IPAC2021 - List of Keywords (high-voltage)

Paper	Title	Other Keywords	Page
MOPAB324	High Voltage Design and Evaluation of Wien Filters for the CEBAF 200 keV Injector Upgrade	electron, vacuum, GUI, simulation	1000
	G.G. Palacios Serrano, P.A. Adderley, J.F. Benesch, D.B. Bullard, J.M. Grames, C. Hernandez-Garcia, A.S. Hofler, D. Machie, M. Poelker, M.L. Stutzman, R. Suleiman JLab, Newport News, Virginia, USA H. Baumgart, G.G. Palacios Serrano ODU, Norfolk, 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. High-energy nuclear physics experiments at the Jefferson Lab Continuous Electron Beam Accelerator Facility (CEBAF) require highly spin-polarization electron beams, produced from strained super-lattice GaAs photocathodes, activated to negative electron affinity in a photogun operating at 130 kV dc. A pair of Wien filter spin rotators in the injector defines the orientation of the electron beam polarization at the end station target. An upgrade of the CEBAF injector to better support the upcoming MOLLER experiment requires increasing the electron beam energy to 200 keV, to reduce unwanted helicity correlated intensity and position systematics and provide precise control of the polarization orientation. Our contribution describes design, fabrication and testing of the high voltage system to upgrade the Wien spin rotator to be compatible with the 200 keV beam. This required Solidworks modeling, CST and Opera electro- and magnetostatic simulations, upgrading HV vacuum feedthroughs, and assembly techniques for improving electrode alignment. The electric and magnetic fields required by the Wien condition and the successful HV characterization under vacuum conditions are also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB324
About •	paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 29 August 2021
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TUPAB033	Photocathode Stress Test Bench at INFN LASA	cathode, laser, gun, electron	1413
	D. Sertore, D. Giove, G. Guerini Rocco, L. Monaco INFN/LASA, Segrate (MI), Italy A. Bacci, F. Canella, S. Cialdi, I. Drebot, D. Giannotti, L. Serafini INFN-Milano, Milano, Italy D. Cipriani, E. Suerra Università degli Studi di Milano, Milano, Italy G. Galzerano POLIMI, Milano, Italy
	In the framework of the preparatory activities to the BriXSino project, a test bench for testing Cs₂Te photocathode at 100 MHz laser repetition rate has been installed at INFN LASA. This high repetition operation mode is foreseen to be the base operation mode of BriXSino and a qualification of the Cs₂Te photocathodes is a key component. While we are not at full specification due to the limited HV of the present DC gun, we discuss the status of the test bench and the initial results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB033
About •	paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 19 August 2021
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TUPAB182	The Electron Cooling for High Energy	electron, gun, collider, experiment	1831
	V.B. Reva, E.A. Bekhtenev, O.V. Belikov, M.I. Bryzgunov, A.V. Bubley, V.A. Chekavinskiy, A.P. Denisov, M.G. Fedotov, A.D. Goncharov, K. Gorchakov, V.C. Gosteyev, I.A. Gusev, G.V. Karpov, M.N. Kondaurov, V.R. Kozak, N.S. Kremnev, V.M. Panasyuk, V.V. Parkhomchuk, A.V. Petrozhitskii, D.N. Pureskin, A.A. Putmakov, D.V. Senkov, K.S. Shtro, D.N. Skorobogatov, R.V. Vakhrushev, A.A. Zharikov BINP SB RAS, Novosibirsk, Russia
	The project of new accelerator complex NICA relating to nuclear and hadron physics require a more powerful longitudinal and transverse cooling that stimulates searching new technical solutions. The new accelerator complex NICA is designed at the Joint Institute for Nuclear Research (JINR, Dubna, Russia) to do experiment with ion-ion and ion-proton collision in the energy range 1-4.5 GeV/u for studying the properties of dense baryonic matter at extreme values of temperature and density with planned luminosity 10²⁷ cm^-2s^-1. This value can be obtained with help of very short bunches with small transverse size. This beam quality can be realized with help of stochastic and electron cooling at energy of the physics experiment. The electron cooling system on 2.5 MeV consists of two coolers, which cool both ion beams simultaneously. The Budker Institute of Nuclear Physics (BINP SB RAS) has already built and commissioned the electron cooling system for the NICA booster, and now it develops the high voltage electron cooling system for the collider. The article describes the construction and status of the cooler development.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB182
About •	paper received ※ 18 May 2021 paper accepted ※ 22 June 2021 issue date ※ 11 August 2021
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TUPAB355	Design and Implementation of a Production Model Bias Tee	multipactoring, MMI, cavity, linac	2339
	T.L. Larter, E. Gutierrez, S.H. Kim, D.G. Morris, J.T. Popielarski, T. Xu, S. Zhao FRIB, East Lansing, Michigan, USA
	Funding: This work is supported by the US Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University. The Facility for Rare Isotope Beams (FRIB) includes two types of half wave SC resonators (HWR) operating at 322MHz. The fundamental power couplers used to transmit RF power into the HWRs commonly suffer from multipacting which can result in long conditioning times. A bias tee can be used to apply a high voltage to the couplers to help alleviate multipacting. A production version of the bias tee was commissioned for use at FRIB. The bias tee went through several design revisions to diagnose and correct thermal dissipation issues. This paper will discuss details of design and challenges faced during production validation of the bias tee.
