac Injector

booster, cavity, vacuum, MMI

1080

A. Neumann, W. Anders, 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.
Helmholtz Zentrum Berlin is currently finalizing the construction of the demonstrator Energy Recovery Linac bERLinPro *. The first part, which will be commissioned, will be the injector consisting of a superconducting RF (SRF) photo-injector (Gun) and a Booster module made up of three two cell SRF cavities. For the latter the 2.3 MeV beam from the gun needs to be accelerated to 6.5 MeV, whereas one Booster cavity will be operated in zero-crossing mode for bunch-shortening. Thus, for the final stage with a 100 mA beam, the twin power couplers of the Booster cavity need to deliver up to 120 kW in travelling continous wave (CW) mode at 1.3 GHz each. To achieve that, a dedicated coupler conditioning setup was installed and commissioned. Here, we will present the first conditioning results with the bERLinPro Booster fundamental power couplers in pulsed and CW regime.
* 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

Poster MOPAB347 [3.256 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB347

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paper received ※ 18 May 2021 paper accepted ※ 08 June 2021 issue date ※ 23 August 2021

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MOPAB359

Operational Experience and Redesign of the Tuner without Spring Fingers for the LEReC Warm Cavity

cavity, operation, vacuum, electron

1116

B.P. Xiao, J.M. Brennan, J.C. Brutus, K. Mernick, S. Polizzo, S.K. Seberg, F. Severino, K.S. Smith, 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.
A folded coaxial tuner without spring fingers was designed for the Low Energy RHIC electron Cooler (LEReC) 2.1 GHz warm cavity. During RHIC run 2019, this tuner was found to cause cavity trips via different failure modes. After analyzing these failure modes, a new straight coaxial tuner without spring fingers was proposed and was installed. We show the operational experience of the new tuner in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB359

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paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 12 August 2021

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MOPAB376

Design and Fabrication of a Quadrupole Resonator for SRF R&D

cavity, quadrupole, niobium, radio-frequency

1158

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
R. Monroy-Villa, D. Reschke, J.H. Thie
DESY, Hamburg, Germany

As Nb superconducting radio-frequency (SRF) cavities are now approaching the theoretical limits of the material, a variety of different surface treatments have been developed to further improve their performance; although no fully understood theory is yet available. Small superconducting samples are studied to characterize their material properties and their evolution under different surface treatments. To study the RF properties of such samples under realistic SRF conditions at low temperatures, a test cavity called quadrupole resonator (QPR) is currently being fabricated. In this work 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 under cavity-like conditions, i.e., at temperatures between 2K and 8 K, under magnetic fields up to 120mT 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 a status report on the current manufacturing process, will be presented.

Poster MOPAB376 [1.119 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB376

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paper received ※ 26 May 2021 paper accepted ※ 09 June 2021 issue date ※ 23 August 2021

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MOPAB383

Pressure Test for Large Grain and Fine Grain Niobium Cavities

cavity, niobium, experiment, FEM

1173

M. Yamanaka, T. Dohmae, H. Inoue, T. Saeki, K. Umemori, Y. Watanabe, K. Yoshida
KEK, Ibaraki, Japan
K. Enami
Tsukuba University, Ibaraki, Japan

The pressure test was performed using a fine grain (FG) and a large grain (LG) niobium cavities. The cavity is 1.3 GHz 3-cell TESLA-like shape. The cavity was housed in a steel vessel. Water is supplied into the vessel and the cavity outside is pressurized. The applying pressure and the natural frequency of cavity were measured during the pressure test. The FG and LG cavities were deformed greatly and the pressure dropped suddenly at 3.4 MPa and 1.6 MPa, respectively. The frequency shifted up to 3.4 MHz and 1.3 MHz, respectively. There was no leak after the pressure test, so the cavity did not rupture under above pressure. The result of the pressure at LG cavity is less half than that of the FG cavity. We calculated the stress distribution in the structure by applying outer water pressure using a FEM. The maximum stress at cell when above test pressure is applied, are 146 MPa in FG and 73 MPa in LG, respectively. These stresses are similar to tensile strength of niobium specimen measure by ourselves. The result of pressure tests agrees well with the calculation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB383

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paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 13 August 2021

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MOPAB384

Nb₃Sn Coating of Twin Axis Cavity for Accelerator Applications

cavity, linac, niobium, dipole

1175

J.K. Tiskumara, S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
J.R. Delayen, H. Park, U. Pudasaini, C.E. Reece
JLab, Newport News, Virginia, USA
G.V. Eremeev
Fermilab, Batavia, Illinois, USA

Funding: Research supported by DOE Office of Science Accelerator Stewardship Program Award DE- SC0019399. Partially authored by Jefferson Science Associates under contract no. DEAC0506OR23177
A Superconducting twin axis cavity consisting of two identical beam pipes that can accelerate and decelerate beams within the same structure has been proposed for the Energy Recovery Linac (ERL) applications. There are two niobium twin axis cavities at JLab fabricated with the intention of later Nb₃Sn coating and now we are progressing to coat them using vapor diffusion method. Nb₃Sn is a potential alternate material for replacing Nb in SRF cavities for better performance and reducing operational costs. Because of advanced geometry, larger surface area, increased number of ports and hard to reach areas of the twin axis cavities, the usual coating approach developed for typical elliptical single-axis cavities must be evaluated and requires to be adjusted. In this contribution, we report the first results from the coating of a twin axis cavity and discuss current challenges with an outlook for the future.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB384

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paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 20 August 2021

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MOPAB385

An Overview of RF Systems for the EIC

cavity, electron, HOM, luminosity

1179

R.A. Rimmer, J.P. Preble
JLab, Newport News, Virginia, USA
K.S. Smith, A. Zaltsman
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under DOE Contract No. DE-SC0012704, by Jefferson Science Associates under contract DE-SC0002769, and by SLAC under Contract No. DE-AC02-76SF00515.
The Electron Ion Collider (EIC) to be constructed at Brookhaven National Laboratory in the USA will be a complex system of accelerators providing high luminosity, high polarization, variable center of mass energy collisions between electrons and protons or ions. To achieve this a variety of RF systems are required. They must provide for capture, formation and storage of Ampere-class beams in the electron and hadron storage rings (ESR and HSR), fast acceleration of high-charge polarized electron bunches in the rapid cycling synchrotron (RCS), provision of cold high current electron bunches in the high-energy cooler ERL and precise high-gradient crabbing of electrons and hadrons either side of the interaction point. The challenges include strong HOM damping in the storage ring cavities and cooler ERL, very high fundamental mode power in the ESR and cooler injector, extremely stable low-noise operation of the crab cavities, mitigation of transient beam loading from gaps, and operating over a wide range of energies and beam currents. We describe the high-level system parameters and principal design choices made and progress on the R&D plan to develop these state of the art systems.

