PAC2013 - Table of Session: TUPMA (Poster Session)

Paper	Title	Page
TUPMA01	Status and Future Plan of the Development of a Compact X-ray Source Based on ICS at Laser Undulator Compact X-ray (LUCX)	589
	M.K. Fukuda, S. Araki, A.S. Aryshev, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan K. Sakaue, M. Washio RISE, Tokyo, Japan
	Funding: Work supported by the Quantum Beam Technology Program of MEXT We have developed a compact X-ray source via inverse Compton scattering (ICS) between multi-bunch electron beam and a laser pulse stacked in an optical cavity at Laser Undulator Compact X-ray (LUCX) accelerator in KEK. Since the autumn of 2011, we have begun X-ray imaging test. In the beginning, it had taken two hours to get an X-ray image because of low intensity of X-ray with 10⁴ photons/pulse. To get a clear X-ray image in a shorter period of times, we have upgraded the accelerator, which consists of a 3.6 cell photo-cathode rf-gun, a 12cell standing wave accelerating structure and a 4-mirror planar optical cavity. The target intensity of an electron beam is 500nC/train with 1000 bunches at 30 MeV. The one of laser pulse is also 6mJ/pulse. The expected number of X-ray is 1.7x10⁷ photons/train with 10% bandwidth. We have already started the multi-bunch beam generation and X-ray imaging test after upgrade. The accelerator produces 24 MeV beam with the total charge of 180nC in 150 bunches per pulse. The aging process is also continued to increase energy and intensity. We will report the results of the beam test and future plan of the development of a compact X-ray source at LUCX.

TUPMA02	High-Chromaticity Optics for the MAX IV 3 GeV Storage Ring	592
	T. Olsson, S.C. Leemann MAX-lab, Lund, Sweden
	The ultralow emittance lattice of the MAX IV 3 GeV storage ring has a large negative natural chromaticity. This has to be corrected to positive values to prevent head-tail instabilities. On the other hand, high linear chromaticity can lead to a large tune footprint which limits Touschek lifetime. Therefore, the linear chromaticity is corrected to +1 in both planes with sextupoles while octupoles are used to further reduce the tune footprint. Studies indicate this design leads to threshold currents for resistive wall and transverse mode coupling instabilities beyond what is expected during regular user operation. However, since these are only preliminary studies based on approximations, the possibility of instability issues during commissioning needs to be considered. A short term solution is to operate the storage ring at a higher chromaticity. This paper describes the developed high-chromaticity optics for the MAX IV 3 GeV storage ring. It focuses on reduction of chromatic and amplitude-dependent tune shifts to maximize dynamic aperture and Touschek lifetime. A comparison between the performance of the new high-chromaticity optics and the design optics is also presented.

TUPMA03	Creation of High-charge Bunch Trains from the APS Injector for Swap-out Injection	595
	C. Yao, M. Borland, L. Donley, L. Emery, F. Lenkszus, B.X. Yang ANL, Argonne, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. A multi-bend-achromat (MBA) extreme low-emittance lattice has been proposed for the future APS Upgrade. Due to its small dynamic aperture, the traditional injection scheme must be replaced with bunch train swap-out scheme. Several options were considered for the creation of a high-charge bunch train from the injector, and we selected an option that builds the bunch train in the particle accumulator ring (PAR). This option enables both single-bunch mode, which is necessary to support current APS operation, and bunch-train mode. This report provides a description of the injection process, simulation results, and specifications of injector timing, kicker, and rf subsystems.

TUPMA04	Observation of +1 Bucket Bunch Impurity Growth at the APS Storage Ring	598
	C. Yao, M. Borland, B.X. Yang ANL, Argonne, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. The APS storage ring has three fill patterns: 24-singlet, hybrid, and 324 singlet. Bunch purity of better than 10^-6 is required for +3 and higher bucket numbers for the first two fill patterns during user operations. A PAR bunch cleaning system is used to clean up the satellite bunches. During top-up user operation, beam charge in satellite bunches grows due to the long lifetime of the low charge satellites. Recent storage ring development, including operating with the bunch-by-bunch feedback system, reduction of chromaticity, and lattice correction, has increased the beam dynamic aperture of the storage ring. We have observed unusual beam charge growth in +1 buckets, which indicates leakage of electrons from the main bunches to the +1 buckets. This report describes the observation and the dependency of leakage on chromaticity settings, and our analysis.

