NAPAC2022 - List of Keywords (accelerating-gradient)

Paper	Title	Other Keywords	Page
MOYE3	Experiments on a Conduction Cooled Superconducting Radio Frequency Cavity with Field Emission Cathode	cavity, niobium, experiment, SRF	16
	Y. Ji, R. Dhuley, C.J. Edwards, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA V. Korampally, D. Mihalcea, O. Mohsen, P. Piot, I. Salehinia Northern Illinois University, DeKalb, Illinois, USA
	Funding: The project is supported by DOE HEP Accelerator Stewardship award to Fermilab and Northern Illinois University To achieve Ampere-class electron beam accelerators the pulse delivery rate need to be much higher than the typical photo injector repetition rate of the order of a few kilohertz. We propose here an injector which can, in principle, generate electron bunches at the same rate as the operating RF frequency. A conduction-cooled superconducting radio frequency (SRF) cavity operating in the CW mode and housing a field emission element at its region of high axial electric field can be a viable method of generating high-repetition-rate electron bunches. In this paper, we report the development and experiments on a conduction-cooled Nb₃Sn cavity with a niobium rod intended as a field emitter support. The initial experiments demonstrate ~0.4 MV/m average accelerating gradient, which is equivalent of peak gradient of 3.2 MV/m. The measured RF cavity quality factor is 1.4 × 10⁸ slightly above our goal. The achieved field gradient is limited by the relatively low input RF power and by the poor coupling between the external power supply and the RF cavity. With ideal coupling the field gradient can be as high as 0.6 MV/m still below our goal of about 1 MV/m
	Slides MOYE3 [1.444 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOYE3
About •	Received ※ 01 August 2022 — Revised ※ 03 August 2022 — Accepted ※ 05 August 2022 — Issue date ※ 30 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOZE4	Ceramic Enhanced Accelerator Structure Low Power Test and Designs of High Power and Beam Tests	cavity, electron, impedance, simulation	49
	H. Xu, M.R. Bradley, L.D. Duffy, M.A. Holloway, J. Upadhyay LANL, Los Alamos, New Mexico, USA
	Funding: Research was supported by the Laboratory Directed Research and Development program of Los Alamos National Laboratory, under project number 20210083ER. A ceramic enhanced accelerator structure (CEAS) uses a concentric ceramic ring placed inside a metallic pillbox cavity to significantly increase the shunt impedance of the cavity. Single cell standing wave CEAS cavities are designed, built, and tested at low power at 5.1 GHz. The results indicate 40% increase in shunt impedance compared to that of a purely metallic pillbox cavity. A beam test setup has been designed to use a single cell CEAS cavity to modulate a 30-keV direct-current (DC) electron beam at an accelerating gradient of 1 to 2 MV/m to verify the beam acceleration capability of the CEAS concept and to study the potential charging effect on the ceramic component during the operation. Another single cell standing wave CEAS cavity has been designed for high power test at 5.7 GHz for the high accelerating gradient capability.
	Slides MOZE4 [1.652 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOZE4
About •	Received ※ 01 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 07 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOZE5	Simulation and Experimental Results of Dielectric Disk Accelerating Structures	experiment, wakefield, impedance, simulation	52
	S. Weatherly, E.E. Wisniewski Illinois Institute of Technology, Chicago, Illinois, USA D.S. Doran, C.-J. Jing, J.F. Power, E.E. Wisniewski ANL, Lemont, Illinois, USA B.T. Freemire, C.-J. Jing Euclid Beamlabs, Bolingbrook, USA
	Funding: Contract DE-SC0019864 to Euclid Beamlabs LLC. AWA work from U.S. DOE Office of Science under Contract DE-AC02-06CH11357. Chicagoland Accelerator Science Traineeship U.S. DOE award number DE-SC-0020379 A method of decreasing the required footprint of linear accelerators and improving their energy efficiency is to employ Dielectric Disk Accelerators (DDAs) with short RF pulses ( ∼ 9 ns). A DDA is an accelerating structure that utilizes dielectric disks to improve the shunt impedance. Two DDA structures have been designed and tested at the Argonne Wakefield Accelerator. A single cell clamped DDA structure recently achieved an accelerating gradient of 1{02} MV/m. A multi-cell clamped DDA structure has been designed and is being fabricated. Simulation results for this new structure show a 1{08} MV/m accelerating gradient with 400 MW of input power with a high shunt impedance and group velocity. The engineering design has been improved from the single cell structure to ensure consistent clamping over the entire structure.
	Slides MOZE5 [9.338 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOZE5
