IPAC2021 - List of Authors (Jing, C.-J.)

Paper	Title	Page
WEPAB163	An X-Band Ultra-High Gradient Photoinjector	2986
	S.V. Kuzikov, S.P. Antipov, P.V. Avrakhov, E. Dosov, C.-J. Jing, E.W. Knight Euclid TechLabs, Solon, Ohio, USA G. Ha, C.-J. Jing, W. Liu, P. Piot, J.G. Power, D.S. Scott, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing Euclid Beamlabs, Bolingbrook, USA X. Lu MIT/PSFC, Cambridge, Massachusetts, USA X. Lu SLAC, Menlo Park, California, USA P. Piot Fermilab, Batavia, Illinois, USA P. Piot, W.H. Tan Northern Illinois University, DeKalb, Illinois, USA E.E. Wisniewski IIT, Chicago, Illinois, USA
	Funding: This work was supported by DoE SBIR grant # DE-SC0018709. High brightness beams appealing for XFELs and UEM essentially imply a high current and a low emittance. To obtain such beams we propose to raise the accelerating voltage in the gun mitigating repealing Coulomb forces. An ultra-high gradient is achieved utilizing a short-pulse technology. We have designed a room temperature X-band 1,5 cell gun that is able to inject 4 MeV, 100 pC bunches with as low as 0.15 mcm normalized transverse emittance. The gun is operated with as high gradients as 400 MV/m and fed by 200 MW, 10 ns RF pulses generated with Argonne Wakefield Accelerator (AWA) power extractor. We report results of low RF power tests, laser alignment test results, and successful gun conditioning results carried out at nominal RF power.
	Poster WEPAB163 [5.427 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB163
About •	paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 19 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAB129	Beam Dynamics Simulations in a High-Gradient X-Band Photoinjector	4013
	W.H. Tan, P. Piot Northern Illinois University, DeKalb, Illinois, USA G. Chen, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA G. Chen IIT, Chicago, Illinois, USA G. Ha, C.-J. Jing ANL, Lemont, Illinois, USA C.-J. Jing Euclid Beamlabs, Bolingbrook, USA
	A high-gradient X-band (11.7-GHz) photoinjector was recently developed by Euclid Techlabs and is in its commissioning phase at the Argonne Wakefield Accelerator (AWA). This contribution discuss the beam-dynamics modeling of the photoinjector system comprising an RF gun and linac section. We especially discuss beam-dynamics optimization of setup for an integrated proof-of-principle experiments. We also discuss the use of such a photoinjector as a witness-bunch source for a future high-gradient collinear-wakefield accelerator experiments at the AWA. * S. V. Kuzikov, et al. these proceedings.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB129
About •	paper received ※ 20 May 2021 paper accepted ※ 14 July 2021 issue date ※ 31 August 2021
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MOPAB352	High Power Test of a Dielectric Disk Loaded Accelerator for a Two Beam Wakefield Accelerator	1096
	B.T. Freemire, C.-J. Jing, S. Poddar Euclid Beamlabs, Bolingbrook, USA M.E. Conde, D.S. Doran, G. Ha, W. Liu, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA M.M. Peng TUB, Beijing, People’s Republic of China E.E. Wisniewski Illinois Institute of Technology, Chicago, Illinois, USA Y. Zhao Euclid TechLabs, Solon, Ohio, USA
	Funding: Small Business Innovation Research Contract No. DE-SC0019864 U.S. DOE Office of Science Contract No. DE-AC02-06CH11357 As part of the Argonne 500 MeV short pulse Two Beam Wakefield Acceleration Demonstrator, a single cell X-band dielectric disk loaded accelerator (DDA) has been designed, fabricated, and tested at high power at the Argonne Wakefield Accelerator. The DDA should provide a short pulse (~20 ns) high gradient (>300 MV/m) accelerator while maintaining a reasonable r/Q and high group velocity. This will allow a significantly larger RF-to-beam efficiency than is currently possible for conventional accelerating structures. A low loss barium titantate ceramic, µ_r = 50, was selected, and a low temperature brazing alloy chosen to preserve the dielectric properties of the ceramic during brazing. High power testing produced breakdown at the triple junction, resulting from the braze joint design. No evidence of breakdown was observed on the iris of the disk, indicating that the maximum surface electric field on the dielectric was not reached. An improved braze joint has been designed and is in production, with high power testing to follow.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB352
About •	paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 21 August 2021
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WEPAB102	Half-Metal Spin Filter for Highly Polarized Emission from GaAs Photocathodes	2833
	S. Poddar, C.-J. Jing, E.J. Montgomery Euclid Beamlabs, Bolingbrook, USA P. Lukashev University of Northern Iowa, Cedar Falls, Iowa, USA C. Palmstrøm UCSB, Santa Barbara, California, USA M.L. Stutzman, S. Zhang JLab, Newport News, Virginia, USA
