NAPAC2019 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOYBA6	Accelerator Performance During the Beam Energy Scan II at RHIC in 2019	electron, operation, luminosity, MMI	26
	C. Liu, I. Blacker, M. Blaskiewicz, K.A. Brown, D. Bruno, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, C.E. Giorgio, X. Gu, T. Hayes, H. Huang, R.L. Hulsart, D. Kayran, N.A. Kling, Y. Luo, D. Maffei, G.J. Marr, B. Martin, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, C. Naylor, S. Nemesure, I. Pinayev, S. Polizzo, V.H. Ranjbar, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, S. Tepikian, P. Thieberger, A. Zaltsman, K. Zeno, I.Y. Zhang, W. Zhang BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. RHIC provided Au-Au collisions at beam energies of 9.8, 7.3, 4.59 and 3.85 GeV/nucleon during the first year of the Beam Energy Scan II in 2019. The physics goals at the first two higher beam energies were achieved. At the two lower beam energies, bunched electron beam cooling has been demonstrated successfully. The accelerator performance was improved compared to when RHIC was operated at these energies in earlier years. This article will introduce the challenges to operate RHIC at low energies and the corresponding countermeasures, and review the improvement of accelerator performance during the operation in 2019.
	Slides MOYBA6 [6.579 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBA6
About •	paper received ※ 21 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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MOYBB3	Progress in Nb₃Sn SRF Cavities at Cornell University	SRF, accelerating-gradient, site, superconductivity	37
	R.D. Porter, H. Hu, M. Liepe, N.A. Stilin, Z. Sun, M.J. Tao Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Niobium-3 Tin (NbSn) is the most promising alternative material for next-generation SRF cavities. The material can obtain high quality factors (> 10¹⁰) at 4.2 K and could theoretically support ~ 96 MV/m operation of a TESLA elliptical style cavity. Current Nb₃Sn cavities made at Cornell University achieve high quality factors but are limited to about 17 MV/m in CW operation due to the presence of a surface defect. Here we examine recent results on studying the quench mechanism and propose that surface roughness is a major limiter for accelerating gradients. Furthermore, we discuss recent work on reducing the surface roughness including chemical polishing, modification of material growth, and tin electroplating.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB3
About •	paper received ※ 02 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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MOYBB4	Large-Scale Dewar Testing of FRIB Production Cavities: Statistical Analysis	SRF, multipactoring, linac, cryomodule	41
	C. Zhang, W. Chang, W. Hartung, S.H. Kim, J.T. Popielarski, K. Saito, J.F. Schwartz, T. Xu FRIB, East Lansing, Michigan, USA
	The Facility for Rare Isotope Beams (FRIB) requires a driver linac with 324 superconducting cavities to deliver ion beams at 200 MeV per nucleon. About 1/3 of the cavities are quarter-wave resonators (QWRs, 805. MHz); the rest are half-wave resonators (HWRs, 322 MHz). FRIB cavity production is nearly complete, with more than 90% of the required cavities certified for installation into cryomodules (as of May 2019). We have accumulated a large data set on performance of production QWRs and HWRs during Dewar certificating testing of jacketed cavities. In this paper, we will report on the data analysis, including statistics on the BCS resistance, residual resistance, energy gap, and Q-slope. Additionally, we will discuss performance limitations and conditioning (multipacting, field emission).
	Slides MOYBB4 [1.200 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB4
About •	paper received ※ 01 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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MOYBB6	X-Ray Detector Array for Spatial and Temporal Diagnostic at the LANSCE Linac	detector, linac, shielding, photon	47
	M. Sanchez Barrueta, G.O. Bolme, J.T.M. Lyles, J.E. Zane LANL, Los Alamos, New Mexico, USA R.Z. Pinsky NERS-UM, Ann Arbor, Michigan, USA
	Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract 89233218CNA000001 A recent industrial development has made possible the use of chip-scale radiation detectors by combining a Cerium-doped Lutetium based scintillator crystal optically coupled with a Silicon Photomultiplier (SiPM) as a detector. At the Los Alamos Neutron Science Center (LANSCE), there has been an ongoing effort to determine the location of high voltage breakdowns of the accelerating radio-frequency field inside of an evacuated resonant cavity. Tests were conducted with an array of 8 X-ray detectors with each detector observing a cell of the Drift Tube Linac (DTL) cavity. The array can be moved along the DTL cavity and record X-ray emissions from a section of the cavity and their timing with respect to the RF field quench using a fast 8 channel mixed-signal oscilloscope. This new diagnostic allowed us to map the most energetic emissions along the cavity and reduce the area to investigate. A thorough visual inspection revealed that one of the ion pump grating welds in the suspected area was exposing a small gap and melting copper on both sides. Sparking across this discontinuity is believed to be a source of electrons that drive the high voltage breakdowns in the drift tube cells.
	Slides MOYBB6 [39.283 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB6
About •	paper received ※ 28 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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MOZBA1	LCLS-II SC Linac: Challenges and Status	cryomodule, SRF, linac, FEL	51
	M.C. Ross SLAC, Menlo Park, California, USA
	Funding: ∗ This work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 The Linac Coherent Light Source II (LCLS-II) project requires the assembly, test, and installation of 37 cry-omodules (CM) in order to deliver a 4 GeV CW electron beam to the FEL undulators for production of both hard and soft X-ray pulses at a repetition rate of up to 1 MHz. All of the cryomodules will operation in continuous wave mode, with 35 operating at 1.3 GHz for acceleration and 2 operating at 3.9 GHz to linearize the longitudinal beam profile. The assembly and testing of the 1.3 GHz cry-omodules is nearing completion and the 3.9 GHz cry-omodules work is entering to assembly and testing phase. Roughly 60% of the cryomodules have been shipped to SLAC for installation in the accelerator enclosure. The status and challenges of these efforts will be reported in this paper.
	Slides MOZBA1 [80.533 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA1
About •	paper received ※ 02 September 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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MOZBA6	The Broad-Band Impedance Budget of the Accumulator Ring in the ALS-U Project	impedance, wakefield, simulation, vacuum	74
	D. Wang, S. De Santis, D. Li, T.H. Luo, M. Venturini LBNL, Berkeley, California, USA K.L.F. Bane SLAC, Menlo Park, California, USA
	Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. It consists of an accumulator and a storage ring. In both rings, coupling-impedance driven instabilities need careful evaluation to ensure meeting the machine high-performance goals. This paper presents the impedance budget of the accumulator ring both longitudinally and transversely. The budget includes the resistive wall impedance as well as the geometric impedance from the main vacuum components. Our calculations primarily rely on electromagnetic simulations with the CST code; when possible validation has been sought against analytical modeling, typically in the low-frequency limit, and good agreement generally found. Collective-instability current thresholds are also discussed.
	Slides MOZBA6 [8.926 MB]
	Poster MOZBA6 [3.542 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA6
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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MOPLM09	High-Power Design of a Cavity Combiner for a 352-MHz Solid State Amplifier System at the Advanced Photon Source	storage-ring, klystron, interface, network	113
	G.J. Waldschmidt, D.J. Bromberek, A. Goel, D. Horan, A. Nassiri ANL, Lemont, Illinois, USA
	A cavity combiner has been designed as part of a solid state amplifier system at the Advanced Photon Source with a power requirement of up to 200 kW for the full system. Peak field levels and thermal loading have been optimized to enhance the rf and mechanical perfor-mance of the cavity and to augment its reliability. The combiner consists of 16 rotatable input couplers, a re-duced-field output coupler, and static tuning. The power handling capability of the cavity will be evaluated during a back-feed test where an external klystron source will be used to transmit power through the cavity into loads on each of the input couplers.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM09
About •	paper received ※ 28 August 2019 paper accepted ※ 04 December 2019 issue date ※ 08 October 2019
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MOPLM17	Longitudinal Impedance Modeling of APS Particle Accumulator Ring with CST	impedance, simulation, kicker, vacuum	140
	C. Yao, J. Carvelli, K.C. Harkay, L.H. Morrison ANL, Lemont, Illinois, USA D. Hui University of Arizona, Tucson, Arizona, USA J.S. Wang Dassault Systems Simulia, Waltham, Massachusetts, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. The APS-U (APS upgrade) ring plans implement a "swap out" injection scheme, which requires a injected beam of 15.6 nC single-bunch beam. The Particle Accumulator Ring (PAR), originally designed for up to 6 nC charge, must be upgraded to provide 20 nC single bunch beam. Our studies have shown that bunch length of the PAR beam, typically 300 ps at lower charge, increases to 800 ps at high charge due to longitudinal instabilities, which causes low injection efficiency of the downstream Booster ring. We completed beam impedance of all the PAR vacuum components recently with CST wakefield solver. 3D CAD models are directly imported into CST and various techniques were explored to improve and verify the results. The results are also cross-checked with that from GdfidL and Echo simulation. We identified 23 bellow- and 24 non-bellow flanges that contribute to as much as 50% of the total loss factor. We are considering upgrade options to reduce over all beam loading and longitudinal impedance. Beam tracking simulation is in progress that including the longitudinal impedance results from the simulations. We report the results and methods of the CST impedance simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM17
About •	paper received ※ 22 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOPLM20	Impedance Considerations for the APS Upgrade	impedance, photon, vacuum, simulation	147
	R.R. Lindberg ANL, Lemont, Illinois, USA A. Blednykh BNL, Upton, New York, USA
	Funding: Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 The APS-Upgrade is targeting a 42 pm lattice that requires strong magnets and small vacuum chambers. Hence, impedance is of significant concern. We overview recent progress on identifying and modelling vacuum components that are important sources of impedance in the ring, including photon absorbers, BPMs, and flange joints. We also show how these impact collective dynamics in the APS-U lattice.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM20
About •	paper received ※ 27 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019
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MOPLH04	Design for HyRES Cathode Nanotip Electron Source	electron, solenoid, gun, cathode	177
	R.M. Hessami, A.F. Amhaz, P. Musumeci UCLA, Los Angeles, USA
	A new ultrafast electron diffraction (UED) instrument is being developed by UCLA-Colorado University collaboration for the STROBE NSF Center with the goal of using electron and EUV photon beams to reveal the structural dynamics of materials in non-equilibrium states at fundamental atomic and temporal scales. This paper describes the design of the electron beamline of this instrument. In order to minimize the initial emittance, a nanotip photocathode, 25 nm in radius, will be used. This requires a redesign of the cathode and anode components of the electron gun to allow for the tip to be properly aligned. Solenoidal lenses are used to focus the beam transversely to a sub-micron spot at the sample and a radiofrequency (RF) cavity, driven by a continuous wave S-band RF source, longitudinally compresses the beam to below 100 fs, required for atomic resolution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH04
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOPLH10	Field-Emission Electron Source Embedded in a Field-Enhanced Conduction-Cooled Superconducting RF Cavity	electron, cathode, experiment, niobium	192
	D. Mihalcea, V. Korampally, A. McKeown, O. Mohsen, P. Piot, I. Salehinia Northern Illinois University, DeKalb, Illinois, USA R. Dhuley, M.G. Geelhoed, P. Piot, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA
	We present simulations and experimental progress toward the development of a high-current electron source with the potential to deliver high charge electron bunches at GHz-level repetition rates. To achieve these goals electrons are generated through field-emission and the cathode is immersed in a conduction-cooled superconducting 650-MHz RF cavity. The field-emitters consist of microscopic silicon pyramids and have a typical enhancement factor of about 500. To trigger field-emission, the peak field inside the RF cavity of about 6 MV/m is further enhanced by placing the field-emitters on the top of a superconducting Nb rod inserted in the RF cavity. So far, we cannot control the duration of the electron bunches which is of the order of RF period. Also, the present cryo-cooler power of about 2 W limits the beam current to microamp level.
	Poster MOPLH10 [1.063 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH10
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOPLH23	An Analysis of Potential Compact Positron Beam Source	positron, plasma, emittance, simulation	220
	R.M. Hessami UCLA, Los Angeles, USA S.J. Gessner CERN, Geneva, Switzerland
	For positron studies in plasma wakefield accelerators such as AWAKE, the development of new, cheaper, and compact positron beam sources is necessary. Using an electrostatic trap with parameters similar to other experiments, this paper explores converting that trapped positron plasma into a usable beam. Bunching is initially accomplished by an electrostatic buncher and the beam is accelerated to 148 keV by pulsed electrostatic accelerators. This is necessary for injection into the beta-matched rf cavities operating at 600 MHz, which bring the positron beam to a transverse emittance of 1.3 pi mrad mm, a longitudinal emittance of 93.3 pi keV mm, stdz of 1.85 mm and an energy of 22 MeV. The beamline used here is far simpler and less expensive than those at many facilities, such as SLAC, allowing for a cheap source of positron beams, potentially opening up positron beam studies to many facilities that could not previously afford such a source.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH23
About •	paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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MOPLO04	Progress in Time-Resolved MeV Transmission Electron Microscopy at UCLA	electron, quadrupole, alignment, detector	243
	P.E. Denham UCLA, Los Angeles, USA
	We describe here two new enhancements developed for the time-resolved microscope at the UCLA PEGASUS Lab based on the use of a radiofrequency photoinjector as an ultrafast electron source and permanent magnet quadrupoles as electron lenses. The first enhancement is a flexible optical column design including hybrid-style stronger focusing quadrupoles, yielding a 60% magnification increase, and a collimator to improve imaging contrast. This new optical system will have the ability to switch between real-space imaging and diffraction pattern imaging with variable magnification. The second enhancement is a high-frequency (X-band) cavity downstream from the (S-band) photoinjector to reduce the beam energy spread. These enhancements are crucial for improving contrast and image quality. In addition, a pulse-wire alignment method to fiducialize the quadrupole positions to better than 20-um precision is used to reduce the aberrations induced by misalignment and achieve spatial resolution at the 20 nm-level.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO04
About •	paper received ※ 28 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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MOPLO17	Large-Scale Dewar Testing of FRIB Production Cavities: Results	cryomodule, SRF, MMI, linac	270
	W. Hartung, W. Chang, S.H. Kim, D. Norton, J.T. Popielarski, K. Saito, J.F. Schwartz, T. Xu, C. Zhang FRIB, East Lansing, Michigan, USA
	The Facility for Rare Isotope Beams (FRIB), under construction at Michigan State University (MSU), includes a superconducting driver linac to deliver ion beams at 200 MeV per nucleon. The driver linac requires 10⁴ quarter-wave resonators (QWRs, β = 0.041 and 0.085) and 220 half-wave resonators (HWRs, β = 0.29 and 0.54). The jacketed resonators are Dewar tested at MSU before installation into cryomodules. The cryomodules for β = 0.041, 0.085, and 0.29 have been completed and certified; 89% of the β = 0.54 HWRs have been certified (as of May 2019). The Dewar certification tests have provided valuable information on the performance of production QWRs and HWRs at 4.3 K and 2 K and on performance limits. Results will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO17
About •	paper received ※ 08 November 2019 paper accepted ※ 26 November 2019 issue date ※ 08 October 2019
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MOPLO19	Test Results of PIP2IT MEBT Vacuum Protection System	vacuum, cryomodule, MEBT, SRF	278
	A.Z. Chen, R. Andrews, C.M. Baffes, D.D. Lambert, L.R. Prost, A.V. Shemyakin, T.J. Zuchnik Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics The central part of PIP-II program of upgrades proposed for the Fermilab injection complex is an 800 MeV, 2 mA, CW-compatible SRF linac. Acceleration in superconducting cavities begins from a low energy of 2.1 MeV, so that the first cryomodule, Half Wave Resonator (HWR) borders the warm Medium Beam Transport (MEBT) line. To minimize the amount of gas that may enter the SRF linac in a case if a vacuum failure occurs in the warm front end, a vacuum protection system is envisioned to be used in the PIP-II MEBT. It features a fast closing valve with two sensors and a differential pumping insert. The system prototype is installed in the PIP-II Injector Test (PIP2IT) accelerator and recently is successfully tested in several modes modelling the vacuum failures. The report presents the design of the vacuum protection system and results of its tests.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO19
About •	paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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MOPLO24	A Novel Technique for Pulsed Operation of Magnetrons without Modulation of Cathode Voltage	controls, cathode, operation, injection	290
	G.M. Kazakevich, R.P. Johnson Muons, Inc, Illinois, USA T.N. Khabiboulline, V.A. Lebedev, G.V. Romanov, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Modern pulsed superconducting accelerators of megawatt beams require efficient RF sources controllable in phase and power. For each Superconducting RF (SRF) cavity is desirable a separate RF source with power up to hundreds of kW with pulse duration in the millisecond range. The efficiency of the traditional RF sources (klystrons, IOTs, solid-state amplifiers) is lower than that of the magnetrons, while the cost of a unit of RF power is much higher. Therefore the magnetron-based RF sources would significantly reduce the capital and operation costs in comparison with the traditional RF sources. A recently developed an innovative technique makes possible the pulsed generation of magnetrons powered below the self-excitation threshold voltage. This technique does not require pulse modulators to form RF pulses. The magnetron operation in this regime is stable, low noise, controllable in phase and power, and provides higher efficiency than other types of RF power sources. It allows operation in pulsed modes with large duty factor. The developed technique and its experimental verification are considered and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO24
About •	paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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TUXBA4	Rapid Radio-Frequency Beam Energy Modulator for Proton Therapy	proton, simulation, GUI, klystron	298
	X. Lu, G.B. Bowden, V.A. Dolgashev, Z. Li, E.A. Nanni, A.V. Sy, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This work is supported by US Department of Energy (DOE) Contract No. DE-AC02-76SF00515. We present the design for a rapid proton energy modulator with radio-frequency (RF) accelerator cavities. The energy modulator is designed as a multi-cell one-meter long accelerator working at 2.856 GHz. We envision that each individual accelerator cavity is powered by a 400 kW low-voltage klystron to provide an accelerating / decelerating gradient of 30 MV/m. We have performed beam dynamics simulations showing that the modulator can provide ± 30MeV of beam energy change, with an energy spread of 3 MeV for a 7 mm long (full length) proton bunch. A prototype experiment of a single cell is in preparation at the Next Linear Collider Test Accelerator (NLCTA) at SLAC.
	Slides TUXBA4 [3.275 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUXBA4
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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TUYBA4	Optimization of an SRF Gun Design for UEM Applications	SRF, gun, laser, electron	305
	A. Liu, P.V. Avrakhov Euclid TechLabs, LLC, Solon, Ohio, USA C. Jing, R.A. Kostin Euclid Beamlabs LLC, Bolingbrook, USA
	Funding: DOE contract DE-SC0018621 Benefiting from the rapid progress on RF photocathode gun 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, which may lead to breakthroughs in fundamental science and applied technologies . Euclid is designing an SRF cavity as the UEM electron gun. As implementing a solenoid for emittance compensation in the gun is limited by the superconductivity performance and available space, the geometry of the first 0.3 cell of the cavity is optimized for transverse focusing and emittance reduction. : T. Chase, et al, "Ultrafast electron diffraction from non- equilibrium phonons in femtosecond laser heated Au films." Applied Physics Letters, 2016
	Slides TUYBA4 [7.583 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBA4
About •	paper received ※ 30 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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TUZBA1	Commissioning of the Electron Accelerator LEReC for Bunched Beam Cooling	electron, operation, cathode, gun	330
	D. Kayran, Z. Altinbas, D. Bruno, M.R. Costanzo, K.A. Drees, A.V. Fedotov, W. Fischer, M. Gaowei, D.M. Gassner, X. Gu, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, J. Kewisch, C.J. Liaw, C. Liu, J. Ma, K. Mernick, T.A. Miller, M.G. Minty, L.K. Nguyen, M.C. Paniccia, I. Pinayev, V. Ptitsyn, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, A. Sukhanov, P. Thieberger, J.E. Tuozzolo, E. Wang, G. Wang, W. Xu, A. Zaltsman, H. Zhao, Z. Zhao BNL, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The brand-new state of the art electron accelerator, LEReC, was built and commissioned at BNL. LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. Electron beam quality suitable for cooling in the Relativistic Heavy Ion Collider (RHIC) was achieved [1], which lead to the first demonstration of bunched beam electron cooling of hadron beams [2]. This presentation will discuss commissioning results, achieved beam parameters and performance of the LEReC systems. [1] D.Kayran et al., First results from Commissioning of LEReC, in Proc of IPAC2019 [2] A.Fedotov et al., First electron cooling of hadron beams using a bunched electron beam, presented at NAPAC2019
	Slides TUZBA1 [18.343 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBA1
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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TUPLM13	Two-Energy Storage-Ring Electron Cooler for Relativistic Ion Beams	storage-ring, electron, emittance, damping	399
	B. Dhital, J.R. Delayen, G.A. Krafft ODU, Norfolk, Virginia, USA J.R. Delayen, Y.S. Derbenev, D. Douglas, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang JLab, Newport News, Virginia, USA
	An electron beam based cooling system for the ion beam is one of the commonly used approaches. The proposed two’energy storage-ring electron cooler consists of damping and cooling sections at markedly different energies connected by an energy recovering superconducting RF structure. The parameters in the cooling and damping sections are adjusted for optimum cooling of a stored ion beam and for optimum damping of the electron beam respectively. This paper briefly describes a two cavities model along with a third cavity model to accelerate and decelerate the electron beam in two energy storage ring. Based on our assumed value of equilibrium emittance shows that these models give a bunch length of the order of cm and energy spread of the order of 〖10〗^-5 in the cooling section which are required parameters for the better cooling. Numerical calculations along with elegant simulation are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM13
About •	paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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TUPLM18	Improving Energy Resolution and Compensating Chromatic Aberration With a TM010 Microwave Cavity	electron, gun, simulation, laser	411
	C.J.R. Duncan Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA P. Cueva, J.M. Maxson, D.A. Muller Cornell University, Ithaca, New York, USA
	Funding: National Science Foundation under Award OIA-1549132, the Center for Bright Beams The intrinsic energy spread of electron sources limits the achievable resolution of electron microscopes in both spectroscopic and spatially resolved measurements. We propose that the TM010 mode of a single radio frequency (RF) cavity be used to dramatically reduce this energy spread in a pulsed beam. We show with analytic approximations, confirmed in simulations, that the non-linear time-energy correlations that develop in an electron gun can be undone by the RF cavity running near-crest. We derive an expression that gives the required RF field strength as a function of accelerating voltage. We explore multiple applications, including EELS and SEM. By pulsing a photocathode with commercially available, high repetition-rate lasers, our scheme could yield competitive energy spread reduction at higher currents when compared with monochromated continuous-wave sources for electron microscopes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM18
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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TUPLM36	Temperature Measurements of the NSLS-II Vacuum Components	impedance, vacuum, experiment, detector	443
	A. Blednykh, G. Bassi, C. Hetzel, B.N. Kosciuk, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, G.M. Wang BNL, Upton, New York, USA
	This paper is dedicated to the analysis of our recent experience from ramp-up of operating current at NSLS-II from 25 mA at the end of commissioning in 2014 to 475 mA achieved in studies today. To approach the design level of the ring intensity we had to solve major problems in overheating of the chamber components. Since the beginning of the NSLS-II commissioning, the temperature of the vacuum components has been monitored by the Resistance Temperature Detectors located predominantly outside of the vacuum chamber and attached to the chamber body. A couple of vacuum components were designed with the possibility for internal temperature measurements under the vacuum as diagnostic assemblies. Temperature map helps us to control overheating of the vacuum components around the ring especially during the current ramp-up. The average current of 475mA has been achieved with two main 500MHz RF cavities and w/o any harmonic cavities. In this paper we discuss the heating results for a 15ps bunch length (at low current) of the following vacuum components: Large Aperture BPM, Small Aperture BPM, Bellows, Flanges, Ceramics Chambers and Stripline Kickers.
	Poster TUPLM36 [3.696 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM36
About •	paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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TUPLH03	Double-Bend Achromat Beamline for Injection Into a High-Power Superconducting Electron Linac	solenoid, electron, gun, dipole	494
	C.H. Boulware, T.L. Grimm, R. Hipple Niowave, Inc., Lansing, Michigan, USA S.M. Lund FRIB, East Lansing, Michigan, USA V.S. Morozov JLab, Newport News, Virginia, USA
	To take advantage of the high duty cycle operation of superconducting electron linacs, commercial systems use thermionic cathode electron guns that fill every RF bucket with an electron bunch. In continuous operation, the exit energy is limited when compared to pulsed systems. Bunch length and energy spread at the exit of the gun are incompatible with low losses in the superconducting cavity. A solenoid double-bend achromatic beamline is in operation at Niowave which allows energy and bunch length filtering of the beam leaving the gun before injection into the superconducting cavity. This system uses two solenoids and two dipoles to produce a round beam, using the edge angles of the dipoles to balance the focusing effects in the two transverse planes. The design allows beam filtering on the symmetry plane where the dispersion is maximum. Additionally, the bend angle moves the electron gun off the high-energy beam axis, allowing multiple-pass operation of the superconducting booster. This contribution will discuss the beam optics design of the double-bend achromat along with the design of the magnets and beam chambers and the operational experience with the system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH03
About •	paper received ※ 28 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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TUPLH17	Design Study of Low-Level RF Control System for CW Superconducting Electron Linear Accelerator in KAERI	controls, SRF, LLRF, linac	512
	S.H. Lee, J.Y. Lee Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea P. Buaphad, I.G. Jeong, Y.J. Joo, H.R. Lee University of Science and Technology of Korea (UST), Daejeon, Republic of Korea M.-H. Chun, I.H. Yu PAL, Pohang, Republic of Korea Y. Kim KAERI, Jeongeup-si, Republic of Korea
	Korea Atomic Energy Research Institute (KAERI) has been operating a 20 MeV superconducting RF linear accelerator (SRF LINAC) to conduct research on atom/nuclear reaction using neutron Time-Of-Flight (nTOF). It can accelerate electron beams up to 20 MeV with 1 kW continuous wave (CW) operation mode. Unfortunately, this machine has been aged over 15 years that brings about considerably difficulty in normal operation due to the performance degradation of sub-systems. To improve the operation condition of 20 MeV SRF LINAC, we has been carrying out an upgrade project with replacement and repair of old sub-systems from 2018. This paper describes a design study of Low-Level RF (LLRF) feedback system to raise the stability and acceleration efficiency of the electric field generated in the superconducting RF cavity structure in 20 MeV SRF LINAC.
	Poster TUPLH17 [0.644 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH17
About •	paper received ※ 30 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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TUPLO06	Weak-Strong Beam-Beam Simulation for eRHIC	proton, simulation, luminosity, electron	545
	Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, C. Montag, V. Ptitsyn, F.J. Willeke BNL, Upton, New York, USA Y. Hao, D. Xu FRIB, East Lansing, Michigan, USA J. Qiang LBNL, Berkeley, California, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In the eRHIC, to compensate the geometric luminosity loss due to the crossing angle, crab cavities are to be installed on both sides of the interaction point. When the proton bunch length is comparable to the wavelength of its crab cavities, protons will not be perfectly tilted in the x-z plane. In the article, we employ weak-strong beam-beam interaction model to calculate the proton beam size growth rates and luminosity degradation rate with various machine and time parameters. The goal of these studies is to optimize the the beam-beam related machine and beam parameters of eRHIC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO06
About •	paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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TUPLO07	Calculation of Action Diffusion With Crabbed Collision in eRHIC	proton, electron, simulation, luminosity	549
	Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, C. Montag, V. Ptitsyn, F.J. Willeke BNL, Upton, New York, USA Y. Hao, D. Xu FRIB, East Lansing, Michigan, USA J. Qiang LBNL, Berkeley, California, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In the eRHIC, to compensate the geometric luminosity loss due to the crossing angle, crab cavities are to be installed on both sides of the interaction point. When the proton bunch length is comparable to the wavelength of its crab cavities, protons will not be perfectly tilted in the x-z plane. In the article, we develop a simulation code to calculate the transverse action diffusion rate as function of the initial proton longitudinal action. The goal of this study is to identify the contributions from various protons to the overall emittance growth. Tune scan is also performed to locate optimum working points which yield less proton emittance growth.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO07
About •	paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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TUPLE01	Python Scripts for RF Commissioning at FRIB	EPICS, LLRF, controls, linac	563
	H. Maniar, E. Daykin, D.G. Morris, A.S. Plastun, H.T. Ren, S. Zhao FRIB, East Lansing, Michigan, USA
	Abstract RF commissioning at FRIB involves QWR cavities (β=0.085 and β=0.041), HWR cavities (β=0.29 and β=0.53) and few room temperature devices. Each RF system has many process variables for LLRF and amplifier control located on different pages of CS-Studio. Efficient handling of all these PVs can be challenging for RF experts. Several scripts using Python have been developed to facilitate this process. User interface application has been developed using Qt Designer and PyQt package of Python, for ease of access of all scripts. These scripts are useful for mass ac-tions (for multiple systems) including turning on/ off LLRF controllers and amplifiers, resetting interlocks/ errors, chang-ing a PV value, etc. Python scripts are also used to quickly prototype the auto-start procedure for QWR cavities, which eventually is implemented on IOC driver. The application sends commands to IOC driver with device name, PV name and value to be changed. Future developments can be con-verting to state-notation language on IOC to add channel access security. This application intends to reduce time and efforts for RF commissioning at FRIB.
	Poster TUPLE01 [0.429 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE01
About •	paper received ※ 27 August 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019
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TUPLE08	Commissioning Update on RF Station #5 of AWA	high-voltage, klystron, electron, MMI	580
	W. Liu, M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA C. Jing Euclid Beamlabs LLC, Bolingbrook, USA
	Funding: The US Department of Energy, Office of Science The RF system of Argonne Wakefield Accelerator (AWA) facility has grown over the years from one RF power station into 4 RF power stations. The demand for RF power keeps growing as the capability of AWA continues to grow. Now the 5th RF station is needed to fulfill the RF power needs of AWA facility. Some details regarding the construction and commissioning of the 5th RF station of AWA facility are documented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE08
About •	paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEYBB5	A Crab-Crossing Scheme for Laser-Ion Beam Applications	laser, experiment, linac, injection	639
	A.V. Aleksandrov, S.M. Cousineau, T.V. Gorlov, Y. Liu, A. Rakhman, A.P. Shishlo ORNL, Oak Ridge, Tennessee, USA
	Lasers have recently been used in many applications to H⁻ beams, including laser charge exchange, laser wire scanners, and laser temporal pulse patterning. The H⁻ beam in these applications has wide variation ofμpulse length width dependence on focusing of the RF cavities, energy spread of the beam, and space charge forces. Achieving the required laser pulse length for complete overlap with the H⁻ can be challenging in some scenarios when available laser power constrained. The scheme proposed here utilizes a crab-crossing concept between the laser and the ion beam to achieve overlap of a short laser pulse with an arbitrarily long H⁻ beam pulse. An experiment to test the hypothesis in the context of H⁻ charge exchange is described.
	Slides WEYBB5 [5.201 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBB5
About •	paper received ※ 30 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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WEZBA2	Experience and Lessons in FRIB Superconducting Quarter-Wave Resonator Commissioning	cryomodule, MMI, linac, controls	646
	S.H. Kim, H. Ao, F. Casagrande, W. Chang, C. Compton, A. Facco, V. Ganni, E. Gutierrez, W. Hartung, N. Hasan, P. Knudsen, T.L. Larter, H. Maniar, S.J. Miller, D.G. Morris, P.N. Ostroumov, A.S. Plastun, J.T. Popielarski, L. Popielarski, H.T. Ren, K. Saito, M. Thrush, D.R. Victory, J. Wei, M. Xu, T. Xu, Y. Yamazaki, C. Zhang, S. Zhao FRIB, East Lansing, Michigan, USA
	The superconducting (SC) linear accelerator (linac) for the Facility for Rare Isotope Beams (FRIB) has one quarter-wave resonator (QWR) segment and two half-wave resonator (HWR) segments. The first linac segment (LS1) contains twelve β = 0.041 and ninety-two β = 0.085 QWRs operating at 80.5 MHz, and thirty-nine SC solenoids. Superconducting radiofrequency (SRF) commissioning and beam commissioning of LS1 was completed in April 2019. The design accelerating gradients (5.1 MV/m for β = 0.041 and 5.6 MV/m for β = 0.085) were achieved in all cavities with no multipacting or field emission issues. The cavity field met the design goals: peak-to-peak stability of ±1% in amplitude and ±1° in phase. We achieved 20.3 MeV/u ion beams of Ar, Kr, Ne, and Xe with LS1. In this paper, we will discuss lessons learned from the SRF commissioning of the cryomodules and methods developed for efficient testing, conditioning, and commissioning of more than 100 SC cavities, each with its own independent RF system.
	Slides WEZBA2 [2.841 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEZBA2
About •	paper received ※ 03 September 2019 paper accepted ※ 05 December 2019 issue date ※ 08 October 2019
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WEZBA6	A 100 kW 1.3 GHz Magnetron System with Amplitude and Phase Control	controls, klystron, power-supply, experiment	656
	M.E. Read, T. Bui, G. Collins, R.L. Ives CCR, San Mateo, California, USA B.E. Chase, J. Reid Fermilab, Batavia, Illinois, USA J.R. Conant, C.M. Walker CPI, Beverley, Massachusetts, USA
	Funding: United States Department of Energy Grant No. DE-SC0011229. Calabazas Creek Research, Inc., Fermilab, and Communications & Power Industries, LLC, developed a 100 kW peak, 10 kW average, 1.3 GHz, magnetron-based, RF system for driving accelerators. Efficiency varied between 81% and 87%. Phase locking uses a novel approach that provides fast amplitude and phase control when coupled into a superconducting accelerator cavity [1]. The system was successfully tested at Fermilab and produced 100 kW in 1.5 ms pulses at a repetition rate of 2 pps. A locking bandwidth of 0.9 MHz was achieved with a drive signal of 269 W injected through a 4 port circulator. The phase locking signal was 25 dB below the magnetron output power. The spectrum of the phase locked magnetron was suitable for driving accelerator cavities. Phase modulation was demonstrated to 50 kHz (the limit of the available driver source). The average power was limited by available conditioning time. Scaling indicates 42 kW of average power should be achievable. Estimated cost is less than $1/Watt of delivered RF power, exclusive of power supplies or modulators. System design and performance measurements will be presented. [1] B. Chase, R. Pasquinelli, E. Cullerton, P. Varghese, "Precision Vector Control of a Superconducting RF Cavity driven by an Injection Locked Magnetron," Jou. of Instrumentation, Vol. 10 March 2015.
	Slides WEZBA6 [2.515 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEZBA6
About •	paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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WEPLM01	Studies in Applying Machine Learning to Resonance Control in Superconducting RF Cavities	controls, LLRF, simulation, resonance	659
	J.A. Diaz Cruz, S. Biedron, M. Martinez-Ramon, R. Pirayesh, S.I. Sosa Guitron University of New Mexico, Albuquerque, USA J.A. Diaz Cruz SLAC, Menlo Park, California, USA
	Traditional PID, active resonance and feed-forward controllers are dominant strategies for cavity resonance control, but performance may be limited for systems with tight detuning requirements, as low as 10 Hz peak detuning (few nanometers change in cavity length), that are affected by microphonics and Lorentz Force Detuning. Microphonic sources depend on cavity and cryomodule mechanical couplings with their environment and come from several systems: cryoplant, RF sources, tuners, etc. A promising avenue to overcome the limitations of traditional resonance control techniques is machine learning due to recent theoretical and practical advances in these fields, and in particular Neural Networks (NN), which are known for their high performance in complex and nonlinear systems with large number of parameters and have been applied successfully in other areas of science and technology. In this paper we introduce NN to resonance control and compare initial performance results with traditional control techniques. An LCLS-II superconducting cavity type system is simulated in an FPGA, using the Cryomodule-on-Chip model developed by LBNL, and is used to evaluate machine learning algorithms.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM01
About •	paper received ※ 05 September 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019
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WEPLM03	The LLRF Control Design and Validation at FRIB	LLRF, controls, MMI, cryomodule	667
	S. Zhao, W. Chang, S.H. Kim, H. Maniar, D.G. Morris, P.N. Ostroumov, J.T. Popielarski, H.T. Ren, N.R. Usher FRIB, East Lansing, Michigan, USA N.R. Usher Ionetix, Lansing, Michigan, USA
	Funding: This work is supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661. One of the challenges in designing the low level radio frequency (LLRF) controllers for the Facility for Rare Isotope Beams (FRIB) is the various types of cavities, which include 5 different frequencies ranging from 40.25 MHz up to 322 MHz, and 4 different types of tuners. In this paper, the design strategy taken to achieve flexibility and low cost and the choices made to accommodate the varieties will be discussed. The approach also allowed easy adaptation to major design changes such as replac-ing two cryo-modules with two newly designed room temperature bunchers and the addition of high-voltage bias to suppress multi-pacting in half wave resonators (HWRs). With the successful completion of the third accelerator readiness review (ARR03) commissioning in early 2019, most of the design has been validated in the real accelerator system, leaving only HWRs which are constantly undergoing tests in cryo-module bunker. The integrated spark detector design for HWRs will also be tested in the near future.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM03
About •	paper received ※ 31 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEPLM04	Precision Cavity Higher-Order Mode Tuning Scheme for Stabilizing the Stored Beam in the Advanced Photon Source Upgrade	HOM, damping, impedance, resonance	670
	L. Emery, P.S. Kallakuri, U. Wienands ANL, Lemont, Illinois, USA D. Teytelman Dimtel, Redwood City, California, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 The Advanced Photon Source Upgrade will suffer longitudinal multi-bunch instability because of the presence of several monopole higher-order mode (HOMs) of the 12 352-MHz rf cavities. Even with a feedback system, it would be good to mitigate any driving terms with conventional means such as tuning HOM frequencies with temperature. However the latter is problematic because there will be 90 or so HOMs that are potentially harmful. A scheme is developed, utilizing the measured spectrum of HOMs, to find the best temperature setting for each cavity. We present measurements of 30 or so HOMs, and a thermal model of HOM frequencies using cavity wall power and cooling water temperature as inputs to maintain the optimum tuning condition with sufficient accuracy. The newly acquired Dimtel iGp12 processor box is central to the HOM frequency measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM04
About •	paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEPLM05	Continuous Monitoring of Spectral Features of Electron Beam Orbit Motion at NSLS-II	operation, undulator, controls, feedback	673
	B. Podobedov, A.A. Derbenev, K. Ha, T.V. Shaftan BNL, Upton, New York, USA
	NSLS-II ring is equipped with state-of-the art beam position monitors (BPMs) which are indispensable in all aspects of machine studies and operations. Among other data, they can provide, on demand, up to 10 seconds of fast-acquisition (FA) data, sampled at ~10 kHz. Analysis of these data in time, frequency and spatial domains provides valuable insights into orbit stability, locations of residual noise sources, performance of feedback systems, etc. In addition, changes in FA signal spectral features are often the earliest indicators of potential equipment problems. This is why we recently implemented an Input / Output Controller (IOC) software that runs during regular user operation, and, once a minute, acquires 10 second buffers of FA data from 180 BPMs around the ring. These buffers are processed to determine the amplitudes and frequencies of the strongest spectral peaks as well as some other measures of fast beam orbit noise. Processed results can be monitored in real time and are also archived for offline analysis and troubleshooting. In this paper we discuss the implementation of this system and the insights we gained from it over about two years of operations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM05
About •	paper received ※ 31 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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WEPLM07	Low Level RF Test System for the Compact X-Ray Light Source at Arizona State University	controls, klystron, electron, LLRF	680
	H.S. Marks, W.S. Graves, M.R. Holl, L.E. Malin Arizona State University, Tempe, USA
	A compact femtosecond X-Ray Light Source (CXLS) for time-resolved scientific and medical studies is being constructed at Arizona State University. The CXLS X-rays will be generated by the inverse Compton scattering (ICS) collision of 200 mJ, 1 ps, IR laser pulses with 300 fs electron bunches with energy up to 35 MeV. The electron beam is accelerated via a photoinjector and three standing-wave 20-cell linac sections driven by two klystrons delivering up to 6 MW 1 µs pulses at 9.3 GHz with a pulse repetition rate of 1 kHz. For initial testing of the CXLS klystrons a hybrid digital-analog low-level RF (LLRF) driver has been developed which allows for inter-pulse phase and amplitude corrections based on feedback from waveguide-couplers. The micro-controller based system can also be programmed to adjust continuously in advance of predictable drifts.
	Poster WEPLM07 [2.226 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM07
About •	paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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WEPLM13	Multipactor Electron Cloud Analysis in a 17 GHz Standing Wave Accelerator Cavity	electron, multipactoring, simulation, experiment	687
	H. Xu, M.A. Shapiro, R.J. Temkin MIT/PSFC, Cambridge, Massachusetts, USA
	Funding: US Department of Energy High Energy Physics Theoretical predictions of single-surface one-point multipactor modes have been confirmed in experiments with a 17 GHz standing wave single cell disk-loaded waveguide accelerator structure operated in gradient range of 45-90 MV/m. A dc-biased probe placed outside of a slit in the side wall of the structure was used to measure the internal dark current electron energy distribution. The results indicated that the electrons had kinetic energy up to about 50 eV, in agreement with our CST particle-in-cell (PIC) simulations. Further theoretical calculations were performed to calculate the frequency detuning introduced by the multipactor electron cloud on the cell side wall for different electron cloud thicknesses and densities. We found that the detuning (Δf/f) due to the electron cloud was small, about two orders of magnitude smaller than the reciprocal of the cavity loaded quality factor. This detuning is sufficiently small that it does not cause significant power reflection. Similar calculations were carried out for high gradient operation of accelerator structures at frequencies of 2.856 GHz and 110.0 GHz, showing similar small detuning by multipactor discharges.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM13
About •	paper received ※ 19 August 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019
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WEPLM21	High-Quality Resonators for Quantum Information Systems	SRF, controls, cryogenics, photon	690
	S.V. Kuzikov IAP/RAS, Nizhny Novgorod, Russia S.P. Antipov, P.V. Avrakhov, E. Gomez Euclid TechLabs, LLC, Solon, Ohio, USA
	We analyze ultra-high-quality factor resonators for quantum computer architectures. As qubit operation requires external DC fields, we started our study with a conventional closed copper cavity which naturally allows external magnetic field. In order to increase quality factor and to keep DC magnetic field control at a level less than critical field, an open SRF resonator promises much higher quality. The next step resonator is a photonic band gap (PBG) resonator. This resonator allows easy external either magnetic or electric field control. It consists of a periodic 3D set of sapphire rods assembled between two superconducting plates. The PBG resonator exploits unique properties of the crystalline sapphire. Tangent delta for sapphire in X-band is reported at 10^-9 ’ 10-10 at 4 K. That is why, the Q-factor of the sapphire PBG resonator can be expected as high as 10 billions at mK temperatures which provides long relaxation times (dephasing etc.). The established PBG design implies obtaining a large Purcell factor, i.e. large ratio of quality to mode volume which is important parameter to establish strong interaction of a qubit with the cavity mode rather than RF noise.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM21
About •	paper received ※ 27 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019
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WEPLM47	Analysis of High Field Q-Slope (HFQS) Causes and Development of New Chemical Polishing Acid	SRF, experiment, superconductivity, niobium	699
	D. Luo, E.S. Metzgar, L. Popielarski, K. Saito, S.M. Shanab, G.V. Simpson FRIB, East Lansing, Michigan, USA T. Nakajima, I. Nasu, J. Taguchi Nomura Plating Co, Ltd., Osaka, Japan
	Funding: U.S. National Science Foundation under Grant PHY-1565546. In our previous studies of High Field Q-slope (HFQS) we have concluded that nitrogen contamination from the nitric acid is the main cause of the degradation of the Q in buffered chemical polished cavities. Our conclusion is made based on previously unresolved phenomena which are found from huge amount of published cavity test data, include fine grain, large grain and single crystal cavities treated with EP and BCP. According to this analysis, we have started developing new nitrogen-free chemical polishing acid. Hydrogen peroxide with HF mixture was reported able to react with Nb, and there’s no extra element contamination in it, so we replace the conventional BCP with this mixture to start our study. In this paper, some Nb coupon sample results with new acid will be reported. We complete the first step of developing the new acid and we got the Nb finish roughness no worse than conventional BCP.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM47
About •	paper received ※ 13 September 2019 paper accepted ※ 04 December 2019 issue date ※ 08 October 2019
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WEPLM49	New RF System for First Drift Tube Linac Cavity at LANSCE	controls, DTL, power-supply, LLRF	703
	J.T.M. Lyles, R.E. Bratton, G. Roybal, M. Sanchez Barrueta, G.M. Sandoval, Jr., D.J. Vigil, J.E. Zane LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by the United States Department of Energy, NNSA, under contract 89233218CNA000001 From 2014-2016, the three highest power 201 MHz power amplifier (PA) systems were replaced at the Los Alamos Neutron Science Center 100 MeV DTL. The initial DTL cavity provides 4.25 MeV of energy gain and has been powered by a Photonis (RCA) 4616 tetrode driving a 7835 triode PA for over 30 years. It consumes 110 kW of electrical power for tube filaments, power supplies and anode modulator. The modulator is not required with modern tetrode amplifiers. In 2020 we plan to replace this obsolete 6 tube transmitter with a design using a single tetrode PA stage without anode modulator, and a 20 kW solid-state driver stage. This transmitter needs to produce no more than 400 kW, and will use a coaxial circulator. Cooling water demand will reduce from 260 to 70 gal/min of pure water. High voltage DC power comes from the same power supply/capacitor bank that supplied the old system. The old low-level RF controls will be replaced with digital LLRF with learning capability for feedforward control, I/Q signal processing, and PI feedback. All high power components have been assembled in a complete mockup system for extended testing. Installation of the new RF system begins in January of 2020.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM49
About •	paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEPLM50	Beam Driven Bimodal Cavity Structure for High Gradient Acceleration	simulation, bunching, acceleration, site	707
	X. Chang, Y. Jiang, S.V. Shchelkunov Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA J.L. Hirshfield Omega-P, Inc., New Haven, Connecticut, USA
	Funding: Supported by USA National Science Foundation, Award #1632588 Abstract: Research aiming to increase the RF breakdown threshold in electron/positron accelerators is being conducted at the Yale University Beam Physics Laboratory. Our two-beam accelerator approach employs a beam driven bimodal cavity structure. This cavity includes (i) two modes excited by the drive beam, with the higher mode frequency three times that of the fundamental TM010 mode; (ii) a low-current accelerated beam and high-current drive beam traversing the same cavity structure. This approach has the potential advantages of (a) operating at higher acceleration gradient with lower breakdown and pulsed heating rates than that of a single-mode cavity structure at the same acceleration gradient, due to the spatiotemporal field distribution properties in the bimodal cavities; and (b) obtaining high accelerating gradient with a low energy drive beam. Recent progress in simulations and work towards an experimental test stand is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM50
About •	paper received ※ 23 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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WEPLM51	Ka-Band High Power Harmonic Amplifier for Bunch Phase-Space Linearization	klystron, linac, bunching, simulation	710
	X. Chang, Y. Jiang, S.V. Shchelkunov Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA J.L. Hirshfield Omega-P, Inc., New Haven, Connecticut, USA
	Funding: Supported by USA National Science Foundation, Award #1632588 Abstract: A future European light source CompactLight is being proposed to extend FEL operation further into the x-ray region than other light sources by using a linac operating at X-band (12 GHz) with a short Ka-band (36 GHz) section for linearizing bunch phase space. The Ka-band system requires a high-power RF amplifier, synchronized with the main X-band source. We report here on design of a third-harmonic klystron amplifier for this application. Our design employs a four-cavity system with a multi-cell extended interaction output cavity. Initial simulation results indicate that more than 10 MW of 36-GHz power can be obtained with an efficiency exceeding 20%, and with 12-GHz drive power of 30 W. A preliminary design for a proof-of-principal experimental test of this concept is described
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM51
About •	paper received ※ 23 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEPLM52	Recent Developments of Nb₃Sn at Jefferson Lab for SRF Accelerator Application	SRF, accelerating-gradient, cryomodule, factory	713
	U. Pudasaini, M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics. The desire to reduce the construction and operating costs of future SRF accelerators motivates the search for alternative, higher-performing materials. Nb₃Sn (Tc ~ 18.3 K and Hsh ~ 425 mT) is the front runner. However, tests of early Nb₃Sn-coated cavities encountered strong Q-slopes limiting the performance. Learnings from studies of coated materials related to cavity performance prompted significant changes to the coating process. It is now possible to routinely produce slope-free single-cell cavities having Q₀ ≥ 2×10¹⁰ at 4 K and > 4×10¹⁰ at 2 K up to the accelerating gradient in excess of 15 MV/m at its best. Obtaining similar results in five-cell cavities is a current goal to test them under an accelerator environment. This contribution discusses recent developments at Jefferson Lab.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM52
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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WEPLM53	50 kW CW Multi-Beam Klystron	klystron, electron, gun, cathode	717
	S.V. Shchelkunov Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA J.L. Hirshfield, V.E. Teryaev Omega-P, Inc., New Haven, Connecticut, USA
	Funding: Funded by the US Department of Energy; grant DE-SC-0018471. Main components, which are the electron gun, cavity-chain, magnetic system, and partially- grounded depressed four-stage collector, of a novel klystron were conceptually designed. This klystron is to deliver 50 kW CW at 952.6 MHz and to serve as a microwave power source for ion acceleration at the Electron Ion Collider (EIC) being developed at Thomas Jefferson National Accelerator Facility. The efficiency is 80%, a number to which the power consumption by the solenoid and filament are already factored in. The tube is a combination of proven technologies put together: it uses multiple beams to have its perveance low to boost beam-power to RF-power efficiency. It uses a partially grounded depressed collector to recover energy thereby increasing the overall efficiency. A low operating voltage of 14kV makes the tube more user-friendly avoiding need for costly modulators and oil insulation. A sectioned solenoid is used to insure superb beam-matching to all components downstream of the electron gun, increasing the tube performances. Details of the components designs will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM53
About •	paper received ※ 14 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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WEPLM57	200 kW, 350 - 700 MHz RF Sources using Multiple Beam Triodes	cathode, electron, vacuum, klystron	724
	R.L. Ives, T. Bui, D. Marsden, M.E. Read CCR, San Mateo, California, USA B. Henderson, L. Higgins, R. Ho CPI, Palo Alto, California, USA
	Funding: U.S. Department of Energy Grant No. DE-SC0018838 Calabazas Creek Research, Inc. and Communications & Power Industries, LLC are developing multiple beam triodes to produce more than 200 kW of RF power at extremely low cost and efficiencies exceeding 85%. RF power is achieved by installing the triode inside coaxial input and output cavities at the desired frequency. The multiple beam triodes developed in this program will provide RF power from 350 MHz to 700 MHz using the appropriate, tuned, resonant cavities. This program is using eight grid-cathode assemblies to achieve 200 kW with a target efficiency exceeding 80%. A 350 MHz RF source would be approximately 36 inches high, 18 inches in diameter and weigh approximately 150 pounds. This is significantly smaller than any other RF source at this frequency and power level. The gain is limited to approximately 14 dB, so a single beam triode-based source will serve as a driver. The combined cost and efficiency will still exceed the performance of other comparable RF sources, including solid state sources. Design issues, include grid cooling, uniformity of RF electric fields on the grids, and efficiency, will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM57
About •	paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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WEPLM60	Fast Sn-Ion Transport on Nb Surface for Generating NbxSn Thin Films and XPS Depth Profiling	interface, electron, radio-frequency, SRF	727
	Z. Sun, M. Liepe, J.T. Maniscalco, T.E. Oseroff, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA X. Deng University of Virginia, Charlottesville, Virginia, USA D. Zhang Cornell University, Ithaca, New York, USA
	Funding: U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams In this work, we propose and demonstrate a fast and facile approach for NbxSn thin film deposition through the ion exchange reaction. By simply dipping a tin precursor on the Nb substrate surface, a ~600 nm thin film is generated due to the electronegativity differ-ence between Sn and Nb. Through X-ray photoelec-tron spectroscopy (XPS) depth profiling, the composi-tional information as a function of film thickness was obtained. Results showed a Sn layer on the film sur-face, Sn-rich and Nb-rich NbxSn layers as the majority of the film, and a ~60 nm Nb₃Sn layer at the film/substrate interface. Quantitative analysis con-firmed stoichiometric Nb/Sn ratio for the Nb₃Sn layer. This deposition method is demonstrated to be an alter-native choice for Nb₃Sn film growth.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM60
About •	paper received ※ 05 September 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019
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WEPLM62	First Cold Test Results of a Medium-Beta 644 MHz Superconducting 5-Cell Elliptical Cavity for the FRIB Energy Upgrade	target, pick-up, linac, accelerating-gradient	731
	K.E. McGee, B.W. Barker, K. Elliott, A. Ganshyn, W. Hartung, S.H. Kim, P.N. Ostroumov, J.T. Popielarski, A. Taylor, C. Zhang FRIB, East Lansing, Michigan, USA M.P. Kelly, T. Reid ANL, Lemont, Illinois, USA
	Funding: Work supported by Michigan State University. The superconducting linac for the Facility for Rare Isotope Beams (FRIB) will accelerate ions to 200 MeV per nucleon, with the possibility of a future energy upgrade to 400 MeV per nucleon via additional cavities. A 5-cell superconducting β = 0.65 elliptical cavity was designed for this purpose. Two unjacketed 5-cell niobium cavities were fabricated; the first of these was Dewar tested in February 2019. The surface preparation was bulk electropolishing (EP, 150 µm), hydrogen degassing (600°C, 10 hours), light EP (20 µm), clean-room high-pressure water rinsing, and in-situ baking (120°C, 48 hours). We achieved Q₀ = 2·10¹⁰, equivalent to Rs = 10 nΩ, at the design gradient of 17.5 MV/m. The cavity was tested in a newly refurbished FRIB test Dewar, equipped with a variable input coupler.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM62