TUPMA07	Future Upgrades of the NSLS-II Injector	601
	T.V. Shaftan, R.P. Fliller, R. Heese, J. Rose, G.M. Wang, F.J. Willeke BNL, Upton, Long Island, New York, USA
	In 2013 the NSLS-II injector, which consists of 200 MeV linac, 3 GeV booster, transport lines and storage ring injection straight section, will be entering operations. While building the NSLS-II injection system we invested substantial efforts in developing and preserving options for future upgrades and enchancements. In this paper we discuss the potential of incremental evolution of the NSLS-II injector performance by enabling upgrade options, such as the second gun, flexible bunch patterns, beam stacking in the booster, emittance compensation techniques in the transport lines, etc. These upgrades will expand capabilites of the NSLS-II facility and increase operational reliability.

TUPMA08	Subpicosecond Bunch Train Production for High Power Tunable THz Source	604
	S.P. Antipov, C.-J. Jing, A. Kanareykin, P. Schoessow Euclid TechLabs, LLC, Solon, Ohio, USA M.G. Fedurin BNL, Upton, Long Island, New York, USA W. Gai, A. Zholents ANL, Argonne, USA V. Yakimenko SLAC, Menlo Park, California, USA
	Funding: DOE SBIR An effective method of introducing an energy modulation in an electron bunch by passing it through a dielectric-lined waveguide was recently demonstrated. In the follow up experiment we successfully converted this energy modulation into a density modulation by means of a chicane beamline. The density modulated beam was sent through a foil target, producing THz transition radiation which was characterized using interferometeric techniques. By changing the initial energy chirp of the beam we tuned the center frequency of the generated THz radiation in the range 0.5 - 1 THz. A table top high power narrowband tunable THz source based on this technique is proposed

TUPMA09	Analysis and Optimization of Coupler Kick in APEX	607
	H.J. Qian, S. Kwiatkowski, C. F. Papadopoulos, Z. Paret, F. Sannibale, J.W. Staples, R.P. Wells LBNL, Berkeley, California, USA
	A high repetition rate (~MHz) and high brightness photoinjector, based on VHF band CW normal conducting (NC) RF gun, is being developed under Advanced Photoinjector EXperiment (APEX) at Lawrence Berkeley Lab. A NC 30 MeV L-band linac system will be added after the gun to demonstrate beam brightness with lower repetition rate (~10 Hz). In this paper, coupler kicks from APEX buncher and acceleration cavities are evaluated by 3D RF simulation, analytical model and beam tracking, and coupler cells are optimized to minimize emittance dilution due to coupler kicks.

TUPMA10	LLNL X-band Test Station Status	610
	R.A. Marsh, F. Albert, G.G. Anderson, S.G. Anderson, C.P.J. Barty, E.T. Dayton, S.E. Fisher, D.J. Gibson, F.V. Hartemann, S.S.Q. Wu LLNL, Livermore, California, USA
	Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. An X-band test station is being built at LLNL to support inverse Compton-scattering x-ray and gamma-ray source development. The major components for the X-band test station have been designed, fabricated, installed, and aligned. The XL-4 klystron has been delivered, dressed and installed in the ScandiNova modulator, and tested to full peak power. Final assembly and bakeout of RF transport, test station supports, and accelerator components is complete, and the current status of commissioning and first beam will be presented and discussed. Future upgrade paths and configuration for a variety of x-ray and gamma-ray applications will be discussed along with schedule for planned experiments.

TUPMA13	Shaping Electron Bunches for Ultra-bright Electron Beam Acceleration in Dielectric Loaded Waveguides	613
	E.I. Simakov, C. Huang, T.J. Kwan, D.Y. Shchegolkov LANL, Los Alamos, New Mexico, 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. We present the design of an Emittance Exchanger (EEX) which is employed to generate a pair of a double-triangular drive bunch and a trapezoidal witness bunch for a Dielectric Wakefield Accelerator (DWA). We consider the concept of a high-brightness DWA with the gradient of above 100 MV/m and less than 0.1% induced energy spread in the accelerated beam as a possible afterburner for the proposed Los Alamos Matter-Radiation Interactions in Extremes (MaRIE) signature facility. Scoping studies have identified large induced energy spreads as the major cause of beam quality degradation in high-gradient advanced accelerator technologies. Among advanced accelerator technologies, DWAs hold significant advantages over plasma wakefield accelerators due to the elimination of plasma-induced effects, the fact that having the wakefield in vacuum ensures linearity, and their higher technological maturity. We will present simulations with Elegant of the possible EEX beamline taking into account non-linear effects, coherent synchrotron radiation and longitudinal space charge. Possibilities for producing ideal beam shapes to demonstrate low induced energy spread in a DWA will be discussed.