	Poster TUPAB355 [0.630 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB355
About •	paper received ※ 19 May 2021 paper accepted ※ 28 May 2021 issue date ※ 12 August 2021
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TUPAB357	Development of the X-Band Megawatt-Class Coaxial Magnetrons	linac, radiation, electron, experiment	2346
	J.Y. Liu, H.B. Chen, Y.S. Han, J. Shi, C.-X. Tang, C.J. Wang, J. Wang, H. Zha TUB, Beijing, People’s Republic of China
	X-band coaxial magnetrons are preferred for industrial and medical accelerators owing to the compact size, low cost and high efficiency. A conditioning and high power test stand for X-band magnetrons has been built in Tsinghua University. Two X-band magnetrons named "MGT-1#" and "MGT-2#" were tested at this stand. The maximum anode currents of both magnetrons reached 100 A after the conditioning process. Maximum peak output power of 1.71 MW and 1.89 MW was achieved for "MGT-1#" and "MGT-2#", respectively. The efficiencies of the two magnetrons are both about 50%.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB357
About •	paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 28 August 2021
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TUPAB362	Physical Design of Electrostatic Deflector in CSNS Muon Source	simulation, positron, emittance, operation	2360
	Y.W. Wu, S. Li, J.Y. Tang, X. Wu IHEP, Beijing, People’s Republic of China C.D. Deng, Y. Hong DNSC, Dongguan, People’s Republic of China Y.Q. Liu IHEP CSNS, Guangdong Province, People’s Republic of China
	CSNS will build a muon source at the end of the RTBT. In the current design, the muon source propose two schemes, namely the baseline scheme and the baby scheme. High voltage electrostatic deflectors (ESD) are used to deflect the beam in the two schemes. A three-channel ESD with 400 kV HV is employed in the baseline scheme and a 210 kV dual-channel ESD in the simplified scheme. According to physical requirements, the electric field concentration factor is introduced, and the electrode of ESD is theoretically designed. 2D and 3D simulations are carried out to analyze the characteristics of electric field distribution by OPERA. The geometry of the electrodes also met the requirements of electric field uniformity, high voltage resistance and mechanical strength at the same time. In the baseline scheme and the baby scheme, the ESD electric field concentration factors are 1.36 and 1.53, and the maximum electric field is 6.78MV/m and 4.6MV/m, respectively. The design meets the requirements and is reasonably feasible.
	Poster TUPAB362 [2.214 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB362
About •	paper received ※ 13 May 2021 paper accepted ※ 09 June 2021 issue date ※ 22 August 2021
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WEPAB092	Redesign of the Jefferson Lab -300 kV DC Photo-Gun for High Bunch Charge Operations	cathode, gun, simulation, electron	2802
	S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft, G.G. Palacios Serrano ODU, Norfolk, Virginia, USA J.F. Benesch, J.R. Delayen, C. Hernandez-Garcia, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman JLab, Newport News, Virginia, USA
	Funding: The U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177, JSA initiatives fund program and Laboratory Directed Research and Development program. Production of high bunch charge beams for the Electron-Ion Collider (EIC) is a challenging task. High bunch charge (a few nC) electron beam studies at Jefferson Lab using an inverted insulator DC high voltage photo-gun showed evidence of space charge limitations starting at 0.3 nC, limiting the maximum delivered bunch charge to 0.7 nC for beam at -225 kV, 75 ps (FWHM) pulse width, and 1.64 mm (rms) laser spot size. The low extracted charge is due to the modest longitudinal electric field (Ez) at the photocathode leading to beam loss at the anode and downstream beam pipe. To reach the few nC high bunch charge goal, and to correct the beam deflection exerted by the non-symmetric nature of the inverted insulator photo-gun the existing photo-gun was modified. This contribution discusses the electrostatic design of the modified photo-gun obtained using CST Studio Suite’s electromagnetic field solver. Beam dynamics simulations performed using General Particle Tracer (GPT) with the resulting electrostatic field map obtained from the modified electrodes confirmed the validity of the new design.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB092
About •	paper received ※ 20 May 2021 paper accepted ※ 02 June 2021 issue date ※ 17 August 2021
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WEPAB105	Simulating Electron Impact Ionization Using a General Particle Tracer (GPT) Custom Element	electron, simulation, gun, cathode	2843
	J.T. Yoskowitz, G.A. Krafft ODU, Norfolk, Virginia, USA J.M. Grames JLab, Newport News, Virginia, USA G.R. Montoya Soto Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico C.A. Valerio ECFM-UAS, Culiacan, Sinaloa, Mexico S.B. van der Geer Pulsar Physics, Eindhoven, The Netherlands
	Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177, Consejo Nacional de Ciencia y Tecnología (CONACYT). A new C++ custom element has been developed with the framework of General Particle Tracer (GPT) to simulate electron impact ionization of residual gas molecules. The custom element uses Monte-Carlo routines to determine both the ion production rate and the secondary electron kinetic energy based on user-defined gas densities and theoretical values for the ionization cross section and the secondary electron differential cross section. It then uses relativistic kinematics to track the secondary electron, the scattered electron, and the newly formed ion after ionization. The ion production rate and the secondary electron energy distribution determined by the custom element have been benchmarked against theoretical calculations and against simulations made using the simulation package IBSimu. While the custom element was originally built for particle accelerator simulations, it is readily extensible to other applications. The custom element will be described in detail and examples of applications at the Thomas Jefferson National Accelerator Facility will be presented for ion production in a DC high voltage photo-gun.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB105
About •	paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 19 August 2021
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WEPAB190	DC Break Design for a 2.45 GHz ECR Ion Source	GUI, site, ECR, simulation	3064
	M.S. Dmitriyev, M.V. Dyakonov, S.A. Tumanov, M.I. Zhigailova MEPhI, Moscow, Russia
	New 2.45 GHz Electron Cyclotron Resonance Ion Source (ECRIS) is under development at NRNU MEPhI. The transmission line is designed for transmitting the microwave power into the ECRIS. A DC break up to 80 kV was designed for the electrical insulation between the microwave supply system and the plasma chamber applied to high DC voltage. Current study considers the investigation results as well as the optimization of numerical simulations of the 2.45 GHz DC break with low losses and low emission into the surrounding space.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB190
About •	paper received ※ 20 May 2021 paper accepted ※ 08 June 2021 issue date ※ 30 August 2021
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WEPAB344	Studies for Mitigating Flashover of CERN-LHC Dilution Kicker Magnets	electron, kicker, simulation, vacuum	3498
	A.M. Loebner, M.J. Barnes, W. Bartmann, C. Bracco, L. Ducimetière, V. Namora, V. Senaj CERN, Geneva 23, Switzerland
	The LHC beam dump system is used for extracting beam from the LHC and, as such, is a safety critical system whose proper functionality must be assured. Dilution kicker magnets (MKBs) sweep the extracted beam over the cross-sectional area of a dump block as the energy density would otherwise be too high and damage the block. In 2018, a high voltage flashover occurred in a vertical MKB (MKBV) vacuum tank, during a beam dump, which resulted in non-ideal sweep of the beam over the block. The location of the flashover could not be identified during a subsequent inspection of the magnet. Hence, electrical field simulations have been carried out to identify potentially critical regions, to determine the most probable region of the flashover. One potentially critical region is a rectangular beam pipe (RBP) between the end of the tank and the MKBV magnet, whose purpose is to reduce plasma propagation to the adjacent tank in the event of a flashover. Mitigating measures were studied and are reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB344
About •	paper received ※ 16 May 2021 paper accepted ※ 06 July 2021 issue date ※ 22 August 2021
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WEPAB418	The Power Supply System for 10 MeV & 20 kW Industry Irradiation Facility	power-supply, gun, radiation, electron	3678
	F.L. Shang, L. Shang USTC/NSRL, Hefei, Anhui, People’s Republic of China
	Funding: Work supported by National Key R&D Program of China 2018YFF0109204 The 10 MeV and 20 kW industry irradiation facility (IIF) has been designed by National Synchrotron Radiation Laboratory (NSRL) for years. Modular design power supplies are employed for the latest version, depend on the performance of these power supplies with high precision and high stability, the operating reliability of the IIF has been greatly improved.
	Poster WEPAB418 [0.991 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB418
About •	paper received ※ 15 May 2021 paper accepted ※ 23 June 2021 issue date ※ 13 August 2021
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THPAB178	The SIS100 Extraction and Emergency Kicker Magnet System	vacuum, kicker, extraction, HOM	4115
	J.H. Hottenbacher, K. Dunkel, M. Eisengruber, M. Osemann, A. Padvi, C. Piel RI Research Instruments GmbH, Bergisch Gladbach, Germany S. Heberer, I.J. Petzenhauser GSI, Darmstadt, Germany
	The extraction and emergency kicker system for SIS100 is a bipolar kicker system that allows for an in-situ choice between two directions: extraction to the experiments or to the beam dump. For that, both magnet ends are connected to a PFN each which are being charged simultaneously up to 80kV continuously. Due to the static HV operation, different to usually in other pulsed kicker systems, not only displacement current is flowing in the ferrite material. After less than 1s, the ferrite material is nearly field-free and the E-field is concentrated in the surrounding ceramic magnet clamp mechanism. As the field is further concentrated in gaps between ceramic and metallic parts, the HV layout of the magnet is a critical design task. As a magnetic field homogeneity of ±1% is required, special shaping of the coil is required as found during iterative 3D field simulations. The kicker chamber is designed to operate at a pressure level of 3·10^-11 mBar. As one 3 meter-chamber contains 3.5 m² ferrite surface, careful vacuum heat treatment of the ferrite is required to reach this pressure level. The paper will describe design principles for HV and UHV and effects found by 3D modeling.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB178
