NAPAC2022 - List of Keywords (vacuum)

Paper	Title	Other Keywords	Page
MOYE4	Diagnoses and Repair of a Crack in the Drift Tube LINAC Accelerating Structure at LANSCE	experiment, detector, linac, drift-tube-linac	19
	W.C. Barkley, D.A. Bingham, M.J. Borden, J.A. Burkhart, D.J. Evans, J.T.M. Lyles, J.P. Montross, J.F. O’Hara, B.J. Roller, M. Sanchez Barrueta LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396 Many were perplexed at the inability of Module 3 at LANSCE to operate at peak power and duty factor while running production beam. During the 2018 production run, the DTL began to intermittently break down, leading to a series of root cause investigations. These analyses included eliminating the usual suspects: vacuum leak, debris in tank, driveline window, power coupler, etc. The throttling back of repetition rate from 120 to 60 Hz allowed continued production with a diminished beam, one that reduced neutron flux to three experimental areas. During the annual shutdown in 2019, a more thorough investigation involving the use of x-ray detection, high-resolution cameras and IR detection through site glass windows was performed. After a tenacious search, a 30 cm long crack was discovered in a weld at one of the ion pump port grates. Inaccessibility for welding from the outside and in a confined space, non-intrusive repairs were tried first but were unsuccessful. Ultimately, an expert welder entered the tank to weld the crack under unfamiliar welding conditions. This paper describes the diagnoses, non-intrusive solutions and ultimate repair of the crack in the accelerating structure.
	Slides MOYE4 [3.232 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOYE4
About •	Received ※ 23 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 05 August 2022 — Issue date ※ 13 September 2022
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MOPA01	Realistic CAD-Based Geometries for Arbitrary Magnets with Beam Delivery Simulation (BDSIM)	extraction, simulation, synchrotron, proton	55
	E. Ramoisiaux, R. Dantinne, E. Gnacadja, C. Hernalsteens, S. Musibau, B. Ndihokubwayo, N. Pauly, R. Tesse, M. Vanwelde ULB, Bruxelles, Belgium S.T. Boogert, L.J. Nevay, W. Shields Royal Holloway, University of London, Surrey, United Kingdom C. Hernalsteens CERN, Meyrin, Switzerland
	Monte Carlo simulations are required to evaluate beam losses and secondary radiation accurately in particle accelerators and beamlines. Detailed CAD geometries are critical to account for a realistic distribution of material masses but increase the model complexity and often lead to code duplication. Beam Delivery Simulation (BDSIM) and the Python package pyg4ometry enable handling such accelerator models within a single, simplified workflow to run complete simulations of primary and secondary particle tracking and interactions with matter using Geant4 routines. Additional capabilities have been developed to model arbitrary bent magnets by associating externally modeled geometries to the magnet poles, yoke, and beampipe. Individual field descriptions can be associated with the yoke and vacuum pipe separately to provide fine-grained control of the magnet model. The implementation of these new features is described in detail and applied to the modeling of the CERN Proton Synchrotron (PS) combined function magnets.
	Poster MOPA01 [0.781 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA01
About •	Received ※ 02 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 16 September 2022
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MOPA23	Tests of the Extended Range SRF Cavity Tuners for the LCLS-II HE Project	cavity, operation, cryomodule, SRF	100
	C. Contreras-Martinez, T.T. Arkan, A.T. Cravatta, B.D. Hartsell, J.A. Kaluzny, T.N. Khabiboulline, Y.M. Pischalnikov, S. Posen, G.V. Romanov, J.C. Yun Fermilab, Batavia, Illinois, USA
	The LCLS-II HE superconducting linac will produce multi-energy beams by supporting multiple undulator lines simultaneously. This could be achieved by using the cavity SRF tuner in the off-frequency detune mode. This off-frequency operation method was tested in the verification cryomodule (vCM) and CM 1 at Fermilab at 2 K. In both cases, the tuners achieved a frequency shift of -565±80 kHz. This study will discuss cavity frequency during each step as it is being assembled in the cryomodule string and finally when it is being tested at 2 K. Tracking the cavity frequency helped enable the tuners to reach this large frequency shift. The specific procedures of tuner setting during assembly will be presented.
	Poster MOPA23 [0.654 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA23
About •	Received ※ 03 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 19 August 2022 — Issue date ※ 31 August 2022
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MOPA29	Second Generation Fermilab Main Injector 8 GeV Beamline Collimation Preliminary Design	collimation, shielding, simulation, controls	116
	K.J. Hazelwood, P. Adamson, B.C. Brown, D. Capista, R.M. Donahue, B.L. Klein, N.V. Mokhov, V.S. Pronskikh, V.I. Sidorov, M.C. Vincent Fermilab, Batavia, Illinois, USA
	The current Fermilab Main Injector 8 GeV beamline transverse collimation system was installed in 2006. Since then, proton beam intensities and rates have increased significantly. With the promise of even greater beam intensities and a faster repetition rate when the PIP-II upgrade completes later this decade, the current collimation system will be insufficient. Over the past 18 months, multiple collimation designs have been investigated, some more traditional and others novel. A preliminary design review was conducted and a design chosen. Work is underway to finalize the chosen design, prototype some of its novel components and procure parts for installation Summer 2023.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA29
About •	Received ※ 03 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 15 August 2022 — Issue date ※ 25 September 2022
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MOPA38	Accelerated Lifetime Test of the SRF Dressed Cavity/Tuner System for the LCLS II HE Project	cavity, operation, SRF, LabView	136
	Y.M. Pischalnikov, T.T. Arkan, C. Contreras-Martinez, B.D. Hartsell, J.A. Kaluzny, Y.M. Orlov, R.V. Pilipenko, J.C. Yun Fermilab, Batavia, Illinois, USA W. Lahmadi Wahid Lahmadi, Williston, USA
	The off-frequency detune method is being considered for application in the LCLS-II-HE superconducting linac to produce multi-energy electron beams for supporting multiple undulator lines simultaneously. Design of the tuner has been changed to deliver roughly 3 times larger frequency tuning range. Working requirements for off-frequency operation (OFO) state that cavities be tuned at least twice a month. This specification requires the increase of the tuner longevity by 30 times compared with LCLS-II demands. Accelerated longevity tests of the LCLS-II HE dressed cavity with tuner were conducted at FNAL’s HTS. Detail analysis of wearing and impacts on performances of the tuner’s piezo and stepper motor actuators will be presented. Additionally, results of longevity testing of the dressed cavity bellow, when cooled down to 2 K and compressed by 2.6 mm for roughly 2000 cycles, will be presented.
	Poster MOPA38 [3.026 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA38
About •	Received ※ 29 July 2022 — Revised ※ 06 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 11 August 2022
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MOPA60	HFSS Enables Multipaction Analysis of High Power RF/Microwave Components	multipactoring, electron, simulation, cavity	176
	S.A. Ahmed Ansys, Inc., Canonsburg, USA
	The radiofrequency (RF) components in particle accelerators operated under a vacuum and driven by high RF power may be prone to electron multipaction ’ an RF triggered electron resonance phenomenon causing malfunction or complete breakdown. Therefore, exploring the design challenges of vacuum RF windows, cavities, and other devices for the electron multipaction becomes necessary. Setting up an experiment to mitigate the failure of RF devices is expensive and time-consuming, which may cause a significant delay in the project. Therefore, a high-fidelity computer simulation modeling the arbitrary geometry and tracking the particles (electrons) in a complex electromagnetic environment is desirable. Ansys HFSS through Finite Element Mesh (FEM) for the full-wave RF simulation combined with the particle-in-cell (PIC) technique for tracking particles in EM fields; enables the engineers/physicist successful prediction of system failure against the electron multipaction. This paper will demonstrate the workflow of the HFSS multipaction analysis. The author like to thank Robert Chao for the valuable discussions and his efforts in developing this capability in the Ansys Electronics Desktop.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA60