	Funding: Work supported by Department of Energy grant number DE-SC0020564. GaAs-based photocathodes are one of the major sources of spin-polarized electrons and are crucial for the upcoming Electron-Ion collider experiments which includes study of proton spin and spin parity violation in the standard model. The theoretical polarization limit in unstrained GaAs photocathodes is 50 % but only 35 % is routinely achieved in experiments. Spin selective filtering allows to boost the spin polarization beyond the 50 % theoretical limit. In this work, first-principle electronic calculations using standard Density Functional Theory are performed to predict possible Heusler alloy half-metal candidates to be used as spin-filter. Simulations are also performed to investigate the half-metallicity as function of the magnetic spin direction. Several devices are experimentally fabricated using dedicated Molecular Beam Epitaxy growth system. We implemented Quantum Efficiency and Polarization testing of these half-metal/GaAs heterostructures using a dedicated Mott polarimeter system. Photoemission can also be seen on magnetically switching the spin-filter direction accompanied by a change in sign of the asymmetry which is a qualitative proof of the spin-filtering effect.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB102
About •	paper received ※ 20 May 2021 paper accepted ※ 28 July 2021 issue date ※ 27 August 2021
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MOPAB142	A Compact, Low-Field, Broadband Matching Section for Externally-Powered X-Band Dielectric-Loaded Accelerating Structures	495
	Y. Wei, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom H. Bursali Sapienza University of Rome, Rome, Italy N. Catalán Lasheras, S. Gonzalez Anton, A. Grudiev, R. Wegner, Y. Wei CERN, Meyrin, Switzerland B.T. Freemire, C.-J. Jing Euclid TechLabs, Solon, Ohio, USA J. Sauza-Bedolla Lancaster University, Lancaster, United Kingdom Y. Wei, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	It has been technically challenging to efficiently couple external radiofrequency (RF) power to cylindrical dielectric-loaded accelerating (DLA) structures. This is especially true when the DLA structure has a high dielectric constant. This contribution presents a novel design of a matching section for coupling the RF power from a circular waveguide to an X-band DLA structure with a dielectric constant ε_r=16.66 and a loss tangent \tanθ = 3.43× 10^-5. It consists of a very compact dielectric disk with a width of 2.035 mm and a tilt angle of 60 degrees, resulting in a broadband coupling at a low RF field which has the potential to survive in the high-power environment. To prevent a sharp dielectric corner break, a 45-degree chamfer is added. Moreover, a microscale vacuum gap, caused by metallic clamping between the thin coating and the outer thick copper jacket, is studied in detail. Based on simulation studies, a prototype of the DLA structure with the matching sections was fabricated. Results from preliminary bench measurements and their comparison with design values will also be discussed.
	Poster MOPAB142 [2.617 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB142
About •	paper received ※ 11 May 2021 paper accepted ※ 21 May 2021 issue date ※ 19 August 2021
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MOPAB152	High Power Tests of Brazeless Accelerating Structures	532
	S.P. Antipov, P.V. Avrakhov, C.-J. Jing, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA V.A. Dolgashev SLAC, Menlo Park, California, USA D.S. Doran, W. Liu, J.G. Power, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA
	Funding: DOE SBIR Grant #DE-SC0017749 A typical accelerating structure is a set of copper resonators brazed together. This multi step process is expensive and time consuming. In an effort to optimize production process for rapid prototyping and overall reduction of accelerator cost we developed a split block brazeless accelerating structure. In such structure the vacuum is sealed by the use of knife edges, similar to an industry standard conflat technology. In this paper we present high power tests of several different brazeless structures. First, an inexpensive 1 MeV accelerator powered by radar magnetron. Second, a high gradient power extractor tested at Argonne Wakefield Accelerator Facility. In this experiment a high charge electron beam generated a 180 MW peak power pulse. Finally, we report on high power testing of a brazeless x-band accelerating structure at SLAC.
	Poster MOPAB152 [0.783 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB152
About •	paper received ※ 20 May 2021 paper accepted ※ 24 June 2021 issue date ※ 31 August 2021
