IPAC2021 - List of Keywords (accelerating-gradient)

Paper	Title	Other Keywords	Page
MOPAB151	A Stable Drive Beam for High Gradient Dielectric Wakefield Acceleration	focusing, wakefield, acceleration, quadrupole	528
	T.J. Overton, Y.M. Saveliev, G.X. Xia Cockcroft Institute, Warrington, Cheshire, United Kingdom T.J. Overton, G.X. Xia The University of Manchester, Manchester, United Kingdom T.H. Pacey, Y.M. Saveliev STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: Science and Technology Funding Council (STFC) student grant. A high accelerating gradient, with stable beam transport, is necessary for the next generation of particle accelerators. Dielectric wakefield accelerators are a potential solution to this problem. In these proceedings, we present simulation studies of electron bunches in the self-wake regime inside a planar dielectric structure. This is analogous to driving beams in a dielectric wakefield accelerator. The transverse and longitudinal wake fields are investigated for dielectric plate gaps, various transverse beam sizes, and longitudinal bunch profiles. The effects of these on the stability of drive bunches, and acceleration of a witness bunch, are discussed in the context of electron bunches that can be produced with conventional linac RF technology.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB151
About •	paper received ※ 13 May 2021 paper accepted ※ 07 June 2021 issue date ※ 24 August 2021
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MOPAB155	Magnetic Breakdowns in Side-Coupled X-Band Accelerating Structures	impedance, coupling, simulation, cavity	540
	S.P. Antipov, P.V. Avrakhov, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA V.A. Dolgashev SLAC, Menlo Park, California, USA C. Jing Euclid Beamlabs, Bolingbrook, USA
	Funding: DOE SBIR Side coupled accelerating structures are popular in the industrial realizations of linacs due to their high shunt impedance and ease of tuning. We designed and fabricated a side-coupled X-band accelerating structure that achieved 133 MOhm/m shut impedance. This structure was fabricated out of two halves using a novel brazeless approach. The two copper halves are joined together using a stainless steel joining piece with knife edges that bite into copper. This structure had been tested at high power at SLAC National Accelerator Laboratory. The performance of the structure had been limited by magnetic breakdowns on the side-coupling cells. In this paper we will present results of the high gradient tests and after-test analysis. Scanning electron microscopy images show a typical magnetic-field induced breakdown.
	Poster MOPAB155 [1.069 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB155
About •	paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 01 September 2021
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MOPAB353	Design of a compact Ka-Band Mode Launcher for High-gradient Accelerators	cavity, coupling, simulation, quadrupole	1100
	G. Torrisi, G.S. Mauro, G. Sorbello INFN/LNS, Catania, Italy M. Behtouei, L. Faillace, B. Spataro, A. Variola INFN/LNF, Frascati, Italy V.A. Dolgashev SLAC, Menlo Park, California, USA L. Faillace, M. Migliorati Sapienza University of Rome, Rome, Italy M. Migliorati INFN-Roma1, Rome, Italy J.B. Rosenzweig UCLA, Los Angeles, California, USA G. Sorbello University of Catania, Catania, Italy
	In this work, we present the RF design of a table-top Ka-Band mode launcher operating at 35.98 GHz. The structure consists of a symmetrical 4-port WR28 rectangular-TE10-to-circular-TM01 mode converter that is used to couple a peak output RF power of 5 MW (pulse length up to 50 ns and repetition rate up to 100 Hz) in Ka-Band linear accelerator able to achieve very high accelerating gradients (up to 200 MV/m). Numerical simulations have been carried out with the 3D full-wave commercial simulator Ansys HFSS in order to obtain a preliminary tuning of the accelerating field flatness at the operating frequency f0=35.98 GHz. The main RF parameters, such as reflection coefficient, transmission losses, and conversion efficiency are given together with a verification of the field azimuthal symmetry which avoids dipole and quadrupole deflecting modes. To simplify future manufacturing, reduce fabrication costs, and also reduce the probability of RF breakdown, the proposed new geometry has "open" configuration. This geometry eliminates the flow of RF currents through critical joints and allows this device to be milled from metal blocks.