About •	paper received ※ 02 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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WEPLM63	Development of a Secondary Sn Source for Nb₃Sn Coating of Half-Wave Coaxial Resonator	niobium, SRF, MMI, superconductivity	735
	J.K. Tiskumara, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA G.V. Eremeev JLab, Newport News, Virginia, USA U. Pudasaini The College of William and Mary, Williamsburg, Virginia, USA
	Superconducting thin films have the potential of reducing the cost of particle accelerators. Among the potential materials, Nb₃Sn has a higher critical temperature and higher critical field compared to niobium. Sn vapor diffusion method is the preferred technique to coat niobium cavities. Although there are several thin-film-coated basic cavity models that are tested at their specific frequencies, the Half-wave resonator could provide us data across frequencies of interest for particle accelerators. With its advanced geometry, increased area, increased number of ports and hard to reach areas, the half-wave resonator needs a different coating approach, in particular, a development of a secondary Sn source. We are commissioning a secondary Sn source in the coating system and expand the current coating system at JLab to coat complex cavity models.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM63
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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WEPLM64	High Dynamic Voltage Range Studies of Piezoelectric Multilayer Actuators at Low Temperatures	linac, operation, SRF, vacuum	739
	C. Contreras-Martinez FRIB, East Lansing, Michigan, USA Y.M. Pischalnikov, J.C. Yun Fermilab, Batavia, Illinois, USA
	Piezo actuators are used for resonance control in superconducting linacs. In high accelerating gradients linacs, such as those operated in a pulsed mode, the piezos require a large operating voltage. This is due to the Lorentz forced detuning which causes a large frequency shift and is compensated with an active piezo-tuning system. In this high dynamic voltage range the piezo is expected to warm up drastically due to it being in an insulated vacuum. This study characterizes the dielectric properties (capacitance, dielectric losses), the piezo stroke (from geophone), and thermal properties such as heating. Results obtained in the temperature range of 20K to 300K will be presented and discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM64
About •	paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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WEPLM66	Microphonics Studies at STC in Fermilab	resonance, ion-source, cryomodule, controls	743
	C. Contreras-Martinez FRIB, East Lansing, Michigan, USA Y.M. Pischalnikov, W. Schappert, A.I. Sukhanov, J.C. Yun Fermilab, Batavia, Illinois, USA
	The spoke test cryostat is used to qualify the 325 MHz single spoke resonators at Fermilab (FNAL). During these tests a large detuning on the cavity was observed. The data acquisition for continuous captures were based on measurements from the piezoelectric actuators. A com-parison of the cavity vibrations measured with RF signal from the cavity and piezoelectric actuator signals are shown. The effects of microphonics on the cavity are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM66
About •	paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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WEPLM70	FRIB Tuner Performance and Improvement	linac, cryomodule, controls, MMI	755
	J.T. Popielarski, W. Chang, C. Compton, W. Hartung, S.H. Kim, E.S. Metzgar, S.J. Miller, K. Saito, J.F. Schwartz, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 The Facility for Rare Isotope Beams (FRIB) is under construction at Michigan State University (MSU). The FRIB superconducting driver linac will accelerate ion beams to 200 MeV per nucleon. The driver linac requires 10⁴ quarter-wave resonators (QWRs, β = 0.041 and 0.085) and 220 half-wave resonators (HWRs, β = 0.29 and 0.54). The cryomodules for β = 0.041, 0.085, and 0.29 have been completed and certified; 32 out of 49 cryomodules are certified via bunker test (as of March 2019). FRIB QWR cavities have a demountable niobium tuning plate which uses a warm external stepper motor and the FRIB HWR cavities use pneumatic actuated bellows. Progress on the preparation and performance of the tuners is presented in this paper along with improvements made to ensure meeting frequency specification.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM70
About •	paper received ※ 26 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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WEPLM71	Thermal Performance of FRIB Cryomodules	cryomodule, cryogenics, solenoid, operation	759
	M. Xu, W. Chang, C. Compton, A. Ganshyn, S.H. Kim, S.J. Miller, J.T. Popielarski, K. Saito, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 and the National Science Foundation under Cooperative Agreement PHY-1102511. Now SRF cavity development is advancing high-Q/high gradient by nitrogen doping, infusion, or the new low temperature bake recipe. Once cavity dynamic loss is reduced, the static heat load of the cryomodule will be of concern from the cryogenic plant capability point of view. FRIB gives us a good chance to statistically compare the cryogenic plant design and the measured results, along with a thought for future updated cryomodule design using a low/medium beta cryomodule. FRIB cryomodules have two cooling lines: 4.5 K for solenoids and 2K for cavities. The boil-off liquid helium method was used to measure the cryomodule’s heat load. So far, FRIB has completed certification testing (bunker tests) on 39 of 49 cryomodules (80%). This paper reports the static heat load measurement results, which are important for future FRIB upgrades to estimate remaining cryogenic capability. The cryomodule’s evolution related to heat load is introduced too.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM71
About •	paper received ※ 05 September 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019
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WEPLM72	Design of a High-Gradient S-Band Annular Coupled Structure	coupling, linac, Windows, operation	762
	B. Mustapha, A. Abogoda, A. Barcikowski, R.L. Fischer, A. Nassiri ANL, Lemont, Illinois, USA
	Funding: This work was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 through ANL’s LDRD program. At Argonne, we have recently developed a conceptual design for a compact linear accelerator for ion beam therapy named ACCIL [1]. A linac-based ion-beam therapy facility offers many advantages over existing synchrotron based facilities. In addition to the reduced footprint, ACCIL offers more flexibility in beam tuning, including pulse-per-pulse energy and intensity modulation and fast switching between ion species. Essential to the compactness of the ACCIL linac are high-gradient structures for low to intermediate velocity ions, capable of accelerating fields of ~ 50 MV/m. For this purpose, we have designed an S-band annular-coupled structure (ACS). An ACS has the desired qualities of high electric field limit, high shunt-impedance, large area for magnetic coupling and good cooling capacity, making it a very promising candidate for high-gradient operations. We here present the optimized RF design for a β ~ 0.4 ACS. * P. Ostroumov, et al., "Compact Carbon Ion Linac", Proceedings of NAPAC2016, Oct 10-14 2016, Chicago, IL
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM72
About •	paper received ※ 04 October 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019
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WEPLM73	Bunker Testing of FRIB Cryomodules	cryomodule, solenoid, SRF, dipole	765
	W. Chang, S. Caton, A. Ganshyn, W. Hartung, S.H. Kim, B. Laumer, H. Maniar, J.T. Popielarski, K. Saito, M. Xu, T. Xu, C. Zhang, S. Zhao FRIB, East Lansing, Michigan, USA
	The FRIB superconducting driver Linac requires 10⁴ quarter-wave resonators (QWRs, β = 0.041, 0.085), 220 half-wave resonators (HWRs, β = 0.29, 0.53), and 74 superconducting solenoid packages. Resonators and solenoids are assembled into cryomodules; 4 accelerating and 2 matching cryomodule types are required. Each cryomodule undergoes cryogenic and RF testing in a bunker prior to installation in the tunnel. The cryomodule test verifies operation of the cavities, couplers, tuners, solenoid packages, magnetic shield, and thermal shield at 4.3 K and 2 K. All of the required cryomodules for β = 0.041, 0.085, and 0.29 have been tested and certified. As of May 2019, five of the β = 0.53 cryomodules have been certified; the remaining modules are being assembled or are in the queue for testing. Cryomodule test results will be presented, including cavity performance (accelerating gradient, field emission X-rays, multipacting conditioning); solenoid package operation (current, current-lead cooling flow rate); and cryomodule heat load (static and dynamic).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM73
About •	paper received ※ 06 September 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019
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WEPLS02	Simulation of a Klystron Input Cavity using a Steady-State Full-Wave Solver	simulation, experiment, klystron, electron	768
	A.R. Gold, S.G. Tantawi SLAC, Menlo Park, California, USA
	The simulation of vacuum electronic radio-frequency (RF) power sources is generally done through semi-analytical modeling approaches. These techniques are computationally efficient as they make assumptions on the source topology, such as the requirement that the electron beam travel longitudinally and interact with cylindrical modes. To simulate more general interactions, transient particle-in-cell (PIC) codes are currently required. We present here simulation results of a 5045 klystron using a newly developed steady state code which does not make assumptions on the beam configuration or geometry of the structure and resonant modes. As we solve directly for the steady-state system dynamics, this approach is computationally efficient yet, as demonstrated through comparison with experimental results, provides similar accuracy.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS02
About •	paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEPLS05	Simulation Analysis of the LCLS-II Injector using ACE3P and IMPACT	simulation, emittance, booster, lattice	779
	D.A. Bizzozero, J. Qiang LBNL, Berkeley, California, USA L. Ge, Z. Li, C.-K. Ng, L. Xiao SLAC, Menlo Park, California, USA
	Funding: This work is supported by the Director of the Office of Science of the US Department of Energy under contracts DEAC02-05CH11231 and DE-AC02-76-SF00515. The LCLS-II beam injector system consists of a 186 MHz normal-conducting RF gun, a two-cell 1.3 GHz normal-conducting buncher cavity, two transverse focusing solenoids, and eight 1.3 GHz 9-cell Tesla-like super-conducting booster cavities. With a coordinated effort between LBNL and SLAC, we have developed a simulation workflow combining the electromagnetic field solvers from ACE3P with the beam dynamics modeling code IMPACT. This workflow will be used to improve performance and minimize beam emittance for given accelerator structures through iterative optimization. In our current study, we use this workflow to compare beam quality parameters between using 2D axisymmetric field profiles and fully 3D non-axisymmetric fields caused by geometrical asymmetries (e.g. RF coupler ports).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS05
About •	paper received ※ 20 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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WEPLS12	A Semi-Analytical Approach to Six-Dimensional Path-Dependent Transport Matrices With Application to High-Brightness Charged-Particle Beam Transport	solenoid, simulation, emittance, electron	792
	C.-Y. Tsai HUST, Wuhan, People’s Republic of China K. Fan Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People’s Republic of China
	Funding: This work was supported by the Fundamental Research Funds for the Central Universities under Project No. 5003131049. Efficient and accurate estimate of high-brightness electron beam dynamics is an important step to the overall performance evaluation in modern particle accelerators. Utilizing the moment description to study multi-particle beam dynamics, it is necessary to develop a path-dependent transport matrix, together with application of the drift-kick algorithm. In this paper we will construct semi-analytical models for three typical beam transport elements, solenoid with fringe fields, transverse deflecting cavity, and a beam slit. To construct the semi-analytical models for these elements, we begin by formulating the simplified single-particle equations of motion, and apply typical numerical techniques to solve the corresponding six-by-six transport matrix as a function of the path coordinate. The developed semi-analytical models are demonstrated with three practical examples, where our numerical results are discussed, compared with and validated by particle tracking simulations. These path-dependent transport matrix models can be incorporated to the analysis based on beam matrix method for the application to high-brightness charged-particle beam transport. C.-Y. Tsai et al., Nuclear Inst. And Methods in Physics Research, A 937 (2019) 1-20
	Poster WEPLS12 [3.099 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS12
About •	paper received ※ 20 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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WEPLH06	Commissioning Status of the FRIB Front End	rfq, MMI, linac, ECR	813
	H.T. Ren, J. Brandon, N.K. Bultman, K.D. Davidson, E. Daykin, T. Elkin, B. Galecka, P.E. Gibson, L. Hodges, K. Holland, D.D. Jager, M.G. Konrad, B.R. Kortum, S.M. Lidia, G. Machicoane, I.M. Malloch, H. Maniar, T. Maruta, G. Morgan, D.G. Morris, P. Morrison, A.C. Morton, P.N. Ostroumov, A.S. Plastun, E. Pozdeyev, X. Rao, T. Russo, J.W. Stetson, R. Walker, J. Wei, Y. Yamazaki, T. Yoshimoto, Q. Zhao, S. Zhao FRIB, East Lansing, Michigan, USA S. Renteria NSCL, East Lansing, Michigan, USA
	Funding: This work is supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661. The FRIB Front End was successfully commissioned in 2017 with commissioning goals achieved and Key Per-formance Parameters (KPP) demonstrated for both 40Ar⁹⁺ and 86Kr¹⁷⁺ beams. Two more ion species, 20Ne⁶⁺ and 129Xe²⁶⁺, have been commissioned on the Front End and delivered to the superconducting linac during the beam commissioning of Linac Segment 1 (LS1) in March 2019. In August 2019, Radio Frequency Quadrupole (RFQ) conditioning reached the full design power of 100 kW continuous wave (CW) that is required to accelerate Ura-nium beams. Start-up/shutdown procedures and opera-tional screens were developed for the Front End subsys-tems for trained operators, and auto-start and RF fast re-covery functions have been implemented for the Front End RFQ and bunchers. In this paper, we will present the current commissioning status of the Front End, and per-formance of the main technical systems, such as the ECR ion source and RFQ.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH06
About •	paper received ※ 01 September 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEPLH07	Commissioning of the FRIB/NSCL New ReA3 4-Rod Radio Frequency Quadrupole Accelerator	rfq, vacuum, operation, MMI	817
	S. Nash, J.F. Brandon, D.B. Crisp, T. Summers, A.C.C. Villari, Q. Zhao NSCL, East Lansing, Michigan, USA P.N. Ostroumov, A.S. Plastun FRIB, East Lansing, Michigan, USA
	Funding: This work was supported by the National Science Foundation under Grant PHY-15-65546 The reaccelerator facility ReA3 at the National Superconducting Cyclotron Laboratory is a state-of-the-art accelerator for ions of rare and stable isotopes. The first stage of acceleration is provided by a 4-rod radio-frequency quadrupole (RFQ) at 80.5 MHz, which accelerates ions from 12 keV/u to 530 keV/u. The internal copper acceleration structure of the RFQ was re-designed. The goal was to improve transmission while allowing to operate the RFQ in CW and accelerating ions with A/Q from 2 to 5. In this paper, we summarize the steps involved in the disassembly of the existing structure, preparation work on the retrofitted vacuum vessel, installation of the new components, acceptance testing, and commissioning of the completed RFQ.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH07
About •	paper received ※ 29 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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WEPLH09	FRIB Driver Linac Integration to be ready for Phased Beam Commissioning	MMI, SRF, cryomodule, linac	823
	H. Ao, S. Beher, N.K. Bultman, F. Casagrande, C. Compton, J.C. Curtin, K.D. Davidson, K. Elliott, V. Ganni, A. Ganshyn, P.E. Gibson, I. Grender, W. Hartung, L. Hodges, K. Holland, A. Hussain, M. Ikegami, S. Jones, P. Knudsen, S.M. Lidia, G. Machicoane, S.J. Miller, D.G. Morris, P.N. Ostroumov, J.T. Popielarski, L. Popielarski, J. Priller, T. Russo, K. Saito, S. Stanley, D.R. Victory, X. Wang, J. Wei, M. Xu, T. Xu, Y. Yamazaki, S. Zhao FRIB, East Lansing, Michigan, USA A. Facco INFN/LNL, Legnaro (PD), Italy R.E. Laxdal TRIUMF, Vancouver, Canada
	Funding: Work supported by the U.S. Department of Energy (DOE) Office of Science under Cooperative Agreement DE-SC0000661 The driver linac for Facility for Rare Isotope Beams (FRIB) will accelerate all stable ion beams from proton to uranium beyond 200 MeV/u with beam powers up to 400 kW. The linac now consists of 10⁴ superconducting quarter-wave resonators (QWR), which is the world largest number of low-beta SRF cavities operating at an accelerator facility. The first 3 QWR cryomodules (CM) (β = 0.041) were successfully integrated with cryogenics and other support systems for the 2nd Accelerator Readiness Review (ARR). The 3rd ARR scope that includes 11 QWR CM (β=0.085) and 1 QWR matching CM (β=0.085) was commissioned on schedule by January 2019, and then we met the Key Performance Parameters (KPP), accelerating Ar and Kr > 16 MeV/u at this stage, in a week upon the ARR authorization. We examine a variety of key factors to the successful commissioning, such as component testing prior to system integration, assessment steps of system/device readiness, and phased commissioning. This paper also reports on the integration process of the β=0.085 CMs including the test results, and the current progress on β=0.29 and 0.53 CMs in preparation for the upcoming 4th ARR.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH09
About •	paper received ※ 02 September 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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WEPLH10	Efficiency Estimation for Sequential Excitation Laser Stripping of H⁻ Beam	laser, experiment, electron, proton	827
	T.V. Gorlov, A.V. Aleksandrov, S.M. Cousineau, Y. Liu, A. Rakhman ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL is managed by UTBattelle, LLC, under contract DEAC0500OR22725 for the U.S. Department of Energy. A new laser stripping scheme for charge exchange injection of H⁻ beam is considered. The sequential scheme for the planned demonstration experiment includes two step excitation that requires much smaller laser power compared to the traditional 1-step excitation. The new scheme can be applied to a wider range of H⁻ beam energies and provides more flexibility on the choice of laser frequency. In this paper we discuss the two-step excitation method and estimate laser stripping parameters and stripping efficiency for the SNS accelerator and its future H⁻ energy upgrade to 1.3 GeV.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH10
About •	paper received ※ 22 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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WEPLH15	Light Ion Injector for NICA	linac, rfq, DTL, proton	834
	H. Höltermann, H. Hähnel, B. Koubek, H. Podlech, U. Ratzinger, A. Schempp, D. Strehl, R. Tiede BEVATECH, Frankfurt, Germany M. Busch, M. Schuett IAP, Frankfurt am Main, Germany A.V. Butenko, D.E. Donets, A.D. Kovalenko, K.A. Levterov, D.A. Lyuosev, A.A. Martynov, D.O. Ponkin, K.V. Shevchenko, I.V. Shirikov, A.O. Sidorin, G.V. Trubnikov JINR/VBLHEP, Dubna, Moscow region, Russia B.V. Golovenskiy, A. Govorov, V.V. Kobets, E. Syresin JINR, Dubna, Moscow Region, Russia
	The Nuclotron ring of the NICA project will get a new light ion injector linac (LILac) for protons and ions with a mass to charge ratio up to 3. The LILac will consist of 2 sections: A 600 A keV RFQ followed by an IH-type DTL up to 7 AMeV, and a postaccelerator IH-cavity for protons only - up to 13 MeV. A switching magnet will additionally allow 13 MeV proton beam injection into a future superconducting testing section. The pulsed Linac up to 7 AMeV and including the postaccelerator for protons up to 13 MeV will be developed in collaboration between JINR and Bevatech GmbH. The technical design of that Linac is discussed in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH15
About •	paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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WEPLO20	High Gradient High Efficiency C-Band Accelerator Structure Research at LANL	simulation, operation, experiment, electron	882
	E.I. Simakov, A.W. Garmon, T.C. Germann, M.F. Kirshner, F.L. Krawczyk, J.W. Lewellen, D. Perez, G. Wang LANL, Los Alamos, New Mexico, USA A. Fukasawa, J.B. Rosenzweig UCLA, Los Angeles, California, USA
	Funding: Los Alamos National Laboratory LDRD Program This poster will report on the status of the new high gradient C-band accelerator project at LANL. Modern applications such as X-ray sources require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. Our goal is to use a multi-disciplinary approach that includes accelerator design, molecular dynamics simulations, and advanced manufacturing to develop high gradient, high efficiency RF structures for both compact and facility-size accelerator systems. We considered common operation frequencies for accelerators and identified C-band as the optimal frequency band for high gradient operations based on achievable gradients and means to control wakefields. We are putting together a high gradient C-band test facility that includes a 50 MW Toshiba klystron and cryo-coolers for operating copper NCRF accelerator cavities at long pulse duration. We plan to conduct high gradient testing of the optimized RF structures made of copper and novel copper alloys. LANL modeling capabilities will be used to systematically study the formation of breakdown precursors at high fields to develop basic theoretical understanding of the breakdown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO20
About •	paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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WEPLE02	Integrated Accelerator Simulation with Electromagnetics and Beam Physics Codes	simulation, plasma, electron, emittance	885
	L. Ge, Z. Li, C.-K. Ng, L. Xiao SLAC, Menlo Park, California, USA D.A. Bizzozero, J. Qiang, J.-L. Vay LBNL, Berkeley, California, USA D.P. Grote LLNL, Livermore, California, USA
	Funding: Work supported by US Department of Energy under contracts AC02-76SF00515, DE-AC02-05CH11231 and DE-AC52-07NA27344. Used resources of the National Energy Research Scientific Computing Center. This paper presents an integrated simulation capability for accelerators including electromagnetic field and beam dynamics effects. The integrated codes include the parallel finite-element code suite ACE3P for electromagnetic field calculation of beamline components, the parallel particle-in-cell (PIC) code IMPACT for beamline particle tracking with space-charge effects, and the parallel self-consistent PIC code Warp for beam and plasma simulations. The common data format OpenPMD has been adopted for efficient field and particle I/O data transfer between codes. One application is to employ ACE3P and IMPACT for studying beam qualities in accelerator beamlines. Another is to combine ACE3P and Warp for investigating plasma processing for operational performance of RF cavities. A module for mapping the CAD geometry used in ACE3P to Warp Cartesian grid representation has been developed. Furthermore, a workflow has been implemented that enables the execution of integrated simulation on HPC systems. Examples for simulation of the LCLS-II injector using ACE3P-IMPACT and plasma ignition in SRF cavities using ACE3P-Warp will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE02
About •	paper received ※ 20 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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WEPLE04	Recent Developments and Applications of Parallel Multi-Physics Accelerator Modeling Suite ACE3P	simulation, cryomodule, dipole, GUI	888
	Z. Li, L. Ge, C.-K. Ng, L. Xiao SLAC, Menlo Park, California, USA
	Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515. SLAC’s ACE3P code suite is developed to harness the power of massively parallel computers to tackle large complex problems with increased memory and solve them at greater speed. ACE3P parallel multi-physics codes are based on higher-order finite elements for superior geometry fidelity and better solution accuracy. ACE3P consists of an integrated set of electromagnetic, thermal and mechanical solvers for accelerator modeling and virtual prototyping. The use of ACE3P has contributed to the design and optimization of existing and future accelerator projects around the world. Multi-physics analysis on high performance computing (HPC) platform enables thermal-mechanical simulations of largescale systems such as the LCLS-II cryomodule. Recently, new capabilities have been added to ACE3P including a nonlinear eigenvalue solver for calculating mode damping, a moving window for pulse propagation in the time domain to reduce computational cost, thin layer coating representation using a surface impedance model, and improved boundary conditions using perfectly matched layers (PML) to terminate wave propagation. These new developments are presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE04
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEPLE05	Tracking With Space Harmonics in ELEGANT Code	electromagnetic-fields, simulation, electron, photon	892
	Y.P. Sun, C. Yao ANL, Lemont, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The elegant code has the capability of simulating particle motion in accelerating or deflecting RF cavities, with a simplified (or ideal) model of the electromagnetic fields. To improve the accuracy of RF cavity simulations, the ability to track with space harmonics has been added to the elegant code. The sum of all the space harmonics will mimic the real electromagnetic fields in the RF cavity. These space harmonics will be derived from electromagnetic fields simulation of the RF cavity. This method should be general, which can be applied to any RF cavity structure, including accelerating and deflecting cavities.
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About •	paper received ※ 31 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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THYBA1	Status of the CBETA Cornell-BNL ERL Prototype	MMI, radiation, beam-loading, electron	923
	K.E. Deitrick, N. Banerjee, A.C. Bartnik, J.A. Crittenden, L. Cultrera, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter, W. Lou, P. Quigley, D. Sagan, K.W. Smolenski, D. Widger Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA J.S. Berg, S.J. Brooks, R.L. Hulsart, R.J. Michnoff, S. Peggs, D. Trbojevic BNL, Upton, New York, USA
	CBETA, the Cornell-BNL ERL Test Accelerator, is an SRF multi-turn ERL which has been commissioned in the one-turn configuration from March to July 2019. During this time, the project has demonstrated an energy acceptance of 1.5 in the FFA arc, high-transmission energy recovery performance, and increased the CBETA energy-recovered maximum average current.
	Slides THYBA1 [11.605 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA1
About •	paper received ※ 28 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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THYBB3	Compact 1 MeV Electron Accelerator	GUI, gun, vacuum, electron	942
	S.V. Kuzikov IAP/RAS, Nizhny Novgorod, Russia S.P. Antipov, P.V. Avrakhov Euclid TechLabs, LLC, Solon, Ohio, USA
	The cost of the accelerating structure in modern medical accelerators and industrial linacs is substantial. This comes to no surprise, as the accelerating waveguide is a set of diamond-turned copper resonators brazed together. Such a multistep manufacturing process is not only expensive, but also prone to manufacturing errors, which decrease the production yield. In the big picture, the cost of the accelerating waveguide precludes the use of accelerators as a replacement option for radioactive sources. Here we present a new cheap brazeless electron accelerating structure made out of two copper plates tightened together by means of an additional stainless steel plate. This additional plate, having sharp blades, is aimed to provide vacuum inside the whole system. The designed X-band 1 MeV structure consists of eight different length cells and accelerates field-emitted electrons from copper cathode. The structure is fed by 9 GHz magnetron which produces 240 kW, 1 µs pulses. The average gradient is as high as 10.6 MV/m, maximum surface fields do not exceed 50 MV/m.
	Slides THYBB3 [19.559 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBB3
About •	paper received ※ 27 August 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019
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THZBA2	The MYRRHA Project	linac, rfq, proton, operation	945
	H. Podlech, P. Britten, K. Kümpel, S. Lamprecht, N.F. Petry IAP, Frankfurt am Main, Germany M. Abs, J. Brison IBA, Louvain-la-Neuve, Belgium C. Angulo, J. Belmans, F. Doucet, A. Gatera, F. Pompon, A. Ponton, D. Vandeplassche SCK•CEN, Mol, Belgium A. Apollonio, J.A. Uythoven CERN, Meyrin, Switzerland A. Bechtold NTG Neue Technologien GmbH & Co KG, Gelnhausen, Germany J.-L. Biarrotte, C. Joly, D. Longuevergne Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France F. Bouly LPSC, Grenoble Cedex, France P. Fernandez Ramos, A.E. Pitigoi Empresarios Agrupados, Madrid, Spain H. Höltermann, U. Ratzinger BEVATECH, Frankfurt, Germany T. Junquera Accelerators and Cryogenic Systems, Orsay, France R. Modic Cosylab, Ljubljana, Slovenia F. Senée, D.U. Uriot CEA-IRFU, Gif-sur-Yvette, France C. Zhang GSI, Darmstadt, Germany
	The main objective of the MYRRHA project at SCK•CEN, the Belgian Nuclear Research Centre, is to demonstrate the feasibility of nuclear waste transmutation using an Accelerator Driven System (ADS). It is based on a High Power CW operated 600 MeV proton Linac with an average beam power of 2.4 MW. Due to the coupling of the accelerator with a subcritical reactor, a major concern is reliability and availability of the accelerator. The MYRRHA Linac consists of a room temperature 17 MeV Injector based on CH-cavities and the superconducting main Linac using different RF structures as Single Spokes, Double-Spokes and elliptical cavities. In 2017, it has been decided to stage the project and to start with the construction of a 100 MeV Linac (Injector and Single Spoke section) including a 400 kW proton target station. This facility (MINERVA) will be operational in 2026 aiming to evaluate the reliability potential of the 600 MeV Linac. The Front-End consisting of an ECR source, LEBT and 1.5 MeV RFQ is already operational while the first 7 CH-cavities are under construction. The presentation gives an overview about the MYRRHA Project, its challenges and the status of construction and testing.
	Slides THZBA2 [27.209 MB]