Poster MOPAB385 [1.268 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB385

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paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 22 August 2021

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MOPAB386

Development of Nitrogen-Doping Technology for SHINE

cavity, niobium, ECR, linac

1182

Y. Zong, X. Huang, Z. Wang
SINAP, Shanghai, People’s Republic of China
J.F. Chen, H.T. Hou, D. Wang, J.N. Wu, Y.X. Zhang
SARI-CAS, Pudong, Shanghai, People’s Republic of China
P.C. Dong
Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
Y.W. Huang
ShanghaiTech University, Shanghai, People’s Republic of China
J. Rong
SSRF, Shanghai, People’s Republic of China

The Shanghai HIgh repetition rate XFEL aNd Extreme light facility (SHINE) is under construction, which needs six hundred 1.3GHz cavities with high quality factor. In this paper, we present the newest studies on single cell cavities with nitrogen doping and cold EP treatment, showing an obvious improvement compared with the previous results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB386

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paper received ※ 21 May 2021 paper accepted ※ 08 June 2021 issue date ※ 12 August 2021

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MOPAB388

Status of the High Power Couplers for ESS Elliptical Cavities

cavity, cryomodule, simulation, vacuum

1186

C. Arcambal, P. Bosland, G. Devanz, T. Hamelin, C. Madec, C. Marchand, M. Oublaid, G. Perreu, C. Servouin, C. Simon
CEA-IRFU, Gif-sur-Yvette, France
M. Baudrier, C. Mayri, S. Regnaud, T.V. Vacher
CEA-DRF-IRFU, France

In the framework of the European Spallation Source (ESS), CEA Paris-Saclay is responsible for the delivery of 30 cryomodules (9 medium beta (β = 0.67) and 21 high beta (β = 0.86) ones). Each cryomodule contains 4 elliptical cavities equipped with a radio frequency power coupler. The ESS nominal pulse is 1.1 MW maximum peak power over a width of 3.6 ms at a repetition rate of 14 Hz. The design of the couplers for medium beta and for high beta cavities is the same, except a small difference of the antenna penetration to adjust the Q_ext. The mass production of the 120 couplers started and all the medium beta couplers have been conditioned at room temperature. The first cryomodules equipped with the power couplers were successfully tested at high RF power and with cavities at 2K reaching the ESS nominal pulse. The main issue at the start of the series production could be fixed and it was due to bad TiN coatings that caused abnormal dielectric losses in the window. Thus, this paper deals with the TiN coating defect, presents the conditioning procedure and gives a conditioning report of these 36 couplers.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB388

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paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 30 August 2021

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MOPAB391

Conduction Cooling Methods for Nb₃Sn SRF Cavities and Cryomodules

cavity, controls, accelerating-gradient, simulation

1192

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

Rapid progress in the performance of Nb₃Sn SRF cavities during the last few years has made Nb₃Sn 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 critical property enables the use of new, robust, turn-key style cryogenic cooling schemes based on conduction cooling with commercial 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 and the measured thermal dynamics match what is found in numerical simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB391

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paper received ※ 20 May 2021 paper accepted ※ 10 June 2021 issue date ※ 17 August 2021

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MOPAB394

Preliminary BCP Flow Field Investigation by CFD Simulations and PIV in a Transparent Model of a SRF Elliptical Low Beta Cavity

cavity, experiment, simulation, laser

1204

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

Standard vertical Buffered Chemical Polishing (BCP) is one of the main surface treatment for Superconducting Radiofrequency (SRF) cavities. A finite element Computational Fluid Dynamic (CFD) model has been developed. Uncertainties in the solution of fluid simulations are not negligible due to the complex geometry of a SRF cavity; thus without an experimental validation, results from this type of simulations cannot be confidently used to improve the process. To this aim, an experimental study was started to investigate the fluid dynamics of the BCP process by means of Particle Image Velocimetry (PIV) technique. Similitude on Reynolds number and Refractive Index Matching (RIM) technique were also implemented to replace the dangerous BCP mixture with a glycerine-water mixture. The paper describes the preliminary results from simulations and experiment.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB394

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paper received ※ 19 May 2021 paper accepted ※ 24 June 2021 issue date ※ 14 August 2021

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MOPAB396

Measurements of Magnetic Field Penetration in Superconducting Materials for SRF Cavities

cavity, experiment, solenoid, accelerating-gradient

1208

I.H. Senevirathne, J.R. Delayen, A.V. Gurevich
ODU, Norfolk, Virginia, USA
J.R. Delayen, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: This work is supported by NSF Grants PHY-1734075 and PHY-1416051, and DOE Award DE-SC0010081 and DE-SC0019399
Superconducting radiofrequency (SRF) cavities used in particle accelerators operate in the Meissner state. To achieve high accelerating gradients, the cavity material should stay in the Meissner state under high RF magnetic field without penetration of vortices through the cavity wall. The field onset of flux penetration into a superconductor is an important parameter of merit of alternative superconducting materials other than Nb which can enhance the performance of SRF cavities. There is a need for a simple and efficient technique to measure the onset of field penetration into a superconductor directly. We have developed a Hall probe experimental setup for the measurement of the flux penetration field through a superconducting sample placed under a small superconducting solenoid magnet which can generate magnetic fields up to 500 mT. The system has been calibrated and used to measure different bulk and thin film superconducting materials. This system can also be used to study SIS multilayer coatings that have been proposed to enhance the vortex penetration field in Nb cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB396

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 11 August 2021

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TUXC03

Ferro-Electric Fast Reactive Tuner Applications for SRF Cavities

cavity, beam-loading, operation, controls

1305

N.C. Shipman, A. Castilla, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley, H. Timko
CERN, Geneva, Switzerland
I. Ben-Zvi
BNL, Upton, New York, USA
G. Burt, A. Castilla
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
C.-J. Jing, A. Kanareykin
Euclid TechLabs, Solon, Ohio, USA

A Ferro-Electric fast Reactive Tuner (FE-FRT) is a novel type of RF cavity tuner containing a low loss ferroelectric material. FE-FRTs have no moving parts and allow cavity frequencies to be changed extremely quickly (on the timescale of 100s of ns or less). They are of particular interest for SRF cavities as they can be placed outside the liquid helium environment and without an FE-FRT it’s typically very difficult to tune SRF cavities quickly. FE-FRTs can be used for a wide variety of use cases including microphonics suppression, RF switching, and transient beam loading compensation. This promises entirely new operational capabilities, increased performance and cost savings for a variety of existing and proposed accelerators. An overview of the theory and potential applications will be discussed in detail.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXC03