	Poster MOPAB353 [3.131 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB353
About •	paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 27 August 2021
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MOPAB391	Conduction Cooling Methods for Nb₃Sn SRF Cavities and Cryomodules	cavity, SRF, controls, simulation	1192
	N.A. Stilin, A.T. Holic, M. Liepe, R.D. Porter, J. Sears, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Rapid progress in the performance of Nb₃Sn SRF cavities during the last few years has made Nb₃Sn an energy efficient alternative to traditional Nb cavities, thereby initiating a fundamental shift in SRF technology. These Nb₃Sn cavities can operate at significantly higher temperatures than Nb cavities while simultaneously requiring less cooling power. This critical property enables the use of new, robust, turn-key style cryogenic cooling schemes based on conduction cooling with commercial cryocoolers. Cornell University has developed and tested a 2.6 GHz Nb₃Sn cavity assembly which utilizes such cooling methods. These tests have demonstrated stable RF operation at 10 MV/m and the measured thermal dynamics match what is found in numerical simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB391
About •	paper received ※ 20 May 2021 paper accepted ※ 10 June 2021 issue date ※ 17 August 2021
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MOPAB396	Measurements of Magnetic Field Penetration in Superconducting Materials for SRF Cavities	cavity, SRF, experiment, solenoid	1208
	I.H. Senevirathne, J.R. Delayen, A.V. Gurevich ODU, Norfolk, Virginia, USA J.R. Delayen, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	Funding: This work is supported by NSF Grants PHY-1734075 and PHY-1416051, and DOE Award DE-SC0010081 and DE-SC0019399 Superconducting radiofrequency (SRF) cavities used in particle accelerators operate in the Meissner state. To achieve high accelerating gradients, the cavity material should stay in the Meissner state under high RF magnetic field without penetration of vortices through the cavity wall. The field onset of flux penetration into a superconductor is an important parameter of merit of alternative superconducting materials other than Nb which can enhance the performance of SRF cavities. There is a need for a simple and efficient technique to measure the onset of field penetration into a superconductor directly. We have developed a Hall probe experimental setup for the measurement of the flux penetration field through a superconducting sample placed under a small superconducting solenoid magnet which can generate magnetic fields up to 500 mT. The system has been calibrated and used to measure different bulk and thin film superconducting materials. This system can also be used to study SIS multilayer coatings that have been proposed to enhance the vortex penetration field in Nb cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB396
About •	paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021
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MOPAB400	Development of Helium Vessel Welding Process for SNS PPU Cavities	cavity, proton, cryomodule, neutron	1212
	P. Dhakal, E. Daly, G.K. Davis, J.F. Fischer, N.A. Huque, K. Macha, P.D. Owen, K.M. Wilson, M. Wiseman JLab, Newport News, Virginia, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The Spallation Neutron Source Proton Power Upgrade cavities are produced by Research Instrument with all the cavity processing done at vendor sites with final chemistry applied to the cavity to be electropolishing. Cavities are delivered to Jefferson Lab, ready to be tested. One of the tasks to be completed before the arrival of production-ready PPU cavities is to develop a robust helium vessel welding protocol. We have successfully developed the process and applied it to three six-cell high beta cavities. Here, we present the summary of RF results, welding process development, and post helium vessel RF results.
	Poster MOPAB400 [1.313 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB400
About •	paper received ※ 18 May 2021 paper accepted ※ 26 May 2021 issue date ※ 01 September 2021
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TUPAB076	High-Gradient Breakdown Studies of an X-Band Accelerating Structure Operated in the Reversed Taper Direction	linac, linear-collider, klystron, collider	1543
	X.W. Wu, N. Catalán Lasheras, A. Grudiev, G. McMonagle, I. Syratchev, W. Wuensch CERN, Meyrin, Switzerland M. Boronat IFIC, Valencia, Spain A. Castilla, A.V. Edwards, W.L. Millar Lancaster University, Lancaster, United Kingdom