About •	paper received ※ 18 May 2021 paper accepted ※ 28 July 2021 issue date ※ 26 August 2021
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THPAB252	Machine Learning for Improved Availability of the SNS Klystron High Voltage Converter Modulators	operation, klystron, controls, real-time	4303
	G.C. Pappas ORNL RAD, Oak Ridge, Tennessee, USA D. Lu ORNL, Oak Ridge, Tennessee, USA M. Schram JLab, Newport News, Virginia, USA D.L. Vrabie PNNL, Richland, Washington, USA
	Funding: SNS/ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy Beam availability has increased at the SNS, however, the targeted availability is greater than 95 %, while the SNS has failed to meet lower targets in the past. The HVCM used to power the linac klystrons have been one source of lost beam time and was chosen to explore using AI/ML techniques to improve reliability. Among the possibilities being explored are automating the tuning of HVCMs and predicting component failures such as capacitor aging, rectifier assemblies containing hundreds of diodes, and insulating oil degradation. The methodology pursued includes data cleaning, de-noising, post-analysis data labeling, and machine learning model development. We explore using Long Short-Term Memory and autoencoders for anomaly detection and prognostication used to schedule maintenance. We evaluate the use of model regularizers and constraints to improve the performance of the model and investigate methods to estimate the uncertainty of the models to provide a robust prediction with statistical interoperability. This paper describes the operational experience and known failures of the HVCMs and the proposed ML methodology and the preliminary results of training the AI/ML algorithms. * G. Dodson, Approach to Reliable Operations, 26-Dodson_Approach to Reliable Operation-r1.pdf, Feb., 2010.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB252
About •	paper received ※ 18 May 2021 paper accepted ※ 14 July 2021 issue date ※ 29 August 2021
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THPAB340	Sub-Nanosecond Switching of HV SiC MOS Transistors for Impact Ionisation Triggering	plasma, kicker, electron, laser	4454
	V. Senaj, T. Kramer, A.A. del Barrio Montañés CERN, Geneva 23, Switzerland M. Sack KIT, Karlsruhe, Germany
	Pulse generators with multi kV/kA pulses are necessary for the particle accelerator environment for beam transfer magnets. Traditionally these generators are using thyratrons - until recently the only switches capable of switching such pulses within tens of ns. There is a strong demand to replace thyratrons with semiconductor switches to avoid their future obsolescence. Very promising candidates are components from the family of fast ionization dynistors triggered by impact ionization. Their sub-nanosecond switching time and extreme current densities can provide performances superior to that of thyratrons. Recent investigations showed that impact ionization triggering is feasible also in cheap industrial thyristors. The main issue is the generation of triggering pulses with slew rates in the multi kV/ns region and with the required output current for charging the parasitic capacitance of the thyristor. We present an approach of generating > 1 kV/ns pulses by ultra-boosted gate driving of HV SiC MOS transistors. We found that the MOS lifetime under these extreme triggering conditions can still reach more than 10⁸ pulses, enough for kicker generator applications.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB340
About •	paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 27 August 2021
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THPAB341	TiN Metalizing and Coating for Multi-Megawatt RF Vacuum Windows	Windows, electron, vacuum, multipactoring	4457
	M.L. Neubauer, A. Dudas, R.P. Johnson Muons, Inc, Illinois, USA
	Coatings on microwave windows and high-voltage ceramics are required to eliminate secondary electron emission (SEE), which initiates multipactoring discharge causing local heating and ceramic failures due to cracking and loss of vacuum. The region surrounding the triple junction (ceramic+metal+vacuum) is the primary source of free electrons and in microwave windows and high-voltage ceramics. This region is located at the metalizing and braze joint of the ceramic support structure making the vacuum seal. On very large microwave windows typically at low frequencies, this critical region is difficult to coat by the traditional techniques of sputter coating anti-multipactoring titanium nitride or other materials. The novel processes proposed here include a means for applying and controlling the thickness of titanium nitride both in the metallizing (controlling the source) and on the surface of the window, eliminating SEE and the multipactoring discharge.
	Poster THPAB341 [0.845 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB341
About •	paper received ※ 23 May 2021 paper accepted ※ 21 July 2021 issue date ※ 01 September 2021
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Paper