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 01 September 2021

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TUPAB017

Study of Conduction-Cooled Superconducting Quadrupole Magnets Combined with Dipole Correctors for the ILC Main Linac

quadrupole, dipole, linac, cavity

1375

Y. Arimoto, S. Michizono, Y. Morikawa, N. Ohuchi, T. Oki, H. Shimizu, K. Umemori, X. Wang, A. Yamamoto, Y. Yamamoto, Z.G. Zong
KEK, Ibaraki, Japan
V.S. Kashikhin
Fermilab, Batavia, Illinois, USA

A superconducting rf (SRF) cryomodule for International Linear Collider(ILC) Main Linac equips focus/steering magnets. The magnets are "superferric" magnets with four superconducting (SC) race track coils conductively cooled from the cryomodule LHe supply pipe. The quadrupole field gradient and dipole field are 40 T/m and 0.1 T, respectively. The magnet length and iron-pole radius are 1 m and 0.045 m, respectively. It is known that dark current is generated at SRF cavities and accelerated through the following linac string. The dark current reaches and heats the SC magnets. It is estimated that the power deposition in the magnet may reach more than a few watts and temperature of the SC coils may locally reach to critical temperature of NbTi. It is important to make the magnet not reach quench with sufficient conduction cooling. We aim to realize the SC magnet which can stably operate under such condition. We plan to develop test coils made of three types of SC materials, NbTi, Nb₃Sn, and MgB₂ and study thermal characteristics and stability . We will develop a short model magnet, based on the test coil results. Here, we will present the magnet design study and the R&D plan.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB017

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paper received ※ 19 May 2021 paper accepted ※ 16 June 2021 issue date ※ 20 August 2021

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TUPAB035

ESS Medium Beta Cavities Status at INFN LASA

cavity, linac, multipactoring, 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 ※ 15 August 2021

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TUPAB048

HMBA Optics Correction Experience at ESRF

optics, lattice, MMI, closed-orbit

1462

S.M. Liuzzo, N. Carmignani, L.R. Carver, L. Farvacque, T.P. Perron, P. Raimondi, S.M. White
ESRF, Grenoble, France

The ESRF-EBS storage ring, successfully commissioned in 2020, operates the HMBA lattice, first proposed in * and then adopted in several recent upgrade programs. The successful and timely commissioning of the storage is in large part due to the excellent optics control achieved over that period. Design performance were obtained with lower than predicted correction strengths, localized for the most part in the vicinity of sextupoles. This remarkable behavior is not only the result of the corrective actions taken during the commissioning but also of the extremely accurate conception and alignment of the machine. This report summarizes the steps that lead to the present performances and discusses their stability over time.
* J.Biasci et al. Synchrotron Radiation News27, 8 (2014), https://doi.org/10.1080/08940886.2014.970931.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB048

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paper received ※ 10 May 2021 paper accepted ※ 11 June 2021 issue date ※ 21 August 2021

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TUPAB049

USSR HMBA Storage Ring Lattice Options

injection, emittance, lattice, optics

1466

S.M. Liuzzo, N. Carmignani, L.R. Carver, J. Chavanne, L. Hoummi, J. Jacob, T.P. Perron, R. Versteegen, S.M. White
ESRF, Grenoble, France
I.A. Ashanin, V.S. Dyubkov, S.M. Polozov
MEPhI, Moscow, Russia
I.A. Ashanin, V.S. Dyubkov, T. Kulevoy, S.M. Polozov
NRC, Moscow, Russia
T. Kulevoy
ITEP, Moscow, Russia

Funding: European Union’s Horizon 2020 research and innovation program under grant #871072 Russian federation resolution #287
Several new accelerator facilities will be built in Russia in a few years from now. One of those facilities is a 6GeV storage ring (SR) light source (USSR - Ultimate Source of Synchrotron Radiation) to be built in Protvino, near Moscow. The Cremlin+ project aims to incorporate in this activity the best experience of European Accelerator Laboratories. The design of the optics for this SR is presented here in two declinations leading to 70 pm-rad equilibrium horizontal emittance. The first is a 40 cells lattice, the second is the same but includes high field Short Bending magnet sources in each cell. Optics and high order multipole optimizations are performed to obtain sufficient lifetime and dynamic aperture for a conservative off-axis injection.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB049

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paper received ※ 12 May 2021 paper accepted ※ 11 June 2021 issue date ※ 01 September 2021

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TUPAB098

Recent Progress Toward a Conduction-Cooled Superconducting Radiofrequency Electron Gun

cavity, simulation, electron, accelerating-gradient

1604

O. Mohsen, N. Adams, V. Korampally, A. McKeown, D. Mihalcea, P. Piot, I. Salehinia, N. Tom
Northern Illinois University, DeKalb, Illinois, USA
R. Dhuley, M.G. Geelhoed, D. Mihalcea, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA
P. Piot
ANL, Lemont, Illinois, USA

Funding: This work was supported by the US Department of Energy (DOE) under contract DE-SC0018367
High-repetition-rate electron sources have widespread applications. This contribution discusses the progress toward a proof-of-principle demonstration for a conduction-cooled electron source. The source consists of a simple modification of an elliptical cavity that enhances the field electric field at the photocathode surface. The source was cooled to cryogenic temperatures and preliminary measurements for the quality factor and accelerating field were performed. Additionally, we present future plans to improve the source along with simulated beam-dynamics performances.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB098

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paper received ※ 29 May 2021 paper accepted ※ 17 June 2021 issue date ※ 14 August 2021

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TUPAB166

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

cavity, multipactoring, 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 ※ 12 August 2021

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TUPAB167

Status of Conduction Cooled SRF Photogun for UEM/UED

gun, cavity, cryomodule, shielding

1773

R.A. Kostin, C. Jing
Euclid Beamlabs, Bolingbrook, USA
P.V. Avrakhov, A. Liu, Y. Zhao
Euclid TechLabs, Solon, Ohio, USA

Funding: DOE #DE-SC0018621
Benefiting from the rapid progress on RF photogun technologies in the past two decades, the development of MeV range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation. UEM or UED use low power electron beams with modest energies of a few MeV to study ultrafast phenomena in a variety of novel and exotic materials. SRF photoguns become a promising candidate to produce highly stable electrons for UEM/UED applications because of the ultrahigh shot-to-shot stability compared to room temperature RF photoguns. SRF technology was prohibitively expensive for industrial use until two recent advancements: Nb₃Sn and conduction cooling. The use of Nb₃Sn allows to operate SRF cavities at higher temperatures (4K) with low power dissipation which is within the reach of commercially available closed-cycle cryocoolers. Euclid is developing a continuous wave (CW), 1.5-cell, MeV-scale SRF conduction cooled photogun operating at 1.3 GHz. In this paper, the technical details of the design and first experimental data are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB167