	The results of high-gradient tests of a tapered X-band traveling-wave accelerator structure powered in reversed direction are presented. Powering the tapered structure from the small aperture, normally output, at the end of the structure provides unique conditions for the study of gradient limits. This allows high fields in the first cell for a comparatively low input power and a field distribution that rapidly falls off along the length of the structure. A maximum gradient of 130 MV/m in the first cell at a pulse length of 100 ns was reached for an input power of 31.9 MW. Details of the conditioning and operation at high-gradient are presented. Various breakdown rate measurements were conducted at different power levels and rf pulse widths. The structure was standard T24 CLIC test structure and was tested in Xbox-3 at CERN.
	Poster TUPAB076 [1.077 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB076
About •	paper received ※ 19 May 2021 paper accepted ※ 12 July 2021 issue date ※ 12 August 2021
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TUPAB098	Recent Progress Toward a Conduction-Cooled Superconducting Radiofrequency Electron Gun	cavity, simulation, SRF, electron	1604
	O. Mohsen, N. Adams, V. Korampally, A. McKeown, D. Mihalcea, P. Piot, I. Salehinia, N. Tom Northern Illinois University, DeKalb, Illinois, USA R. Dhuley, M.G. Geelhoed, D. Mihalcea, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA P. Piot ANL, Lemont, Illinois, USA
	Funding: This work was supported by the US Department of Energy (DOE) under contract DE-SC0018367 High-repetition-rate electron sources have widespread applications. This contribution discusses the progress toward a proof-of-principle demonstration for a conduction-cooled electron source. The source consists of a simple modification of an elliptical cavity that enhances the field electric field at the photocathode surface. The source was cooled to cryogenic temperatures and preliminary measurements for the quality factor and accelerating field were performed. Additionally, we present future plans to improve the source along with simulated beam-dynamics performances.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB098
About •	paper received ※ 29 May 2021 paper accepted ※ 17 June 2021 issue date ※ 17 August 2021
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TUPAB155	Obtaining Accelerated Electron Bunch of High Quality in Plasma Wakefield Accelerator	plasma, wakefield, electron, acceleration	1744
	R.T. Ovsiannikov KhNU, Kharkov, Ukraine I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: "This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299." Earlier, high-gradient accelerating electrons of a relativistic beam was demonstrated. However, due to dynamic processes in the plasma, there are problems in maintaining the small size and small energy spread of the accelerated electron bunch while maintaining sufficient values of the accelerating wakefields. Also, the question arises about the values of the limiting bunch dimensions at which the accelerating process is stable. To form a stable accelerated electron bunch, a method is usually used that involves the formation of the same accelerating fields at the location of the bunch. The same fields (plateau due to beam loading (see , )) in the region of the accelerated bunch allow all its parts to move as a whole, and ensure the preservation of the spatial distribution of electrons over time, which, in fact, means an accelerated beam of good quality. In this report, the problem of electron bunch accelerating by a short or long electron driver-bunch is considered. Romeo S., Ferrario M., Rossi A.R. Phys. Rev. Accel. Beams. 23 (2020) 071301. ** Maslov V.I. et al. Problems of Atomic Science and Technology. 6 (2020) 47.
	Poster TUPAB155 [1.723 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB155
About •	paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 23 August 2021
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TUPAB174	Basic Design Study for Disk-Loaded Structure in Muon LINAC	acceleration, linac, impedance, experiment	1801
	K. Sumi, T. Iijima, K. Inami, Y. Sue, M. Yotsuzuka Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan H. Ego, T. Mibe, M. Yoshida KEK, Ibaraki, Japan T. Iijima KMI, Nagoya, AIchi Prefecture, Japan Y. Kondo JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y. Nakazawa Ibaraki University, Hitachi, Ibaraki, Japan M. Otani, N. Saito J-PARC, KEK & JAEA, Ibaraki-ken, Japan Y. Takeuchi Kyushu University, Fukuoka, Japan H.Y. Yasuda University of Tokyo, Tokyo, Japan