About •	Received ※ 03 August 2022 — Revised ※ 13 August 2022 — Accepted ※ 26 August 2022 — Issue date ※ 06 October 2022
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MOPA61	Modular Solid-State Switching and Arc Suppression for Vacuum Tube Bias Circuits	high-voltage, power-supply, pulsed-power, operation	179
	E.L. Atkinson, T.J. Houlahan, B.E. Jurczyk, R.A. Stubbers Starfire Industries LLC, Champaign, USA
	In this work, we present operational and performance data for a solid-state switching circuit that delivers pulsed power at up to 12 kV and 100 A. This circuit, which is comprised of a series configuration of IGBT-based subcircuits, is suitable for driving the high-power vacuum-tube amplifiers that are typically used in RF accelerator systems. Each subcircuit can switch up to 3 kV, and the subcircuits can be stacked in series to extend the overall voltage capabilities of the switch. The circuit is designed to prevent overvoltaging any single transistor during switching transients or faults, regardless of the number of series subcircuits. Further, the circuit also includes the capability for rapid arc detection and suppression. Testing has shown effective switching at up to 100 A at 12 kV and for pulse repetition frequencies and durations in the range of 1-200 Hz and 10-50 µs, respectively. Additionally, the arc suppression circuitry has been shown to reliably limit arcs at 8-12 kV with a quench time of <1 µs and with a total energy of <0.2 J, minimizing the grid erosion in the vacuum-tube during an arc.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA61
About •	Received ※ 01 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 20 August 2022 — Issue date ※ 10 September 2022
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MOPA70	Film Dosimetry Characterization of the Research Linac at the University of Maryland	electron, linac, radiation, experiment	203
	A.S. Johnson, L.T. Gilde, M.K. Hottinger, T.W. Koeth UMD, College Park, Maryland, USA
	A heavily modified Varian linac was installed as part of the University of Maryland Radiation Facilities in the early 1980s. The electron linac was initially used for materials testing and pulsed radiolysis. Overtime, diagnostics such as a spectrometer magnet and scintillator screens have been removed, limiting the ability to describe the electron beam. The beamline is currently configured with a thin titanium window to allow the electrons to escape the vacuum region and interact with samples in air. A calibrated film dosimetry system was used to characterize the transverse beam dimensions and uniformity in air. The results of these experimental measurements will be described in this paper.
	Poster MOPA70 [3.423 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA70
About •	Received ※ 27 July 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 20 August 2022
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TUPA15	Development of a CVD System for Next-Generation SRF Cavities	cavity, controls, SRF, GUI	372
	G. Gaitan, P. Bishop, A.T. Holic, G. Kulina, J. Sears, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA M. Liepe Cornell University, Ithaca, New York, USA B.W. Wendland University of Minnesota, Minnesota, USA
	Funding: This research is funded by the National Science Foundation under Grant No. PHY-1549132, the Center for Bright Beams. Next-generation, thin-film surfaces employing Nb₃Sn, NbN, NbTiN, and other compound superconductors are destined to allow reaching superior RF performance levels in SRF cavities. Optimized, advanced deposition processes are required to enable high-quality films of such materials on large and complex-shaped cavities. For this purpose, Cornell University is developing a remote plasma-enhanced chemical vapor deposition (CVD) system that facilitates coating on complicated geometries with a high deposition rate. This system is based on a high-temperature tube furnace with a clean vacuum and furnace loading system. The use of plasma alongside reacting precursors will significantly reduce the required processing temperature and promote precursor decomposition. The system can also be used for annealing cavities after the CVD process to improve the surface layer. The chlorine precursors have the potential to be corrosive to the equipment and pose specific safety concerns. A MATLAB GUI has been developed to control and monitor the CVD system at Cornell.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA15
About •	Received ※ 14 July 2022 — Revised ※ 08 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 22 August 2022
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TUPA52	Initial Results of the 201.25 MHz Coaxial Window Test Stand	multipactoring, Windows, DTL, electron	458
	T.W. Hall, J.T.M. Lyles, A. Poudel, A.S. Waghmare LANL, Los Alamos, New Mexico, USA
	We have recently commissioned an RF window test stand for the Drift Tube Linear Accelerator (DTL) portion of the Los Alamos Neutron Science Center (LANSCE). The window test stand consists of two RF windows that create a vacuum chamber which allows the windows to be tested to the peak power levels used in the DTL. Initial results clearly indicated multipactoring due to the increase of pressure at specific regions of peak forward power levels. Temperature measured at various azimuthal locations on both windows showed increased multipactor heating on the downstream window versus the upstream window. We present the effect of the titanium nitride coating that is presently applied to windows on both multipactor and window temperature. These results are discussed with respect to their impact on the LANSCE DTL performance.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA52
About •	Received ※ 25 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 05 August 2022 — Issue date ※ 07 September 2022
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TUPA56	Beam Coupling Impedances of Asymmetric Components of the Scorpius Induction Linac	impedance, resonance, linac, dipole	469
	S.S. Kurennoy LANL, Los Alamos, New Mexico, USA
	The transverse beam coupling impedance of induction linacs must be minimized to avoid beam breakdown instability. The vacuum chamber of the Scorpius linac contains complicated asymmetric elements. We present calculations of the transverse impedance for three asymmetric discontinuities: (1) a pumping section between accelerating cells, which contains vacuum plenum, pumping grid, and bellows; (2) a fast flapper valve; and (3) a debris blocker at the end of the linac. The dipole transverse impedance is calculated with CST Studio using both wakefield solver and eigen solver.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA56
About •	Received ※ 01 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 06 October 2022
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TUPA85	First Results from a Multileaf Collimator and Emittance Exchange Beamline	wakefield, plasma, acceleration, laser	531
	N. Majernik, G. Andonian, C.D. Lorch, W.J. Lynn, J.B. Rosenzweig UCLA, Los Angeles, California, USA D.S. Doran, S.Y. Kim, P. Piot, J.G. Power, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA
	Funding: Department of Energy DE-SC0017648 and National Science Foundation PHY-1549132. By shaping the transverse profile of a particle beam prior to an emittance exchange (EEX) beamline, drive and witness beams with variable current profiles and bunch spacing can be produced. Presently at AWA, this transverse shaping is accomplished with individually laser-cut tungsten masks, making the refinement of beam profiles a slow process. In contrast, a multileaf collimator (MLC) is a device that can selectively mask the profile of a beam using many independently actuated leaves. Since an MLC permits real-time adjustment of the beam shape, its use as a beam mask would permit much faster optimization in a manner highly synergistic with machine learning. Beam dynamics simulations have shown that such an approach is functionally equivalent to that offered by the laser cut masks. In this work, the construction and first results from a 40-leaf, UHV compatible MLC are discussed.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA85
About •	Received ※ 16 July 2022 — Revised ※ 02 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 12 August 2022
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WEYE6	Thermionic Sources for Electron Cooling at IOTA	electron, cathode, proton, space-charge	588