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MOPAB169	Generating 510 MW of X-Band Power for Structure-Based Wakefield Acceleration Using a Metamaterial-Based Power Extractor	578
	J.F. Picard, I. Mastovsky, M.A. Shapiro, R.J. Temkin MIT/PSFC, Cambridge, Massachusetts, USA M.E. Conde, D.S. Doran, J.G. Power, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing Euclid TechLabs, Solon, Ohio, USA X. Lu Northern Illinois University, DeKalb, Illinois, USA
	Funding: Research sponsored under Award No. DE-SC0015566 by U.S. Department of Energy, Office of Science, Office of High Energy Physics and Contract No. DE-AC02-06CH11357 by the Office of Science. We present our recent results generating 510 MW of power at 11.7 GHz using a metamaterial-based metallic power-extractor for application in structure-based wakefield acceleration (SWFA). SWFA is a novel acceleration scheme in which high-charge electron bunches are passed through a power extractor structure to produce a high-intensity wakefield. This wakefield can then be used to accelerate a witness bunch in the same beamline or passed to a separate acceleration beamline. MIT’s approach uses a specialized metamaterial for the power extractor design. By using a metamaterial, we can overcome some of the challenges faced by other SWFA techniques. Here, we discuss the Stage 3 experiment. The Stage 1 and Stage 2 experiments successfully demonstrated the functionality of the metamaterial approach by generating high power RF pulses using the 65 MeV electron beam at the Argonne Wakefield Accelerator (AWA) facility. The 510 MW result from Stage 3 experiment is the highest power generated to-date for SWFA at AWA, and was enable by significant design improvements, including an all-copper structure, fully-symmetric coupler design, and breakdown risk-reduction treatment.
	Poster MOPAB169 [8.882 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB169
About •	paper received ※ 08 May 2021 paper accepted ※ 16 July 2021 issue date ※ 25 August 2021
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TUXC03	Ferro-Electric Fast Reactive Tuner Applications for SRF Cavities	1305
	N.C. Shipman, A. Castilla, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley, H. Timko CERN, Meyrin, Switzerland I. Ben-Zvi BNL, Upton, New York, USA G. Burt, A. Castilla Cockcroft Institute, Lancaster University, Lancaster, United Kingdom C.-J. Jing, A. Kanareykin Euclid TechLabs, Solon, Ohio, USA
	A Ferro-Electric fast Reactive Tuner (FE-FRT) is a novel type of RF cavity tuner containing a low loss ferroelectric material. FE-FRTs have no moving parts and allow cavity frequencies to be changed extremely quickly (on the timescale of 100s of ns or less). They are of particular interest for SRF cavities as they can be placed outside the liquid helium environment and without an FE-FRT it’s typically very difficult to tune SRF cavities quickly. FE-FRTs can be used for a wide variety of use cases including microphonics suppression, RF switching, and transient beam loading compensation. This promises entirely new operational capabilities, increased performance and cost savings for a variety of existing and proposed accelerators. An overview of the theory and potential applications will be discussed in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXC03
About •	paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 25 August 2021
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THPAB331	High-Power Test of a Highly Over-Coupled X-Band RF Gun Driven by Short RF Pulses	4432
	J.H. Shao, D.S. Doran, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA X. Lu, P. Piot, W.H. Tan Northern Illinois University, DeKalb, Illinois, USA
	Beam brightness, a key figure of merit of RF photocathode guns, can be improved by increasing the cathode surface field which suppresses emittance growth from space charge. The surface field in normal-conducting structures is mainly limited by RF breakdown and it has been experimentally discovered that RF breakdown rate exponentially depends on RF pulse length. A highly over-coupled 1.5-cell X-band photocathode gun has been developed to be powered by 9 ns RF pulses with 3 ns rising time, 3 ns flat-top, and 3 ns falling time generated by an X-band metallic power extractor. In the recent experiment at Argonne Wakefield Accelerator facility, cathode surface field up to ~350 MV/m with a low breakdown rate has been obtained under ~250 MW input power. Strong beam loading from dark current was observed during RF conditioning and quickly recovered to a negligible level after the gun reached the maximum gradient. Detailed high-power test results and data analysis will be reported in this manuscript.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB331
About •	paper received ※ 25 May 2021 paper accepted ※ 14 July 2021 issue date ※ 23 August 2021
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Paper

