IPAC2015 - List of Authors (Shchegolkov, D.Y.)

Paper	Title	Page
WEPJE006	Dielectric Wakefield Accelerator Experiments at ATF	2681
	D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA S.P. Antipov Euclid TechLabs, LLC, Solon, Ohio, USA M.G. Fedurin BNL, Upton, Long Island, New York, USA
	Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory. Dielectric wakefield acceleration (DWA) presents us with means to achieve the accelerating gradient high above the limits of conventional accelerators. In a typical DWA scheme a higher energy lower charge main bunch is accelerated in the wakefield produced by a preceding lower energy higher charge drive bunch inside of a hollow metal-encapsulated dielectric tube. To make use of as much energy of the drive bunch as possible, it is highly important that all parts of it decelerate uniformly. Close to uniform drive bunch deceleration can be achieved if its current is properly shaped.* At Accelerator Test Facility (ATF) at BNL we shaped the current of a chirped electron beam with an adjustable mask placed inside of the highly dispersive region in the magnetic dogleg. We passed the shaped beam current through a quartz tube and observed the beam particles’ energy modulation at the tube’s output with a spectrometer. By tuning the mask we were able to control the beam energy modulation and thus the wakefield profile in the tube. * B. Jiang, C. Jing, P. Schoessow, J. Power, and W. Gai, PRSTAB 15, 011301 (2012).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE006
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WEPJE007	Simulation Studies of BBU Suppression Methods and Acceptable Tolerances in Dielectric Wakefield Accelerators	2685
	D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA A. Zholents ANL, Argonne, Illinois, USA
	Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory. The advantage of dielectric wakefield accelerators (DWAs) is the ability to achieve accelerating gradients well above the limits of conventional accelerators. However DWAs will also produce high transverse wakefields if the beam propagates off-center, which grow even faster than the accelerating gradient when the width of the beam channel is decreased.* It is highly important to suppress single beam breakup (BBU) instability in order for the beam to propagate long enough so that a reasonable amount of energy (e.g., 80%) from the drive bunch is extracted. In addition bending of the dielectric channel has a similar effect to off-center steering of the beam with the required tolerances on the channel straightness typically in a few micron range. For both rectangular and circular dielectric lined waveguides we use a FODO lattice with a tapered strength for suppression of BBU. We impose initial energy chirp on the drive beam to make use of the BNS damping. We change rectangular waveguide orientation by 90 degrees with a small step to make use of the quadrupole wakefield focusing. These and other techniques and tolerance requirements are discussed and simulation results are presented in this presentation. * C. Li, W. Gai, C. Jing, J.G. Power, C.X. Tang, and A. Zholents, High gradient limits due to single bunch beam breakup in a collinear dielectric wakefield accelerator, PRSTAB 17, 091302 (2014).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE007
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WEPTY082	High Gradient Testing of the Five-cell Superconducting RF Module with a PBG Coupler Cell	3471
	S. Arsenyev, W.B. Haynes, D.Y. Shchegolkov, E.I. Simakov, T. Tajima LANL, Los Alamos, New Mexico, USA C.H. Boulware, T.L. Grimm, A. Rogacki Niowave, Inc., Lansing, Michigan, USA
	We report results of high-gradient testing of the first 5- cell superconducting radio frequency (SRF) module with a photonic band gap cell (PBG). Higher order mode (HOM) damping is vital for preserving the quality of high-current electron beams in novel SRF accelerators. Because HOMs are not confined by the PBG array, they can be effectively damped in order to raise the current threshold for beam instabilities. The PBG design increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of via the beam pipe at the ends of the cavity. A superconducting multi-cell cavity with a PBG damping cell is therefore an attractive option for high-current linacs. The first-ever SRF multi-cell cavity incorporating a PBG cell was designed a LANL and built at Niowave Inc. The cavity was tuned to a desired gradient profile and underwent surface treatment at Niowave. A vertical test (VTS) was then performed at LANL, demonstrating an abnormally low cavity quality factor in the accelerating mode of 1.6*10⁶. Future tests are proposed to determine the source of the losses and resolve the problem.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY082
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WEPTY083	Five-cell Superconducting RF Module with a PBG Coupler Cell: Design and Cold Testing of the Copper Prototype	3475
	S. Arsenyev, D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA C.H. Boulware, T.L. Grimm, A. Rogacki Niowave, Inc., Lansing, Michigan, USA
	We report the design and experimental data for a copper prototype of a superconducting radio-frequency (SRF) accelerator module. The five-cell module has an incorporated photonic band gap (PBG) cell with couplers. The purpose of the PBG cell is to achieve better higher order mode (HOM) damping which is vital for preserving the quality of highcurrent electron beams. Better HOM damping raises the current threshold for beam instabilities in novel SRF accelerators. The PBG design also increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of on the beam pipe via complicated end assemblies. First, we will discuss the design and accelerating properties of the structure. The five-cell module was optimized to provide good HOM damping while maintaining the same accelerating properties as conventional elliptical-cell modules. We will then discuss the process of tuning the structure to obtain the desired accelerating gradient profile. Finally, we will list measured quality factors for the accelerating mode and the most dangerous HOMs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY083
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Paper