TUPMA15	Monte Carlo Simulations of Charge Transport and Electron Emission from GaAs Photocathodes	616
	Y. Choi, D.A. Dimitrov, C. Nieter Tech-X, Boulder, Colorado, USA I.V. Bazarov, S.S. Karkare Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: The authors wish to acknowledge the support of the U.S. Department of Energy (DOE) under SBIR grant DE-SC0006246 and Early Career DE-SC0003965. The need for a bright electron beam is increasing in the fields of x-ray science, electron diffraction and electron microscopy which are required for colliders. GaAs-based photocathodes have the potential to produce high-brightness, unpolarized and polarized, electron beams with performance that meets modern collider requirements. Even after decades of investigation, however, the exact mechanism of electron emission from GaAs is not well understood. Therefore, we investigate photoemission from a GaAs photocathode using detailed Monte Carlo electron transport simulations. Instead of a simple stepwise potential, we consider a triangular barrier including the effect of the image charge to take into account the effect of the applied field on the emission probability. The simulation results are compared with the experimental results for quantum eﬃciency, angular and energy distributions of emitted electrons without the assumption of any ad hoc parameters.

TUPMA16	High Capture Low Energy Spread Inverse Free Electron Laser Accelerator	619
	J.P. Duris, R.K. Li, P. Musumeci, E.W. Threlkeld UCLA, Los Angeles, California, USA
	Funding: This work was supported by DOE grant DE-FG02-92ER40693, Defense of Threat Reduction Agency award HDTRA1-10-1-0073, and University of California Office of the President award 09-LR-04-117055-MUSP. We present the design and construction of a strongly period-, field-, and gap-tapered helical undulator for use in a high-gradient, high-efficiency helical IFEL experiment at Brookhaven ATF. The undulator design achieves efficient acceleration without prebunching by matching the ponderomotive and resonant energy gradients along the length of the interaction for the measured laser parameters. Simulations based on the measured undulator fields and experimental parameters suggest that as much as 43 % of a 50 MeV beam will be accelerated to 94 MeV with 2.3 % rms energy spread.

TUPMA19	Wisconsin SRF Electron Gun Commissioning	622
	J. Bisognano, M.J. Bissen, R.A. Bosch, M.Y. Efremov, D. Eisert, M.V. Fisher, M.A. Green, K. Jacobs, R.G. Keil, K.J. Kleman, G.C. Rogers, M.C. Severson, D. Yavuz UW-Madison/SRC, Madison, Wisconsin, USA R. Bachimanchi, C. Hovater, R.A. Legg, T. E. Plawski, T. Powers JLAB, Newport News, Virginia, USA
	Funding: Work supported by DOE Award #DE-SC0005264 and the University of Wisconsin The University of Wisconsin has completed fabrication and commissioning of a low frequency (199.6 MHz) superconducting electron gun based on a quarter wave resonator (QWR) cavity. Its concept was optimized to be the source for a CW free electron laser facility. The gun design includes active tuning and a high temperature superconducting solenoid. We will report on the status of the Wisconsin SRF electron gun program, including commissioning experience and first beam measurements.

TUPMA20	Effect of RF Gradient upon the Performance of the Wisconsin SRF Electron Gun	625
	R.A. Bosch UW-Madison/SRC, Madison, Wisconsin, USA R.A. Legg JLAB, Newport News, Virginia, USA
	The performance of the Wisconsin 200-MHz SRF electron gun is simulated for several values of the RF gradient. Bunches with charge of 200 pC are modeled for the case where emittance compensation is completed during post-acceleration to 85 MeV in a TESLA module. We first perform simulations in which the initial bunch radius is optimal for the design gradient of 41 MV/m. We then optimize the radius as a function of RF gradient to improve the performance for low gradients.