Paper

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MOYBA6

Accelerator Performance During the Beam Energy Scan II at RHIC in 2019

electron, operation, luminosity, MMI

26

C. Liu, I. Blacker, M. Blaskiewicz, K.A. Brown, D. Bruno, K.A. Drees, A.V. Fedotov, W. Fischer, C.J. Gardner, C.E. Giorgio, X. Gu, T. Hayes, H. Huang, R.L. Hulsart, D. Kayran, N.A. Kling, Y. Luo, D. Maffei, G.J. Marr, B. Martin, A. Marusic, K. Mernick, R.J. Michnoff, M.G. Minty, C. Montag, J. Morris, C. Naylor, S. Nemesure, I. Pinayev, S. Polizzo, V.H. Ranjbar, D. Raparia, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, S. Tepikian, P. Thieberger, A. Zaltsman, K. Zeno, I.Y. Zhang, W. Zhang
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
RHIC provided Au-Au collisions at beam energies of 9.8, 7.3, 4.59 and 3.85 GeV/nucleon during the first year of the Beam Energy Scan II in 2019. The physics goals at the first two higher beam energies were achieved. At the two lower beam energies, bunched electron beam cooling has been demonstrated successfully. The accelerator performance was improved compared to when RHIC was operated at these energies in earlier years. This article will introduce the challenges to operate RHIC at low energies and the corresponding countermeasures, and review the improvement of accelerator performance during the operation in 2019.