Title

Other Keywords

Page

MOPAB324

High Voltage Design and Evaluation of Wien Filters for the CEBAF 200 keV Injector Upgrade

electron, vacuum, GUI, simulation

1000

G.G. Palacios Serrano, P.A. Adderley, J.F. Benesch, D.B. Bullard, J.M. Grames, C. Hernandez-Garcia, A.S. Hofler, D. Machie, M. Poelker, M.L. Stutzman, R. Suleiman
JLab, Newport News, Virginia, USA
H. Baumgart, G.G. Palacios Serrano
ODU, Norfolk, 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.
High-energy nuclear physics experiments at the Jefferson Lab Continuous Electron Beam Accelerator Facility (CEBAF) require highly spin-polarization electron beams, produced from strained super-lattice GaAs photocathodes, activated to negative electron affinity in a photogun operating at 130 kV dc. A pair of Wien filter spin rotators in the injector defines the orientation of the electron beam polarization at the end station target. An upgrade of the CEBAF injector to better support the upcoming MOLLER experiment requires increasing the electron beam energy to 200 keV, to reduce unwanted helicity correlated intensity and position systematics and provide precise control of the polarization orientation. Our contribution describes design, fabrication and testing of the high voltage system to upgrade the Wien spin rotator to be compatible with the 200 keV beam. This required Solidworks modeling, CST and Opera electro- and magnetostatic simulations, upgrading HV vacuum feedthroughs, and assembly techniques for improving electrode alignment. The electric and magnetic fields required by the Wien condition and the successful HV characterization under vacuum conditions are also presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB324

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paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 29 August 2021

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TUPAB033

Photocathode Stress Test Bench at INFN LASA

cathode, laser, gun, electron

1413

D. Sertore, D. Giove, G. Guerini Rocco, L. Monaco
INFN/LASA, Segrate (MI), Italy
A. Bacci, F. Canella, S. Cialdi, I. Drebot, D. Giannotti, L. Serafini
INFN-Milano, Milano, Italy
D. Cipriani, E. Suerra
Università degli Studi di Milano, Milano, Italy
G. Galzerano
POLIMI, Milano, Italy

In the framework of the preparatory activities to the BriXSino project, a test bench for testing Cs₂Te photocathode at 100 MHz laser repetition rate has been installed at INFN LASA. This high repetition operation mode is foreseen to be the base operation mode of BriXSino and a qualification of the Cs₂Te photocathodes is a key component. While we are not at full specification due to the limited HV of the present DC gun, we discuss the status of the test bench and the initial results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB033

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

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TUPAB182

The Electron Cooling for High Energy

electron, gun, collider, experiment

1831

V.B. Reva, E.A. Bekhtenev, O.V. Belikov, M.I. Bryzgunov, A.V. Bubley, V.A. Chekavinskiy, A.P. Denisov, M.G. Fedotov, A.D. Goncharov, K. Gorchakov, V.C. Gosteyev, I.A. Gusev, G.V. Karpov, M.N. Kondaurov, V.R. Kozak, N.S. Kremnev, V.M. Panasyuk, V.V. Parkhomchuk, A.V. Petrozhitskii, D.N. Pureskin, A.A. Putmakov, D.V. Senkov, K.S. Shtro, D.N. Skorobogatov, R.V. Vakhrushev, A.A. Zharikov
BINP SB RAS, Novosibirsk, Russia