	M.K. Bossard, Y.K. Kim University of Chicago, Chicago, Illinois, USA N. Banerjee, J.A. Brandt Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA B.L. Cathey, S. Nagaitsev, G. Stancari Fermilab, Batavia, Illinois, USA M.A. Krieg Saint Olaf College, Northfield, MN, USA
	We are planning a new electron cooling experiment at the Integrable Optics Test Accelerator (IOTA) at Fermilab for cooling ~2.5 MeV protons in the presence of intense space-charge. Here we present the simulations and design of a thermionic electron source for cooling at IOTA. We particularly discuss parameters of the thermionic source electrodes, as well as the simulation results. We also present a new electron source test-stand at the University of Chicago, which will be used to test the new thermionic electron source, as well as other electron sources. In addition, we discuss results from analyzing the test stand operations with a currently existing electron source. Furthermore, we present future steps for the test stand as well as production and commissioning of the thermionic source at IOTA.
	Slides WEYE6 [3.182 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYE6
About •	Received ※ 02 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 28 August 2022
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WEZE3	Compact, High-Power Superconducting Electron Linear Accelerators for MW Industrial Applications	cavity, electron, SRF, gun	604
	J.C.T. Thangaraj, R. Dhuley Fermilab, Batavia, Illinois, USA
	Fermilab has developed a novel concept for an industrial electron linac using Nb₃Sn coating technology and conduction cooling. We will show the range of multi-cavity linac designs targeted toward various applications. We will also discuss technology development status with results on conduction cooling of SRF cavities based on cryocoolers, which removes the need for liquid Helium, thus making SRF technology accessible to industrial applications. These conduction-cooled linacs can generate electron beam energies up to 10 MeV in continuous-wave operation and can reach higher power (>=1 MW) by combing several modules. Compact and light enough to mount on mobile platforms, our machine is anticipated to enable new in-situ environmental remediation applications such as waste-water treatment for urban areas, X-ray medical device sterilization, and innovative pavement applications. We also show cost-economics and key R&D areas that much be addressed for a practical machine.
	Slides WEZE3 [3.811 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEZE3
About •	Received ※ 02 August 2022 — Revised ※ 12 August 2022 — Accepted ※ 13 August 2022 — Issue date ※ 30 August 2022
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WEPA10	Determination of LCLS-II Gun-2 Prototype Dimensions	gun, cavity, cathode, simulation	637
	L. Xiao, C. Adolphsen, E.N. Jongewaard, X. Liu, F. Zhou SLAC, Menlo Park, California, USA
	The LCLS-II spare gun (Gun-2) design is largely based on the existing LCLS-II gun (Gun-1), in which there is significant captured dark current (DC) that originates on the high field copper surface near the cathode plug gap opening. To help suppress DC, the Gun-2 cathode and anode noses and the cathode plug opening are elliptically shaped to minimize the peak surface field for a given cathode gradient. Stainless steel (SS) cathode and anode inserts are used in Gun-2 to further reduce dark current. The RF simulations were performed using a model that includes all the 3D features. The thermal and structural analyses were done to investigate the effects of the air pressure and RF heating. The multi-physics simulation results provided the information needed to compute the overall frequency change from the basic 2D model to the nominal frequency during operation. The Gun-2 cathode-to-anode gap distance will be made 1 mm longer than the nominal gap with the expectation that less than 1 mm will be machined off to meet the target frequency. In this paper, the Gun-2 frequency correction calculations are presented, and the cathode-to-anode gap determination is discussed.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA10
About •	Received ※ 30 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022
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WEPA19	HE Production Update at JLab - Introducing an Enhanced Nitrogen Purge for Clean String Assembly	cavity, controls, cryomodule, hardware	659
	P.D. Owen JLab, Newport News, Virginia, USA
	A major limitation to cryomodule performance is field emission caused by particulates within the superconducting cavities. To reduce contamination of the inner surfaces during assembly in a cleanroom, the whole string can be connected to a purge system, which maintains a constant overpressure of dry, clean nitrogen gas. Following successes of similar systems at XFEL and Fermilab, Jefferson Lab followed this example for the production of LCLS-II HE cryomodules. Implementing this system required new procedures, infrastructure, and hardware, as well as significant testing of the system before production began. This paper will summarize the implemented controls and procedures, including lessons learned from Fermilab, as well as the results of mock-up tests. Based on the latter, the system was used to assemble the first article string in April 2022, and was also used during a rework required due to issues with cold FPC ceramics two months later. The benefits of using a purge system with regards to procedure, time savings, and added flexibility for potential rework have already proven to provide a significant improvement for the production of LCLS-II-HE cryomodules at Jefferson Lab.
	Poster WEPA19 [1.538 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA19
About •	Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 21 August 2022
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WEPA20	High-Gradient Wien Spin Rotators at Jefferson Lab	electron, operation, high-voltage, gun	662
	G.G. Palacios Serrano, P.A. Adderley, J.M. Grames, C. Hernandez-Garcia, M. Poelker JLab, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Nuclear physics experiments performed in the Contin-uous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) require spin manipulation of electron beams. Two Wien spin rotators in the injector keV region are essential at CEBAF to establish longitudinal polarization at the end station target, and to flip the polarization direction by π rad to rule out false asymmetries. In a Wien filter, the homogeneous and independent electric and magnetic fields, along with the velocity vectors of the electrons that traverse it, form a mutually orthogonal system. The magnitude of the electrostatic field, established by biasing two highly-polished elec-trodes, defines the desired spin angle at the target yet deviates the beam trajectory due to the Lorentz force. The beam trajectory in the Wien is then re-established by adjusting the magnetic field, induced by an electromag-net encasing the device vacuum chamber. This contribu-tion describes the evolution design and high voltage testing of Wien filters for spin manipulation at increased beam energies in the keV injector region, required by high precision parity violation experiments like MOLLER.
	Poster WEPA20 [1.434 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA20
About •	Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 05 September 2022
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WEPA55	Applications of Machine Automation with Robotics and Computer Vision in Cleanroom Assemblies	controls, SRF, cavity, operation	756
	A. Liu, J.R. Callahan, E. Gomez, S.M. Milller, W. Si Euclid TechLabs, Solon, Ohio, USA
	Funding: This work is supported by the US DOE SBIR program under contract number DE-SC0021736. Modern linear particle accelerators use superconducting radio frequency (SRF) cavities for achieving extremely high-quality factors (Q) and higher beam stability. The assembly process of the system, although with a much more stringent cleanness requirement, is very similar to the ultrahigh vacuum (UHV) system operation procedure. Humans, who are conventionally the operators in this procedure, can only avoid contaminating the system by wearing proper sterile personal protection equipment to avoid direct skin contact with the systems, or dropping particulates. However, humans unavoidably make unintentional mistakes that can contaminate the environment: cross contamination of the coverall suits during wearing, slippage of masks or goggles, damaged gloves, and so forth. Besides, humans are limited when operating heavy weights, which may lead to incorrect procedures, or even worse, injury. In this paper, we present our recent work on a viable and cost-effective machine automation system composed of a robotic arm and a computer vision system for the assembly process in a cleanroom environment, for example for SRF string assemblies, and more.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA55