Slides MOYBA6 [6.579 MB]

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MOYBB3

Progress in Nb₃Sn SRF Cavities at Cornell University

SRF, accelerating-gradient, site, superconductivity

37

R.D. Porter, H. Hu, M. Liepe, N.A. Stilin, Z. Sun, M.J. Tao
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Niobium-3 Tin (NbSn) is the most promising alternative material for next-generation SRF cavities. The material can obtain high quality factors (> 10¹⁰) at 4.2 K and could theoretically support ~ 96 MV/m operation of a TESLA elliptical style cavity. Current Nb₃Sn cavities made at Cornell University achieve high quality factors but are limited to about 17 MV/m in CW operation due to the presence of a surface defect. Here we examine recent results on studying the quench mechanism and propose that surface roughness is a major limiter for accelerating gradients. Furthermore, we discuss recent work on reducing the surface roughness including chemical polishing, modification of material growth, and tin electroplating.

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MOYBB4

Large-Scale Dewar Testing of FRIB Production Cavities: Statistical Analysis

SRF, multipactoring, linac, cryomodule

41

C. Zhang, W. Chang, W. Hartung, S.H. Kim, J.T. Popielarski, K. Saito, J.F. Schwartz, T. Xu
FRIB, East Lansing, Michigan, USA

The Facility for Rare Isotope Beams (FRIB) requires a driver linac with 324 superconducting cavities to deliver ion beams at 200 MeV per nucleon. About 1/3 of the cavities are quarter-wave resonators (QWRs, 805. MHz); the rest are half-wave resonators (HWRs, 322 MHz). FRIB cavity production is nearly complete, with more than 90% of the required cavities certified for installation into cryomodules (as of May 2019). We have accumulated a large data set on performance of production QWRs and HWRs during Dewar certificating testing of jacketed cavities. In this paper, we will report on the data analysis, including statistics on the BCS resistance, residual resistance, energy gap, and Q-slope. Additionally, we will discuss performance limitations and conditioning (multipacting, field emission).

Slides MOYBB4 [1.200 MB]

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MOYBB6

X-Ray Detector Array for Spatial and Temporal Diagnostic at the LANSCE Linac

detector, linac, shielding, photon

47

M. Sanchez Barrueta, G.O. Bolme, J.T.M. Lyles, J.E. Zane
LANL, Los Alamos, New Mexico, USA
R.Z. Pinsky
NERS-UM, Ann Arbor, Michigan, USA

Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract 89233218CNA000001
A recent industrial development has made possible the use of chip-scale radiation detectors by combining a Cerium-doped Lutetium based scintillator crystal optically coupled with a Silicon Photomultiplier (SiPM) as a detector. At the Los Alamos Neutron Science Center (LANSCE), there has been an ongoing effort to determine the location of high voltage breakdowns of the accelerating radio-frequency field inside of an evacuated resonant cavity. Tests were conducted with an array of 8 X-ray detectors with each detector observing a cell of the Drift Tube Linac (DTL) cavity. The array can be moved along the DTL cavity and record X-ray emissions from a section of the cavity and their timing with respect to the RF field quench using a fast 8 channel mixed-signal oscilloscope. This new diagnostic allowed us to map the most energetic emissions along the cavity and reduce the area to investigate. A thorough visual inspection revealed that one of the ion pump grating welds in the suspected area was exposing a small gap and melting copper on both sides. Sparking across this discontinuity is believed to be a source of electrons that drive the high voltage breakdowns in the drift tube cells.

Slides MOYBB6 [39.283 MB]

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MOZBA1

LCLS-II SC Linac: Challenges and Status

cryomodule, SRF, linac, FEL

51

M.C. Ross
SLAC, Menlo Park, California, USA

Funding: ∗ This work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515
The Linac Coherent Light Source II (LCLS-II) project requires the assembly, test, and installation of 37 cry-omodules (CM) in order to deliver a 4 GeV CW electron beam to the FEL undulators for production of both hard and soft X-ray pulses at a repetition rate of up to 1 MHz. All of the cryomodules will operation in continuous wave mode, with 35 operating at 1.3 GHz for acceleration and 2 operating at 3.9 GHz to linearize the longitudinal beam profile. The assembly and testing of the 1.3 GHz cry-omodules is nearing completion and the 3.9 GHz cry-omodules work is entering to assembly and testing phase. Roughly 60% of the cryomodules have been shipped to SLAC for installation in the accelerator enclosure. The status and challenges of these efforts will be reported in this paper.

Slides MOZBA1 [80.533 MB]

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MOZBA6

The Broad-Band Impedance Budget of the Accumulator Ring in the ALS-U Project

impedance, wakefield, simulation, vacuum

74

D. Wang, S. De Santis, D. Li, T.H. Luo, M. Venturini
LBNL, Berkeley, California, USA
K.L.F. Bane
SLAC, Menlo Park, California, USA

Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. It consists of an accumulator and a storage ring. In both rings, coupling-impedance driven instabilities need careful evaluation to ensure meeting the machine high-performance goals. This paper presents the impedance budget of the accumulator ring both longitudinally and transversely. The budget includes the resistive wall impedance as well as the geometric impedance from the main vacuum components. Our calculations primarily rely on electromagnetic simulations with the CST code; when possible validation has been sought against analytical modeling, typically in the low-frequency limit, and good agreement generally found. Collective-instability current thresholds are also discussed.

Slides MOZBA6 [8.926 MB]

Poster MOZBA6 [3.542 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA6

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MOPLM09

High-Power Design of a Cavity Combiner for a 352-MHz Solid State Amplifier System at the Advanced Photon Source

storage-ring, klystron, interface, network

113

G.J. Waldschmidt, D.J. Bromberek, A. Goel, D. Horan, A. Nassiri
ANL, Lemont, Illinois, USA

A cavity combiner has been designed as part of a solid state amplifier system at the Advanced Photon Source with a power requirement of up to 200 kW for the full system. Peak field levels and thermal loading have been optimized to enhance the rf and mechanical perfor-mance of the cavity and to augment its reliability. The combiner consists of 16 rotatable input couplers, a re-duced-field output coupler, and static tuning. The power handling capability of the cavity will be evaluated during a back-feed test where an external klystron source will be used to transmit power through the cavity into loads on each of the input couplers.

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MOPLM17

Longitudinal Impedance Modeling of APS Particle Accumulator Ring with CST

impedance, simulation, kicker, vacuum

140

C. Yao, J. Carvelli, K.C. Harkay, L.H. Morrison
ANL, Lemont, Illinois, USA
D. Hui
University of Arizona, Tucson, Arizona, USA
J.S. Wang
Dassault Systems Simulia, Waltham, Massachusetts, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The APS-U (APS upgrade) ring plans implement a "swap out" injection scheme, which requires a injected beam of 15.6 nC single-bunch beam. The Particle Accumulator Ring (PAR), originally designed for up to 6 nC charge, must be upgraded to provide 20 nC single bunch beam. Our studies have shown that bunch length of the PAR beam, typically 300 ps at lower charge, increases to 800 ps at high charge due to longitudinal instabilities, which causes low injection efficiency of the downstream Booster ring. We completed beam impedance of all the PAR vacuum components recently with CST wakefield solver. 3D CAD models are directly imported into CST and various techniques were explored to improve and verify the results. The results are also cross-checked with that from GdfidL and Echo simulation. We identified 23 bellow- and 24 non-bellow flanges that contribute to as much as 50% of the total loss factor. We are considering upgrade options to reduce over all beam loading and longitudinal impedance. Beam tracking simulation is in progress that including the longitudinal impedance results from the simulations. We report the results and methods of the CST impedance simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM17

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paper received ※ 22 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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MOPLM20

Impedance Considerations for the APS Upgrade

impedance, photon, vacuum, simulation

147

R.R. Lindberg
ANL, Lemont, Illinois, USA
A. Blednykh
BNL, Upton, New York, USA

Funding: Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
The APS-Upgrade is targeting a 42 pm lattice that requires strong magnets and small vacuum chambers. Hence, impedance is of significant concern. We overview recent progress on identifying and modelling vacuum components that are important sources of impedance in the ring, including photon absorbers, BPMs, and flange joints. We also show how these impact collective dynamics in the APS-U lattice.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM20

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paper received ※ 27 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019

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MOPLH04

Design for HyRES Cathode Nanotip Electron Source

electron, solenoid, gun, cathode

177

R.M. Hessami, A.F. Amhaz, P. Musumeci
UCLA, Los Angeles, USA

A new ultrafast electron diffraction (UED) instrument is being developed by UCLA-Colorado University collaboration for the STROBE NSF Center with the goal of using electron and EUV photon beams to reveal the structural dynamics of materials in non-equilibrium states at fundamental atomic and temporal scales. This paper describes the design of the electron beamline of this instrument. In order to minimize the initial emittance, a nanotip photocathode, 25 nm in radius, will be used. This requires a redesign of the cathode and anode components of the electron gun to allow for the tip to be properly aligned. Solenoidal lenses are used to focus the beam transversely to a sub-micron spot at the sample and a radiofrequency (RF) cavity, driven by a continuous wave S-band RF source, longitudinally compresses the beam to below 100 fs, required for atomic resolution.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH04

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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MOPLH10

Field-Emission Electron Source Embedded in a Field-Enhanced Conduction-Cooled Superconducting RF Cavity

electron, cathode, experiment, niobium

192

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

We present simulations and experimental progress toward the development of a high-current electron source with the potential to deliver high charge electron bunches at GHz-level repetition rates. To achieve these goals electrons are generated through field-emission and the cathode is immersed in a conduction-cooled superconducting 650-MHz RF cavity. The field-emitters consist of microscopic silicon pyramids and have a typical enhancement factor of about 500. To trigger field-emission, the peak field inside the RF cavity of about 6 MV/m is further enhanced by placing the field-emitters on the top of a superconducting Nb rod inserted in the RF cavity. So far, we cannot control the duration of the electron bunches which is of the order of RF period. Also, the present cryo-cooler power of about 2 W limits the beam current to microamp level.

Poster MOPLH10 [1.063 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH10

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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MOPLH23

An Analysis of Potential Compact Positron Beam Source

positron, plasma, emittance, simulation

220

R.M. Hessami
UCLA, Los Angeles, USA
S.J. Gessner
CERN, Geneva, Switzerland

For positron studies in plasma wakefield accelerators such as AWAKE, the development of new, cheaper, and compact positron beam sources is necessary. Using an electrostatic trap with parameters similar to other experiments, this paper explores converting that trapped positron plasma into a usable beam. Bunching is initially accomplished by an electrostatic buncher and the beam is accelerated to 148 keV by pulsed electrostatic accelerators. This is necessary for injection into the beta-matched rf cavities operating at 600 MHz, which bring the positron beam to a transverse emittance of 1.3 pi mrad mm, a longitudinal emittance of 93.3 pi keV mm, stdz of 1.85 mm and an energy of 22 MeV. The beamline used here is far simpler and less expensive than those at many facilities, such as SLAC, allowing for a cheap source of positron beams, potentially opening up positron beam studies to many facilities that could not previously afford such a source.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH23

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paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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MOPLO04

Progress in Time-Resolved MeV Transmission Electron Microscopy at UCLA

electron, quadrupole, alignment, detector

243

P.E. Denham
UCLA, Los Angeles, USA

We describe here two new enhancements developed for the time-resolved microscope at the UCLA PEGASUS Lab based on the use of a radiofrequency photoinjector as an ultrafast electron source and permanent magnet quadrupoles as electron lenses. The first enhancement is a flexible optical column design including hybrid-style stronger focusing quadrupoles, yielding a 60% magnification increase, and a collimator to improve imaging contrast. This new optical system will have the ability to switch between real-space imaging and diffraction pattern imaging with variable magnification. The second enhancement is a high-frequency (X-band) cavity downstream from the (S-band) photoinjector to reduce the beam energy spread. These enhancements are crucial for improving contrast and image quality. In addition, a pulse-wire alignment method to fiducialize the quadrupole positions to better than 20-um precision is used to reduce the aberrations induced by misalignment and achieve spatial resolution at the 20 nm-level.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO04

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paper received ※ 28 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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MOPLO17

Large-Scale Dewar Testing of FRIB Production Cavities: Results

cryomodule, SRF, MMI, linac

270

W. Hartung, W. Chang, S.H. Kim, D. Norton, J.T. Popielarski, K. Saito, J.F. Schwartz, T. Xu, C. Zhang
FRIB, East Lansing, Michigan, USA

The Facility for Rare Isotope Beams (FRIB), under construction at Michigan State University (MSU), includes a superconducting driver linac to deliver ion beams at 200 MeV per nucleon. The driver linac requires 10⁴ quarter-wave resonators (QWRs, β = 0.041 and 0.085) and 220 half-wave resonators (HWRs, β = 0.29 and 0.54). The jacketed resonators are Dewar tested at MSU before installation into cryomodules. The cryomodules for β = 0.041, 0.085, and 0.29 have been completed and certified; 89% of the β = 0.54 HWRs have been certified (as of May 2019). The Dewar certification tests have provided valuable information on the performance of production QWRs and HWRs at 4.3 K and 2 K and on performance limits. Results will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO17

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paper received ※ 08 November 2019 paper accepted ※ 26 November 2019 issue date ※ 08 October 2019

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MOPLO19

Test Results of PIP2IT MEBT Vacuum Protection System

vacuum, cryomodule, MEBT, SRF

278

A.Z. Chen, R. Andrews, C.M. Baffes, D.D. Lambert, L.R. Prost, A.V. Shemyakin, T.J. Zuchnik
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics
The central part of PIP-II program of upgrades proposed for the Fermilab injection complex is an 800 MeV, 2 mA, CW-compatible SRF linac. Acceleration in superconducting cavities begins from a low energy of 2.1 MeV, so that the first cryomodule, Half Wave Resonator (HWR) borders the warm Medium Beam Transport (MEBT) line. To minimize the amount of gas that may enter the SRF linac in a case if a vacuum failure occurs in the warm front end, a vacuum protection system is envisioned to be used in the PIP-II MEBT. It features a fast closing valve with two sensors and a differential pumping insert. The system prototype is installed in the PIP-II Injector Test (PIP2IT) accelerator and recently is successfully tested in several modes modelling the vacuum failures. The report presents the design of the vacuum protection system and results of its tests.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO19

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paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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MOPLO24

A Novel Technique for Pulsed Operation of Magnetrons without Modulation of Cathode Voltage

controls, cathode, operation, injection

290

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

Modern pulsed superconducting accelerators of megawatt beams require efficient RF sources controllable in phase and power. For each Superconducting RF (SRF) cavity is desirable a separate RF source with power up to hundreds of kW with pulse duration in the millisecond range. The efficiency of the traditional RF sources (klystrons, IOTs, solid-state amplifiers) is lower than that of the magnetrons, while the cost of a unit of RF power is much higher. Therefore the magnetron-based RF sources would significantly reduce the capital and operation costs in comparison with the traditional RF sources. A recently developed an innovative technique makes possible the pulsed generation of magnetrons powered below the self-excitation threshold voltage. This technique does not require pulse modulators to form RF pulses. The magnetron operation in this regime is stable, low noise, controllable in phase and power, and provides higher efficiency than other types of RF power sources. It allows operation in pulsed modes with large duty factor. The developed technique and its experimental verification are considered and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO24

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paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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TUXBA4

Rapid Radio-Frequency Beam Energy Modulator for Proton Therapy

proton, simulation, GUI, klystron

298

X. Lu, G.B. Bowden, V.A. Dolgashev, Z. Li, E.A. Nanni, A.V. Sy, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This work is supported by US Department of Energy (DOE) Contract No. DE-AC02-76SF00515.
We present the design for a rapid proton energy modulator with radio-frequency (RF) accelerator cavities. The energy modulator is designed as a multi-cell one-meter long accelerator working at 2.856 GHz. We envision that each individual accelerator cavity is powered by a 400 kW low-voltage klystron to provide an accelerating / decelerating gradient of 30 MV/m. We have performed beam dynamics simulations showing that the modulator can provide ± 30MeV of beam energy change, with an energy spread of 3 MeV for a 7 mm long (full length) proton bunch. A prototype experiment of a single cell is in preparation at the Next Linear Collider Test Accelerator (NLCTA) at SLAC.

Slides TUXBA4 [3.275 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUXBA4

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paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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TUYBA4

Optimization of an SRF Gun Design for UEM Applications

SRF, gun, laser, electron

305

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

Funding: DOE contract DE-SC0018621
Benefiting from the rapid progress on RF photocathode gun 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, which may lead to breakthroughs in fundamental science and applied technologies *. Euclid is designing an SRF cavity as the UEM electron gun. As implementing a solenoid for emittance compensation in the gun is limited by the superconductivity performance and available space, the geometry of the first 0.3 cell of the cavity is optimized for transverse focusing and emittance reduction.
*: T. Chase, et al, "Ultrafast electron diffraction from non- equilibrium phonons in femtosecond laser heated Au films." Applied Physics Letters, 2016

Slides TUYBA4 [7.583 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUYBA4

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paper received ※ 30 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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TUZBA1

Commissioning of the Electron Accelerator LEReC for Bunched Beam Cooling

electron, operation, cathode, gun

330

D. Kayran, Z. Altinbas, D. Bruno, M.R. Costanzo, K.A. Drees, A.V. Fedotov, W. Fischer, M. Gaowei, D.M. Gassner, X. Gu, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, J. Kewisch, C.J. Liaw, C. Liu, J. Ma, K. Mernick, T.A. Miller, M.G. Minty, L.K. Nguyen, M.C. Paniccia, I. Pinayev, V. Ptitsyn, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, A. Sukhanov, P. Thieberger, J.E. Tuozzolo, E. Wang, G. Wang, W. Xu, A. Zaltsman, H. Zhao, Z. Zhao
BNL, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The brand-new state of the art electron accelerator, LEReC, was built and commissioned at BNL. LEReC accelerator includes a photocathode DC gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a SRF booster cavity, and a set of Normal Conducting RF cavities to provide sufficient flexibility to tune the beam in the longitudinal phase space. Electron beam quality suitable for cooling in the Relativistic Heavy Ion Collider (RHIC) was achieved [1], which lead to the first demonstration of bunched beam electron cooling of hadron beams [2]. This presentation will discuss commissioning results, achieved beam parameters and performance of the LEReC systems.
[1] D.Kayran et al., First results from Commissioning of LEReC, in Proc of IPAC2019
[2] A.Fedotov et al., First electron cooling of hadron beams using a bunched electron beam, presented at NAPAC2019

Slides TUZBA1 [18.343 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBA1

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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TUPLM13

Two-Energy Storage-Ring Electron Cooler for Relativistic Ion Beams

storage-ring, electron, emittance, damping

399

B. Dhital, J.R. Delayen, G.A. Krafft
ODU, Norfolk, Virginia, USA
J.R. Delayen, Y.S. Derbenev, D. Douglas, G.A. Krafft, F. Lin, V.S. Morozov, Y. Zhang
JLab, Newport News, Virginia, USA

An electron beam based cooling system for the ion beam is one of the commonly used approaches. The proposed two’energy storage-ring electron cooler consists of damping and cooling sections at markedly different energies connected by an energy recovering superconducting RF structure. The parameters in the cooling and damping sections are adjusted for optimum cooling of a stored ion beam and for optimum damping of the electron beam respectively. This paper briefly describes a two cavities model along with a third cavity model to accelerate and decelerate the electron beam in two energy storage ring. Based on our assumed value of equilibrium emittance shows that these models give a bunch length of the order of cm and energy spread of the order of 〖10〗^-5 in the cooling section which are required parameters for the better cooling. Numerical calculations along with elegant simulation are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM13

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paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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TUPLM18

Improving Energy Resolution and Compensating Chromatic Aberration With a TM010 Microwave Cavity

electron, gun, simulation, laser

411

C.J.R. Duncan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
P. Cueva, J.M. Maxson, D.A. Muller
Cornell University, Ithaca, New York, USA

Funding: National Science Foundation under Award OIA-1549132, the Center for Bright Beams
The intrinsic energy spread of electron sources limits the achievable resolution of electron microscopes in both spectroscopic and spatially resolved measurements. We propose that the TM010 mode of a single radio frequency (RF) cavity be used to dramatically reduce this energy spread in a pulsed beam. We show with analytic approximations, confirmed in simulations, that the non-linear time-energy correlations that develop in an electron gun can be undone by the RF cavity running near-crest. We derive an expression that gives the required RF field strength as a function of accelerating voltage. We explore multiple applications, including EELS and SEM. By pulsing a photocathode with commercially available, high repetition-rate lasers, our scheme could yield competitive energy spread reduction at higher currents when compared with monochromated continuous-wave sources for electron microscopes.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM18

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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TUPLM36

Temperature Measurements of the NSLS-II Vacuum Components

impedance, vacuum, experiment, detector

443

A. Blednykh, G. Bassi, C. Hetzel, B.N. Kosciuk, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, G.M. Wang
BNL, Upton, New York, USA

This paper is dedicated to the analysis of our recent experience from ramp-up of operating current at NSLS-II from 25 mA at the end of commissioning in 2014 to 475 mA achieved in studies today. To approach the design level of the ring intensity we had to solve major problems in overheating of the chamber components. Since the beginning of the NSLS-II commissioning, the temperature of the vacuum components has been monitored by the Resistance Temperature Detectors located predominantly outside of the vacuum chamber and attached to the chamber body. A couple of vacuum components were designed with the possibility for internal temperature measurements under the vacuum as diagnostic assemblies. Temperature map helps us to control overheating of the vacuum components around the ring especially during the current ramp-up. The average current of 475mA has been achieved with two main 500MHz RF cavities and w/o any harmonic cavities. In this paper we discuss the heating results for a 15ps bunch length (at low current) of the following vacuum components: Large Aperture BPM, Small Aperture BPM, Bellows, Flanges, Ceramics Chambers and Stripline Kickers.