Paper

Title

Page

Status and Future Plan of the Development of a Compact X-ray Source Based on ICS at Laser Undulator Compact X-ray (LUCX)

589

M.K. Fukuda, S. Araki, A.S. Aryshev, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
K. Sakaue, M. Washio
RISE, Tokyo, Japan

Funding: Work supported by the Quantum Beam Technology Program of MEXT
We have developed a compact X-ray source via inverse Compton scattering (ICS) between multi-bunch electron beam and a laser pulse stacked in an optical cavity at Laser Undulator Compact X-ray (LUCX) accelerator in KEK. Since the autumn of 2011, we have begun X-ray imaging test. In the beginning, it had taken two hours to get an X-ray image because of low intensity of X-ray with 10⁴ photons/pulse. To get a clear X-ray image in a shorter period of times, we have upgraded the accelerator, which consists of a 3.6 cell photo-cathode rf-gun, a 12cell standing wave accelerating structure and a 4-mirror planar optical cavity. The target intensity of an electron beam is 500nC/train with 1000 bunches at 30 MeV. The one of laser pulse is also 6mJ/pulse. The expected number of X-ray is 1.7x10⁷ photons/train with 10% bandwidth. We have already started the multi-bunch beam generation and X-ray imaging test after upgrade. The accelerator produces 24 MeV beam with the total charge of 180nC in 150 bunches per pulse. The aging process is also continued to increase energy and intensity. We will report the results of the beam test and future plan of the development of a compact X-ray source at LUCX.

TUPMA02

High-Chromaticity Optics for the MAX IV 3 GeV Storage Ring

592

T. Olsson, S.C. Leemann
MAX-lab, Lund, Sweden

The ultralow emittance lattice of the MAX IV 3 GeV storage ring has a large negative natural chromaticity. This has to be corrected to positive values to prevent head-tail instabilities. On the other hand, high linear chromaticity can lead to a large tune footprint which limits Touschek lifetime. Therefore, the linear chromaticity is corrected to +1 in both planes with sextupoles while octupoles are used to further reduce the tune footprint. Studies indicate this design leads to threshold currents for resistive wall and transverse mode coupling instabilities beyond what is expected during regular user operation. However, since these are only preliminary studies based on approximations, the possibility of instability issues during commissioning needs to be considered. A short term solution is to operate the storage ring at a higher chromaticity. This paper describes the developed high-chromaticity optics for the MAX IV 3 GeV storage ring. It focuses on reduction of chromatic and amplitude-dependent tune shifts to maximize dynamic aperture and Touschek lifetime. A comparison between the performance of the new high-chromaticity optics and the design optics is also presented.

TUPMA03

Creation of High-charge Bunch Trains from the APS Injector for Swap-out Injection

595

C. Yao, M. Borland, L. Donley, L. Emery, F. Lenkszus, B.X. Yang
ANL, Argonne, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
A multi-bend-achromat (MBA) extreme low-emittance lattice has been proposed for the future APS Upgrade. Due to its small dynamic aperture, the traditional injection scheme must be replaced with bunch train swap-out scheme. Several options were considered for the creation of a high-charge bunch train from the injector, and we selected an option that builds the bunch train in the particle accumulator ring (PAR). This option enables both single-bunch mode, which is necessary to support current APS operation, and bunch-train mode. This report provides a description of the injection process, simulation results, and specifications of injector timing, kicker, and rf subsystems.

TUPMA04

Observation of +1 Bucket Bunch Impurity Growth at the APS Storage Ring

598

C. Yao, M. Borland, B.X. Yang
ANL, Argonne, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The APS storage ring has three fill patterns: 24-singlet, hybrid, and 324 singlet. Bunch purity of better than 10^-6 is required for +3 and higher bucket numbers for the first two fill patterns during user operations. A PAR bunch cleaning system is used to clean up the satellite bunches. During top-up user operation, beam charge in satellite bunches grows due to the long lifetime of the low charge satellites. Recent storage ring development, including operating with the bunch-by-bunch feedback system, reduction of chromaticity, and lattice correction, has increased the beam dynamic aperture of the storage ring. We have observed unusual beam charge growth in +1 buckets, which indicates leakage of electrons from the main bunches to the +1 buckets. This report describes the observation and the dependency of leakage on chromaticity settings, and our analysis.