Title

Page

Dielectric Wakefield Accelerator Experiments at ATF

2681

D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
S.P. Antipov
Euclid TechLabs, LLC, Solon, Ohio, USA
M.G. Fedurin
BNL, Upton, Long Island, New York, USA

Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.
Dielectric wakefield acceleration (DWA) presents us with means to achieve the accelerating gradient high above the limits of conventional accelerators. In a typical DWA scheme a higher energy lower charge main bunch is accelerated in the wakefield produced by a preceding lower energy higher charge drive bunch inside of a hollow metal-encapsulated dielectric tube. To make use of as much energy of the drive bunch as possible, it is highly important that all parts of it decelerate uniformly. Close to uniform drive bunch deceleration can be achieved if its current is properly shaped.* At Accelerator Test Facility (ATF) at BNL we shaped the current of a chirped electron beam with an adjustable mask placed inside of the highly dispersive region in the magnetic dogleg. We passed the shaped beam current through a quartz tube and observed the beam particles’ energy modulation at the tube’s output with a spectrometer. By tuning the mask we were able to control the beam energy modulation and thus the wakefield profile in the tube.
* B. Jiang, C. Jing, P. Schoessow, J. Power, and W. Gai, PRSTAB 15, 011301 (2012).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE006

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

WEPJE007

Simulation Studies of BBU Suppression Methods and Acceptable Tolerances in Dielectric Wakefield Accelerators

2685

D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
A. Zholents
ANL, Argonne, Illinois, USA

Funding: This work is supported by the U.S. Department of Energy through the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.
The advantage of dielectric wakefield accelerators (DWAs) is the ability to achieve accelerating gradients well above the limits of conventional accelerators. However DWAs will also produce high transverse wakefields if the beam propagates off-center, which grow even faster than the accelerating gradient when the width of the beam channel is decreased.* It is highly important to suppress single beam breakup (BBU) instability in order for the beam to propagate long enough so that a reasonable amount of energy (e.g., 80%) from the drive bunch is extracted. In addition bending of the dielectric channel has a similar effect to off-center steering of the beam with the required tolerances on the channel straightness typically in a few micron range. For both rectangular and circular dielectric lined waveguides we use a FODO lattice with a tapered strength for suppression of BBU. We impose initial energy chirp on the drive beam to make use of the BNS damping. We change rectangular waveguide orientation by 90 degrees with a small step to make use of the quadrupole wakefield focusing. These and other techniques and tolerance requirements are discussed and simulation results are presented in this presentation.
* C. Li, W. Gai, C. Jing, J.G. Power, C.X. Tang, and A. Zholents, High gradient limits due to single bunch beam breakup in a collinear dielectric wakefield accelerator, PRSTAB 17, 091302 (2014).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE007

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WEPTY082

High Gradient Testing of the Five-cell Superconducting RF Module with a PBG Coupler Cell

3471

S. Arsenyev, W.B. Haynes, D.Y. Shchegolkov, E.I. Simakov, T. Tajima
LANL, Los Alamos, New Mexico, USA
C.H. Boulware, T.L. Grimm, A. Rogacki
Niowave, Inc., Lansing, Michigan, USA

We report results of high-gradient testing of the first 5- cell superconducting radio frequency (SRF) module with a photonic band gap cell (PBG). Higher order mode (HOM) damping is vital for preserving the quality of high-current electron beams in novel SRF accelerators. Because HOMs are not confined by the PBG array, they can be effectively damped in order to raise the current threshold for beam instabilities. The PBG design increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of via the beam pipe at the ends of the cavity. A superconducting multi-cell cavity with a PBG damping cell is therefore an attractive option for high-current linacs. The first-ever SRF multi-cell cavity incorporating a PBG cell was designed a LANL and built at Niowave Inc. The cavity was tuned to a desired gradient profile and underwent surface treatment at Niowave. A vertical test (VTS) was then performed at LANL, demonstrating an abnormally low cavity quality factor in the accelerating mode of 1.6*10⁶. Future tests are proposed to determine the source of the losses and resolve the problem.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY082

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WEPTY083

Five-cell Superconducting RF Module with a PBG Coupler Cell: Design and Cold Testing of the Copper Prototype

3475

S. Arsenyev, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
C.H. Boulware, T.L. Grimm, A. Rogacki
Niowave, Inc., Lansing, Michigan, USA

We report the design and experimental data for a copper prototype of a superconducting radio-frequency (SRF) accelerator module. The five-cell module has an incorporated photonic band gap (PBG) cell with couplers. The purpose of the PBG cell is to achieve better higher order mode (HOM) damping which is vital for preserving the quality of highcurrent electron beams. Better HOM damping raises the current threshold for beam instabilities in novel SRF accelerators. The PBG design also increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of on the beam pipe via complicated end assemblies. First, we will discuss the design and accelerating properties of the structure. The five-cell module was optimized to provide good HOM damping while maintaining the same accelerating properties as conventional elliptical-cell modules. We will then discuss the process of tuning the structure to obtain the desired accelerating gradient profile. Finally, we will list measured quality factors for the accelerating mode and the most dangerous HOMs.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY083

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