	The world’s first disk-loaded structure (DLS) at the high-velocity part of a muon LINAC is under development for the J-PARC muon g-2/EDM experiment. We have simulated the first designed constant impedance DLS to accelerate muons from ß = 0.7 to 0.94 at an operating frequency of 1296 MHz and a phase of -10 degrees to ensure longitudinal acceptance and have shown the quality of the beam meets our requirements. Because the structure needs a high RF power of 80 MW to generate a gradient of 20 MV/m, a constant gradient DLS with the higher acceleration efficiency is being studied for lower operating RF power. In this poster, we will show the cell structure design yielding a gradient of 20 MV/m with lower RF power.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB174
About •	paper received ※ 19 May 2021 paper accepted ※ 31 August 2021 issue date ※ 18 August 2021
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WEPAB020	The Relation Between Field Flatness and the Passband Frequency in the Elliptical Cavities	cavity, SRF, simulation, gun	2636
	G.-T. Park, R.A. Rimmer, H. Wang JLab, Newport News, Virginia, USA
	A technique that predicts the field flatness of the operating pi-mode based on the passband frequency is highly desirable when the direct measurement of the field is not available. Such a technique was developed for the SNS-PPU cavity, a 6-cell SRF cavity whose field flatness is important for cold operation. In this paper, we will present the theory on the relations between field profile and passband frequencies of the arbitrary deformed cavities, the simulation studies, and comparison with the experimental measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB020
About •	paper received ※ 17 May 2021 paper accepted ※ 24 June 2021 issue date ※ 20 August 2021
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WEPAB258	Beam Dynamics Design of a 162.5 MHz Superconducting RFQ Accelerator	rfq, emittance, cavity, focusing	3248
	Ying. Xia, H.P. Li, Y.R. Lu, Q.Y. Tan, Z. Wang PKU, Beijing, People’s Republic of China Y.R. Lu IAP, Frankfurt am Main, Germany
	Superconducting(SC) RFQ has lower power consumption, larger aperture and higher accelerating gradient than room temperature RFQ. We plan to design a 162.5MHz SC RFQ to accelerate the 30 mA proton beams from 35 keV to 2.5 MeV, which will be used as a neutron source for BNCT and neutron imaging project. At an inter-vane voltage of 180kV, the beam dynamics design was carried out with acceptable peak surface electric field, high transmission efficiency, and relatively short cavity length.
	Poster WEPAB258 [1.251 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB258
About •	paper received ※ 17 May 2021 paper accepted ※ 06 July 2021 issue date ※ 14 August 2021
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THPAB069	Design Concepts for a High-Gradient C-Band Linac	cavity, FEL, electron, linac	3919
	T.B. Bolin, S.I. Sosa Guitron UNM-ECE, Albuquerque, USA S. Biedron UNM-ME, Albuquerque, New Mexico, USA J.R. Cary Tech-X, Boulder, Colorado, USA M. Dal Forno SLAC, Menlo Park, California, USA
	Funding: This work was performed under Contract No. 89233218CNA000001, supported by the U.S. DOE’s National Nuclear Security Administration, for the operation of Los Alamos National Laboratory (LANL). During the last decade, the production of soft to hard x-rays (up to 25 keV) at XFEL facilities has enabled new developments in a broad range of disciplines. One caveat is that these instruments can require a large amount of real estate. For example, the XFEL driver is typically an electron beam linear accelerator (LINAC) and the need for higher electron beam energies capable of generating higher energy X-rays can require longer linacs; costs quickly become prohibitive, requiring state of art methods. One cost-saving measure is to produce a high accelerating gradient while reducing cavity size. Compact accelerating structures are also high-frequency. Here, we describe design concepts for a high-gradient, cryo-cooled LINAC for XFEL facilities in the C-band regime (~4-8 GHz). We are also exploring C-band for different applications including drivers for security applications. We investigate 2 different traveling wave (TW) geometries optimized for high-gradient operation as modeled with VSim software.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB069
About •	paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 14 August 2021
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Paper