TUPMA07

Future Upgrades of the NSLS-II Injector

601

T.V. Shaftan, R.P. Fliller, R. Heese, J. Rose, G.M. Wang, F.J. Willeke
BNL, Upton, Long Island, New York, USA

In 2013 the NSLS-II injector, which consists of 200 MeV linac, 3 GeV booster, transport lines and storage ring injection straight section, will be entering operations. While building the NSLS-II injection system we invested substantial efforts in developing and preserving options for future upgrades and enchancements. In this paper we discuss the potential of incremental evolution of the NSLS-II injector performance by enabling upgrade options, such as the second gun, flexible bunch patterns, beam stacking in the booster, emittance compensation techniques in the transport lines, etc. These upgrades will expand capabilites of the NSLS-II facility and increase operational reliability.

TUPMA08

Subpicosecond Bunch Train Production for High Power Tunable THz Source

604

S.P. Antipov, C.-J. Jing, A. Kanareykin, P. Schoessow
Euclid TechLabs, LLC, Solon, Ohio, USA
M.G. Fedurin
BNL, Upton, Long Island, New York, USA
W. Gai, A. Zholents
ANL, Argonne, USA
V. Yakimenko
SLAC, Menlo Park, California, USA

Funding: DOE SBIR
An effective method of introducing an energy modulation in an electron bunch by passing it through a dielectric-lined waveguide was recently demonstrated. In the follow up experiment we successfully converted this energy modulation into a density modulation by means of a chicane beamline. The density modulated beam was sent through a foil target, producing THz transition radiation which was characterized using interferometeric techniques. By changing the initial energy chirp of the beam we tuned the center frequency of the generated THz radiation in the range 0.5 - 1 THz. A table top high power narrowband tunable THz source based on this technique is proposed

TUPMA09

Analysis and Optimization of Coupler Kick in APEX

607

H.J. Qian, S. Kwiatkowski, C. F. Papadopoulos, Z. Paret, F. Sannibale, J.W. Staples, R.P. Wells
LBNL, Berkeley, California, USA

A high repetition rate (~MHz) and high brightness photoinjector, based on VHF band CW normal conducting (NC) RF gun, is being developed under Advanced Photoinjector EXperiment (APEX) at Lawrence Berkeley Lab. A NC 30 MeV L-band linac system will be added after the gun to demonstrate beam brightness with lower repetition rate (~10 Hz). In this paper, coupler kicks from APEX buncher and acceleration cavities are evaluated by 3D RF simulation, analytical model and beam tracking, and coupler cells are optimized to minimize emittance dilution due to coupler kicks.

TUPMA10

LLNL X-band Test Station Status

610

R.A. Marsh, F. Albert, G.G. Anderson, S.G. Anderson, C.P.J. Barty, E.T. Dayton, S.E. Fisher, D.J. Gibson, F.V. Hartemann, S.S.Q. Wu
LLNL, Livermore, California, USA

Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
An X-band test station is being built at LLNL to support inverse Compton-scattering x-ray and gamma-ray source development. The major components for the X-band test station have been designed, fabricated, installed, and aligned. The XL-4 klystron has been delivered, dressed and installed in the ScandiNova modulator, and tested to full peak power. Final assembly and bakeout of RF transport, test station supports, and accelerator components is complete, and the current status of commissioning and first beam will be presented and discussed. Future upgrade paths and configuration for a variety of x-ray and gamma-ray applications will be discussed along with schedule for planned experiments.

TUPMA13

Shaping Electron Bunches for Ultra-bright Electron Beam Acceleration in Dielectric Loaded Waveguides

613

E.I. Simakov, C. Huang, T.J. Kwan, D.Y. Shchegolkov
LANL, Los Alamos, New Mexico, 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.
We present the design of an Emittance Exchanger (EEX) which is employed to generate a pair of a double-triangular drive bunch and a trapezoidal witness bunch for a Dielectric Wakefield Accelerator (DWA). We consider the concept of a high-brightness DWA with the gradient of above 100 MV/m and less than 0.1% induced energy spread in the accelerated beam as a possible afterburner for the proposed Los Alamos Matter-Radiation Interactions in Extremes (MaRIE) signature facility. Scoping studies have identified large induced energy spreads as the major cause of beam quality degradation in high-gradient advanced accelerator technologies. Among advanced accelerator technologies, DWAs hold significant advantages over plasma wakefield accelerators due to the elimination of plasma-induced effects, the fact that having the wakefield in vacuum ensures linearity, and their higher technological maturity. We will present simulations with Elegant of the possible EEX beamline taking into account non-linear effects, coherent synchrotron radiation and longitudinal space charge. Possibilities for producing ideal beam shapes to demonstrate low induced energy spread in a DWA will be discussed.