About •	Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 21 August 2022 — Issue date ※ 06 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA46	Cryogenic Dielectric Structure with GΩ/m Level Shunt Impedance	impedance, cryogenics, simulation, acceleration	157
	R.A. Kostin, C. Jing Euclid Beamlabs, Bolingbrook, USA
	Shunt impedance is one of the most important parameters characterizing particle acceleration efficiency. It is known that RF losses are reduced at cryogenic temperatures. For example, a record high shunt impedance of 350 MΩ/m was demonstrated recently for all metal X-band accelerating structure, which is more than 2 times higher than that at room temperature. In this article we present a novel hybrid dielectric structure which can achieve even higher shunt impedance due to the fact that losses in dielectric materials reduced much more than in pure copper.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA46
About •	Received ※ 12 August 2022 — Revised ※ 16 August 2022 — Accepted ※ 23 August 2022 — Issue date ※ 17 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA74	Design of a W-Band Corrugated Waveguide for Structure Wakefield Acceleration	wakefield, GUI, electron, acceleration	210
	B. Leung, X. Lu, C.L. Phillips, P. Piot Northern Illinois University, DeKalb, Illinois, USA D.S. Doran, X. Lu, P. Piot, J.G. Power ANL, Lemont, Illinois, USA
	Current research on structure wakefield acceleration aims to develop radio-frequency structures that can produce high gradients, with work in the sub-terahertz regime being particularly interesting because of the potential to create more compact and economical accelerators. Metallic corrugated waveguides at sub-terahertz frequencies are one such structure. We have designed a W-band corrugated waveguide for a collinear wakefield acceleration experiment at the Argonne Wakefield Accelerator (AWA). Using the CST Studio Suite, we have optimized the structure for the maximum achievable gradient in the wakefield from a nominal AWA electron bunch at 65 MeV. Simulation results from different solvers of CST were benchmarked with each other, with analytical models, and with another simulation code, ECHO. We are investigating the mechanical design, suitable fabrication technologies, and the possibility to apply advanced bunch shaping techniques to improve the structure performance.
	Poster MOPA74 [1.518 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA74
About •	Received ※ 30 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 26 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPA82	Transverse Stability in an Alternating Symmetry Planar Dielectric Wakefield Structure	wakefield, simulation, experiment, quadrupole	519
	W.J. Lynn, G. Andonian, N. Majernik, S.M. OTool, J.B. Rosenzweig UCLA, Los Angeles, California, USA D.S. Doran, S.Y. Kim, J.F. Power, E.E. Wisniewski ANL, Lemont, Illinois, USA P. Piot Northern Illinois University, DeKalb, Illinois, USA
	Funding: DE-SC0017648 - AWA. Dielectric Wakefield Acceleration (DWA) is a promising technique for realizing the next generation of linear colliders. It provides access to significantly higher accelerating gradients than traditional radio-frequency cavities. One impediment to realizing a DWA-powered accelerator is the issue of the transverse stability of the beams within the dielectric structure due to short-range wakefields. These short-range wakefields have a tendency to induce a phenomenon known as single-bunch beam breakup, which acts as its name implies and destroys the relevant beam. We attempt to solve this issue by leveraging the quadrupole mode excited in a planar dielectric structure and then alternating the orientation of said structure to turn an unstable system into a stable one. We examine this issue computationally to determine the limits of stability and based on those simulations describe a future experimental realization of this strategy.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA82
About •	Received ※ 02 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 30 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEZE4	First High-Gradient Results of UED/UEM SRF Gun at Cryogenic Temperatures	gun, cavity, SRF, cryogenics	607
	R.A. Kostin, C. Jing Euclid Beamlabs, Bolingbrook, USA D.J. Bice, T.N. Khabiboulline, S. Posen Fermilab, Batavia, Illinois, USA