The project of new accelerator complex NICA relating to nuclear and hadron physics require a more powerful longitudinal and transverse cooling that stimulates searching new technical solutions. The new accelerator complex NICA is designed at the Joint Institute for Nuclear Research (JINR, Dubna, Russia) to do experiment with ion-ion and ion-proton collision in the energy range 1-4.5 GeV/u for studying the properties of dense baryonic matter at extreme values of temperature and density with planned luminosity 10²⁷ cm^-2s^-1. This value can be obtained with help of very short bunches with small transverse size. This beam quality can be realized with help of stochastic and electron cooling at energy of the physics experiment. The electron cooling system on 2.5 MeV consists of two coolers, which cool both ion beams simultaneously. The Budker Institute of Nuclear Physics (BINP SB RAS) has already built and commissioned the electron cooling system for the NICA booster, and now it develops the high voltage electron cooling system for the collider. The article describes the construction and status of the cooler development.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB182

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paper received ※ 18 May 2021 paper accepted ※ 22 June 2021 issue date ※ 11 August 2021

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TUPAB355

Design and Implementation of a Production Model Bias Tee

multipactoring, MMI, cavity, linac

2339

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

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

Poster TUPAB355 [0.630 MB]

DOI •

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

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

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TUPAB357

Development of the X-Band Megawatt-Class Coaxial Magnetrons

linac, radiation, electron, experiment

2346

J.Y. Liu, H.B. Chen, Y.S. Han, J. Shi, C.-X. Tang, C.J. Wang, J. Wang, H. Zha
TUB, Beijing, People’s Republic of China

X-band coaxial magnetrons are preferred for industrial and medical accelerators owing to the compact size, low cost and high efficiency. A conditioning and high power test stand for X-band magnetrons has been built in Tsinghua University. Two X-band magnetrons named "MGT-1#" and "MGT-2#" were tested at this stand. The maximum anode currents of both magnetrons reached 100 A after the conditioning process. Maximum peak output power of 1.71 MW and 1.89 MW was achieved for "MGT-1#" and "MGT-2#", respectively. The efficiencies of the two magnetrons are both about 50%.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB357

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paper received ※ 19 May 2021 paper accepted ※ 02 June 2021 issue date ※ 28 August 2021

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TUPAB362

Physical Design of Electrostatic Deflector in CSNS Muon Source

simulation, positron, emittance, operation

2360

Y.W. Wu, S. Li, J.Y. Tang, X. Wu
IHEP, Beijing, People’s Republic of China
C.D. Deng, Y. Hong
DNSC, Dongguan, People’s Republic of China
Y.Q. Liu
IHEP CSNS, Guangdong Province, People’s Republic of China

CSNS will build a muon source at the end of the RTBT. In the current design, the muon source propose two schemes, namely the baseline scheme and the baby scheme. High voltage electrostatic deflectors (ESD) are used to deflect the beam in the two schemes. A three-channel ESD with 400 kV HV is employed in the baseline scheme and a 210 kV dual-channel ESD in the simplified scheme. According to physical requirements, the electric field concentration factor is introduced, and the electrode of ESD is theoretically designed. 2D and 3D simulations are carried out to analyze the characteristics of electric field distribution by OPERA. The geometry of the electrodes also met the requirements of electric field uniformity, high voltage resistance and mechanical strength at the same time. In the baseline scheme and the baby scheme, the ESD electric field concentration factors are 1.36 and 1.53, and the maximum electric field is 6.78MV/m and 4.6MV/m, respectively. The design meets the requirements and is reasonably feasible.

Poster TUPAB362 [2.214 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB362

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paper received ※ 13 May 2021 paper accepted ※ 09 June 2021 issue date ※ 22 August 2021

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WEPAB092

Redesign of the Jefferson Lab -300 kV DC Photo-Gun for High Bunch Charge Operations

cathode, gun, simulation, electron

2802

S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft, G.G. Palacios Serrano
ODU, Norfolk, Virginia, USA
J.F. Benesch, J.R. Delayen, C. Hernandez-Garcia, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman
JLab, Newport News, Virginia, USA

Funding: The U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177, JSA initiatives fund program and Laboratory Directed Research and Development program.
Production of high bunch charge beams for the Electron-Ion Collider (EIC) is a challenging task. High bunch charge (a few nC) electron beam studies at Jefferson Lab using an inverted insulator DC high voltage photo-gun showed evidence of space charge limitations starting at 0.3 nC, limiting the maximum delivered bunch charge to 0.7 nC for beam at -225 kV, 75 ps (FWHM) pulse width, and 1.64 mm (rms) laser spot size. The low extracted charge is due to the modest longitudinal electric field (Ez) at the photocathode leading to beam loss at the anode and downstream beam pipe. To reach the few nC high bunch charge goal, and to correct the beam deflection exerted by the non-symmetric nature of the inverted insulator photo-gun the existing photo-gun was modified. This contribution discusses the electrostatic design of the modified photo-gun obtained using CST Studio Suite’s electromagnetic field solver. Beam dynamics simulations performed using General Particle Tracer (GPT) with the resulting electrostatic field map obtained from the modified electrodes confirmed the validity of the new design.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB092