Title

Other Keywords

Page

MOPAB151

A Stable Drive Beam for High Gradient Dielectric Wakefield Acceleration

focusing, wakefield, acceleration, quadrupole

528

T.J. Overton, Y.M. Saveliev, G.X. Xia
Cockcroft Institute, Warrington, Cheshire, United Kingdom
T.J. Overton, G.X. Xia
The University of Manchester, Manchester, United Kingdom
T.H. Pacey, Y.M. Saveliev
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Science and Technology Funding Council (STFC) student grant.
A high accelerating gradient, with stable beam transport, is necessary for the next generation of particle accelerators. Dielectric wakefield accelerators are a potential solution to this problem. In these proceedings, we present simulation studies of electron bunches in the self-wake regime inside a planar dielectric structure. This is analogous to driving beams in a dielectric wakefield accelerator. The transverse and longitudinal wake fields are investigated for dielectric plate gaps, various transverse beam sizes, and longitudinal bunch profiles. The effects of these on the stability of drive bunches, and acceleration of a witness bunch, are discussed in the context of electron bunches that can be produced with conventional linac RF technology.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB151

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paper received ※ 13 May 2021 paper accepted ※ 07 June 2021 issue date ※ 24 August 2021

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MOPAB155

Magnetic Breakdowns in Side-Coupled X-Band Accelerating Structures

impedance, coupling, simulation, cavity

540

S.P. Antipov, P.V. Avrakhov, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
V.A. Dolgashev
SLAC, Menlo Park, California, USA
C. Jing
Euclid Beamlabs, Bolingbrook, USA

Funding: DOE SBIR
Side coupled accelerating structures are popular in the industrial realizations of linacs due to their high shunt impedance and ease of tuning. We designed and fabricated a side-coupled X-band accelerating structure that achieved 133 MOhm/m shut impedance. This structure was fabricated out of two halves using a novel brazeless approach. The two copper halves are joined together using a stainless steel joining piece with knife edges that bite into copper. This structure had been tested at high power at SLAC National Accelerator Laboratory. The performance of the structure had been limited by magnetic breakdowns on the side-coupling cells. In this paper we will present results of the high gradient tests and after-test analysis. Scanning electron microscopy images show a typical magnetic-field induced breakdown.

Poster MOPAB155 [1.069 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB155

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paper received ※ 20 May 2021 paper accepted ※ 23 June 2021 issue date ※ 01 September 2021

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MOPAB353

Design of a compact Ka-Band Mode Launcher for High-gradient Accelerators

cavity, coupling, simulation, quadrupole

1100

G. Torrisi, G.S. Mauro, G. Sorbello
INFN/LNS, Catania, Italy
M. Behtouei, L. Faillace, B. Spataro, A. Variola
INFN/LNF, Frascati, Italy
V.A. Dolgashev
SLAC, Menlo Park, California, USA
L. Faillace, M. Migliorati
Sapienza University of Rome, Rome, Italy
M. Migliorati
INFN-Roma1, Rome, Italy
J.B. Rosenzweig
UCLA, Los Angeles, California, USA
G. Sorbello
University of Catania, Catania, Italy

In this work, we present the RF design of a table-top Ka-Band mode launcher operating at 35.98 GHz. The structure consists of a symmetrical 4-port WR28 rectangular-TE10-to-circular-TM01 mode converter that is used to couple a peak output RF power of 5 MW (pulse length up to 50 ns and repetition rate up to 100 Hz) in Ka-Band linear accelerator able to achieve very high accelerating gradients (up to 200 MV/m). Numerical simulations have been carried out with the 3D full-wave commercial simulator Ansys HFSS in order to obtain a preliminary tuning of the accelerating field flatness at the operating frequency f0=35.98 GHz. The main RF parameters, such as reflection coefficient, transmission losses, and conversion efficiency are given together with a verification of the field azimuthal symmetry which avoids dipole and quadrupole deflecting modes. To simplify future manufacturing, reduce fabrication costs, and also reduce the probability of RF breakdown, the proposed new geometry has "open" configuration. This geometry eliminates the flow of RF currents through critical joints and allows this device to be milled from metal blocks.

Poster MOPAB353 [3.131 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB353

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paper received ※ 19 May 2021 paper accepted ※ 09 June 2021 issue date ※ 27 August 2021

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MOPAB391

Conduction Cooling Methods for Nb₃Sn SRF Cavities and Cryomodules

cavity, SRF, controls, simulation

1192

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

Rapid progress in the performance of Nb₃Sn SRF cavities during the last few years has made Nb₃Sn an energy efficient alternative to traditional Nb cavities, thereby initiating a fundamental shift in SRF technology. These Nb₃Sn cavities can operate at significantly higher temperatures than Nb cavities while simultaneously requiring less cooling power. This critical property enables the use of new, robust, turn-key style cryogenic cooling schemes based on conduction cooling with commercial cryocoolers. Cornell University has developed and tested a 2.6 GHz Nb₃Sn cavity assembly which utilizes such cooling methods. These tests have demonstrated stable RF operation at 10 MV/m and the measured thermal dynamics match what is found in numerical simulations.