Poster TUPLM36 [3.696 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM36

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paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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TUPLH03

Double-Bend Achromat Beamline for Injection Into a High-Power Superconducting Electron Linac

solenoid, electron, gun, dipole

494

C.H. Boulware, T.L. Grimm, R. Hipple
Niowave, Inc., Lansing, Michigan, USA
S.M. Lund
FRIB, East Lansing, Michigan, USA
V.S. Morozov
JLab, Newport News, Virginia, USA

To take advantage of the high duty cycle operation of superconducting electron linacs, commercial systems use thermionic cathode electron guns that fill every RF bucket with an electron bunch. In continuous operation, the exit energy is limited when compared to pulsed systems. Bunch length and energy spread at the exit of the gun are incompatible with low losses in the superconducting cavity. A solenoid double-bend achromatic beamline is in operation at Niowave which allows energy and bunch length filtering of the beam leaving the gun before injection into the superconducting cavity. This system uses two solenoids and two dipoles to produce a round beam, using the edge angles of the dipoles to balance the focusing effects in the two transverse planes. The design allows beam filtering on the symmetry plane where the dispersion is maximum. Additionally, the bend angle moves the electron gun off the high-energy beam axis, allowing multiple-pass operation of the superconducting booster. This contribution will discuss the beam optics design of the double-bend achromat along with the design of the magnets and beam chambers and the operational experience with the system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH03

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paper received ※ 28 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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TUPLH17

Design Study of Low-Level RF Control System for CW Superconducting Electron Linear Accelerator in KAERI

controls, SRF, LLRF, linac

512

S.H. Lee, J.Y. Lee
Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea
P. Buaphad, I.G. Jeong, Y.J. Joo, H.R. Lee
University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
M.-H. Chun, I.H. Yu
PAL, Pohang, Republic of Korea
Y. Kim
KAERI, Jeongeup-si, Republic of Korea

Korea Atomic Energy Research Institute (KAERI) has been operating a 20 MeV superconducting RF linear accelerator (SRF LINAC) to conduct research on atom/nuclear reaction using neutron Time-Of-Flight (nTOF). It can accelerate electron beams up to 20 MeV with 1 kW continuous wave (CW) operation mode. Unfortunately, this machine has been aged over 15 years that brings about considerably difficulty in normal operation due to the performance degradation of sub-systems. To improve the operation condition of 20 MeV SRF LINAC, we has been carrying out an upgrade project with replacement and repair of old sub-systems from 2018. This paper describes a design study of Low-Level RF (LLRF) feedback system to raise the stability and acceleration efficiency of the electric field generated in the superconducting RF cavity structure in 20 MeV SRF LINAC.

Poster TUPLH17 [0.644 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH17

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paper received ※ 30 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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TUPLO06

Weak-Strong Beam-Beam Simulation for eRHIC

proton, simulation, luminosity, electron

545

Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, C. Montag, V. Ptitsyn, F.J. Willeke
BNL, Upton, New York, USA
Y. Hao, D. Xu
FRIB, East Lansing, Michigan, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the eRHIC, to compensate the geometric luminosity loss due to the crossing angle, crab cavities are to be installed on both sides of the interaction point. When the proton bunch length is comparable to the wavelength of its crab cavities, protons will not be perfectly tilted in the x-z plane. In the article, we employ weak-strong beam-beam interaction model to calculate the proton beam size growth rates and luminosity degradation rate with various machine and time parameters. The goal of these studies is to optimize the the beam-beam related machine and beam parameters of eRHIC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO06

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paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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TUPLO07

Calculation of Action Diffusion With Crabbed Collision in eRHIC

proton, electron, simulation, luminosity

549

Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, C. Montag, V. Ptitsyn, F.J. Willeke
BNL, Upton, New York, USA
Y. Hao, D. Xu
FRIB, East Lansing, Michigan, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the eRHIC, to compensate the geometric luminosity loss due to the crossing angle, crab cavities are to be installed on both sides of the interaction point. When the proton bunch length is comparable to the wavelength of its crab cavities, protons will not be perfectly tilted in the x-z plane. In the article, we develop a simulation code to calculate the transverse action diffusion rate as function of the initial proton longitudinal action. The goal of this study is to identify the contributions from various protons to the overall emittance growth. Tune scan is also performed to locate optimum working points which yield less proton emittance growth.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO07

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paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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TUPLE01

Python Scripts for RF Commissioning at FRIB

EPICS, LLRF, controls, linac

563

H. Maniar, E. Daykin, D.G. Morris, A.S. Plastun, H.T. Ren, S. Zhao
FRIB, East Lansing, Michigan, USA

Abstract RF commissioning at FRIB involves QWR cavities (β=0.085 and β=0.041), HWR cavities (β=0.29 and β=0.53) and few room temperature devices. Each RF system has many process variables for LLRF and amplifier control located on different pages of CS-Studio. Efficient handling of all these PVs can be challenging for RF experts. Several scripts using Python have been developed to facilitate this process. User interface application has been developed using Qt Designer and PyQt package of Python, for ease of access of all scripts. These scripts are useful for mass ac-tions (for multiple systems) including turning on/ off LLRF controllers and amplifiers, resetting interlocks/ errors, chang-ing a PV value, etc. Python scripts are also used to quickly prototype the auto-start procedure for QWR cavities, which eventually is implemented on IOC driver. The application sends commands to IOC driver with device name, PV name and value to be changed. Future developments can be con-verting to state-notation language on IOC to add channel access security. This application intends to reduce time and efforts for RF commissioning at FRIB.

Poster TUPLE01 [0.429 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE01

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paper received ※ 27 August 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019

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TUPLE08

Commissioning Update on RF Station #5 of AWA

high-voltage, klystron, electron, MMI

580

W. Liu, M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C. Jing
Euclid Beamlabs LLC, Bolingbrook, USA

Funding: The US Department of Energy, Office of Science
The RF system of Argonne Wakefield Accelerator (AWA) facility has grown over the years from one RF power station into 4 RF power stations. The demand for RF power keeps growing as the capability of AWA continues to grow. Now the 5th RF station is needed to fulfill the RF power needs of AWA facility. Some details regarding the construction and commissioning of the 5th RF station of AWA facility are documented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE08

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paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEYBB5

A Crab-Crossing Scheme for Laser-Ion Beam Applications

laser, experiment, linac, injection

639

A.V. Aleksandrov, S.M. Cousineau, T.V. Gorlov, Y. Liu, A. Rakhman, A.P. Shishlo
ORNL, Oak Ridge, Tennessee, USA

Lasers have recently been used in many applications to H⁻ beams, including laser charge exchange, laser wire scanners, and laser temporal pulse patterning. The H⁻ beam in these applications has wide variation ofμpulse length width dependence on focusing of the RF cavities, energy spread of the beam, and space charge forces. Achieving the required laser pulse length for complete overlap with the H⁻ can be challenging in some scenarios when available laser power constrained. The scheme proposed here utilizes a crab-crossing concept between the laser and the ion beam to achieve overlap of a short laser pulse with an arbitrarily long H⁻ beam pulse. An experiment to test the hypothesis in the context of H⁻ charge exchange is described.

Slides WEYBB5 [5.201 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBB5

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paper received ※ 30 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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WEZBA2

Experience and Lessons in FRIB Superconducting Quarter-Wave Resonator Commissioning

cryomodule, MMI, linac, controls

646

S.H. Kim, H. Ao, F. Casagrande, W. Chang, C. Compton, A. Facco, V. Ganni, E. Gutierrez, W. Hartung, N. Hasan, P. Knudsen, T.L. Larter, H. Maniar, S.J. Miller, D.G. Morris, P.N. Ostroumov, A.S. Plastun, J.T. Popielarski, L. Popielarski, H.T. Ren, K. Saito, M. Thrush, D.R. Victory, J. Wei, M. Xu, T. Xu, Y. Yamazaki, C. Zhang, S. Zhao
FRIB, East Lansing, Michigan, USA

The superconducting (SC) linear accelerator (linac) for the Facility for Rare Isotope Beams (FRIB) has one quarter-wave resonator (QWR) segment and two half-wave resonator (HWR) segments. The first linac segment (LS1) contains twelve β = 0.041 and ninety-two β = 0.085 QWRs operating at 80.5 MHz, and thirty-nine SC solenoids. Superconducting radiofrequency (SRF) commissioning and beam commissioning of LS1 was completed in April 2019. The design accelerating gradients (5.1 MV/m for β = 0.041 and 5.6 MV/m for β = 0.085) were achieved in all cavities with no multipacting or field emission issues. The cavity field met the design goals: peak-to-peak stability of ±1% in amplitude and ±1° in phase. We achieved 20.3 MeV/u ion beams of Ar, Kr, Ne, and Xe with LS1. In this paper, we will discuss lessons learned from the SRF commissioning of the cryomodules and methods developed for efficient testing, conditioning, and commissioning of more than 100 SC cavities, each with its own independent RF system.

Slides WEZBA2 [2.841 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEZBA2

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paper received ※ 03 September 2019 paper accepted ※ 05 December 2019 issue date ※ 08 October 2019

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WEZBA6

A 100 kW 1.3 GHz Magnetron System with Amplitude and Phase Control

controls, klystron, power-supply, experiment

656

M.E. Read, T. Bui, G. Collins, R.L. Ives
CCR, San Mateo, California, USA
B.E. Chase, J. Reid
Fermilab, Batavia, Illinois, USA
J.R. Conant, C.M. Walker
CPI, Beverley, Massachusetts, USA

Funding: United States Department of Energy Grant No. DE-SC0011229.
Calabazas Creek Research, Inc., Fermilab, and Communications & Power Industries, LLC, developed a 100 kW peak, 10 kW average, 1.3 GHz, magnetron-based, RF system for driving accelerators. Efficiency varied between 81% and 87%. Phase locking uses a novel approach that provides fast amplitude and phase control when coupled into a superconducting accelerator cavity [1]. The system was successfully tested at Fermilab and produced 100 kW in 1.5 ms pulses at a repetition rate of 2 pps. A locking bandwidth of 0.9 MHz was achieved with a drive signal of 269 W injected through a 4 port circulator. The phase locking signal was 25 dB below the magnetron output power. The spectrum of the phase locked magnetron was suitable for driving accelerator cavities. Phase modulation was demonstrated to 50 kHz (the limit of the available driver source). The average power was limited by available conditioning time. Scaling indicates 42 kW of average power should be achievable. Estimated cost is less than $1/Watt of delivered RF power, exclusive of power supplies or modulators. System design and performance measurements will be presented.
[1] B. Chase, R. Pasquinelli, E. Cullerton, P. Varghese, "Precision Vector Control of a Superconducting RF Cavity driven by an Injection Locked Magnetron," Jou. of Instrumentation, Vol. 10 March 2015.

Slides WEZBA6 [2.515 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEZBA6

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paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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WEPLM01

Studies in Applying Machine Learning to Resonance Control in Superconducting RF Cavities

controls, LLRF, simulation, resonance

659

J.A. Diaz Cruz, S. Biedron, M. Martinez-Ramon, R. Pirayesh, S.I. Sosa Guitron
University of New Mexico, Albuquerque, USA
J.A. Diaz Cruz
SLAC, Menlo Park, California, USA

Traditional PID, active resonance and feed-forward controllers are dominant strategies for cavity resonance control, but performance may be limited for systems with tight detuning requirements, as low as 10 Hz peak detuning (few nanometers change in cavity length), that are affected by microphonics and Lorentz Force Detuning. Microphonic sources depend on cavity and cryomodule mechanical couplings with their environment and come from several systems: cryoplant, RF sources, tuners, etc. A promising avenue to overcome the limitations of traditional resonance control techniques is machine learning due to recent theoretical and practical advances in these fields, and in particular Neural Networks (NN), which are known for their high performance in complex and nonlinear systems with large number of parameters and have been applied successfully in other areas of science and technology. In this paper we introduce NN to resonance control and compare initial performance results with traditional control techniques. An LCLS-II superconducting cavity type system is simulated in an FPGA, using the Cryomodule-on-Chip model developed by LBNL, and is used to evaluate machine learning algorithms.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM01

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paper received ※ 05 September 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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WEPLM03

The LLRF Control Design and Validation at FRIB

LLRF, controls, MMI, cryomodule

667

S. Zhao, W. Chang, S.H. Kim, H. Maniar, D.G. Morris, P.N. Ostroumov, J.T. Popielarski, H.T. Ren, N.R. Usher
FRIB, East Lansing, Michigan, USA
N.R. Usher
Ionetix, Lansing, Michigan, USA

Funding: This work is supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
One of the challenges in designing the low level radio frequency (LLRF) controllers for the Facility for Rare Isotope Beams (FRIB) is the various types of cavities, which include 5 different frequencies ranging from 40.25 MHz up to 322 MHz, and 4 different types of tuners. In this paper, the design strategy taken to achieve flexibility and low cost and the choices made to accommodate the varieties will be discussed. The approach also allowed easy adaptation to major design changes such as replac-ing two cryo-modules with two newly designed room temperature bunchers and the addition of high-voltage bias to suppress multi-pacting in half wave resonators (HWRs). With the successful completion of the third accelerator readiness review (ARR03) commissioning in early 2019, most of the design has been validated in the real accelerator system, leaving only HWRs which are constantly undergoing tests in cryo-module bunker. The integrated spark detector design for HWRs will also be tested in the near future.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM03

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paper received ※ 31 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLM04

Precision Cavity Higher-Order Mode Tuning Scheme for Stabilizing the Stored Beam in the Advanced Photon Source Upgrade

HOM, damping, impedance, resonance

670

L. Emery, P.S. Kallakuri, U. Wienands
ANL, Lemont, Illinois, USA
D. Teytelman
Dimtel, Redwood City, California, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
The Advanced Photon Source Upgrade will suffer longitudinal multi-bunch instability because of the presence of several monopole higher-order mode (HOMs) of the 12 352-MHz rf cavities. Even with a feedback system, it would be good to mitigate any driving terms with conventional means such as tuning HOM frequencies with temperature. However the latter is problematic because there will be 90 or so HOMs that are potentially harmful. A scheme is developed, utilizing the measured spectrum of HOMs, to find the best temperature setting for each cavity. We present measurements of 30 or so HOMs, and a thermal model of HOM frequencies using cavity wall power and cooling water temperature as inputs to maintain the optimum tuning condition with sufficient accuracy. The newly acquired Dimtel iGp12 processor box is central to the HOM frequency measurements.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM04

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paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLM05

Continuous Monitoring of Spectral Features of Electron Beam Orbit Motion at NSLS-II

operation, undulator, controls, feedback

673

B. Podobedov, A.A. Derbenev, K. Ha, T.V. Shaftan
BNL, Upton, New York, USA

NSLS-II ring is equipped with state-of-the art beam position monitors (BPMs) which are indispensable in all aspects of machine studies and operations. Among other data, they can provide, on demand, up to 10 seconds of fast-acquisition (FA) data, sampled at ~10 kHz. Analysis of these data in time, frequency and spatial domains provides valuable insights into orbit stability, locations of residual noise sources, performance of feedback systems, etc. In addition, changes in FA signal spectral features are often the earliest indicators of potential equipment problems. This is why we recently implemented an Input / Output Controller (IOC) software that runs during regular user operation, and, once a minute, acquires 10 second buffers of FA data from 180 BPMs around the ring. These buffers are processed to determine the amplitudes and frequencies of the strongest spectral peaks as well as some other measures of fast beam orbit noise. Processed results can be monitored in real time and are also archived for offline analysis and troubleshooting. In this paper we discuss the implementation of this system and the insights we gained from it over about two years of operations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM05

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paper received ※ 31 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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WEPLM07

Low Level RF Test System for the Compact X-Ray Light Source at Arizona State University

controls, klystron, electron, LLRF

680

H.S. Marks, W.S. Graves, M.R. Holl, L.E. Malin
Arizona State University, Tempe, USA

A compact femtosecond X-Ray Light Source (CXLS) for time-resolved scientific and medical studies is being constructed at Arizona State University. The CXLS X-rays will be generated by the inverse Compton scattering (ICS) collision of 200 mJ, 1 ps, IR laser pulses with 300 fs electron bunches with energy up to 35 MeV. The electron beam is accelerated via a photoinjector and three standing-wave 20-cell linac sections driven by two klystrons delivering up to 6 MW 1 µs pulses at 9.3 GHz with a pulse repetition rate of 1 kHz. For initial testing of the CXLS klystrons a hybrid digital-analog low-level RF (LLRF) driver has been developed which allows for inter-pulse phase and amplitude corrections based on feedback from waveguide-couplers. The micro-controller based system can also be programmed to adjust continuously in advance of predictable drifts.