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paper received ※ 29 May 2021 paper accepted ※ 21 June 2021 issue date ※ 31 August 2021

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TUPAB211

The Accelerator System of IFMIF-DONES Multi-MW Facility

linac, cavity, rfq, cryomodule

1910

I. Podadera, A. Ibarra, D. Jimenez-Rey, J. Mollá, C. Oliver, D. Regidor, R. Varela, C. de la Morena
CIEMAT, Madrid, Spain
F. Arbeiter, V. Hauer
KIT, Eggenstein-Leopoldshafen, Germany
N. Bazin, J. Dumas, L. Seguí
CEA-IRFU, Gif-sur-Yvette, France
L. Bellan, E. Fagotti, A. Palmieri, A. Pisent
INFN/LNL, Legnaro (PD), Italy
N. Chauvin, S. Chel, J. Plouin
CEA-DRF-IRFU, France
G. Duglue, H. Dzitko
F4E, Germany
W.C. Grabowski, A. Wysocka-Rabin
NCBJ, Świerk/Otwock, Poland
M. Jaksic, T. Tadic
RBI, Zagreb, Croatia
W. Królas
IFJ-PAN, Kraków, Poland
R. López, A. Muñoz, C. Prieto
Empresarios Agrupados, Madrid, Spain
O. Nomen, M. Sanmartí, F.J. Saura Esteban, B.K. Singh, D. Sánchez-Herranz
IREC, Sant Adria del Besos, Spain

Funding: Work carried out within EUROfusion Consortium and DONES-PreP and received funding from the Euratom research and training programme 2014-2018 & 2019-2020 under grants agreement No. 633053 & 870186
The IFMIF-DONES (DEMO-Oriented Neutron Early Source) facility has passed the preliminary design phase and the detailed design phase is very much advanced. Next step will be the preparation phase for the construction of the facility. The DONES facility aims at developing a database of fusion-like radiation effects on materials to be used in future fusion reactors up to damage levels expected in the EU DEMO. It will be based on an intense neutron source created by an accelerated deuteron beam (125 mA CW, 40 MeV) impinging on a liquid lithium curtain. The DONES Accelerator Systems (AS) will be responsible of delivering this 5 MW D⁺ beam with very high availability. The beam acceleration will be performed by several stages: an ion source and LEBT, an RFQ, a MEBT, an SRF Linac and a HEBT transporting and delivering an optimized profile down to the target. A high power RF system and several ancillaries will ensure the equipment is properly operated. This contribution will report the present status of the AS design, the main challenges faced, the R&D programme to overcome them, and the prospects for the construction and commissioning of the DONES accelerator in Granada (Spain).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB211

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 13 August 2021

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TUPAB302

Arrival Time Stabilization at Flash Using the Bunch Arrival Corrector Cavity (BACCA)

cavity, electron, feedback, laser

2194

B. Lautenschlager, L. Butkowski, M.K. Czwalinna, B. Dursun, M. Hierholzer, S. Pfeiffer, H. Schlarb, Ch. Schmidt
DESY, Hamburg, Germany

For pump-probe and seeding experiments at free electron lasers, a femtosecond precise bunch arrival time stability is mandatory. To stabilize the arrival times a fast longitudinal intra bunch-train feedback (L-IBFB) using bunch arrival time monitors is applied. The electron bunch energy prior to a bunch compression chicane is modulated by superconducting radio frequency (SRF) cavities to compensate fast arrival time fluctuations of the subsequent bunches. A broadband normal conducting RF cavity was installed in front of the first bunch compression chicane at FLASH. The L-IBFB uses the normal conducting cavity for small but fast energy corrections together with the SRF cavities for larger and slower corrections. Current measurements show arrival time stabilities of the electron bunches towards 5 fs (rms) at the end of the linac, if the normal conducting cavity acts together with the SRF cavities in the L-IBFB system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB302

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 12 August 2021

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TUPAB328

Machine Learning for Time Series Prediction of an Accelerator Beam to Recognize Equipment Malfunction

cavity, linac, ion-source, neutron

2272

C.C. Peters
ORNL RAD, Oak Ridge, Tennessee, USA
W. Blokland, D.L. Brown, F. Liu, C.D. Long, D. Lu, P. Ramuhalli, D.E. Womble, J. Zhang, A.P. Zhukov
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05- 00OR22725 for the U.S. Department of Energy.
The Spallation Neutron Source (SNS) is an accelerator based pulsed neutron source based on a 1 GeV pulsed proton Superconducting Radio Frequency (SRF) linear accelerator (linac). Since beginning high power beam operation in 2006 correlations have been found linking abrupt beam loss events to SRF cavity instabilities. With the planned upgrades to double the beam power we expect increased rates of degradation and the importance of minimizing these beam loss events will become ever more important. To further limit degradation, we are developing machine learning approaches to monitor the beam and to detect, predict and prevent beam loss events. Initial research has shown that precursors to beam loss events are detectable. The initial steps are to use ML-based classification to recognize anomalies and to use Long Short-Term Memory (LSTM) autoencoders to predict beam loss. In this paper, we describe recent progress in applying machine learning for recognizing anomalies and predicting beam loss and present initial results of our research using acquired data from different diagnostics and the Machine Protection System (MPS).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB328

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paper received ※ 23 May 2021 paper accepted ※ 28 May 2021 issue date ※ 23 August 2021

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TUPAB333

Status of PIP-II 650 MHz Prototype Dressed Cavity Qualification

cavity, cryomodule, status, superconductivity

2279

G.V. Eremeev, D.J. Bice, C. Boffo, S.K. Chandrasekaran, S. Cheban, F. Furuta, I.V. Gonin, C.J. Grimm, S. Kazakov, T.N. Khabiboulline, A. Lunin, M. Martinello, N. Nigam, J.P. Ozelis, Y.M. Pischalnikov, K.S. Premo, O.V. Prokofiev, O.V. Pronitchev, G.V. Romanov, N. Solyak, A.I. Sukhanov, G. Wu
Fermilab, Batavia, Illinois, USA
M. Bagre, V. Jain, A. Puntambekar, S. Raghvendra, P. Shrivastava
RRCAT, Indore (M.P.), India
P. Bhattacharyya, S. Ghosh, S. Seth
VECC, Kolkata, India
R. Kumar
BARC, Mumbai, India
J. Lewis, P.A. McIntosh, A.E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
C. Pagani, R. Paparella
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy
T. Reid
ANL, Lemont, Illinois, USA
A.D. Shabalina
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

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.
Low-beta and high-beta sections of PIP-II linac will use nine low-beta cryomodules with four cavities each and four high-beta cryomodules with six cavities each. These cavities will be produced and qualified in collaboration between Fermilab and the international partner labs. Prior to their installation into prototype cryomodules, several dressed cavities, which include jacketed cavities, high power couplers, and tuners, will be qualified in STC horizontal test bed at Fermilab. After qualification of bare β = 0.9 cavities at Fermilab, several pre-production β = 0.92 and β = 0.61 cavities have been and are being fabricated and qualified. Procurements have also been started for high power couplers and tuners. In this contribution we present the current status of prototype dressed cavity qualification for PIP-II.