	Funding: The project is funded by DOE SBIR #DE-SC0018621 Benefiting from the rapid progress on RF photogun technologies in the past two decades, the development of MeV range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation. UEM or UED use low power electron beams with modest energies of a few MeV to study ultrafast phenomena in a variety of novel and exotic materials. SRF photoguns become a promising candidate to produce highly stable electrons for UEM/UED applications because of the ultrahigh shot-to-shot stability compared to room temperature RF photoguns. SRF technology was prohibitively expensive for industrial use until two recent advancements: Nb₃Sn and conduction cooling. The use of Nb₃Sn allows to operate SRF cavities at higher temperatures (4K) with low power dissipation which is within the reach of commercially available closed-cycle cryocoolers. Euclid is developing a continuous wave (CW), 1.5-cell, MeV-scale SRF conduction cooled photogun operating at 1.3 GHz. In this paper, we present first high gradient results of the gun conducted in liquid helium.
	Slides WEZE4 [2.817 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEZE4
About •	Received ※ 05 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 29 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA27	Effect of Duration of 120 °C Baking on the Performance of Superconducting Radio Frequency Niobium Cavities	cavity, niobium, SRF, radio-frequency	683
	B.D. Khanal ODU, Norfolk, Virginia, USA P. Dhakal JLab, Newport News, Virginia, USA
	Over the last decade much attention was given in increasing the quality factor of superconducting radio frequency (SRF) cavities by impurity doping. Prior to the era of doping, the final cavity processing technique to achieve the high accelerating gradient includes the "in situ" low temperature baking of SRF cavities at temperature ~ 120°C for several hours. Here, we present the results of a series of measurements on 1.3 GHz TESLA shape single-cell cavities with successive low temperature baking at 120°C up to 96 hours. The experimental data were analyzed with available theory of superconductivity to elucidate the effect of the duration of low temperature baking on the superconducting properties of cavity materials as well as the RF performance. In addition, the RF loss related to the trapping of residual magnetic field refereed as flux trapping sensitivity was measured with respect to the duration of 120°C bake.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA27
About •	Received ※ 01 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 19 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA52	Demonstration of Twice-Reduced Lorentz-Force Detuning in SRF Cavity by Copper Cold Spraying	cavity, SRF, site, niobium	749
	R.A. Kostin, C.-J. Jing, A. Kanareykin Euclid TechLabs, Solon, Ohio, USA G. Ciovati JLab, Newport News, Virginia, USA
	Funding: The project is funded by DOE SBIR # DE-SC0019589 Superconducting RF (SRF) cavities usually are made from thin-walled high RRR Niobium and are susceptible to Lorentz Force Detuning (LFD) ’ cavity deformation phenomena by RF fields. In this paper, we present high gradient cryogenic results of an SRF cavity with two times reduced LFD achieved by copper cold spray reinforcement without sacrificing cavity flexibility for tuning. Finite-element model was developed first to find the best geometry for LFD reduction, which incorporated coupled RF, structural and thermal modules, and is also presented.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA52
About •	Received ※ 27 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 16 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYE5	Analysis of Low RRR SRF Cavities	cavity, SRF, niobium, radio-frequency	877
	K. Howard, Y.K. Kim University of Chicago, Chicago, Illinois, USA D. Bafia, A. Grassellino Fermilab, Batavia, Illinois, USA
	Recent findings in the superconducting radio-frequency (SRF) community have shown that introducing certain impurities into high-purity niobium can improve quality factors and accelerating gradients. Success has been found in nitrogen-doping, diffusion of the native oxide into the niobium surface, and thin films of alternate superconductors atop a niobium bulk cavity. We question why some impurities improve RF performance while others hinder it. The purpose of this study is to characterize the impurity profile of niobium with a low residual resistance ratio (RRR) and correlate these impurities with the RF performance of low RRR cavities so that the mechanism of recent impurity-based improvements can be better understood and improved upon. Additionally, we performed surface treatments, low temperature baking and nitrogen-doping, on low RRR cavities to evaluate how the intentional addition of more impurities to the RF layer affects performance. We have found that low RRR cavities experience low temperature-dependent BCS resistance behavior more prominently than their high RRR counterparts. The results of this study have the potential to unlock a new understanding on SRF materials.
	Slides THYE5 [5.013 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYE5
About •	Received ※ 03 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 01 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOYE3