Poster WEPLM07 [2.226 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM07

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paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLM13

Multipactor Electron Cloud Analysis in a 17 GHz Standing Wave Accelerator Cavity

electron, multipactoring, simulation, experiment

687

H. Xu, M.A. Shapiro, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA

Funding: US Department of Energy High Energy Physics
Theoretical predictions of single-surface one-point multipactor modes have been confirmed in experiments with a 17 GHz standing wave single cell disk-loaded waveguide accelerator structure operated in gradient range of 45-90 MV/m. A dc-biased probe placed outside of a slit in the side wall of the structure was used to measure the internal dark current electron energy distribution. The results indicated that the electrons had kinetic energy up to about 50 eV, in agreement with our CST particle-in-cell (PIC) simulations. Further theoretical calculations were performed to calculate the frequency detuning introduced by the multipactor electron cloud on the cell side wall for different electron cloud thicknesses and densities. We found that the detuning (Δf/f) due to the electron cloud was small, about two orders of magnitude smaller than the reciprocal of the cavity loaded quality factor. This detuning is sufficiently small that it does not cause significant power reflection. Similar calculations were carried out for high gradient operation of accelerator structures at frequencies of 2.856 GHz and 110.0 GHz, showing similar small detuning by multipactor discharges.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM13

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paper received ※ 19 August 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019

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WEPLM21

High-Quality Resonators for Quantum Information Systems

SRF, controls, cryogenics, photon

690

S.V. Kuzikov
IAP/RAS, Nizhny Novgorod, Russia
S.P. Antipov, P.V. Avrakhov, E. Gomez
Euclid TechLabs, LLC, Solon, Ohio, USA

We analyze ultra-high-quality factor resonators for quantum computer architectures. As qubit operation requires external DC fields, we started our study with a conventional closed copper cavity which naturally allows external magnetic field. In order to increase quality factor and to keep DC magnetic field control at a level less than critical field, an open SRF resonator promises much higher quality. The next step resonator is a photonic band gap (PBG) resonator. This resonator allows easy external either magnetic or electric field control. It consists of a periodic 3D set of sapphire rods assembled between two superconducting plates. The PBG resonator exploits unique properties of the crystalline sapphire. Tangent delta for sapphire in X-band is reported at 10^-9 ’ 10-10 at 4 K. That is why, the Q-factor of the sapphire PBG resonator can be expected as high as 10 billions at mK temperatures which provides long relaxation times (dephasing etc.). The established PBG design implies obtaining a large Purcell factor, i.e. large ratio of quality to mode volume which is important parameter to establish strong interaction of a qubit with the cavity mode rather than RF noise.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM21

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paper received ※ 27 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019

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WEPLM47

Analysis of High Field Q-Slope (HFQS) Causes and Development of New Chemical Polishing Acid

SRF, experiment, superconductivity, niobium

699

D. Luo, E.S. Metzgar, L. Popielarski, K. Saito, S.M. Shanab, G.V. Simpson
FRIB, East Lansing, Michigan, USA
T. Nakajima, I. Nasu, J. Taguchi
Nomura Plating Co, Ltd., Osaka, Japan

Funding: U.S. National Science Foundation under Grant PHY-1565546.
In our previous studies of High Field Q-slope (HFQS) we have concluded that nitrogen contamination from the nitric acid is the main cause of the degradation of the Q in buffered chemical polished cavities. Our conclusion is made based on previously unresolved phenomena which are found from huge amount of published cavity test data, include fine grain, large grain and single crystal cavities treated with EP and BCP. According to this analysis, we have started developing new nitrogen-free chemical polishing acid. Hydrogen peroxide with HF mixture was reported able to react with Nb, and there’s no extra element contamination in it, so we replace the conventional BCP with this mixture to start our study. In this paper, some Nb coupon sample results with new acid will be reported. We complete the first step of developing the new acid and we got the Nb finish roughness no worse than conventional BCP.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM47

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paper received ※ 13 September 2019 paper accepted ※ 04 December 2019 issue date ※ 08 October 2019

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WEPLM49

New RF System for First Drift Tube Linac Cavity at LANSCE

controls, DTL, power-supply, LLRF

703

J.T.M. Lyles, R.E. Bratton, G. Roybal, M. Sanchez Barrueta, G.M. Sandoval, Jr., D.J. Vigil, J.E. Zane
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the United States Department of Energy, NNSA, under contract 89233218CNA000001
From 2014-2016, the three highest power 201 MHz power amplifier (PA) systems were replaced at the Los Alamos Neutron Science Center 100 MeV DTL. The initial DTL cavity provides 4.25 MeV of energy gain and has been powered by a Photonis (RCA) 4616 tetrode driving a 7835 triode PA for over 30 years. It consumes 110 kW of electrical power for tube filaments, power supplies and anode modulator. The modulator is not required with modern tetrode amplifiers. In 2020 we plan to replace this obsolete 6 tube transmitter with a design using a single tetrode PA stage without anode modulator, and a 20 kW solid-state driver stage. This transmitter needs to produce no more than 400 kW, and will use a coaxial circulator. Cooling water demand will reduce from 260 to 70 gal/min of pure water. High voltage DC power comes from the same power supply/capacitor bank that supplied the old system. The old low-level RF controls will be replaced with digital LLRF with learning capability for feedforward control, I/Q signal processing, and PI feedback. All high power components have been assembled in a complete mockup system for extended testing. Installation of the new RF system begins in January of 2020.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM49

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paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLM50

Beam Driven Bimodal Cavity Structure for High Gradient Acceleration

simulation, bunching, acceleration, site

707

X. Chang, Y. Jiang, S.V. Shchelkunov
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield
Omega-P, Inc., New Haven, Connecticut, USA

Funding: Supported by USA National Science Foundation, Award #1632588
Abstract: Research aiming to increase the RF breakdown threshold in electron/positron accelerators is being conducted at the Yale University Beam Physics Laboratory. Our two-beam accelerator approach employs a beam driven bimodal cavity structure. This cavity includes (i) two modes excited by the drive beam, with the higher mode frequency three times that of the fundamental TM010 mode; (ii) a low-current accelerated beam and high-current drive beam traversing the same cavity structure. This approach has the potential advantages of (a) operating at higher acceleration gradient with lower breakdown and pulsed heating rates than that of a single-mode cavity structure at the same acceleration gradient, due to the spatiotemporal field distribution properties in the bimodal cavities; and (b) obtaining high accelerating gradient with a low energy drive beam. Recent progress in simulations and work towards an experimental test stand is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM50

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paper received ※ 23 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLM51

Ka-Band High Power Harmonic Amplifier for Bunch Phase-Space Linearization

klystron, linac, bunching, simulation

710

X. Chang, Y. Jiang, S.V. Shchelkunov
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield
Omega-P, Inc., New Haven, Connecticut, USA

Funding: Supported by USA National Science Foundation, Award #1632588
Abstract: A future European light source CompactLight is being proposed to extend FEL operation further into the x-ray region than other light sources by using a linac operating at X-band (12 GHz) with a short Ka-band (36 GHz) section for linearizing bunch phase space. The Ka-band system requires a high-power RF amplifier, synchronized with the main X-band source. We report here on design of a third-harmonic klystron amplifier for this application. Our design employs a four-cavity system with a multi-cell extended interaction output cavity. Initial simulation results indicate that more than 10 MW of 36-GHz power can be obtained with an efficiency exceeding 20%, and with 12-GHz drive power of 30 W. A preliminary design for a proof-of-principal experimental test of this concept is described

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM51

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paper received ※ 23 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLM52

Recent Developments of Nb₃Sn at Jefferson Lab for SRF Accelerator Application

SRF, accelerating-gradient, cryomodule, factory

713

U. Pudasaini, M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
The desire to reduce the construction and operating costs of future SRF accelerators motivates the search for alternative, higher-performing materials. Nb₃Sn (Tc ~ 18.3 K and Hsh ~ 425 mT) is the front runner. However, tests of early Nb₃Sn-coated cavities encountered strong Q-slopes limiting the performance. Learnings from studies of coated materials related to cavity performance prompted significant changes to the coating process. It is now possible to routinely produce slope-free single-cell cavities having Q₀ ≥ 2×10¹⁰ at 4 K and > 4×10¹⁰ at 2 K up to the accelerating gradient in excess of 15 MV/m at its best. Obtaining similar results in five-cell cavities is a current goal to test them under an accelerator environment. This contribution discusses recent developments at Jefferson Lab.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM52

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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WEPLM53

50 kW CW Multi-Beam Klystron

klystron, electron, gun, cathode

717

S.V. Shchelkunov
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield, V.E. Teryaev
Omega-P, Inc., New Haven, Connecticut, USA

Funding: Funded by the US Department of Energy; grant DE-SC-0018471.
Main components, which are the electron gun, cavity-chain, magnetic system, and partially- grounded depressed four-stage collector, of a novel klystron were conceptually designed. This klystron is to deliver 50 kW CW at 952.6 MHz and to serve as a microwave power source for ion acceleration at the Electron Ion Collider (EIC) being developed at Thomas Jefferson National Accelerator Facility. The efficiency is 80%, a number to which the power consumption by the solenoid and filament are already factored in. The tube is a combination of proven technologies put together: it uses multiple beams to have its perveance low to boost beam-power to RF-power efficiency. It uses a partially grounded depressed collector to recover energy thereby increasing the overall efficiency. A low operating voltage of 14kV makes the tube more user-friendly avoiding need for costly modulators and oil insulation. A sectioned solenoid is used to insure superb beam-matching to all components downstream of the electron gun, increasing the tube performances. Details of the components designs will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM53

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paper received ※ 14 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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WEPLM57

200 kW, 350 - 700 MHz RF Sources using Multiple Beam Triodes

cathode, electron, vacuum, klystron

724

R.L. Ives, T. Bui, D. Marsden, M.E. Read
CCR, San Mateo, California, USA
B. Henderson, L. Higgins, R. Ho
CPI, Palo Alto, California, USA

Funding: U.S. Department of Energy Grant No. DE-SC0018838
Calabazas Creek Research, Inc. and Communications & Power Industries, LLC are developing multiple beam triodes to produce more than 200 kW of RF power at extremely low cost and efficiencies exceeding 85%. RF power is achieved by installing the triode inside coaxial input and output cavities at the desired frequency. The multiple beam triodes developed in this program will provide RF power from 350 MHz to 700 MHz using the appropriate, tuned, resonant cavities. This program is using eight grid-cathode assemblies to achieve 200 kW with a target efficiency exceeding 80%. A 350 MHz RF source would be approximately 36 inches high, 18 inches in diameter and weigh approximately 150 pounds. This is significantly smaller than any other RF source at this frequency and power level. The gain is limited to approximately 14 dB, so a single beam triode-based source will serve as a driver. The combined cost and efficiency will still exceed the performance of other comparable RF sources, including solid state sources. Design issues, include grid cooling, uniformity of RF electric fields on the grids, and efficiency, will be discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM57

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paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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WEPLM60

Fast Sn-Ion Transport on Nb Surface for Generating NbxSn Thin Films and XPS Depth Profiling

interface, electron, radio-frequency, SRF

727

Z. Sun, M. Liepe, J.T. Maniscalco, T.E. Oseroff, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
X. Deng
University of Virginia, Charlottesville, Virginia, USA
D. Zhang
Cornell University, Ithaca, New York, USA

Funding: U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams
In this work, we propose and demonstrate a fast and facile approach for NbxSn thin film deposition through the ion exchange reaction. By simply dipping a tin precursor on the Nb substrate surface, a ~600 nm thin film is generated due to the electronegativity differ-ence between Sn and Nb. Through X-ray photoelec-tron spectroscopy (XPS) depth profiling, the composi-tional information as a function of film thickness was obtained. Results showed a Sn layer on the film sur-face, Sn-rich and Nb-rich NbxSn layers as the majority of the film, and a ~60 nm Nb₃Sn layer at the film/substrate interface. Quantitative analysis con-firmed stoichiometric Nb/Sn ratio for the Nb₃Sn layer. This deposition method is demonstrated to be an alter-native choice for Nb₃Sn film growth.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM60

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paper received ※ 05 September 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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WEPLM62

First Cold Test Results of a Medium-Beta 644 MHz Superconducting 5-Cell Elliptical Cavity for the FRIB Energy Upgrade

target, pick-up, linac, accelerating-gradient

731

K.E. McGee, B.W. Barker, K. Elliott, A. Ganshyn, W. Hartung, S.H. Kim, P.N. Ostroumov, J.T. Popielarski, A. Taylor, C. Zhang
FRIB, East Lansing, Michigan, USA
M.P. Kelly, T. Reid
ANL, Lemont, Illinois, USA

Funding: Work supported by Michigan State University.
The superconducting linac for the Facility for Rare Isotope Beams (FRIB) will accelerate ions to 200 MeV per nucleon, with the possibility of a future energy upgrade to 400 MeV per nucleon via additional cavities. A 5-cell superconducting β = 0.65 elliptical cavity was designed for this purpose. Two unjacketed 5-cell niobium cavities were fabricated; the first of these was Dewar tested in February 2019. The surface preparation was bulk electropolishing (EP, 150 µm), hydrogen degassing (600°C, 10 hours), light EP (20 µm), clean-room high-pressure water rinsing, and in-situ baking (120°C, 48 hours). We achieved Q₀ = 2·10¹⁰, equivalent to Rs = 10 nΩ, at the design gradient of 17.5 MV/m. The cavity was tested in a newly refurbished FRIB test Dewar, equipped with a variable input coupler.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM62

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paper received ※ 02 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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WEPLM63

Development of a Secondary Sn Source for Nb₃Sn Coating of Half-Wave Coaxial Resonator

niobium, SRF, MMI, superconductivity

735

J.K. Tiskumara, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
G.V. Eremeev
JLab, Newport News, Virginia, USA
U. Pudasaini
The College of William and Mary, Williamsburg, Virginia, USA

Superconducting thin films have the potential of reducing the cost of particle accelerators. Among the potential materials, Nb₃Sn has a higher critical temperature and higher critical field compared to niobium. Sn vapor diffusion method is the preferred technique to coat niobium cavities. Although there are several thin-film-coated basic cavity models that are tested at their specific frequencies, the Half-wave resonator could provide us data across frequencies of interest for particle accelerators. With its advanced geometry, increased area, increased number of ports and hard to reach areas, the half-wave resonator needs a different coating approach, in particular, a development of a secondary Sn source. We are commissioning a secondary Sn source in the coating system and expand the current coating system at JLab to coat complex cavity models.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM63

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paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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WEPLM64

High Dynamic Voltage Range Studies of Piezoelectric Multilayer Actuators at Low Temperatures

linac, operation, SRF, vacuum

739

C. Contreras-Martinez
FRIB, East Lansing, Michigan, USA
Y.M. Pischalnikov, J.C. Yun
Fermilab, Batavia, Illinois, USA

Piezo actuators are used for resonance control in superconducting linacs. In high accelerating gradients linacs, such as those operated in a pulsed mode, the piezos require a large operating voltage. This is due to the Lorentz forced detuning which causes a large frequency shift and is compensated with an active piezo-tuning system. In this high dynamic voltage range the piezo is expected to warm up drastically due to it being in an insulated vacuum. This study characterizes the dielectric properties (capacitance, dielectric losses), the piezo stroke (from geophone), and thermal properties such as heating. Results obtained in the temperature range of 20K to 300K will be presented and discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM64

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paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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WEPLM66

Microphonics Studies at STC in Fermilab

resonance, ion-source, cryomodule, controls

743

C. Contreras-Martinez
FRIB, East Lansing, Michigan, USA
Y.M. Pischalnikov, W. Schappert, A.I. Sukhanov, J.C. Yun
Fermilab, Batavia, Illinois, USA

The spoke test cryostat is used to qualify the 325 MHz single spoke resonators at Fermilab (FNAL). During these tests a large detuning on the cavity was observed. The data acquisition for continuous captures were based on measurements from the piezoelectric actuators. A com-parison of the cavity vibrations measured with RF signal from the cavity and piezoelectric actuator signals are shown. The effects of microphonics on the cavity are discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM66

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paper received ※ 28 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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WEPLM70

FRIB Tuner Performance and Improvement

linac, cryomodule, controls, MMI

755

J.T. Popielarski, W. Chang, C. Compton, W. Hartung, S.H. Kim, E.S. Metzgar, S.J. Miller, K. Saito, J.F. Schwartz, T. Xu
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Facility for Rare Isotope Beams (FRIB) is under construction at Michigan State University (MSU). The FRIB superconducting driver linac will accelerate ion beams to 200 MeV per nucleon. The driver linac requires 10⁴ quarter-wave resonators (QWRs, β = 0.041 and 0.085) and 220 half-wave resonators (HWRs, β = 0.29 and 0.54). The cryomodules for β = 0.041, 0.085, and 0.29 have been completed and certified; 32 out of 49 cryomodules are certified via bunker test (as of March 2019). FRIB QWR cavities have a demountable niobium tuning plate which uses a warm external stepper motor and the FRIB HWR cavities use pneumatic actuated bellows. Progress on the preparation and performance of the tuners is presented in this paper along with improvements made to ensure meeting frequency specification.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM70

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paper received ※ 26 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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WEPLM71

Thermal Performance of FRIB Cryomodules

cryomodule, cryogenics, solenoid, operation

759

M. Xu, W. Chang, C. Compton, A. Ganshyn, S.H. Kim, S.J. Miller, J.T. Popielarski, K. Saito, T. Xu
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 and the National Science Foundation under Cooperative Agreement PHY-1102511.
Now SRF cavity development is advancing high-Q/high gradient by nitrogen doping, infusion, or the new low temperature bake recipe. Once cavity dynamic loss is reduced, the static heat load of the cryomodule will be of concern from the cryogenic plant capability point of view. FRIB gives us a good chance to statistically compare the cryogenic plant design and the measured results, along with a thought for future updated cryomodule design using a low/medium beta cryomodule. FRIB cryomodules have two cooling lines: 4.5 K for solenoids and 2K for cavities. The boil-off liquid helium method was used to measure the cryomodule’s heat load. So far, FRIB has completed certification testing (bunker tests) on 39 of 49 cryomodules (80%). This paper reports the static heat load measurement results, which are important for future FRIB upgrades to estimate remaining cryogenic capability. The cryomodule’s evolution related to heat load is introduced too.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM71

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paper received ※ 05 September 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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WEPLM72

Design of a High-Gradient S-Band Annular Coupled Structure

coupling, linac, Windows, operation

762

B. Mustapha, A. Abogoda, A. Barcikowski, R.L. Fischer, A. Nassiri
ANL, Lemont, Illinois, USA

Funding: This work was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 through ANL’s LDRD program.
At Argonne, we have recently developed a conceptual design for a compact linear accelerator for ion beam therapy named ACCIL [1]. A linac-based ion-beam therapy facility offers many advantages over existing synchrotron based facilities. In addition to the reduced footprint, ACCIL offers more flexibility in beam tuning, including pulse-per-pulse energy and intensity modulation and fast switching between ion species. Essential to the compactness of the ACCIL linac are high-gradient structures for low to intermediate velocity ions, capable of accelerating fields of ~ 50 MV/m. For this purpose, we have designed an S-band annular-coupled structure (ACS). An ACS has the desired qualities of high electric field limit, high shunt-impedance, large area for magnetic coupling and good cooling capacity, making it a very promising candidate for high-gradient operations. We here present the optimized RF design for a β ~ 0.4 ACS.
* P. Ostroumov, et al., "Compact Carbon Ion Linac", Proceedings of NAPAC2016, Oct 10-14 2016, Chicago, IL

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM72

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paper received ※ 04 October 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019

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WEPLM73

Bunker Testing of FRIB Cryomodules

cryomodule, solenoid, SRF, dipole

765

W. Chang, S. Caton, A. Ganshyn, W. Hartung, S.H. Kim, B. Laumer, H. Maniar, J.T. Popielarski, K. Saito, M. Xu, T. Xu, C. Zhang, S. Zhao
FRIB, East Lansing, Michigan, USA

The FRIB superconducting driver Linac requires 10⁴ quarter-wave resonators (QWRs, β = 0.041, 0.085), 220 half-wave resonators (HWRs, β = 0.29, 0.53), and 74 superconducting solenoid packages. Resonators and solenoids are assembled into cryomodules; 4 accelerating and 2 matching cryomodule types are required. Each cryomodule undergoes cryogenic and RF testing in a bunker prior to installation in the tunnel. The cryomodule test verifies operation of the cavities, couplers, tuners, solenoid packages, magnetic shield, and thermal shield at 4.3 K and 2 K. All of the required cryomodules for β = 0.041, 0.085, and 0.29 have been tested and certified. As of May 2019, five of the β = 0.53 cryomodules have been certified; the remaining modules are being assembled or are in the queue for testing. Cryomodule test results will be presented, including cavity performance (accelerating gradient, field emission X-rays, multipacting conditioning); solenoid package operation (current, current-lead cooling flow rate); and cryomodule heat load (static and dynamic).

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM73

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paper received ※ 06 September 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019

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WEPLS02

Simulation of a Klystron Input Cavity using a Steady-State Full-Wave Solver

simulation, experiment, klystron, electron

768

A.R. Gold, S.G. Tantawi
SLAC, Menlo Park, California, USA

The simulation of vacuum electronic radio-frequency (RF) power sources is generally done through semi-analytical modeling approaches. These techniques are computationally efficient as they make assumptions on the source topology, such as the requirement that the electron beam travel longitudinally and interact with cylindrical modes. To simulate more general interactions, transient particle-in-cell (PIC) codes are currently required. We present here simulation results of a 5045 klystron using a newly developed steady state code which does not make assumptions on the beam configuration or geometry of the structure and resonant modes. As we solve directly for the steady-state system dynamics, this approach is computationally efficient yet, as demonstrated through comparison with experimental results, provides similar accuracy.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS02

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paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLS05

Simulation Analysis of the LCLS-II Injector using ACE3P and IMPACT

simulation, emittance, booster, lattice

779

D.A. Bizzozero, J. Qiang
LBNL, Berkeley, California, USA
L. Ge, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA

Funding: This work is supported by the Director of the Office of Science of the US Department of Energy under contracts DEAC02-05CH11231 and DE-AC02-76-SF00515.
The LCLS-II beam injector system consists of a 186 MHz normal-conducting RF gun, a two-cell 1.3 GHz normal-conducting buncher cavity, two transverse focusing solenoids, and eight 1.3 GHz 9-cell Tesla-like super-conducting booster cavities. With a coordinated effort between LBNL and SLAC, we have developed a simulation workflow combining the electromagnetic field solvers from ACE3P with the beam dynamics modeling code IMPACT. This workflow will be used to improve performance and minimize beam emittance for given accelerator structures through iterative optimization. In our current study, we use this workflow to compare beam quality parameters between using 2D axisymmetric field profiles and fully 3D non-axisymmetric fields caused by geometrical asymmetries (e.g. RF coupler ports).