About •	Received ※ 30 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 12 August 2022
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WEPA56	Encapsulation of Photocathodes Using High Power Pulsed RF Sputtering of hBN	cathode, simulation, electron, ion-effects	760
	A. Liu, J.R. Callahan, S. Poddar Euclid TechLabs, Solon, Ohio, USA J.P. Biswas, M. Gaowei BNL, Upton, New York, USA
	Funding: This work is supported by the US DOE SBIR program under contract number DE-SC0021511 and DE-SC0020573. Photocathodes of various materials are used in photoinjectors for generating photoelectron beams. Of particular interest are the alkali antimonides because of their ultra-high quantum efficiency (QE) and relatively low requirements for growth, and metallic materials such as Cu and Mg which have lower QE but are easier to maintain and have longer lifetime. The biggest challenge of using the alkali antimonide photocathode is that it has an extremely stringent requirement on vacuum and is destroyed rapidly by residual air in the system, while exposure of Mg and Cu in air also impacts the photocathode performance because of the oxidation. The photocathode can be protected against harmful gas molecules by using one or two monolayers of a 2D material such as graphene or hexagonal boron nitride (hBN). Furthermore, hBN monolayers even have the potential to improve the QE of the photocathode when working as the encapsulation thin-film. In this paper, we will discuss the feasibility of coating a photocathode with hBN by high power pulsed RF sputtering by using metallic photocathodes as examples, and compare the performance with encapsulated photocathodes with transferred hBN thin-films.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA56
About •	Received ※ 31 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022
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WEPA72	Analysis of Beam-Induced Heating of the NSLS-II Ceramic Vacuum Chambers	impedance, kicker, simulation, injection	799
	G. Bassi, C. Hetzel, A. Khan, B.N. Kosciuk, M. Seegitz, V.V. Smaluk, R.J. Todd BNL, Upton, New York, USA A. Blednykh Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
	We discuss impedance calculations and related heating issues of the titanium-coated NSLS-II kicker ceramic chambers, with the titanium coating thickness estimated from in situ measurements of the end-to-end resistance of each chamber. Power densities are calculated on the titanium coating to allow for thermal analysis with the code ANSYS and comparison with heating measurements. The impedance analysis is performed using a realistic model of the ceramic complex permittivity, and special consideration is given to the impedance calculation in the limit of zero titanium coating thickness.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA72
About •	Received ※ 03 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 26 September 2022
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WEPA73	Numerical Studies of Geometric Impedance at NSLS-II with GdfidL and ECHO3D	impedance, simulation, wakefield, radiation	802
	A. Khan, M. Seegitz, V.V. Smaluk, R.J. Todd BNL, Upton, New York, USA A. Blednykh Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
	The beam intensity in future low-emittance light sources with small gap wigglers and undulators is limited by the effects of short-range wakefields, especially by the beam-induced heating of the vacuum chamber components. We have cross-checked two electromagnetic solvers, GdfidL and ECHO3D, by simulation of the short-range wakefields in the NSLS-II flange absorber and in the taper transition of an in-vacuum undulator to test the consistency and precision of the wakefield models.
	Poster WEPA73 [1.057 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA73
About •	Received ※ 01 August 2022 — Revised ※ 03 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 01 September 2022
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WEPA85	Localized Beam Induced Heating Analysis of the EIC Vacuum Chamber Components	kicker, electron, simulation, injection	833
	M.P. Sangroula, D.M. Gassner, C.J. Liaw, C. Liu, P. Thieberger BNL, Upton, New York, USA J.R. Bellon, A. Blednykh, C. Hetzel, S. Verdú-Andrés Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy The Electron-Ion Collider (EIC), to be built at Brookhaven National Laboratory (BNL), is designed to provide a high electron-proton luminosity of 10³⁴ cm^-2 s^-1. One of the challenging tasks for the Electron Storage Ring (ESR) is to operate at an average beam current of 2.5 A within 1160 bunches with a ~ 7 mm bunch length. The Hadron Storage Ring (HSR) will accumulate an average current of 0.69 A within 290 bunches with a 60 mm bunch length. Both rings require the impedance budget simulations. The intense e-beam in the ESR can lead to the overheating of vacuum chamber components due to localized metallic losses. This paper focuses on the beam-induced heating analysis of the ESR vacuum components including bellows, gate-valve, and BPM. To perform thermal analysis, the resistive loss on individual components is calculated with CST and then fed to ANSYS to determine the temperature distribution on the vacuum components. Preliminary results suggest that active water cooling will be required for most of the ESR vacuum components. Similar approach is applied to the HSR vacuum components. The thermal analysis of the HSR stripline injection kicker is presented.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA85
About •	Received ※ 03 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 10 September 2022
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THYE4	Development of an Ultra-Low Vibration Cryostat Based on a Closed-Cycle Cryocooler	radiation, cryogenics, instrumentation, synchrotron	874
	R.W. Roca Illinois Institute of Technology, Chicago, Illinois, USA E.W. Knight, R.A. Kostin, Y. Zhao Euclid TechLabs, Solon, Ohio, USA
	Low temperature and low vibration cryostats are useful in a variety of applications such as x-ray diffraction, quantum computing, x-ray monochromators and cryo-TEMs. In this project, we explore an ultra-low vibration cryostat with the cooling provided by a closed cycle cryocooler. Closed-cycle cryocoolers inevitably introduce vibrations into the system, and in this project, flexible copper braiding was used to decouple vibrations and provide cooling at the same time. In order to develop the cryostat, capacity map of a two stage Sumitomo cryocooler was measured as well as vibration transmission through different copper braids using an IR interferometer. This paper covers the capacity map and vibration measurements in the first prototype.
	Slides THYE4 [4.989 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYE4
About •	Received ※ 16 July 2022 — Revised ※ 10 August 2022 — Accepted ※ 20 August 2022 — Issue date ※ 12 September 2022
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THZE3	An Electrodeless Diamond Beam Monitor	electron, experiment, detector, controls	904
	S.V. Kuzikov, P.V. Avrakhov, C.-J. Jing, E.W. Knight Euclid TechLabs, Solon, Ohio, USA D.S. Doran, C.-J. Jing, J.G. Power, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing Euclid Beamlabs, Bolingbrook, USA
	Funding: The work was supported by DoE SBIR grant #DE-SC0019642. Being a wide-band semiconductor, diamond can be used to measure the flux of passing particles based on a particle-induced conductivity effect. We recently demonstrated a diamond electrodeless electron beam halo monitor. That monitor was based on a thin piece of diamond (blade) placed in an open high-quality microwave resonator. The blade partially intercepted the beam. By measuring the change in RF properties of the resonator, one could infer the beam parameters. At Argonne Wakefield Accelerator we have tested 1D and 2D monitors. To enhance the sensitivity of our diamond sensor, we proposed applying a bias voltage to the diamond which can sustain the avalanche of free carriers. In experiment carried out with 120 kV, ~1 µA beam we showed that the response signal for the avalanche monitor biased with up to 5 kV voltage can be up to 100 times larger in comparison with the signal of the same non-biased device.
	Slides THZE3 [4.257 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THZE3
About •	Received ※ 20 July 2022 — Revised ※ 28 July 2022 — Accepted ※ 06 August 2022 — Issue date ※ 08 August 2022
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Paper