Poster TUPAB333 [6.247 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB333

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paper received ※ 23 May 2021 paper accepted ※ 19 July 2021 issue date ※ 25 August 2021

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TUPAB338

Surface Roughness Reduction of Nb₃Sn Thin Films via Laser Annealing for Superconducting Radio-Frequency Cavities

laser, cavity, superconductivity, HOM

2283

Z. Sun, M. Ge, M. Liepe, T.E. Oseroff, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A.B. Connolly, M.O. Thompson
Cornell University, Ithaca, USA

Superconducting radio frequency (SRF) cavities, a key component of particle accelerators, await new SRF materials beyond the state-of-the-art niobium. Nb₃Sn is one of the most competitive candidates, since it increases the superheating field, allows the operation temperature up to 4K, and improves cavity efficiency. Surface roughness and grain boundaries, however, significantly affect the RF performance of current Nb₃Sn cavities. Here, we explore a post laser annealing technique to reduce the surface roughness. In doing so, we deposited a TiN laser-absorber on Nb₃Sn and Nb surfaces, and then annealed the samples by laser scanning via different laser systems. The Nb₃Sn surface roughness was minimized to 101 nm (Ra) by laser annealing via 308 nm, 35 ns pulses. Surface imaging and Fourier analysis revealed laser annealing is able to remove sharp edges and <1 um wavelength features.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB338

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paper received ※ 20 May 2021 paper accepted ※ 09 June 2021 issue date ※ 19 August 2021

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TUPAB342

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

cavity, niobium, multipactoring, 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 ※ 30 August 2021

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TUPAB343

Final Design Studies for the VSR DEMO 1.5 GHz Coupler

multipactoring, 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

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 01 September 2021

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TUPAB344

Evaluation of Anisotropic Magnetoresistive (AMR) Sensors for a Magnetic Field Scanning System for SRF Cavities

cavity, experiment, niobium, MMI

2304

I.P. Parajuli, G. Ciovati, J.R. Delayen, A.V. Gurevich
ODU, Norfolk, Virginia, USA
G. Ciovati, J.R. Delayen
JLab, Newport News, Virginia, USA

Funding: Work supported by NSF Grant 100614-010. G. C. is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
One of the significant causes of residual losses in superconducting radio-frequency (SRF) cavities is trapped magnetic flux. The flux trapping mechanism depends on many factors that include cool-down conditions, surface preparation techniques, and ambient magnetic field orientation. Suitable diagnostic tools are not yet available to quantitatively correlate such factors’ effect on the flux trapping mechanism. A magnetic field scanning system (MFSS) consisting of AMR sensors, fluxgate magnetometers, or Hall probes is recently commissioned to scan the local magnetic field of trapped vortices around 1.3 GHz single-cell SRF cavities. In this contribution, we will present results from sensitivity calibration and the first tests of AMR sensors in the MFSS.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB344

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 25 August 2021

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TUPAB345

Availability Modeling of the Solid-State Power Amplifiers for the CERN SPS RF Upgrade

operation, cavity, simulation, MMI

2308

L. Felsberger, A. Apollonio, T. Cartier-Michaud, E. Montesinos, J.C. Oliveira, J.A. Uythoven
CERN, Geneva, Switzerland

Funding: This project has received funding from the Euratom research and training programme 2019-2020 under grant agreement No 945077.
As part of the LHC Injector Upgrade program a complete overhaul of the Super Proton Synchrotron Radio-Frequency (RF) system took place. New cavities have been installed for which the solid-state technology was chosen to deliver a combined RF power of 2 MW from 2560 RF amplifiers. This strategy promises high availability as the system continues operation when some of the amplifiers fail. This study quantifies the operational availability that can be achieved with this new installation. The evaluation is based on a Monte Carlo simulation of the system using the novel AvailSim4 simulation software. A model based on lifetime estimations of the RF modules is compared against data from early operational experience. Sensitivity analyses have been made, that give insight to the chosen operational scenario. With the increasing use of solid-state RF power amplifiers, the findings of this study provide a useful reference for future application of this technology in particle accelerators.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB345

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 02 September 2021

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TUPAB350

Design of 71 MHz Power Amplifier in a Single-ended Architecture for IRANCYC-10 Cyclotron

cyclotron, simulation, impedance, factory

2325

F. Babagoli Moziraji, H. Afarideh
AUT, Tehran, Iran
M. Dehghan
Shahid Beheshti University, Tehran, Iran
F. Ghasemi
NSTRI, Tehran, Iran

In this paper, the design and simulation of a high power amplifier to provide the required power of a cyclotron accelerator (IRANCYC-10) is presented step-by-step. By combining four modules of this amplifier, a power of 2.5 kW can be achieved to start the main power amplifier. The single ended designs amplifier can generate 1 kW the operating frequency of 71MHz continuous wave (CW). The purpose of choosing this type of design is simplicity to build without the need for a balun, low weight to build high power, as well as cost-effectiveness. The gain and PAE of the SSPA are 21.21 and 71%, respectively. There are also ways to reduce the size of the amplifier.

Poster TUPAB350 [1.008 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB350

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paper received ※ 19 May 2021 paper accepted ※ 15 August 2021 issue date ※ 25 August 2021

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TUPAB369

A Fast Non-Linear Model for the EBS Combined Sextupole-Corrector Magnets

sextupole, dipole, multipole, quadrupole

2381

G. Le Bec
ESRF, Grenoble, France

Corrector are often integrated in higher order accelerator magnets. In the new ESRF-EBS storage ring, the sextupoles include additional windings allowing for dipole and skew quadrupole corrections. The accurate modelization of such magnets is not as trivial as it may appear, due to their non-linearities and to the crosstalk between their channels. Changing any corrector current induce non-linear errors in the other corrector channels and in the main sextupole strength, making difficult the trimming of the magnets. A model based on a non-linear excitation curve and quadratic contributions from corrector currents was developed. This model is very fast and was included in the accelerator control system to compute the corrector currents in real-time. It was tested against 3D magnetic simulations and magnetic measurements and compared to a simpler matrix-based model.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB369

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paper received ※ 17 May 2021 paper accepted ※ 15 August 2021 issue date ※ 31 August 2021