TUPMA15

Monte Carlo Simulations of Charge Transport and Electron Emission from GaAs Photocathodes

616

Y. Choi, D.A. Dimitrov, C. Nieter
Tech-X, Boulder, Colorado, USA
I.V. Bazarov, S.S. Karkare
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: The authors wish to acknowledge the support of the U.S. Department of Energy (DOE) under SBIR grant DE-SC0006246 and Early Career DE-SC0003965.
The need for a bright electron beam is increasing in the fields of x-ray science, electron diffraction and electron microscopy which are required for colliders. GaAs-based photocathodes have the potential to produce high-brightness, unpolarized and polarized, electron beams with performance that meets modern collider requirements. Even after decades of investigation, however, the exact mechanism of electron emission from GaAs is not well understood. Therefore, we investigate photoemission from a GaAs photocathode using detailed Monte Carlo electron transport simulations. Instead of a simple stepwise potential, we consider a triangular barrier including the effect of the image charge to take into account the effect of the applied field on the emission probability. The simulation results are compared with the experimental results for quantum eﬃciency, angular and energy distributions of emitted electrons without the assumption of any ad hoc parameters.

TUPMA16

High Capture Low Energy Spread Inverse Free Electron Laser Accelerator

619

J.P. Duris, R.K. Li, P. Musumeci, E.W. Threlkeld
UCLA, Los Angeles, California, USA

Funding: This work was supported by DOE grant DE-FG02-92ER40693, Defense of Threat Reduction Agency award HDTRA1-10-1-0073, and University of California Office of the President award 09-LR-04-117055-MUSP.
We present the design and construction of a strongly period-, field-, and gap-tapered helical undulator for use in a high-gradient, high-efficiency helical IFEL experiment at Brookhaven ATF. The undulator design achieves efficient acceleration without prebunching by matching the ponderomotive and resonant energy gradients along the length of the interaction for the measured laser parameters. Simulations based on the measured undulator fields and experimental parameters suggest that as much as 43 % of a 50 MeV beam will be accelerated to 94 MeV with 2.3 % rms energy spread.

TUPMA19

Wisconsin SRF Electron Gun Commissioning

622

J. Bisognano, M.J. Bissen, R.A. Bosch, M.Y. Efremov, D. Eisert, M.V. Fisher, M.A. Green, K. Jacobs, R.G. Keil, K.J. Kleman, G.C. Rogers, M.C. Severson, D. Yavuz
UW-Madison/SRC, Madison, Wisconsin, USA
R. Bachimanchi, C. Hovater, R.A. Legg, T. E. Plawski, T. Powers
JLAB, Newport News, Virginia, USA

Funding: Work supported by DOE Award #DE-SC0005264 and the University of Wisconsin
The University of Wisconsin has completed fabrication and commissioning of a low frequency (199.6 MHz) superconducting electron gun based on a quarter wave resonator (QWR) cavity. Its concept was optimized to be the source for a CW free electron laser facility. The gun design includes active tuning and a high temperature superconducting solenoid. We will report on the status of the Wisconsin SRF electron gun program, including commissioning experience and first beam measurements.

TUPMA20

Effect of RF Gradient upon the Performance of the Wisconsin SRF Electron Gun

625

R.A. Bosch
UW-Madison/SRC, Madison, Wisconsin, USA
R.A. Legg
JLAB, Newport News, Virginia, USA

The performance of the Wisconsin 200-MHz SRF electron gun is simulated for several values of the RF gradient. Bunches with charge of 200 pC are modeled for the case where emittance compensation is completed during post-acceleration to 85 MeV in a TESLA module. We first perform simulations in which the initial bunch radius is optimal for the design gradient of 41 MV/m. We then optimize the radius as a function of RF gradient to improve the performance for low gradients.