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paper received ※ 20 May 2021 paper accepted ※ 02 June 2021 issue date ※ 17 August 2021

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WEPAB105

Simulating Electron Impact Ionization Using a General Particle Tracer (GPT) Custom Element

electron, simulation, gun, cathode

2843

J.T. Yoskowitz, G.A. Krafft
ODU, Norfolk, Virginia, USA
J.M. Grames
JLab, Newport News, Virginia, USA
G.R. Montoya Soto
Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
C.A. Valerio
ECFM-UAS, Culiacan, Sinaloa, Mexico
S.B. van der Geer
Pulsar Physics, Eindhoven, The Netherlands

Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177, Consejo Nacional de Ciencia y Tecnología (CONACYT).
A new C++ custom element has been developed with the framework of General Particle Tracer (GPT) to simulate electron impact ionization of residual gas molecules. The custom element uses Monte-Carlo routines to determine both the ion production rate and the secondary electron kinetic energy based on user-defined gas densities and theoretical values for the ionization cross section and the secondary electron differential cross section. It then uses relativistic kinematics to track the secondary electron, the scattered electron, and the newly formed ion after ionization. The ion production rate and the secondary electron energy distribution determined by the custom element have been benchmarked against theoretical calculations and against simulations made using the simulation package IBSimu. While the custom element was originally built for particle accelerator simulations, it is readily extensible to other applications. The custom element will be described in detail and examples of applications at the Thomas Jefferson National Accelerator Facility will be presented for ion production in a DC high voltage photo-gun.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB105

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paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 19 August 2021

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WEPAB190

DC Break Design for a 2.45 GHz ECR Ion Source

GUI, site, ECR, simulation

3064

M.S. Dmitriyev, M.V. Dyakonov, S.A. Tumanov, M.I. Zhigailova
MEPhI, Moscow, Russia

New 2.45 GHz Electron Cyclotron Resonance Ion Source (ECRIS) is under development at NRNU MEPhI. The transmission line is designed for transmitting the microwave power into the ECRIS. A DC break up to 80 kV was designed for the electrical insulation between the microwave supply system and the plasma chamber applied to high DC voltage. Current study considers the investigation results as well as the optimization of numerical simulations of the 2.45 GHz DC break with low losses and low emission into the surrounding space.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB190

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paper received ※ 20 May 2021 paper accepted ※ 08 June 2021 issue date ※ 30 August 2021

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WEPAB344

Studies for Mitigating Flashover of CERN-LHC Dilution Kicker Magnets

electron, kicker, simulation, vacuum

3498

A.M. Loebner, M.J. Barnes, W. Bartmann, C. Bracco, L. Ducimetière, V. Namora, V. Senaj
CERN, Geneva 23, Switzerland

The LHC beam dump system is used for extracting beam from the LHC and, as such, is a safety critical system whose proper functionality must be assured. Dilution kicker magnets (MKBs) sweep the extracted beam over the cross-sectional area of a dump block as the energy density would otherwise be too high and damage the block. In 2018, a high voltage flashover occurred in a vertical MKB (MKBV) vacuum tank, during a beam dump, which resulted in non-ideal sweep of the beam over the block. The location of the flashover could not be identified during a subsequent inspection of the magnet. Hence, electrical field simulations have been carried out to identify potentially critical regions, to determine the most probable region of the flashover. One potentially critical region is a rectangular beam pipe (RBP) between the end of the tank and the MKBV magnet, whose purpose is to reduce plasma propagation to the adjacent tank in the event of a flashover. Mitigating measures were studied and are reported in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB344

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paper received ※ 16 May 2021 paper accepted ※ 06 July 2021 issue date ※ 22 August 2021

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WEPAB418

The Power Supply System for 10 MeV & 20 kW Industry Irradiation Facility

power-supply, gun, radiation, electron

3678

F.L. Shang, L. Shang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

Funding: Work supported by National Key R&D Program of China 2018YFF0109204
The 10 MeV and 20 kW industry irradiation facility (IIF) has been designed by National Synchrotron Radiation Laboratory (NSRL) for years. Modular design power supplies are employed for the latest version, depend on the performance of these power supplies with high precision and high stability, the operating reliability of the IIF has been greatly improved.