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WEXC03

Review of Superconducting Radio Frequency Gun

cathode, gun, cavity, operation

2556

R. Xiang
HZDR, Dresden, Germany

The success of proposed high power free-electron lasers (FELs) and energy recovery linac (ERL) largely depends on the development of the electron source, which requires the best beam quality and CW operation. An elegant way to realize this average brilliance is to combine the high beam quality of mature normal conducting radio frequency photoinjector with the quick developing superconducting radio frequency technology, to build superconducting rf photoinjectors (SRF guns). In last decade, several SRF gun programs based on different approaches have achieved promising progress, even succeeded in routine operation at BNL and HZDR [*,**]. In the near future SRF guns are expected to play an important role for hard X-ray FEL facilities. In this contribution, we will review the design concepts, parameters, and the status of the major SRF gun projects.
*I. Petrushina et al., Phys. Rev. Lett. 124, 244801
**J. Teichert at al., Phys. Rev. Accel. Beams 24, 033401

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXC03

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paper received ※ 19 May 2021 paper accepted ※ 28 June 2021 issue date ※ 11 August 2021

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WEPAB020

The Relation Between Field Flatness and the Passband Frequency in the Elliptical Cavities

cavity, simulation, gun, accelerating-gradient

2636

G.-T. Park, R.A. Rimmer, H. Wang
JLab, Newport News, Virginia, USA

A technique that predicts the field flatness of the operating pi-mode based on the passband frequency is highly desirable when the direct measurement of the field is not available. Such a technique was developed for the SNS-PPU cavity, a 6-cell SRF cavity whose field flatness is important for cold operation. In this paper, we will present the theory on the relations between field profile and passband frequencies of the arbitrary deformed cavities, the simulation studies, and comparison with the experimental measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB020

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paper received ※ 17 May 2021 paper accepted ※ 24 June 2021 issue date ※ 31 August 2021

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WEPAB138

Superconducting RF Gun with High Current and the Capability to Generate Polarized Electron Beams

gun, electron, cathode, cavity

2936

I. Petrushina
SUNY SB, Stony Brook, New York, USA
S.A. Belomestnykh, S. Kazakov, T.N. Khabiboulline, M. Martinello, Y.M. Pischalnikov, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
J.C. Brutus, P. Inacker, Y.C. Jing, V. Litvinenko, J. Skaritka, E. Wang
BNL, Upton, New York, USA
J.M. Grames, M. Poelker, R. Suleiman, E.J-M. Voutier
JLab, Newport News, Virginia, USA

High-current low-emittance CW electron beams are indispensable for nuclear and high-energy physics fixed target and collider experiments, cooling high energy hadron beams, generating CW beams of monoenergetic X-rays (in FELs) and gamma-rays (in Compton sources). Polarization of electrons in these beams provides extra value by opening a new set of observables and frequently improving the data quality. We report on the upgrade of the unique and fully functional CW SRF 1.25 MeV SRF gun, built as part of the Coherent electron Cooling (CeC) project, which has demonstrated sustained CW operation with CsK2Sb photocathodes generating electron bunches with record-low transverse emittances and record-high bunch charge exceeding 10 nC. We propose to extend the capabilities of this system to high average current of 100 milliampere in two steps: increasing the current 30-fold at each step with the goal to demonstrate reliable long-term operation of the high-current low-emittance CW SRF guns. We also propose to test polarized GaAs photocathodes in the ultra-high vacuum (UHV) environment of the SRF gun, which has never been successfully demonstrated in RF accelerators.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB138

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paper received ※ 25 May 2021 paper accepted ※ 29 July 2021 issue date ※ 23 August 2021

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WEPAB165

Metamaterial Waveguide HOM Loads for SRF Accelerating Cavities

HOM, GUI, vacuum, cavity

2994

S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA

Suppression of beam induced HOMs is necessary for most SRF accelerating cavities driven with high currents. One of the problems in design of a HOM load is that vacuum compatible materials with high enough imaginary part of the dielectric permittivity, which provides absorption, have also a high real part of the permittivity. This does not allow absorbing RF radiation at short distance and in broad frequency band. We propose considering artificial metamaterials where besides lossy dielectric pieces, an absorber with high magnetic permeability is included. In our proposal, we suggest composing a waveguide HOM load of a metamaterial consisted of well-known ceramic and ferrite plates placed periodically in a stack. Such a design provides low return losses, compactness and broad frequency range of the operation.

Poster WEPAB165 [1.844 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB165

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 15 August 2021

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WEPAB360

Future Prospective for Bent Crystals in Accelerators

lattice, collimation, scattering, experiment

3545

M. Romagnoni
INFN-Ferrara, Ferrara, Italy
M. Romagnoni
Universita’ degli Studi di Milano, Milano, Italy

Super magnet dipoles employed to steer high energy particle beams are massive instruments requiring cryogenic cooling and featuring large energy consumption. A bent crystal has the potential in a few millimeters to deflect 100-1000 GeV particle beams as much as an hundreds-tesla magnetic dipole. Indeed, within the lattice of a crystal, large electric fields up to several GeV/cm are present. Positive charged particles can be efficiently channeled between two adjacent lattice planes, thus following their curvature. These features and the possibility to selectively affect only the portion of the beam intercepting the crystal led to the proposal of exploiting bent crystals for several purposes, such as the collimation of ions at LHC. In this scheme, the particles on the beam halo instead of being scattered by tens-centimeters long collimators are directly separated from the beam using a 4 mm long silicon crystal. The production of a bent crystal suitable for installation in the LHC beamline requires strict control over lattice features and bending apparatus. The results obtained by the years long research of the INFN research team in Ferrara are presented in this work.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB360

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paper received ※ 14 May 2021 paper accepted ※ 28 July 2021 issue date ※ 29 August 2021

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THPAB007

Technology Spinoff and Lessons Learned from the 4-Turn ERL CBETA

permanent-magnet, cavity, radiation, linac

3762

K.E. Deitrick, N. Banerjee, A.C. Bartnik, D.C. Burke, J.A. Crittenden, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter, Y. Li, W. Lou, P. Quigley, D. Sagan, K.W. Smolenski
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.S. Berg, S.J. Brooks, R.L. Hulsart, G.J. Mahler, F. Méot, R.J. Michnoff, S. Peggs, T. Roser, D. Trbojevic, N. Tsoupas
BNL, Upton, New York, USA
T. Miyajima
KEK, Ibaraki, Japan

The Cornell-BNL ERL Test Accelerator (CBETA) developed several energy-saving measures: multi-turn energy recovery, low-loss superconducting radiofrequency (SRF) cavities, and permanent magnets. With green technology becoming imperative for new high-power accelerators, the lessons learned will be important for projects like the FCC-ee or new light sources, where spinoffs and lessons learned from CBETA are already considered for modern designs.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB007