Title

Page

An X-Band Ultra-High Gradient Photoinjector

2986

S.V. Kuzikov, S.P. Antipov, P.V. Avrakhov, E. Dosov, C.-J. Jing, E.W. Knight
Euclid TechLabs, Solon, Ohio, USA
G. Ha, C.-J. Jing, W. Liu, P. Piot, J.G. Power, D.S. Scott, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid Beamlabs, Bolingbrook, USA
X. Lu
MIT/PSFC, Cambridge, Massachusetts, USA
X. Lu
SLAC, Menlo Park, California, USA
P. Piot
Fermilab, Batavia, Illinois, USA
P. Piot, W.H. Tan
Northern Illinois University, DeKalb, Illinois, USA
E.E. Wisniewski
IIT, Chicago, Illinois, USA

Funding: This work was supported by DoE SBIR grant # DE-SC0018709.
High brightness beams appealing for XFELs and UEM essentially imply a high current and a low emittance. To obtain such beams we propose to raise the accelerating voltage in the gun mitigating repealing Coulomb forces. An ultra-high gradient is achieved utilizing a short-pulse technology. We have designed a room temperature X-band 1,5 cell gun that is able to inject 4 MeV, 100 pC bunches with as low as 0.15 mcm normalized transverse emittance. The gun is operated with as high gradients as 400 MV/m and fed by 200 MW, 10 ns RF pulses generated with Argonne Wakefield Accelerator (AWA) power extractor. We report results of low RF power tests, laser alignment test results, and successful gun conditioning results carried out at nominal RF power.

Poster WEPAB163 [5.427 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB163

About •

paper received ※ 18 May 2021 paper accepted ※ 02 June 2021 issue date ※ 19 August 2021

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THPAB129

Beam Dynamics Simulations in a High-Gradient X-Band Photoinjector

4013

W.H. Tan, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
G. Chen, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
G. Chen
IIT, Chicago, Illinois, USA
G. Ha, C.-J. Jing
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid Beamlabs, Bolingbrook, USA

A high-gradient X-band (11.7-GHz) photoinjector was recently developed by Euclid Techlabs and is in its commissioning phase at the Argonne Wakefield Accelerator (AWA). This contribution discuss the beam-dynamics modeling of the photoinjector system comprising an RF gun and linac section. We especially discuss beam-dynamics optimization of setup for an integrated proof-of-principle experiments. We also discuss the use of such a photoinjector as a witness-bunch source for a future high-gradient collinear-wakefield accelerator experiments at the AWA.
* S. V. Kuzikov, et al. these proceedings.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB129

About •

paper received ※ 20 May 2021 paper accepted ※ 14 July 2021 issue date ※ 31 August 2021

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MOPAB352

High Power Test of a Dielectric Disk Loaded Accelerator for a Two Beam Wakefield Accelerator

1096

B.T. Freemire, C.-J. Jing, S. Poddar
Euclid Beamlabs, Bolingbrook, USA
M.E. Conde, D.S. Doran, G. Ha, W. Liu, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
M.M. Peng
TUB, Beijing, People’s Republic of China
E.E. Wisniewski
Illinois Institute of Technology, Chicago, Illinois, USA
Y. Zhao
Euclid TechLabs, Solon, Ohio, USA

Funding: Small Business Innovation Research Contract No. DE-SC0019864 U.S. DOE Office of Science Contract No. DE-AC02-06CH11357
As part of the Argonne 500 MeV short pulse Two Beam Wakefield Acceleration Demonstrator, a single cell X-band dielectric disk loaded accelerator (DDA) has been designed, fabricated, and tested at high power at the Argonne Wakefield Accelerator. The DDA should provide a short pulse (~20 ns) high gradient (>300 MV/m) accelerator while maintaining a reasonable r/Q and high group velocity. This will allow a significantly larger RF-to-beam efficiency than is currently possible for conventional accelerating structures. A low loss barium titantate ceramic, µ_r = 50, was selected, and a low temperature brazing alloy chosen to preserve the dielectric properties of the ceramic during brazing. High power testing produced breakdown at the triple junction, resulting from the braze joint design. No evidence of breakdown was observed on the iris of the disk, indicating that the maximum surface electric field on the dielectric was not reached. An improved braze joint has been designed and is in production, with high power testing to follow.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB352

About •

paper received ※ 19 May 2021 paper accepted ※ 08 June 2021 issue date ※ 21 August 2021