Poster WEPAB418 [0.991 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB418

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paper received ※ 15 May 2021 paper accepted ※ 23 June 2021 issue date ※ 13 August 2021

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THPAB178

The SIS100 Extraction and Emergency Kicker Magnet System

vacuum, kicker, extraction, HOM

4115

J.H. Hottenbacher, K. Dunkel, M. Eisengruber, M. Osemann, A. Padvi, C. Piel
RI Research Instruments GmbH, Bergisch Gladbach, Germany
S. Heberer, I.J. Petzenhauser
GSI, Darmstadt, Germany

The extraction and emergency kicker system for SIS100 is a bipolar kicker system that allows for an in-situ choice between two directions: extraction to the experiments or to the beam dump. For that, both magnet ends are connected to a PFN each which are being charged simultaneously up to 80kV continuously. Due to the static HV operation, different to usually in other pulsed kicker systems, not only displacement current is flowing in the ferrite material. After less than 1s, the ferrite material is nearly field-free and the E-field is concentrated in the surrounding ceramic magnet clamp mechanism. As the field is further concentrated in gaps between ceramic and metallic parts, the HV layout of the magnet is a critical design task. As a magnetic field homogeneity of ±1% is required, special shaping of the coil is required as found during iterative 3D field simulations. The kicker chamber is designed to operate at a pressure level of 3·10^-11 mBar. As one 3 meter-chamber contains 3.5 m² ferrite surface, careful vacuum heat treatment of the ferrite is required to reach this pressure level. The paper will describe design principles for HV and UHV and effects found by 3D modeling.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB178

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paper received ※ 18 May 2021 paper accepted ※ 28 July 2021 issue date ※ 26 August 2021

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THPAB252

Machine Learning for Improved Availability of the SNS Klystron High Voltage Converter Modulators

operation, klystron, controls, real-time

4303

G.C. Pappas
ORNL RAD, Oak Ridge, Tennessee, USA
D. Lu
ORNL, Oak Ridge, Tennessee, USA
M. Schram
JLab, Newport News, Virginia, USA
D.L. Vrabie
PNNL, Richland, Washington, USA

Funding: SNS/ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
Beam availability has increased at the SNS, however, the targeted availability is greater than 95 %, while the SNS has failed to meet lower targets in the past. The HVCM used to power the linac klystrons have been one source of lost beam time and was chosen to explore using AI/ML techniques to improve reliability. Among the possibilities being explored are automating the tuning of HVCMs and predicting component failures such as capacitor aging, rectifier assemblies containing hundreds of diodes, and insulating oil degradation. The methodology pursued includes data cleaning, de-noising, post-analysis data labeling, and machine learning model development. We explore using Long Short-Term Memory and autoencoders for anomaly detection and prognostication used to schedule maintenance. We evaluate the use of model regularizers and constraints to improve the performance of the model and investigate methods to estimate the uncertainty of the models to provide a robust prediction with statistical interoperability. This paper describes the operational experience and known failures of the HVCMs and the proposed ML methodology and the preliminary results of training the AI/ML algorithms.
* G. Dodson, Approach to Reliable Operations, 26-Dodson_Approach to Reliable Operation-r1.pdf, Feb., 2010.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB252

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paper received ※ 18 May 2021 paper accepted ※ 14 July 2021 issue date ※ 29 August 2021

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THPAB340

Sub-Nanosecond Switching of HV SiC MOS Transistors for Impact Ionisation Triggering

plasma, kicker, electron, laser

4454

V. Senaj, T. Kramer, A.A. del Barrio Montañés
CERN, Geneva 23, Switzerland
M. Sack
KIT, Karlsruhe, Germany

Pulse generators with multi kV/kA pulses are necessary for the particle accelerator environment for beam transfer magnets. Traditionally these generators are using thyratrons - until recently the only switches capable of switching such pulses within tens of ns. There is a strong demand to replace thyratrons with semiconductor switches to avoid their future obsolescence. Very promising candidates are components from the family of fast ionization dynistors triggered by impact ionization. Their sub-nanosecond switching time and extreme current densities can provide performances superior to that of thyratrons. Recent investigations showed that impact ionization triggering is feasible also in cheap industrial thyristors. The main issue is the generation of triggering pulses with slew rates in the multi kV/ns region and with the required output current for charging the parasitic capacitance of the thyristor. We present an approach of generating > 1 kV/ns pulses by ultra-boosted gate driving of HV SiC MOS transistors. We found that the MOS lifetime under these extreme triggering conditions can still reach more than 10⁸ pulses, enough for kicker generator applications.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB340

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paper received ※ 18 May 2021 paper accepted ※ 01 July 2021 issue date ※ 27 August 2021

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THPAB341

TiN Metalizing and Coating for Multi-Megawatt RF Vacuum Windows

Windows, electron, vacuum, multipactoring

4457

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

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

Poster THPAB341 [0.845 MB]

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

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

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