DOI •

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

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

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MOPAB396

Measurements of Magnetic Field Penetration in Superconducting Materials for SRF Cavities

cavity, SRF, experiment, solenoid

1208

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

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

DOI •

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

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021

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MOPAB400

Development of Helium Vessel Welding Process for SNS PPU Cavities

cavity, proton, cryomodule, neutron

1212

P. Dhakal, E. Daly, G.K. Davis, J.F. Fischer, N.A. Huque, K. Macha, P.D. Owen, K.M. Wilson, M. Wiseman
JLab, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The Spallation Neutron Source Proton Power Upgrade cavities are produced by Research Instrument with all the cavity processing done at vendor sites with final chemistry applied to the cavity to be electropolishing. Cavities are delivered to Jefferson Lab, ready to be tested. One of the tasks to be completed before the arrival of production-ready PPU cavities is to develop a robust helium vessel welding protocol. We have successfully developed the process and applied it to three six-cell high beta cavities. Here, we present the summary of RF results, welding process development, and post helium vessel RF results.

Poster MOPAB400 [1.313 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB400

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paper received ※ 18 May 2021 paper accepted ※ 26 May 2021 issue date ※ 01 September 2021

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TUPAB076

High-Gradient Breakdown Studies of an X-Band Accelerating Structure Operated in the Reversed Taper Direction

linac, linear-collider, klystron, collider

1543

X.W. Wu, N. Catalán Lasheras, A. Grudiev, G. McMonagle, I. Syratchev, W. Wuensch
CERN, Meyrin, Switzerland
M. Boronat
IFIC, Valencia, Spain
A. Castilla, A.V. Edwards, W.L. Millar
Lancaster University, Lancaster, United Kingdom

The results of high-gradient tests of a tapered X-band traveling-wave accelerator structure powered in reversed direction are presented. Powering the tapered structure from the small aperture, normally output, at the end of the structure provides unique conditions for the study of gradient limits. This allows high fields in the first cell for a comparatively low input power and a field distribution that rapidly falls off along the length of the structure. A maximum gradient of 130 MV/m in the first cell at a pulse length of 100 ns was reached for an input power of 31.9 MW. Details of the conditioning and operation at high-gradient are presented. Various breakdown rate measurements were conducted at different power levels and rf pulse widths. The structure was standard T24 CLIC test structure and was tested in Xbox-3 at CERN.

Poster TUPAB076 [1.077 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB076

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

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TUPAB098

Recent Progress Toward a Conduction-Cooled Superconducting Radiofrequency Electron Gun

cavity, simulation, SRF, electron

1604

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

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

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

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

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TUPAB155

Obtaining Accelerated Electron Bunch of High Quality in Plasma Wakefield Accelerator

plasma, wakefield, electron, acceleration

1744

R.T. Ovsiannikov
KhNU, Kharkov, Ukraine
I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: "This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299."
Earlier, high-gradient accelerating electrons of a relativistic beam was demonstrated. However, due to dynamic processes in the plasma, there are problems in maintaining the small size and small energy spread of the accelerated electron bunch while maintaining sufficient values of the accelerating wakefields. Also, the question arises about the values of the limiting bunch dimensions at which the accelerating process is stable. To form a stable accelerated electron bunch, a method is usually used that involves the formation of the same accelerating fields at the location of the bunch. The same fields (plateau due to beam loading (see *, **)) in the region of the accelerated bunch allow all its parts to move as a whole, and ensure the preservation of the spatial distribution of electrons over time, which, in fact, means an accelerated beam of good quality. In this report, the problem of electron bunch accelerating by a short or long electron driver-bunch is considered.
* Romeo S., Ferrario M., Rossi A.R. Phys. Rev. Accel. Beams. 23 (2020) 071301.
** Maslov V.I. et al. Problems of Atomic Science and Technology. 6 (2020) 47.