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WEPAB102

Half-Metal Spin Filter for Highly Polarized Emission from GaAs Photocathodes

2833

S. Poddar, C.-J. Jing, E.J. Montgomery
Euclid Beamlabs, Bolingbrook, USA
P. Lukashev
University of Northern Iowa, Cedar Falls, Iowa, USA
C. Palmstrøm
UCSB, Santa Barbara, California, USA
M.L. Stutzman, S. Zhang
JLab, Newport News, Virginia, USA

Funding: Work supported by Department of Energy grant number DE-SC0020564.
GaAs-based photocathodes are one of the major sources of spin-polarized electrons and are crucial for the upcoming Electron-Ion collider experiments which includes study of proton spin and spin parity violation in the standard model. The theoretical polarization limit in unstrained GaAs photocathodes is 50 % but only 35 % is routinely achieved in experiments. Spin selective filtering allows to boost the spin polarization beyond the 50 % theoretical limit. In this work, first-principle electronic calculations using standard Density Functional Theory are performed to predict possible Heusler alloy half-metal candidates to be used as spin-filter. Simulations are also performed to investigate the half-metallicity as function of the magnetic spin direction. Several devices are experimentally fabricated using dedicated Molecular Beam Epitaxy growth system. We implemented Quantum Efficiency and Polarization testing of these half-metal/GaAs heterostructures using a dedicated Mott polarimeter system. Photoemission can also be seen on magnetically switching the spin-filter direction accompanied by a change in sign of the asymmetry which is a qualitative proof of the spin-filtering effect.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB102

About •

paper received ※ 20 May 2021 paper accepted ※ 28 July 2021 issue date ※ 27 August 2021

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

MOPAB142

A Compact, Low-Field, Broadband Matching Section for Externally-Powered X-Band Dielectric-Loaded Accelerating Structures

495

Y. Wei, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
H. Bursali
Sapienza University of Rome, Rome, Italy
N. Catalán Lasheras, S. Gonzalez Anton, A. Grudiev, R. Wegner, Y. Wei
CERN, Meyrin, Switzerland
B.T. Freemire, C.-J. Jing
Euclid TechLabs, Solon, Ohio, USA
J. Sauza-Bedolla
Lancaster University, Lancaster, United Kingdom
Y. Wei, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

It has been technically challenging to efficiently couple external radiofrequency (RF) power to cylindrical dielectric-loaded accelerating (DLA) structures. This is especially true when the DLA structure has a high dielectric constant. This contribution presents a novel design of a matching section for coupling the RF power from a circular waveguide to an X-band DLA structure with a dielectric constant ε_r=16.66 and a loss tangent \tanθ = 3.43× 10^-5. It consists of a very compact dielectric disk with a width of 2.035 mm and a tilt angle of 60 degrees, resulting in a broadband coupling at a low RF field which has the potential to survive in the high-power environment. To prevent a sharp dielectric corner break, a 45-degree chamfer is added. Moreover, a microscale vacuum gap, caused by metallic clamping between the thin coating and the outer thick copper jacket, is studied in detail. Based on simulation studies, a prototype of the DLA structure with the matching sections was fabricated. Results from preliminary bench measurements and their comparison with design values will also be discussed.

Poster MOPAB142 [2.617 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB142

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paper received ※ 11 May 2021 paper accepted ※ 21 May 2021 issue date ※ 19 August 2021

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MOPAB152

High Power Tests of Brazeless Accelerating Structures

532

S.P. Antipov, P.V. Avrakhov, C.-J. Jing, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
V.A. Dolgashev
SLAC, Menlo Park, California, USA
D.S. Doran, W. Liu, J.G. Power, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA

Funding: DOE SBIR Grant #DE-SC0017749
A typical accelerating structure is a set of copper resonators brazed together. This multi step process is expensive and time consuming. In an effort to optimize production process for rapid prototyping and overall reduction of accelerator cost we developed a split block brazeless accelerating structure. In such structure the vacuum is sealed by the use of knife edges, similar to an industry standard conflat technology. In this paper we present high power tests of several different brazeless structures. First, an inexpensive 1 MeV accelerator powered by radar magnetron. Second, a high gradient power extractor tested at Argonne Wakefield Accelerator Facility. In this experiment a high charge electron beam generated a 180 MW peak power pulse. Finally, we report on high power testing of a brazeless x-band accelerating structure at SLAC.