Experiments on a Conduction Cooled Superconducting Radio Frequency Cavity with Field Emission Cathode

cavity, niobium, experiment, SRF

16

Y. Ji, R. Dhuley, C.J. Edwards, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA
V. Korampally, D. Mihalcea, O. Mohsen, P. Piot, I. Salehinia
Northern Illinois University, DeKalb, Illinois, USA

Funding: The project is supported by DOE HEP Accelerator Stewardship award to Fermilab and Northern Illinois University
To achieve Ampere-class electron beam accelerators the pulse delivery rate need to be much higher than the typical photo injector repetition rate of the order of a few kilohertz. We propose here an injector which can, in principle, generate electron bunches at the same rate as the operating RF frequency. A conduction-cooled superconducting radio frequency (SRF) cavity operating in the CW mode and housing a field emission element at its region of high axial electric field can be a viable method of generating high-repetition-rate electron bunches. In this paper, we report the development and experiments on a conduction-cooled Nb₃Sn cavity with a niobium rod intended as a field emitter support. The initial experiments demonstrate ~0.4 MV/m average accelerating gradient, which is equivalent of peak gradient of 3.2 MV/m. The measured RF cavity quality factor is 1.4 × 10⁸ slightly above our goal. The achieved field gradient is limited by the relatively low input RF power and by the poor coupling between the external power supply and the RF cavity. With ideal coupling the field gradient can be as high as 0.6 MV/m still below our goal of about 1 MV/m

Slides MOYE3 [1.444 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOYE3

About •

Received ※ 01 August 2022 — Revised ※ 03 August 2022 — Accepted ※ 05 August 2022 — Issue date ※ 30 September 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOZE4

Ceramic Enhanced Accelerator Structure Low Power Test and Designs of High Power and Beam Tests

cavity, electron, impedance, simulation

49

H. Xu, M.R. Bradley, L.D. Duffy, M.A. Holloway, J. Upadhyay
LANL, Los Alamos, New Mexico, USA

Funding: Research was supported by the Laboratory Directed Research and Development program of Los Alamos National Laboratory, under project number 20210083ER.
A ceramic enhanced accelerator structure (CEAS) uses a concentric ceramic ring placed inside a metallic pillbox cavity to significantly increase the shunt impedance of the cavity. Single cell standing wave CEAS cavities are designed, built, and tested at low power at 5.1 GHz. The results indicate 40% increase in shunt impedance compared to that of a purely metallic pillbox cavity. A beam test setup has been designed to use a single cell CEAS cavity to modulate a 30-keV direct-current (DC) electron beam at an accelerating gradient of 1 to 2 MV/m to verify the beam acceleration capability of the CEAS concept and to study the potential charging effect on the ceramic component during the operation. Another single cell standing wave CEAS cavity has been designed for high power test at 5.7 GHz for the high accelerating gradient capability.

Slides MOZE4 [1.652 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOZE4

About •

Received ※ 01 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 07 October 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOZE5

Simulation and Experimental Results of Dielectric Disk Accelerating Structures

experiment, wakefield, impedance, simulation

52

S. Weatherly, E.E. Wisniewski
Illinois Institute of Technology, Chicago, Illinois, USA
D.S. Doran, C.-J. Jing, J.F. Power, E.E. Wisniewski
ANL, Lemont, Illinois, USA
B.T. Freemire, C.-J. Jing
Euclid Beamlabs, Bolingbrook, USA