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paper received ※ 20 May 2021 paper accepted ※ 05 July 2021 issue date ※ 28 August 2021

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THPAB074

ESRF-EBS: Implementation, Performance and Restart of User Operation

MMI, operation, storage-ring, emittance

3929

J.-L. Revol, P. Berkvens, J.-F. Bouteille, N. Carmignani, L.R. Carver, J.M. Chaize, J. Chavanne, F. Ewald, A. Franchi, L. Hardy, J. Jacob, L. Jolly, G. Le Bec, I. Leconte, S.M. Liuzzo, D. Martin, J. Pasquaud, T.P. Perron, Q. Qin, P. Raimondi, B. Roche, K.B. Scheidt, R. Versteegen, S.M. White
ESRF, Grenoble, France

The European Synchrotron Radiation Facility - Extremely Brilliant Source (ESRF-EBS) is a facility upgrade allowing its scientific users to take advantage of the first high-energy 4th generation light source. In December 2018, after 30 years of operation, the beam stopped for a 12-month shutdown to dismantle the old storage ring and to install the new X-ray source. In December 2019, the first beam was stored and accumulated in the storage ring, allowing the vacuum conditioning and tuning to be started. The beam was delivered to beamlines in March 2020 for their commissioning. On 25 August, the user programme was restarted with beam parameters very close to nominal values. In this report, the milestones and key aspects of the return to user-mode operation are presented and discussed.

Poster THPAB074 [2.864 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB074

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paper received ※ 19 May 2021 paper accepted ※ 26 July 2021 issue date ※ 01 September 2021

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THPAB120

Beam on Demand for High-Repetition-Rate X-Ray Free-Electron Lasers

electron, laser, FEL, linac

3995

Z. Zhang, Y. Ding, Z. Huang
SLAC, Menlo Park, California, USA

High-repetition-rate (HRR) free-electron lasers (FELs) with multiple undulator beamlines will advance the frontiers of X-ray science significantly from the remarkable success of existing X-ray FEL facilities. The wide-ranging requirements for the photon properties from multiple beamlines are extremely challenging to satisfy by the same electron beam from a single superconducting radio-frequency (SRF) accelerator. To realize the full potential of an HRR FEL facility, a new emerging concept of "beam on demand" is proposed here. The concept is based on advanced beam dynamics and radio-frequency (RF) techniques to provide beam properties tailored to each undulator line at the desired repetition rate. The beam properties that will be pursued in this proposal include, but are not limited to, beam energy, bunch charge, bunch length, beam current, and its profile. The realization of "beam on demand" will allow optimization of photon properties of individual beamlines to maximize their performance and drastically improve the multiplexing capabilities of Linac Coherent Light Source II and its high-energy upgrade.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB120

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paper received ※ 17 May 2021 paper accepted ※ 23 July 2021 issue date ※ 26 August 2021

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THPAB153

Design, Construction and Tests of the Cooling System with a Cryocooler for Cavity Testing

cavity, cryogenics, vacuum, simulation

4056

P. Pizzol, J.W. Lewellen, E.R. Olivas, E.I. Simakov, T. Tajima
LANL, Los Alamos, New Mexico, USA

Cryogenically cooled normal-conducting cavities have shown higher gradients than those operated at room temperature. We are constructing a compact cooling system with a cryocooler to test C-band normal-conducting cavities and 1.3 GHz superconducting cavities. This paper describes the design, construction, and cooling test results as well as some low-power cavity Q measurement results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB153

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paper received ※ 17 May 2021 paper accepted ※ 21 June 2021 issue date ※ 12 August 2021

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THPAB156

Built-in Thermionic Electron Source for an SRF Linacs

cathode, cavity, electron, gun

4062

I.V. Gonin, S. Kazakov, R.D. Kephart, T.N. Khabiboulline, T.H. Nicol, N. Solyak, J.C.T. Thangaraj, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

The design of a thermionic electron source connected directly to a superconducting cavity, the key part of an SRF gun, is described. The results of beam dynamics optimization are presented which allow lack of beam current intercepting in the superconducting cavity. The electron source concept is presented including the cathode-grid assembly, thermal insulation of the cathode from the cavity, and the gun resonator design. The cavity thermal load caused by the gun is analyzed including the static heat load, black body radiation, backward electron heating, etc.

Poster THPAB156 [0.670 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB156

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

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THPAB173

Fundamental Study on Electromagnetic Characteristics of Half-Wave Resonator for 200 MeV Energy Upgrade of KOMAC Proton Linac

cavity, simulation, linac, proton

4098

J.J. Dang, Y.-S. Cho, H.S. Kim, H.-J. Kwon, S. Lee
Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea

Funding: This work has been supported through KOMAC operation fund of KAERI by the Korea government (MSIT).
A superconducting linac has been developed at KOrea Multi-purpose Accelerator Complex (KOMAC). A goal of the SRF linac is to increase proton beam energy from 100 MeV to 200 MeV. 350 MHz medium beta half-wave resonator (HWR) should provide 3.6 MV accelerating voltage to achieve the energy upgrade. An electromagnetic (EM) analysis on the parametrically designed HWR cavity was conducted. The cavity design was optimized to reduce a peak electric field and a peak magnetic field while satisfying the required acerating voltage. In addition, a mechanical-EM coupled simulation was conducted to estimate a helium pressure sensitivity. Also, Lorentz force detuning was simulated. The design is being optimized to minimize the frequency detuning due to the helium pressure and Lorentz force.

Poster THPAB173 [0.800 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB173

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 22 August 2021

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THPAB320

ALD-Based NbTiN Studies for SIS R&D

site, cavity, plasma, niobium

4420

I. González Díaz-Palacio, R.H. Blick, R. Zierold
University of Hamburg, Hamburg, Germany
W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Superconductor-Insulator-Superconductor multilayers improve the performance of SRF cavities providing magnetic screening of the bulk cavity and lower surface resistance. In this framework NbTiN mixtures stand as a potential material of interest. Atomic layer deposition (ALD) allows for uniform coating of complex geometries and enables tuning of the stoichiometry and precise thickness control in sub-nm range. In this talk, we report about NbTiN thin films deposited by plasma-enhanced ALD on insulating AlN buffer layer. The deposition process has been optimized by studying the superconducting electrical properties of the films. Post-deposition thermal annealing studies with varying temperatures, annealing times, and gas atmospheres have been performed to further improve the thin film quality and the superconducting properties. Our experimental studies show an increase in Tc by 87.5% after thermal annealing and a maximum Tc of 13.9 K has been achieved for NbTiN of 23 nm thickness. Future steps include lattice characterization, using XRR/XRD/EBSD/PALS, and SRF measurements to obtain Hc1 and the superconducting gap.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB320