Title

Other Keywords

Page

MOYE4

Diagnoses and Repair of a Crack in the Drift Tube LINAC Accelerating Structure at LANSCE

experiment, detector, linac, drift-tube-linac

19

W.C. Barkley, D.A. Bingham, M.J. Borden, J.A. Burkhart, D.J. Evans, J.T.M. Lyles, J.P. Montross, J.F. O’Hara, B.J. Roller, M. Sanchez Barrueta
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396
Many were perplexed at the inability of Module 3 at LANSCE to operate at peak power and duty factor while running production beam. During the 2018 production run, the DTL began to intermittently break down, leading to a series of root cause investigations. These analyses included eliminating the usual suspects: vacuum leak, debris in tank, driveline window, power coupler, etc. The throttling back of repetition rate from 120 to 60 Hz allowed continued production with a diminished beam, one that reduced neutron flux to three experimental areas. During the annual shutdown in 2019, a more thorough investigation involving the use of x-ray detection, high-resolution cameras and IR detection through site glass windows was performed. After a tenacious search, a 30 cm long crack was discovered in a weld at one of the ion pump port grates. Inaccessibility for welding from the outside and in a confined space, non-intrusive repairs were tried first but were unsuccessful. Ultimately, an expert welder entered the tank to weld the crack under unfamiliar welding conditions. This paper describes the diagnoses, non-intrusive solutions and ultimate repair of the crack in the accelerating structure.

Slides MOYE4 [3.232 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOYE4

About •

Received ※ 23 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 05 August 2022 — Issue date ※ 13 September 2022

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MOPA01

Realistic CAD-Based Geometries for Arbitrary Magnets with Beam Delivery Simulation (BDSIM)

extraction, simulation, synchrotron, proton

55

E. Ramoisiaux, R. Dantinne, E. Gnacadja, C. Hernalsteens, S. Musibau, B. Ndihokubwayo, N. Pauly, R. Tesse, M. Vanwelde
ULB, Bruxelles, Belgium
S.T. Boogert, L.J. Nevay, W. Shields
Royal Holloway, University of London, Surrey, United Kingdom
C. Hernalsteens
CERN, Meyrin, Switzerland

Monte Carlo simulations are required to evaluate beam losses and secondary radiation accurately in particle accelerators and beamlines. Detailed CAD geometries are critical to account for a realistic distribution of material masses but increase the model complexity and often lead to code duplication. Beam Delivery Simulation (BDSIM) and the Python package pyg4ometry enable handling such accelerator models within a single, simplified workflow to run complete simulations of primary and secondary particle tracking and interactions with matter using Geant4 routines. Additional capabilities have been developed to model arbitrary bent magnets by associating externally modeled geometries to the magnet poles, yoke, and beampipe. Individual field descriptions can be associated with the yoke and vacuum pipe separately to provide fine-grained control of the magnet model. The implementation of these new features is described in detail and applied to the modeling of the CERN Proton Synchrotron (PS) combined function magnets.

Poster MOPA01 [0.781 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA01

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Received ※ 02 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 16 September 2022

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MOPA23

Tests of the Extended Range SRF Cavity Tuners for the LCLS-II HE Project

cavity, operation, cryomodule, SRF

100

C. Contreras-Martinez, T.T. Arkan, A.T. Cravatta, B.D. Hartsell, J.A. Kaluzny, T.N. Khabiboulline, Y.M. Pischalnikov, S. Posen, G.V. Romanov, J.C. Yun
Fermilab, Batavia, Illinois, USA

The LCLS-II HE superconducting linac will produce multi-energy beams by supporting multiple undulator lines simultaneously. This could be achieved by using the cavity SRF tuner in the off-frequency detune mode. This off-frequency operation method was tested in the verification cryomodule (vCM) and CM 1 at Fermilab at 2 K. In both cases, the tuners achieved a frequency shift of -565±80 kHz. This study will discuss cavity frequency during each step as it is being assembled in the cryomodule string and finally when it is being tested at 2 K. Tracking the cavity frequency helped enable the tuners to reach this large frequency shift. The specific procedures of tuner setting during assembly will be presented.

Poster MOPA23 [0.654 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA23

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Received ※ 03 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 19 August 2022 — Issue date ※ 31 August 2022

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MOPA29

Second Generation Fermilab Main Injector 8 GeV Beamline Collimation Preliminary Design

collimation, shielding, simulation, controls

116

K.J. Hazelwood, P. Adamson, B.C. Brown, D. Capista, R.M. Donahue, B.L. Klein, N.V. Mokhov, V.S. Pronskikh, V.I. Sidorov, M.C. Vincent
Fermilab, Batavia, Illinois, USA

The current Fermilab Main Injector 8 GeV beamline transverse collimation system was installed in 2006. Since then, proton beam intensities and rates have increased significantly. With the promise of even greater beam intensities and a faster repetition rate when the PIP-II upgrade completes later this decade, the current collimation system will be insufficient. Over the past 18 months, multiple collimation designs have been investigated, some more traditional and others novel. A preliminary design review was conducted and a design chosen. Work is underway to finalize the chosen design, prototype some of its novel components and procure parts for installation Summer 2023.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA29

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Received ※ 03 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 15 August 2022 — Issue date ※ 25 September 2022

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MOPA38

Accelerated Lifetime Test of the SRF Dressed Cavity/Tuner System for the LCLS II HE Project

cavity, operation, SRF, LabView

136

Y.M. Pischalnikov, T.T. Arkan, C. Contreras-Martinez, B.D. Hartsell, J.A. Kaluzny, Y.M. Orlov, R.V. Pilipenko, J.C. Yun
Fermilab, Batavia, Illinois, USA
W. Lahmadi
Wahid Lahmadi, Williston, USA

The off-frequency detune method is being considered for application in the LCLS-II-HE superconducting linac to produce multi-energy electron beams for supporting multiple undulator lines simultaneously. Design of the tuner has been changed to deliver roughly 3 times larger frequency tuning range. Working requirements for off-frequency operation (OFO) state that cavities be tuned at least twice a month. This specification requires the increase of the tuner longevity by 30 times compared with LCLS-II demands. Accelerated longevity tests of the LCLS-II HE dressed cavity with tuner were conducted at FNAL’s HTS. Detail analysis of wearing and impacts on performances of the tuner’s piezo and stepper motor actuators will be presented. Additionally, results of longevity testing of the dressed cavity bellow, when cooled down to 2 K and compressed by 2.6 mm for roughly 2000 cycles, will be presented.