Funding: Contract DE-SC0019864 to Euclid Beamlabs LLC. AWA work from U.S. DOE Office of Science under Contract DE-AC02-06CH11357. Chicagoland Accelerator Science Traineeship U.S. DOE award number DE-SC-0020379
A method of decreasing the required footprint of linear accelerators and improving their energy efficiency is to employ Dielectric Disk Accelerators (DDAs) with short RF pulses ( ∼ 9 ns). A DDA is an accelerating structure that utilizes dielectric disks to improve the shunt impedance. Two DDA structures have been designed and tested at the Argonne Wakefield Accelerator. A single cell clamped DDA structure recently achieved an accelerating gradient of 1{02} MV/m. A multi-cell clamped DDA structure has been designed and is being fabricated. Simulation results for this new structure show a 1{08} MV/m accelerating gradient with 400 MW of input power with a high shunt impedance and group velocity. The engineering design has been improved from the single cell structure to ensure consistent clamping over the entire structure.

Slides MOZE5 [9.338 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOZE5

About •

Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 21 August 2022 — Issue date ※ 06 October 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA46

Cryogenic Dielectric Structure with GΩ/m Level Shunt Impedance

impedance, cryogenics, simulation, acceleration

157

R.A. Kostin, C. Jing
Euclid Beamlabs, Bolingbrook, USA

Shunt impedance is one of the most important parameters characterizing particle acceleration efficiency. It is known that RF losses are reduced at cryogenic temperatures. For example, a record high shunt impedance of 350 MΩ/m was demonstrated recently for all metal X-band accelerating structure, which is more than 2 times higher than that at room temperature. In this article we present a novel hybrid dielectric structure which can achieve even higher shunt impedance due to the fact that losses in dielectric materials reduced much more than in pure copper.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA46

About •

Received ※ 12 August 2022 — Revised ※ 16 August 2022 — Accepted ※ 23 August 2022 — Issue date ※ 17 September 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA74

Design of a W-Band Corrugated Waveguide for Structure Wakefield Acceleration

wakefield, GUI, electron, acceleration

210

B. Leung, X. Lu, C.L. Phillips, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
D.S. Doran, X. Lu, P. Piot, J.G. Power
ANL, Lemont, Illinois, USA

Current research on structure wakefield acceleration aims to develop radio-frequency structures that can produce high gradients, with work in the sub-terahertz regime being particularly interesting because of the potential to create more compact and economical accelerators. Metallic corrugated waveguides at sub-terahertz frequencies are one such structure. We have designed a W-band corrugated waveguide for a collinear wakefield acceleration experiment at the Argonne Wakefield Accelerator (AWA). Using the CST Studio Suite, we have optimized the structure for the maximum achievable gradient in the wakefield from a nominal AWA electron bunch at 65 MeV. Simulation results from different solvers of CST were benchmarked with each other, with analytical models, and with another simulation code, ECHO. We are investigating the mechanical design, suitable fabrication technologies, and the possibility to apply advanced bunch shaping techniques to improve the structure performance.

Poster MOPA74 [1.518 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA74

About •

Received ※ 30 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 26 August 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPA82

Transverse Stability in an Alternating Symmetry Planar Dielectric Wakefield Structure

wakefield, simulation, experiment, quadrupole

519

W.J. Lynn, G. Andonian, N. Majernik, S.M. OTool, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
D.S. Doran, S.Y. Kim, J.F. Power, E.E. Wisniewski
ANL, Lemont, Illinois, USA
P. Piot
Northern Illinois University, DeKalb, Illinois, USA

Funding: DE-SC0017648 - AWA.
Dielectric Wakefield Acceleration (DWA) is a promising technique for realizing the next generation of linear colliders. It provides access to significantly higher accelerating gradients than traditional radio-frequency cavities. One impediment to realizing a DWA-powered accelerator is the issue of the transverse stability of the beams within the dielectric structure due to short-range wakefields. These short-range wakefields have a tendency to induce a phenomenon known as single-bunch beam breakup, which acts as its name implies and destroys the relevant beam. We attempt to solve this issue by leveraging the quadrupole mode excited in a planar dielectric structure and then alternating the orientation of said structure to turn an unstable system into a stable one. We examine this issue computationally to determine the limits of stability and based on those simulations describe a future experimental realization of this strategy.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA82