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS05

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paper received ※ 20 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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WEPLS12

A Semi-Analytical Approach to Six-Dimensional Path-Dependent Transport Matrices With Application to High-Brightness Charged-Particle Beam Transport

solenoid, simulation, emittance, electron

792

C.-Y. Tsai
HUST, Wuhan, People’s Republic of China
K. Fan
Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People’s Republic of China

Funding: This work was supported by the Fundamental Research Funds for the Central Universities under Project No. 5003131049.
Efficient and accurate estimate of high-brightness electron beam dynamics is an important step to the overall performance evaluation in modern particle accelerators. Utilizing the moment description to study multi-particle beam dynamics, it is necessary to develop a path-dependent transport matrix, together with application of the drift-kick algorithm*. In this paper we will construct semi-analytical models for three typical beam transport elements, solenoid with fringe fields, transverse deflecting cavity, and a beam slit. To construct the semi-analytical models for these elements, we begin by formulating the simplified single-particle equations of motion, and apply typical numerical techniques to solve the corresponding six-by-six transport matrix as a function of the path coordinate. The developed semi-analytical models are demonstrated with three practical examples, where our numerical results are discussed, compared with and validated by particle tracking simulations. These path-dependent transport matrix models can be incorporated to the analysis based on beam matrix method for the application to high-brightness charged-particle beam transport.
* C.-Y. Tsai et al., Nuclear Inst. And Methods in Physics Research, A 937 (2019) 1-20

Poster WEPLS12 [3.099 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS12

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paper received ※ 20 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLH06

Commissioning Status of the FRIB Front End

rfq, MMI, linac, ECR

813

H.T. Ren, J. Brandon, N.K. Bultman, K.D. Davidson, E. Daykin, T. Elkin, B. Galecka, P.E. Gibson, L. Hodges, K. Holland, D.D. Jager, M.G. Konrad, B.R. Kortum, S.M. Lidia, G. Machicoane, I.M. Malloch, H. Maniar, T. Maruta, G. Morgan, D.G. Morris, P. Morrison, A.C. Morton, P.N. Ostroumov, A.S. Plastun, E. Pozdeyev, X. Rao, T. Russo, J.W. Stetson, R. Walker, J. Wei, Y. Yamazaki, T. Yoshimoto, Q. Zhao, S. Zhao
FRIB, East Lansing, Michigan, USA
S. Renteria
NSCL, East Lansing, Michigan, USA

Funding: This work is supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
The FRIB Front End was successfully commissioned in 2017 with commissioning goals achieved and Key Per-formance Parameters (KPP) demonstrated for both 40Ar⁹⁺ and 86Kr¹⁷⁺ beams. Two more ion species, 20Ne⁶⁺ and 129Xe²⁶⁺, have been commissioned on the Front End and delivered to the superconducting linac during the beam commissioning of Linac Segment 1 (LS1) in March 2019. In August 2019, Radio Frequency Quadrupole (RFQ) conditioning reached the full design power of 100 kW continuous wave (CW) that is required to accelerate Ura-nium beams. Start-up/shutdown procedures and opera-tional screens were developed for the Front End subsys-tems for trained operators, and auto-start and RF fast re-covery functions have been implemented for the Front End RFQ and bunchers. In this paper, we will present the current commissioning status of the Front End, and per-formance of the main technical systems, such as the ECR ion source and RFQ.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH06

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paper received ※ 01 September 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLH07

Commissioning of the FRIB/NSCL New ReA3 4-Rod Radio Frequency Quadrupole Accelerator

rfq, vacuum, operation, MMI

817

S. Nash, J.F. Brandon, D.B. Crisp, T. Summers, A.C.C. Villari, Q. Zhao
NSCL, East Lansing, Michigan, USA
P.N. Ostroumov, A.S. Plastun
FRIB, East Lansing, Michigan, USA

Funding: This work was supported by the National Science Foundation under Grant PHY-15-65546
The reaccelerator facility ReA3 at the National Superconducting Cyclotron Laboratory is a state-of-the-art accelerator for ions of rare and stable isotopes. The first stage of acceleration is provided by a 4-rod radio-frequency quadrupole (RFQ) at 80.5 MHz, which accelerates ions from 12 keV/u to 530 keV/u. The internal copper acceleration structure of the RFQ was re-designed. The goal was to improve transmission while allowing to operate the RFQ in CW and accelerating ions with A/Q from 2 to 5. In this paper, we summarize the steps involved in the disassembly of the existing structure, preparation work on the retrofitted vacuum vessel, installation of the new components, acceptance testing, and commissioning of the completed RFQ.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH07

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paper received ※ 29 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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WEPLH09

FRIB Driver Linac Integration to be ready for Phased Beam Commissioning

MMI, SRF, cryomodule, linac

823

H. Ao, S. Beher, N.K. Bultman, F. Casagrande, C. Compton, J.C. Curtin, K.D. Davidson, K. Elliott, V. Ganni, A. Ganshyn, P.E. Gibson, I. Grender, W. Hartung, L. Hodges, K. Holland, A. Hussain, M. Ikegami, S. Jones, P. Knudsen, S.M. Lidia, G. Machicoane, S.J. Miller, D.G. Morris, P.N. Ostroumov, J.T. Popielarski, L. Popielarski, J. Priller, T. Russo, K. Saito, S. Stanley, D.R. Victory, X. Wang, J. Wei, M. Xu, T. Xu, Y. Yamazaki, S. Zhao
FRIB, East Lansing, Michigan, USA
A. Facco
INFN/LNL, Legnaro (PD), Italy
R.E. Laxdal
TRIUMF, Vancouver, Canada

Funding: Work supported by the U.S. Department of Energy (DOE) Office of Science under Cooperative Agreement DE-SC0000661
The driver linac for Facility for Rare Isotope Beams (FRIB) will accelerate all stable ion beams from proton to uranium beyond 200 MeV/u with beam powers up to 400 kW. The linac now consists of 10⁴ superconducting quarter-wave resonators (QWR), which is the world largest number of low-beta SRF cavities operating at an accelerator facility. The first 3 QWR cryomodules (CM) (β = 0.041) were successfully integrated with cryogenics and other support systems for the 2nd Accelerator Readiness Review (ARR). The 3rd ARR scope that includes 11 QWR CM (β=0.085) and 1 QWR matching CM (β=0.085) was commissioned on schedule by January 2019, and then we met the Key Performance Parameters (KPP), accelerating Ar and Kr > 16 MeV/u at this stage, in a week upon the ARR authorization. We examine a variety of key factors to the successful commissioning, such as component testing prior to system integration, assessment steps of system/device readiness, and phased commissioning. This paper also reports on the integration process of the β=0.085 CMs including the test results, and the current progress on β=0.29 and 0.53 CMs in preparation for the upcoming 4th ARR.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH09

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paper received ※ 02 September 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLH10

Efficiency Estimation for Sequential Excitation Laser Stripping of H⁻ Beam

laser, experiment, electron, proton

827

T.V. Gorlov, A.V. Aleksandrov, S.M. Cousineau, Y. Liu, A. Rakhman
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UTBattelle, LLC, under contract DEAC0500OR22725 for the U.S. Department of Energy.
A new laser stripping scheme for charge exchange injection of H⁻ beam is considered. The sequential scheme for the planned demonstration experiment includes two step excitation that requires much smaller laser power compared to the traditional 1-step excitation. The new scheme can be applied to a wider range of H⁻ beam energies and provides more flexibility on the choice of laser frequency. In this paper we discuss the two-step excitation method and estimate laser stripping parameters and stripping efficiency for the SNS accelerator and its future H⁻ energy upgrade to 1.3 GeV.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH10

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paper received ※ 22 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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WEPLH15

Light Ion Injector for NICA

linac, rfq, DTL, proton

834

H. Höltermann, H. Hähnel, B. Koubek, H. Podlech, U. Ratzinger, A. Schempp, D. Strehl, R. Tiede
BEVATECH, Frankfurt, Germany
M. Busch, M. Schuett
IAP, Frankfurt am Main, Germany
A.V. Butenko, D.E. Donets, A.D. Kovalenko, K.A. Levterov, D.A. Lyuosev, A.A. Martynov, D.O. Ponkin, K.V. Shevchenko, I.V. Shirikov, A.O. Sidorin, G.V. Trubnikov
JINR/VBLHEP, Dubna, Moscow region, Russia
B.V. Golovenskiy, A. Govorov, V.V. Kobets, E. Syresin
JINR, Dubna, Moscow Region, Russia

The Nuclotron ring of the NICA project will get a new light ion injector linac (LILac) for protons and ions with a mass to charge ratio up to 3. The LILac will consist of 2 sections: A 600 A keV RFQ followed by an IH-type DTL up to 7 AMeV, and a postaccelerator IH-cavity for protons only - up to 13 MeV. A switching magnet will additionally allow 13 MeV proton beam injection into a future superconducting testing section. The pulsed Linac up to 7 AMeV and including the postaccelerator for protons up to 13 MeV will be developed in collaboration between JINR and Bevatech GmbH. The technical design of that Linac is discussed in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH15

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paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLO20

High Gradient High Efficiency C-Band Accelerator Structure Research at LANL

simulation, operation, experiment, electron

882

E.I. Simakov, A.W. Garmon, T.C. Germann, M.F. Kirshner, F.L. Krawczyk, J.W. Lewellen, D. Perez, G. Wang
LANL, Los Alamos, New Mexico, USA
A. Fukasawa, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: Los Alamos National Laboratory LDRD Program
This poster will report on the status of the new high gradient C-band accelerator project at LANL. Modern applications such as X-ray sources require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. Our goal is to use a multi-disciplinary approach that includes accelerator design, molecular dynamics simulations, and advanced manufacturing to develop high gradient, high efficiency RF structures for both compact and facility-size accelerator systems. We considered common operation frequencies for accelerators and identified C-band as the optimal frequency band for high gradient operations based on achievable gradients and means to control wakefields. We are putting together a high gradient C-band test facility that includes a 50 MW Toshiba klystron and cryo-coolers for operating copper NCRF accelerator cavities at long pulse duration. We plan to conduct high gradient testing of the optimized RF structures made of copper and novel copper alloys. LANL modeling capabilities will be used to systematically study the formation of breakdown precursors at high fields to develop basic theoretical understanding of the breakdown.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO20

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paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLE02

Integrated Accelerator Simulation with Electromagnetics and Beam Physics Codes

simulation, plasma, electron, emittance

885

L. Ge, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA
D.A. Bizzozero, J. Qiang, J.-L. Vay
LBNL, Berkeley, California, USA
D.P. Grote
LLNL, Livermore, California, USA

Funding: Work supported by US Department of Energy under contracts AC02-76SF00515, DE-AC02-05CH11231 and DE-AC52-07NA27344. Used resources of the National Energy Research Scientific Computing Center.
This paper presents an integrated simulation capability for accelerators including electromagnetic field and beam dynamics effects. The integrated codes include the parallel finite-element code suite ACE3P for electromagnetic field calculation of beamline components, the parallel particle-in-cell (PIC) code IMPACT for beamline particle tracking with space-charge effects, and the parallel self-consistent PIC code Warp for beam and plasma simulations. The common data format OpenPMD has been adopted for efficient field and particle I/O data transfer between codes. One application is to employ ACE3P and IMPACT for studying beam qualities in accelerator beamlines. Another is to combine ACE3P and Warp for investigating plasma processing for operational performance of RF cavities. A module for mapping the CAD geometry used in ACE3P to Warp Cartesian grid representation has been developed. Furthermore, a workflow has been implemented that enables the execution of integrated simulation on HPC systems. Examples for simulation of the LCLS-II injector using ACE3P-IMPACT and plasma ignition in SRF cavities using ACE3P-Warp will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE02

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paper received ※ 20 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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WEPLE04

Recent Developments and Applications of Parallel Multi-Physics Accelerator Modeling Suite ACE3P

simulation, cryomodule, dipole, GUI

888

Z. Li, L. Ge, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA

Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515.
SLAC’s ACE3P code suite is developed to harness the power of massively parallel computers to tackle large complex problems with increased memory and solve them at greater speed. ACE3P parallel multi-physics codes are based on higher-order finite elements for superior geometry fidelity and better solution accuracy. ACE3P consists of an integrated set of electromagnetic, thermal and mechanical solvers for accelerator modeling and virtual prototyping. The use of ACE3P has contributed to the design and optimization of existing and future accelerator projects around the world. Multi-physics analysis on high performance computing (HPC) platform enables thermal-mechanical simulations of largescale systems such as the LCLS-II cryomodule. Recently, new capabilities have been added to ACE3P including a nonlinear eigenvalue solver for calculating mode damping, a moving window for pulse propagation in the time domain to reduce computational cost, thin layer coating representation using a surface impedance model, and improved boundary conditions using perfectly matched layers (PML) to terminate wave propagation. These new developments are presented in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE04

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLE05

Tracking With Space Harmonics in ELEGANT Code

electromagnetic-fields, simulation, electron, photon

892

Y.P. Sun, C. Yao
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The elegant code has the capability of simulating particle motion in accelerating or deflecting RF cavities, with a simplified (or ideal) model of the electromagnetic fields. To improve the accuracy of RF cavity simulations, the ability to track with space harmonics has been added to the elegant code. The sum of all the space harmonics will mimic the real electromagnetic fields in the RF cavity. These space harmonics will be derived from electromagnetic fields simulation of the RF cavity. This method should be general, which can be applied to any RF cavity structure, including accelerating and deflecting cavities.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE05

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paper received ※ 31 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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THYBA1

Status of the CBETA Cornell-BNL ERL Prototype

MMI, radiation, beam-loading, electron

923

K.E. Deitrick, N. Banerjee, A.C. Bartnik, J.A. Crittenden, L. Cultrera, J. Dobbins, C.M. Gulliford, G.H. Hoffstaetter, W. Lou, P. Quigley, D. Sagan, K.W. Smolenski, D. Widger
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.S. Berg, S.J. Brooks, R.L. Hulsart, R.J. Michnoff, S. Peggs, D. Trbojevic
BNL, Upton, New York, USA

CBETA, the Cornell-BNL ERL Test Accelerator, is an SRF multi-turn ERL which has been commissioned in the one-turn configuration from March to July 2019. During this time, the project has demonstrated an energy acceptance of 1.5 in the FFA arc, high-transmission energy recovery performance, and increased the CBETA energy-recovered maximum average current.

Slides THYBA1 [11.605 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBA1

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paper received ※ 28 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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THYBB3

Compact 1 MeV Electron Accelerator

GUI, gun, vacuum, electron

942

S.V. Kuzikov
IAP/RAS, Nizhny Novgorod, Russia
S.P. Antipov, P.V. Avrakhov
Euclid TechLabs, LLC, Solon, Ohio, USA

The cost of the accelerating structure in modern medical accelerators and industrial linacs is substantial. This comes to no surprise, as the accelerating waveguide is a set of diamond-turned copper resonators brazed together. Such a multistep manufacturing process is not only expensive, but also prone to manufacturing errors, which decrease the production yield. In the big picture, the cost of the accelerating waveguide precludes the use of accelerators as a replacement option for radioactive sources. Here we present a new cheap brazeless electron accelerating structure made out of two copper plates tightened together by means of an additional stainless steel plate. This additional plate, having sharp blades, is aimed to provide vacuum inside the whole system. The designed X-band 1 MeV structure consists of eight different length cells and accelerates field-emitted electrons from copper cathode. The structure is fed by 9 GHz magnetron which produces 240 kW, 1 µs pulses. The average gradient is as high as 10.6 MV/m, maximum surface fields do not exceed 50 MV/m.

Slides THYBB3 [19.559 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THYBB3

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paper received ※ 27 August 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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THZBA2

The MYRRHA Project

linac, rfq, proton, operation

945

H. Podlech, P. Britten, K. Kümpel, S. Lamprecht, N.F. Petry
IAP, Frankfurt am Main, Germany
M. Abs, J. Brison
IBA, Louvain-la-Neuve, Belgium
C. Angulo, J. Belmans, F. Doucet, A. Gatera, F. Pompon, A. Ponton, D. Vandeplassche
SCK•CEN, Mol, Belgium
A. Apollonio, J.A. Uythoven
CERN, Meyrin, Switzerland
A. Bechtold
NTG Neue Technologien GmbH & Co KG, Gelnhausen, Germany
J.-L. Biarrotte, C. Joly, D. Longuevergne
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
F. Bouly
LPSC, Grenoble Cedex, France
P. Fernandez Ramos, A.E. Pitigoi
Empresarios Agrupados, Madrid, Spain
H. Höltermann, U. Ratzinger
BEVATECH, Frankfurt, Germany
T. Junquera
Accelerators and Cryogenic Systems, Orsay, France
R. Modic
Cosylab, Ljubljana, Slovenia
F. Senée, D.U. Uriot
CEA-IRFU, Gif-sur-Yvette, France
C. Zhang
GSI, Darmstadt, Germany

The main objective of the MYRRHA project at SCK•CEN, the Belgian Nuclear Research Centre, is to demonstrate the feasibility of nuclear waste transmutation using an Accelerator Driven System (ADS). It is based on a High Power CW operated 600 MeV proton Linac with an average beam power of 2.4 MW. Due to the coupling of the accelerator with a subcritical reactor, a major concern is reliability and availability of the accelerator. The MYRRHA Linac consists of a room temperature 17 MeV Injector based on CH-cavities and the superconducting main Linac using different RF structures as Single Spokes, Double-Spokes and elliptical cavities. In 2017, it has been decided to stage the project and to start with the construction of a 100 MeV Linac (Injector and Single Spoke section) including a 400 kW proton target station. This facility (MINERVA) will be operational in 2026 aiming to evaluate the reliability potential of the 600 MeV Linac. The Front-End consisting of an ECR source, LEBT and 1.5 MeV RFQ is already operational while the first 7 CH-cavities are under construction. The presentation gives an overview about the MYRRHA Project, its challenges and the status of construction and testing.

Slides THZBA2 [27.209 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THZBA2

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paper received ※ 27 August 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019

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THZBA5

First Electron Cooling of Hadron Beams Using a Bunched Electron Beam

electron, MMI, laser, gun

957

A.V. Fedotov, Z. Altinbas, M. Blaskiewicz, J.M. Brennan, D. Bruno, J.C. Brutus, M.R. Costanzo, K.A. Drees, W. Fischer, J.M. Fite, M. Gaowei, D.M. Gassner, X. Gu, J. Halinski, K. Hamdi, L.R. Hammons, T. Hayes, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, P.K. Kankiya, D. Kayran, J. Kewisch, D. Lehn, C.J. Liaw, C. Liu, J. Ma, G.J. Mahler, M. Mapes, A. Marusic, K. Mernick, C. Mi, R.J. Michnoff, T.A. Miller, M.G. Minty, S.K. Nayak, L.K. Nguyen, M.C. Paniccia, I. Pinayev, S. Polizzo, V. Ptitsyn, T. Rao, G. Robert-Demolaize, T. Roser, J. Sandberg, V. Schoefer, S. Seletskiy, F. Severino, T.C. Shrey, L. Smart, K.S. Smith, H. Song, A. Sukhanov, R. Than, P. Thieberger, S.M. Trabocchi, J.E. Tuozzolo, P. Wanderer, E. Wang, G. Wang, D. Weiss, B.P. Xiao, T. Xin, W. Xu, A. Zaltsman, H. Zhao, Z. Zhao
BNL, Upton, New York, USA

Funding: Work supported by the U.S. Department of Energy.
The Low Energy RHIC electron Cooler (LEReC) was recently constructed and commissioned at BNL. The LEReC is the first electron cooler based on the RF acceleration of electron bunches (previous electron coolers all used DC beams). Bunched electron beams are necessary for cooling hadron beams at high energies. The challenges of such an approach include generation of electron beams suitable for cooling, delivery of electron beams of the required quality to the cooling sections without degradation of beam emittances and energy spread, achieving required small angles between electrons and ions in the cooling sections, precise energy matching between the two beams, high-current operation of the electron accelerator, as well as several physics effects related to bunched beam cooling. Following successful commissioning of the electron accelerator in 2018, the focus of the LEReC project in 2019 was on establishing electron-ion interactions and demonstration of cooling process using electron energy of 1.6MeV (ion energy of 3.85GeV/n), which is the lowest energy of interest. Here we report on the first demonstration of Au ion cooling in RHIC using this new approach.

Slides THZBA5 [16.417 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THZBA5

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paper received ※ 16 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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