Poster MOPA38 [3.026 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA38

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Received ※ 29 July 2022 — Revised ※ 06 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 11 August 2022

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MOPA60

HFSS Enables Multipaction Analysis of High Power RF/Microwave Components

multipactoring, electron, simulation, cavity

176

S.A. Ahmed
Ansys, Inc., Canonsburg, USA

The radiofrequency (RF) components in particle accelerators operated under a vacuum and driven by high RF power may be prone to electron multipaction ’ an RF triggered electron resonance phenomenon causing malfunction or complete breakdown. Therefore, exploring the design challenges of vacuum RF windows, cavities, and other devices for the electron multipaction becomes necessary. Setting up an experiment to mitigate the failure of RF devices is expensive and time-consuming, which may cause a significant delay in the project. Therefore, a high-fidelity computer simulation modeling the arbitrary geometry and tracking the particles (electrons) in a complex electromagnetic environment is desirable. Ansys HFSS through Finite Element Mesh (FEM) for the full-wave RF simulation combined with the particle-in-cell (PIC) technique for tracking particles in EM fields; enables the engineers/physicist successful prediction of system failure against the electron multipaction. This paper will demonstrate the workflow of the HFSS multipaction analysis.
The author like to thank Robert Chao for the valuable discussions and his efforts in developing this capability in the Ansys Electronics Desktop.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA60

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Received ※ 03 August 2022 — Revised ※ 13 August 2022 — Accepted ※ 26 August 2022 — Issue date ※ 06 October 2022

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MOPA61

Modular Solid-State Switching and Arc Suppression for Vacuum Tube Bias Circuits

high-voltage, power-supply, pulsed-power, operation

179

E.L. Atkinson, T.J. Houlahan, B.E. Jurczyk, R.A. Stubbers
Starfire Industries LLC, Champaign, USA

In this work, we present operational and performance data for a solid-state switching circuit that delivers pulsed power at up to 12 kV and 100 A. This circuit, which is comprised of a series configuration of IGBT-based subcircuits, is suitable for driving the high-power vacuum-tube amplifiers that are typically used in RF accelerator systems. Each subcircuit can switch up to 3 kV, and the subcircuits can be stacked in series to extend the overall voltage capabilities of the switch. The circuit is designed to prevent overvoltaging any single transistor during switching transients or faults, regardless of the number of series subcircuits. Further, the circuit also includes the capability for rapid arc detection and suppression. Testing has shown effective switching at up to 100 A at 12 kV and for pulse repetition frequencies and durations in the range of 1-200 Hz and 10-50 µs, respectively. Additionally, the arc suppression circuitry has been shown to reliably limit arcs at 8-12 kV with a quench time of <1 µs and with a total energy of <0.2 J, minimizing the grid erosion in the vacuum-tube during an arc.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA61

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Received ※ 01 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 20 August 2022 — Issue date ※ 10 September 2022

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MOPA70

Film Dosimetry Characterization of the Research Linac at the University of Maryland

electron, linac, radiation, experiment

203

A.S. Johnson, L.T. Gilde, M.K. Hottinger, T.W. Koeth
UMD, College Park, Maryland, USA

A heavily modified Varian linac was installed as part of the University of Maryland Radiation Facilities in the early 1980s. The electron linac was initially used for materials testing and pulsed radiolysis. Overtime, diagnostics such as a spectrometer magnet and scintillator screens have been removed, limiting the ability to describe the electron beam. The beamline is currently configured with a thin titanium window to allow the electrons to escape the vacuum region and interact with samples in air. A calibrated film dosimetry system was used to characterize the transverse beam dimensions and uniformity in air. The results of these experimental measurements will be described in this paper.

Poster MOPA70 [3.423 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA70

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Received ※ 27 July 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 20 August 2022

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TUPA15

Development of a CVD System for Next-Generation SRF Cavities

cavity, controls, SRF, GUI

372

G. Gaitan, P. Bishop, A.T. Holic, G. Kulina, J. Sears, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
M. Liepe
Cornell University, Ithaca, New York, USA
B.W. Wendland
University of Minnesota, Minnesota, USA

Funding: This research is funded by the National Science Foundation under Grant No. PHY-1549132, the Center for Bright Beams.
Next-generation, thin-film surfaces employing Nb₃Sn, NbN, NbTiN, and other compound superconductors are destined to allow reaching superior RF performance levels in SRF cavities. Optimized, advanced deposition processes are required to enable high-quality films of such materials on large and complex-shaped cavities. For this purpose, Cornell University is developing a remote plasma-enhanced chemical vapor deposition (CVD) system that facilitates coating on complicated geometries with a high deposition rate. This system is based on a high-temperature tube furnace with a clean vacuum and furnace loading system. The use of plasma alongside reacting precursors will significantly reduce the required processing temperature and promote precursor decomposition. The system can also be used for annealing cavities after the CVD process to improve the surface layer. The chlorine precursors have the potential to be corrosive to the equipment and pose specific safety concerns. A MATLAB GUI has been developed to control and monitor the CVD system at Cornell.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA15

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Received ※ 14 July 2022 — Revised ※ 08 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 22 August 2022

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TUPA52

Initial Results of the 201.25 MHz Coaxial Window Test Stand

multipactoring, Windows, DTL, electron

458

T.W. Hall, J.T.M. Lyles, A. Poudel, A.S. Waghmare
LANL, Los Alamos, New Mexico, USA

We have recently commissioned an RF window test stand for the Drift Tube Linear Accelerator (DTL) portion of the Los Alamos Neutron Science Center (LANSCE). The window test stand consists of two RF windows that create a vacuum chamber which allows the windows to be tested to the peak power levels used in the DTL. Initial results clearly indicated multipactoring due to the increase of pressure at specific regions of peak forward power levels. Temperature measured at various azimuthal locations on both windows showed increased multipactor heating on the downstream window versus the upstream window. We present the effect of the titanium nitride coating that is presently applied to windows on both multipactor and window temperature. These results are discussed with respect to their impact on the LANSCE DTL performance.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA52

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Received ※ 25 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 05 August 2022 — Issue date ※ 07 September 2022

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TUPA56

Beam Coupling Impedances of Asymmetric Components of the Scorpius Induction Linac

impedance, resonance, linac, dipole

469

S.S. Kurennoy
LANL, Los Alamos, New Mexico, USA

The transverse beam coupling impedance of induction linacs must be minimized to avoid beam breakdown instability. The vacuum chamber of the Scorpius linac contains complicated asymmetric elements. We present calculations of the transverse impedance for three asymmetric discontinuities: (1) a pumping section between accelerating cells, which contains vacuum plenum, pumping grid, and bellows; (2) a fast flapper valve; and (3) a debris blocker at the end of the linac. The dipole transverse impedance is calculated with CST Studio using both wakefield solver and eigen solver.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA56

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Received ※ 01 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 06 October 2022

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TUPA85

First Results from a Multileaf Collimator and Emittance Exchange Beamline

wakefield, plasma, acceleration, laser

531

N. Majernik, G. Andonian, C.D. Lorch, W.J. Lynn, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
D.S. Doran, S.Y. Kim, P. Piot, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA

Funding: Department of Energy DE-SC0017648 and National Science Foundation PHY-1549132.
By shaping the transverse profile of a particle beam prior to an emittance exchange (EEX) beamline, drive and witness beams with variable current profiles and bunch spacing can be produced. Presently at AWA, this transverse shaping is accomplished with individually laser-cut tungsten masks, making the refinement of beam profiles a slow process. In contrast, a multileaf collimator (MLC) is a device that can selectively mask the profile of a beam using many independently actuated leaves. Since an MLC permits real-time adjustment of the beam shape, its use as a beam mask would permit much faster optimization in a manner highly synergistic with machine learning. Beam dynamics simulations have shown that such an approach is functionally equivalent to that offered by the laser cut masks. In this work, the construction and first results from a 40-leaf, UHV compatible MLC are discussed.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA85