About •

Received ※ 02 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 30 September 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEZE4

First High-Gradient Results of UED/UEM SRF Gun at Cryogenic Temperatures

gun, cavity, SRF, cryogenics

607

R.A. Kostin, C. Jing
Euclid Beamlabs, Bolingbrook, USA
D.J. Bice, T.N. Khabiboulline, S. Posen
Fermilab, Batavia, Illinois, USA

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

Slides WEZE4 [2.817 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEZE4

About •

Received ※ 05 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 29 September 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA27

Effect of Duration of 120 °C Baking on the Performance of Superconducting Radio Frequency Niobium Cavities

cavity, niobium, SRF, radio-frequency

683

B.D. Khanal
ODU, Norfolk, Virginia, USA
P. Dhakal
JLab, Newport News, Virginia, USA

Over the last decade much attention was given in increasing the quality factor of superconducting radio frequency (SRF) cavities by impurity doping. Prior to the era of doping, the final cavity processing technique to achieve the high accelerating gradient includes the "in situ" low temperature baking of SRF cavities at temperature ~ 120°C for several hours. Here, we present the results of a series of measurements on 1.3 GHz TESLA shape single-cell cavities with successive low temperature baking at 120°C up to 96 hours. The experimental data were analyzed with available theory of superconductivity to elucidate the effect of the duration of low temperature baking on the superconducting properties of cavity materials as well as the RF performance. In addition, the RF loss related to the trapping of residual magnetic field refereed as flux trapping sensitivity was measured with respect to the duration of 120°C bake.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA27

About •

Received ※ 01 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 19 August 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA52

Demonstration of Twice-Reduced Lorentz-Force Detuning in SRF Cavity by Copper Cold Spraying

cavity, SRF, site, niobium

749

R.A. Kostin, C.-J. Jing, A. Kanareykin
Euclid TechLabs, Solon, Ohio, USA
G. Ciovati
JLab, Newport News, Virginia, USA

Funding: The project is funded by DOE SBIR # DE-SC0019589
Superconducting RF (SRF) cavities usually are made from thin-walled high RRR Niobium and are susceptible to Lorentz Force Detuning (LFD) ’ cavity deformation phenomena by RF fields. In this paper, we present high gradient cryogenic results of an SRF cavity with two times reduced LFD achieved by copper cold spray reinforcement without sacrificing cavity flexibility for tuning. Finite-element model was developed first to find the best geometry for LFD reduction, which incorporated coupled RF, structural and thermal modules, and is also presented.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA52

About •

Received ※ 27 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 16 August 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYE5

Analysis of Low RRR SRF Cavities

cavity, SRF, niobium, radio-frequency

877

K. Howard, Y.K. Kim
University of Chicago, Chicago, Illinois, USA
D. Bafia, A. Grassellino
Fermilab, Batavia, Illinois, USA

Recent findings in the superconducting radio-frequency (SRF) community have shown that introducing certain impurities into high-purity niobium can improve quality factors and accelerating gradients. Success has been found in nitrogen-doping, diffusion of the native oxide into the niobium surface, and thin films of alternate superconductors atop a niobium bulk cavity. We question why some impurities improve RF performance while others hinder it. The purpose of this study is to characterize the impurity profile of niobium with a low residual resistance ratio (RRR) and correlate these impurities with the RF performance of low RRR cavities so that the mechanism of recent impurity-based improvements can be better understood and improved upon. Additionally, we performed surface treatments, low temperature baking and nitrogen-doping, on low RRR cavities to evaluate how the intentional addition of more impurities to the RF layer affects performance. We have found that low RRR cavities experience low temperature-dependent BCS resistance behavior more prominently than their high RRR counterparts. The results of this study have the potential to unlock a new understanding on SRF materials.

Slides THYE5 [5.013 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYE5

About •

Received ※ 03 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 01 October 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)