Poster TUPAB155 [1.723 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB155

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paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 23 August 2021

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TUPAB174

Basic Design Study for Disk-Loaded Structure in Muon LINAC

acceleration, linac, impedance, experiment

1801

K. Sumi, T. Iijima, K. Inami, Y. Sue, M. Yotsuzuka
Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
H. Ego, T. Mibe, M. Yoshida
KEK, Ibaraki, Japan
T. Iijima
KMI, Nagoya, AIchi Prefecture, Japan
Y. Kondo
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y. Nakazawa
Ibaraki University, Hitachi, Ibaraki, Japan
M. Otani, N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
Y. Takeuchi
Kyushu University, Fukuoka, Japan
H.Y. Yasuda
University of Tokyo, Tokyo, Japan

The world’s first disk-loaded structure (DLS) at the high-velocity part of a muon LINAC is under development for the J-PARC muon g-2/EDM experiment. We have simulated the first designed constant impedance DLS to accelerate muons from ß = 0.7 to 0.94 at an operating frequency of 1296 MHz and a phase of -10 degrees to ensure longitudinal acceptance and have shown the quality of the beam meets our requirements. Because the structure needs a high RF power of 80 MW to generate a gradient of 20 MV/m, a constant gradient DLS with the higher acceleration efficiency is being studied for lower operating RF power. In this poster, we will show the cell structure design yielding a gradient of 20 MV/m with lower RF power.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB174

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paper received ※ 19 May 2021 paper accepted ※ 31 August 2021 issue date ※ 18 August 2021

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WEPAB020

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

cavity, SRF, simulation, gun

2636

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

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

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

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paper received ※ 17 May 2021 paper accepted ※ 24 June 2021 issue date ※ 20 August 2021

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WEPAB258

Beam Dynamics Design of a 162.5 MHz Superconducting RFQ Accelerator

rfq, emittance, cavity, focusing

3248

Ying. Xia, H.P. Li, Y.R. Lu, Q.Y. Tan, Z. Wang
PKU, Beijing, People’s Republic of China
Y.R. Lu
IAP, Frankfurt am Main, Germany

Superconducting(SC) RFQ has lower power consumption, larger aperture and higher accelerating gradient than room temperature RFQ. We plan to design a 162.5MHz SC RFQ to accelerate the 30 mA proton beams from 35 keV to 2.5 MeV, which will be used as a neutron source for BNCT and neutron imaging project. At an inter-vane voltage of 180kV, the beam dynamics design was carried out with acceptable peak surface electric field, high transmission efficiency, and relatively short cavity length.

Poster WEPAB258 [1.251 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB258

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paper received ※ 17 May 2021 paper accepted ※ 06 July 2021 issue date ※ 14 August 2021

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THPAB069

Design Concepts for a High-Gradient C-Band Linac

cavity, FEL, electron, linac

3919

T.B. Bolin, S.I. Sosa Guitron
UNM-ECE, Albuquerque, USA
S. Biedron
UNM-ME, Albuquerque, New Mexico, USA
J.R. Cary
Tech-X, Boulder, Colorado, USA
M. Dal Forno
SLAC, Menlo Park, California, USA

Funding: This work was performed under Contract No. 89233218CNA000001, supported by the U.S. DOE’s National Nuclear Security Administration, for the operation of Los Alamos National Laboratory (LANL).
During the last decade, the production of soft to hard x-rays (up to 25 keV) at XFEL facilities has enabled new developments in a broad range of disciplines. One caveat is that these instruments can require a large amount of real estate. For example, the XFEL driver is typically an electron beam linear accelerator (LINAC) and the need for higher electron beam energies capable of generating higher energy X-rays can require longer linacs; costs quickly become prohibitive, requiring state of art methods. One cost-saving measure is to produce a high accelerating gradient while reducing cavity size. Compact accelerating structures are also high-frequency. Here, we describe design concepts for a high-gradient, cryo-cooled LINAC for XFEL facilities in the C-band regime (~4-8 GHz). We are also exploring C-band for different applications including drivers for security applications. We investigate 2 different traveling wave (TW) geometries optimized for high-gradient operation as modeled with VSim software.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB069

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paper received ※ 20 May 2021 paper accepted ※ 02 July 2021 issue date ※ 14 August 2021

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