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Received ※ 16 July 2022 — Revised ※ 02 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 12 August 2022

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WEYE6

Thermionic Sources for Electron Cooling at IOTA

electron, cathode, proton, space-charge

588

M.K. Bossard, Y.K. Kim
University of Chicago, Chicago, Illinois, USA
N. Banerjee, J.A. Brandt
Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
B.L. Cathey, S. Nagaitsev, G. Stancari
Fermilab, Batavia, Illinois, USA
M.A. Krieg
Saint Olaf College, Northfield, MN, USA

We are planning a new electron cooling experiment at the Integrable Optics Test Accelerator (IOTA) at Fermilab for cooling ~2.5 MeV protons in the presence of intense space-charge. Here we present the simulations and design of a thermionic electron source for cooling at IOTA. We particularly discuss parameters of the thermionic source electrodes, as well as the simulation results. We also present a new electron source test-stand at the University of Chicago, which will be used to test the new thermionic electron source, as well as other electron sources. In addition, we discuss results from analyzing the test stand operations with a currently existing electron source. Furthermore, we present future steps for the test stand as well as production and commissioning of the thermionic source at IOTA.

Slides WEYE6 [3.182 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYE6

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Received ※ 02 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 28 August 2022

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WEZE3

Compact, High-Power Superconducting Electron Linear Accelerators for MW Industrial Applications

cavity, electron, SRF, gun

604

J.C.T. Thangaraj, R. Dhuley
Fermilab, Batavia, Illinois, USA

Fermilab has developed a novel concept for an industrial electron linac using Nb₃Sn coating technology and conduction cooling. We will show the range of multi-cavity linac designs targeted toward various applications. We will also discuss technology development status with results on conduction cooling of SRF cavities based on cryocoolers, which removes the need for liquid Helium, thus making SRF technology accessible to industrial applications. These conduction-cooled linacs can generate electron beam energies up to 10 MeV in continuous-wave operation and can reach higher power (>=1 MW) by combing several modules. Compact and light enough to mount on mobile platforms, our machine is anticipated to enable new in-situ environmental remediation applications such as waste-water treatment for urban areas, X-ray medical device sterilization, and innovative pavement applications. We also show cost-economics and key R&D areas that much be addressed for a practical machine.

Slides WEZE3 [3.811 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEZE3

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Received ※ 02 August 2022 — Revised ※ 12 August 2022 — Accepted ※ 13 August 2022 — Issue date ※ 30 August 2022

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WEPA10

Determination of LCLS-II Gun-2 Prototype Dimensions

gun, cavity, cathode, simulation

637

L. Xiao, C. Adolphsen, E.N. Jongewaard, X. Liu, F. Zhou
SLAC, Menlo Park, California, USA

The LCLS-II spare gun (Gun-2) design is largely based on the existing LCLS-II gun (Gun-1), in which there is significant captured dark current (DC) that originates on the high field copper surface near the cathode plug gap opening. To help suppress DC, the Gun-2 cathode and anode noses and the cathode plug opening are elliptically shaped to minimize the peak surface field for a given cathode gradient. Stainless steel (SS) cathode and anode inserts are used in Gun-2 to further reduce dark current. The RF simulations were performed using a model that includes all the 3D features. The thermal and structural analyses were done to investigate the effects of the air pressure and RF heating. The multi-physics simulation results provided the information needed to compute the overall frequency change from the basic 2D model to the nominal frequency during operation. The Gun-2 cathode-to-anode gap distance will be made 1 mm longer than the nominal gap with the expectation that less than 1 mm will be machined off to meet the target frequency. In this paper, the Gun-2 frequency correction calculations are presented, and the cathode-to-anode gap determination is discussed.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA10

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Received ※ 30 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022

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WEPA19

HE Production Update at JLab - Introducing an Enhanced Nitrogen Purge for Clean String Assembly

cavity, controls, cryomodule, hardware

659

P.D. Owen
JLab, Newport News, Virginia, USA

A major limitation to cryomodule performance is field emission caused by particulates within the superconducting cavities. To reduce contamination of the inner surfaces during assembly in a cleanroom, the whole string can be connected to a purge system, which maintains a constant overpressure of dry, clean nitrogen gas. Following successes of similar systems at XFEL and Fermilab, Jefferson Lab followed this example for the production of LCLS-II HE cryomodules. Implementing this system required new procedures, infrastructure, and hardware, as well as significant testing of the system before production began. This paper will summarize the implemented controls and procedures, including lessons learned from Fermilab, as well as the results of mock-up tests. Based on the latter, the system was used to assemble the first article string in April 2022, and was also used during a rework required due to issues with cold FPC ceramics two months later. The benefits of using a purge system with regards to procedure, time savings, and added flexibility for potential rework have already proven to provide a significant improvement for the production of LCLS-II-HE cryomodules at Jefferson Lab.

Poster WEPA19 [1.538 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA19

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Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 21 August 2022

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WEPA20

High-Gradient Wien Spin Rotators at Jefferson Lab

electron, operation, high-voltage, gun

662

G.G. Palacios Serrano, P.A. Adderley, J.M. Grames, C. Hernandez-Garcia, M. Poelker
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Nuclear physics experiments performed in the Contin-uous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory (JLab) require spin manipulation of electron beams. Two Wien spin rotators in the injector keV region are essential at CEBAF to establish longitudinal polarization at the end station target, and to flip the polarization direction by π rad to rule out false asymmetries. In a Wien filter, the homogeneous and independent electric and magnetic fields, along with the velocity vectors of the electrons that traverse it, form a mutually orthogonal system. The magnitude of the electrostatic field, established by biasing two highly-polished elec-trodes, defines the desired spin angle at the target yet deviates the beam trajectory due to the Lorentz force. The beam trajectory in the Wien is then re-established by adjusting the magnetic field, induced by an electromag-net encasing the device vacuum chamber. This contribu-tion describes the evolution design and high voltage testing of Wien filters for spin manipulation at increased beam energies in the keV injector region, required by high precision parity violation experiments like MOLLER.

Poster WEPA20 [1.434 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA20

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Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 05 September 2022

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WEPA55

Applications of Machine Automation with Robotics and Computer Vision in Cleanroom Assemblies

controls, SRF, cavity, operation

756

A. Liu, J.R. Callahan, E. Gomez, S.M. Milller, W. Si
Euclid TechLabs, Solon, Ohio, USA

Funding: This work is supported by the US DOE SBIR program under contract number DE-SC0021736.
Modern linear particle accelerators use superconducting radio frequency (SRF) cavities for achieving extremely high-quality factors (Q) and higher beam stability. The assembly process of the system, although with a much more stringent cleanness requirement, is very similar to the ultrahigh vacuum (UHV) system operation procedure. Humans, who are conventionally the operators in this procedure, can only avoid contaminating the system by wearing proper sterile personal protection equipment to avoid direct skin contact with the systems, or dropping particulates. However, humans unavoidably make unintentional mistakes that can contaminate the environment: cross contamination of the coverall suits during wearing, slippage of masks or goggles, damaged gloves, and so forth. Besides, humans are limited when operating heavy weights, which may lead to incorrect procedures, or even worse, injury. In this paper, we present our recent work on a viable and cost-effective machine automation system composed of a robotic arm and a computer vision system for the assembly process in a cleanroom environment, for example for SRF string assemblies, and more.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA55