Poster MOPAB152 [0.783 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB152

About •

paper received ※ 20 May 2021 paper accepted ※ 24 June 2021 issue date ※ 31 August 2021

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MOPAB169

Generating 510 MW of X-Band Power for Structure-Based Wakefield Acceleration Using a Metamaterial-Based Power Extractor

578

J.F. Picard, I. Mastovsky, M.A. Shapiro, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA
M.E. Conde, D.S. Doran, J.G. Power, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid TechLabs, Solon, Ohio, USA
X. Lu
Northern Illinois University, DeKalb, Illinois, USA

Funding: Research sponsored under Award No. DE-SC0015566 by U.S. Department of Energy, Office of Science, Office of High Energy Physics and Contract No. DE-AC02-06CH11357 by the Office of Science.
We present our recent results generating 510 MW of power at 11.7 GHz using a metamaterial-based metallic power-extractor for application in structure-based wakefield acceleration (SWFA). SWFA is a novel acceleration scheme in which high-charge electron bunches are passed through a power extractor structure to produce a high-intensity wakefield. This wakefield can then be used to accelerate a witness bunch in the same beamline or passed to a separate acceleration beamline. MIT’s approach uses a specialized metamaterial for the power extractor design. By using a metamaterial, we can overcome some of the challenges faced by other SWFA techniques. Here, we discuss the Stage 3 experiment. The Stage 1 and Stage 2 experiments successfully demonstrated the functionality of the metamaterial approach by generating high power RF pulses using the 65 MeV electron beam at the Argonne Wakefield Accelerator (AWA) facility. The 510 MW result from Stage 3 experiment is the highest power generated to-date for SWFA at AWA, and was enable by significant design improvements, including an all-copper structure, fully-symmetric coupler design, and breakdown risk-reduction treatment.

Poster MOPAB169 [8.882 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB169

About •

paper received ※ 08 May 2021 paper accepted ※ 16 July 2021 issue date ※ 25 August 2021

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TUXC03

Ferro-Electric Fast Reactive Tuner Applications for SRF Cavities

1305

N.C. Shipman, A. Castilla, M.R. Coly, F. Gerigk, A. Macpherson, N. Stapley, H. Timko
CERN, Meyrin, Switzerland
I. Ben-Zvi
BNL, Upton, New York, USA
G. Burt, A. Castilla
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
C.-J. Jing, A. Kanareykin
Euclid TechLabs, Solon, Ohio, USA

A Ferro-Electric fast Reactive Tuner (FE-FRT) is a novel type of RF cavity tuner containing a low loss ferroelectric material. FE-FRTs have no moving parts and allow cavity frequencies to be changed extremely quickly (on the timescale of 100s of ns or less). They are of particular interest for SRF cavities as they can be placed outside the liquid helium environment and without an FE-FRT it’s typically very difficult to tune SRF cavities quickly. FE-FRTs can be used for a wide variety of use cases including microphonics suppression, RF switching, and transient beam loading compensation. This promises entirely new operational capabilities, increased performance and cost savings for a variety of existing and proposed accelerators. An overview of the theory and potential applications will be discussed in detail.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXC03

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paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 25 August 2021

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THPAB331

High-Power Test of a Highly Over-Coupled X-Band RF Gun Driven by Short RF Pulses

4432

J.H. Shao, D.S. Doran, W. Liu, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
X. Lu, P. Piot, W.H. Tan
Northern Illinois University, DeKalb, Illinois, USA

Beam brightness, a key figure of merit of RF photocathode guns, can be improved by increasing the cathode surface field which suppresses emittance growth from space charge. The surface field in normal-conducting structures is mainly limited by RF breakdown and it has been experimentally discovered that RF breakdown rate exponentially depends on RF pulse length. A highly over-coupled 1.5-cell X-band photocathode gun has been developed to be powered by 9 ns RF pulses with 3 ns rising time, 3 ns flat-top, and 3 ns falling time generated by an X-band metallic power extractor. In the recent experiment at Argonne Wakefield Accelerator facility, cathode surface field up to ~350 MV/m with a low breakdown rate has been obtained under ~250 MW input power. Strong beam loading from dark current was observed during RF conditioning and quickly recovered to a negligible level after the gun reached the maximum gradient. Detailed high-power test results and data analysis will be reported in this manuscript.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB331

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paper received ※ 25 May 2021 paper accepted ※ 14 July 2021 issue date ※ 23 August 2021

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