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paper received ※ 24 May 2021 paper accepted ※ 23 July 2021 issue date ※ 26 August 2021

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THPAB322

Transient Beam Loading in the CBETA Multi-Turn ERL

cavity, linac, beam-loading, operation

4422

N. Banerjee
Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by NSF Grant No. DMR0807731, DOE Award No. DE-SC0012704, and NYSERDA Agreement No. 102192.
The Cornell-BNL ERL Test Accelerator (CBETA) is the first superconducting multi-turn ERL that has been commissioned at Cornell University in a low current mode. In this paper, we first discuss a new model of beam loading which is valid for the low injection energies used in CBETA. Using this model, we explore the effect of bunch patterns, beam turn-on, and turn-off transients on the fundamental mode of the 7-cell SRF cavities used in the main linac. In particular, we examine the operational constraints on the rf system at the design current of 40 mA.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB322

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paper received ※ 20 May 2021 paper accepted ※ 29 July 2021 issue date ※ 26 August 2021

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THPAB336

Novel Magnetron Operation and Control Methods for Superconducting RF Accelerators

controls, injection, operation, cavity

4442

G.M. Kazakevich, R.P. Johnson
Muons, Inc, Illinois, USA
T.N. Khabiboulline, G.V. Romanov, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

High power magnetrons designed and optimized for industrial heating, being injection-locked, have been suggested to power superconducting RF cavities for accelerators due to lower cost and higher efficiency. However, standard operation methods do not provide high efficiency with wideband control suppressing microphonics. We have developed and experimentally verified novel methods of operating and controlling the magnetron that provide stable RF generation with higher efficiency and lower noise than other RF sources. By our method the magnetrons operate with the anode voltage notably lower than the self-excitation threshold improving its performance. This is also a promising way to increase tube reliability and longevity. A magnetron operating with the anode voltage lower than the self-excitation threshold, in so-called stimulated coherent generation mode has special advantage for pulse operation with a gated injection-locking signal. This eliminates the need for expensive pulsed HV modulators and additionally increases the magnetron RF source efficiency due to absence of losses in HV modulators.

Poster THPAB336 [0.960 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB336

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paper received ※ 15 May 2021 paper accepted ※ 08 July 2021 issue date ※ 18 August 2021

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THPAB343

Test Results of the Prototype SSR1 Cryomodule for PIP-II at Fermilab

cavity, cryomodule, vacuum, focusing

4461

D. Passarelli, J. Bernardini, C. Boffo, B.M. Hanna, S. Kazakov, T.N. Khabiboulline, A. Lunin, J.P. Ozelis, M. Parise, Y.M. Pischalnikov, V. Roger, B. Squires, A.I. Sukhanov, G. Wu, V.P. Yakovlev, S. Zorzetti
Fermilab, Batavia, Illinois, USA
C. Contreras-Martinez
FRIB, East Lansing, Michigan, USA

Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DEAC02- 07CH11359 with the United States Department of Energy
A prototype cryomodule containing eight Single Spoke Resonators type-1 (SSR1) operating at 325 MHz and four superconducting focusing lenses has been successfully assembled and cold tested in the framework of PIP-II project at Fermilab. The performance of cavities and focusing lenses along with test results of other cryomodule’s key parameters are presented in this contribution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB343

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paper received ※ 20 May 2021 paper accepted ※ 08 August 2021 issue date ※ 26 August 2021

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THPAB348

INFN-LASA for the PIP-II LB650 Linac

cavity, linac, experiment, cryogenics

4474

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

INFN joined the international effort for the PIP-II project at Fermilab and it’s going to contribute to the low-beta section of the PIP-II proton linac. In particular, INFN-LASA is finalizing its commitment to deliver in kind the full set of the LB650 cavities, namely 36 plus spares 5-cell cavities at 650 MHz and geometrical beta 0.61. All cavities, designed by INFN-LASA, will be produced and surface treated in industry, qualified through vertical cold test, and delivered as ready for string installation. This paper reports the status of INFN’s contribution to PIP-II and of ongoing activities toward the experimental qualifications of infrastructures and prototypes.

Poster THPAB348 [4.076 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB348

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paper received ※ 16 May 2021 paper accepted ※ 01 July 2021 issue date ※ 01 September 2021

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THPAB351

INFN-LASA Experimental Activities on PIP-II Low-Beta Cavity Prototypes

cavity, target, experiment, superconductivity

4481

M. Bertucci, A. Bosotti, A. D’Ambros, A.T. Grimaldi, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
A. Gresele, A. Torri
Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
M. Rizzi
Ettore Zanon S.p.A., Schio, Italy

This paper reports on the first results obtained by INFN-LASA on PIP-II low-beta cavity prototypes. The goal of this activity was to validate the reference surface treatment based on Electropolishing as a bulk removal step. The cavity treatment procedures are here presented together with the strategy used for their optimization. The experimental results of cavity cold tests for a single cell prototype are presented and discussed. Having this cavity achieved the requested performance, the baseline procedure is considered as validated and a plan for a future high-Q cavity surface treatment is proposed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB351

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paper received ※ 19 May 2021 paper accepted ※ 23 July 2021 issue date ※ 22 August 2021

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FRXC01

Superconducting Radio-Frequency Cavity Fault Classification Using Machine Learning at Jefferson Laboratory

cavity, cryomodule, network, radio-frequency

4535

C. Tennant, A. Carpenter, T. Powers, L.S. Vidyaratne
JLab, Newport News, Virginia, USA
K.M. Iftekharuddin, M. Rahman
ODU, Norfolk, Virginia, USA
A.D. Shabalina
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

Funding: This work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC05-06OR23177.
We report on the development of machine learning models for classifying C100 superconducting radiofrequency (SRF) cavity faults in the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. Of the 418 SRF cavities in CEBAF, 96 are designed with a digital low-level RF system configured such that a cavity fault triggers recordings of RF signals for each of eight cavities in the cryomodule. Subject matter experts analyze the collected time-series data and identify which of the eight cavities faulted first and classify the type of fault. This information is used to find trends and strategically deploy mitigations to problematic cryomodules. However, manually labeling the data is laborious and time-consuming. By leveraging machine learning, near real-time - rather than postmortem - identification of the offending cavity and classification of the fault type has been implemented. We discuss the performance of the machine learning models during a recent physics run. We also discuss efforts for further insights into fault types through unsupervised learning techniques and present preliminary work on cavity and fault prediction using data collected prior to a failure event.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXC01

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paper received ※ 16 May 2021 paper accepted ※ 01 July 2021 issue date ※ 11 August 2021

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