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Received ※ 30 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 12 August 2022

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WEPA56

Encapsulation of Photocathodes Using High Power Pulsed RF Sputtering of hBN

cathode, simulation, electron, ion-effects

760

A. Liu, J.R. Callahan, S. Poddar
Euclid TechLabs, Solon, Ohio, USA
J.P. Biswas, M. Gaowei
BNL, Upton, New York, USA

Funding: This work is supported by the US DOE SBIR program under contract number DE-SC0021511 and DE-SC0020573.
Photocathodes of various materials are used in photoinjectors for generating photoelectron beams. Of particular interest are the alkali antimonides because of their ultra-high quantum efficiency (QE) and relatively low requirements for growth, and metallic materials such as Cu and Mg which have lower QE but are easier to maintain and have longer lifetime. The biggest challenge of using the alkali antimonide photocathode is that it has an extremely stringent requirement on vacuum and is destroyed rapidly by residual air in the system, while exposure of Mg and Cu in air also impacts the photocathode performance because of the oxidation. The photocathode can be protected against harmful gas molecules by using one or two monolayers of a 2D material such as graphene or hexagonal boron nitride (hBN). Furthermore, hBN monolayers even have the potential to improve the QE of the photocathode when working as the encapsulation thin-film. In this paper, we will discuss the feasibility of coating a photocathode with hBN by high power pulsed RF sputtering by using metallic photocathodes as examples, and compare the performance with encapsulated photocathodes with transferred hBN thin-films.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA56

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Received ※ 31 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 10 August 2022

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WEPA72

Analysis of Beam-Induced Heating of the NSLS-II Ceramic Vacuum Chambers

impedance, kicker, simulation, injection

799

G. Bassi, C. Hetzel, A. Khan, B.N. Kosciuk, M. Seegitz, V.V. Smaluk, R.J. Todd
BNL, Upton, New York, USA
A. Blednykh
Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA

We discuss impedance calculations and related heating issues of the titanium-coated NSLS-II kicker ceramic chambers, with the titanium coating thickness estimated from in situ measurements of the end-to-end resistance of each chamber. Power densities are calculated on the titanium coating to allow for thermal analysis with the code ANSYS and comparison with heating measurements. The impedance analysis is performed using a realistic model of the ceramic complex permittivity, and special consideration is given to the impedance calculation in the limit of zero titanium coating thickness.

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA72

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Received ※ 03 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 26 September 2022

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WEPA73

Numerical Studies of Geometric Impedance at NSLS-II with GdfidL and ECHO3D

impedance, simulation, wakefield, radiation

802

A. Khan, M. Seegitz, V.V. Smaluk, R.J. Todd
BNL, Upton, New York, USA
A. Blednykh
Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA

The beam intensity in future low-emittance light sources with small gap wigglers and undulators is limited by the effects of short-range wakefields, especially by the beam-induced heating of the vacuum chamber components. We have cross-checked two electromagnetic solvers, GdfidL and ECHO3D, by simulation of the short-range wakefields in the NSLS-II flange absorber and in the taper transition of an in-vacuum undulator to test the consistency and precision of the wakefield models.

Poster WEPA73 [1.057 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA73

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Received ※ 01 August 2022 — Revised ※ 03 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 01 September 2022

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WEPA85

Localized Beam Induced Heating Analysis of the EIC Vacuum Chamber Components

kicker, electron, simulation, injection

833

M.P. Sangroula, D.M. Gassner, C.J. Liaw, C. Liu, P. Thieberger
BNL, Upton, New York, USA
J.R. Bellon, A. Blednykh, C. Hetzel, S. Verdú-Andrés
Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy
The Electron-Ion Collider (EIC), to be built at Brookhaven National Laboratory (BNL), is designed to provide a high electron-proton luminosity of 10³⁴ cm^-2 s^-1. One of the challenging tasks for the Electron Storage Ring (ESR) is to operate at an average beam current of 2.5 A within 1160 bunches with a ~ 7 mm bunch length. The Hadron Storage Ring (HSR) will accumulate an average current of 0.69 A within 290 bunches with a 60 mm bunch length. Both rings require the impedance budget simulations. The intense e-beam in the ESR can lead to the overheating of vacuum chamber components due to localized metallic losses. This paper focuses on the beam-induced heating analysis of the ESR vacuum components including bellows, gate-valve, and BPM. To perform thermal analysis, the resistive loss on individual components is calculated with CST and then fed to ANSYS to determine the temperature distribution on the vacuum components. Preliminary results suggest that active water cooling will be required for most of the ESR vacuum components. Similar approach is applied to the HSR vacuum components. The thermal analysis of the HSR stripline injection kicker is presented.

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA85

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Received ※ 03 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 10 September 2022

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THYE4

Development of an Ultra-Low Vibration Cryostat Based on a Closed-Cycle Cryocooler

radiation, cryogenics, instrumentation, synchrotron

874

R.W. Roca
Illinois Institute of Technology, Chicago, Illinois, USA
E.W. Knight, R.A. Kostin, Y. Zhao
Euclid TechLabs, Solon, Ohio, USA

Low temperature and low vibration cryostats are useful in a variety of applications such as x-ray diffraction, quantum computing, x-ray monochromators and cryo-TEMs. In this project, we explore an ultra-low vibration cryostat with the cooling provided by a closed cycle cryocooler. Closed-cycle cryocoolers inevitably introduce vibrations into the system, and in this project, flexible copper braiding was used to decouple vibrations and provide cooling at the same time. In order to develop the cryostat, capacity map of a two stage Sumitomo cryocooler was measured as well as vibration transmission through different copper braids using an IR interferometer. This paper covers the capacity map and vibration measurements in the first prototype.

Slides THYE4 [4.989 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYE4

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Received ※ 16 July 2022 — Revised ※ 10 August 2022 — Accepted ※ 20 August 2022 — Issue date ※ 12 September 2022

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THZE3

An Electrodeless Diamond Beam Monitor

electron, experiment, detector, controls

904

S.V. Kuzikov, P.V. Avrakhov, C.-J. Jing, E.W. Knight
Euclid TechLabs, Solon, Ohio, USA
D.S. Doran, C.-J. Jing, J.G. Power, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid Beamlabs, Bolingbrook, USA

Funding: The work was supported by DoE SBIR grant #DE-SC0019642.
Being a wide-band semiconductor, diamond can be used to measure the flux of passing particles based on a particle-induced conductivity effect. We recently demonstrated a diamond electrodeless electron beam halo monitor. That monitor was based on a thin piece of diamond (blade) placed in an open high-quality microwave resonator. The blade partially intercepted the beam. By measuring the change in RF properties of the resonator, one could infer the beam parameters. At Argonne Wakefield Accelerator we have tested 1D and 2D monitors. To enhance the sensitivity of our diamond sensor, we proposed applying a bias voltage to the diamond which can sustain the avalanche of free carriers. In experiment carried out with 120 kV, ~1 µA beam we showed that the response signal for the avalanche monitor biased with up to 5 kV voltage can be up to 100 times larger in comparison with the signal of the same non-biased device.

Slides THZE3 [4.257 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THZE3

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Received ※ 20 July 2022 — Revised ※ 28 July 2022 — Accepted ※ 06 August 2022 — Issue date ※ 08 August 2022

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