PAC2013 - List of Authors (Gai, W.)

Paper	Title	Page
MOPHO19	A Tunable Energy Chirp Correction	279
	S.P. Antipov, C.-J. Jing, A. Kanareykin, P. Schoessow Euclid TechLabs, LLC, Solon, Ohio, USA S. Baturin LETI, Saint-Petersburg, Russia M.G. Fedurin, C. Swinson BNL, Upton, Long Island, New York, USA W. Gai, A. Zholents ANL, Argonne, USA
	Funding: DOE SBIR Short (subpicosecond) pulses are central to many of the next generation light source initiatives that are based on linear accelerators. Beam compression is performed by means of a chicane utilizing a correlated linear energy chirp. The small energy chirp is kept as the beam goes through the remaining accelerating stage to compensate for wakefield effects. It is necessary to compensate the residual energy spread before the beam enters the undulator stage. We present here a concept for a passive wakefield device- the wakefield silencer- to perform this compensation. We have recently demonstrated a passive energy chirp correction by self-wakefield at the Brookhaven ATF facility. In this paper we present a progress report on development of these tunable chirp correction devices.

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

TUPSM05	Studies of Field and Photo-Emission in a New Short-Pulse, High-Charge Cs2Te RF Photocathode Gun	637
	E.E. Wisniewski, M.E. Conde, W. Gai, C.-J. Jing, W. Liu, J.G. Power ANL, Argonne, USA C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA L.K. Spentzouris, Z.M. Yusof Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: This work was funded by the U.S. Dept. of Energy Office of Science under contract number Agency DE-AC02-06CH11357. A new high-charge RF gun is now operating at the Argonne Wakefield Accelerator (AWA) facility at Argonne National Laboratory (ANL). The 1.5 cell 1.3 GHz gun uses a Cesium telluride photocathode driven with a 248 nm laser to provide short-pulse, high charge electron beams for the new 75 MeV drive beamline. The high-gradient RF gun (peak field on the cathode > 80MV/m) is a key piece of the facility upgrade (see M. E. Conde, this proceedings). The large Cs2Te photocathode (diameter > 30 mm) is fabricated in-house. The photo-injector generates high-charge, short pulse, single bunches (Q > 100 nC) or bunch-trains (Q > 1000 nC) for wakefield experiments, typically involving dielectric-loaded accelerating structures. Field-emitted dark current from the Cs2Te cathode was measured during RF conditioning. Fowler-Nordheim plots of the data are presented and compared to similar measurements made using a copper cathode in the initial phase of conditioning. Results of quantum efficiency (QE) studies are presented with the cathode operating in both single and bunch-train modes.

WEPMA08	Tuning, Conditioning, and Dark Current Measurements of the 1300 MHz NCRF Cavities at Argonne Wakefield Accelerator (AWA) Facility	996
	J.G. Power, M.E. Conde, D.S. Doran, W. Gai, C.-J. Jing ANL, Argonne, USA C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA E.E. Wisniewski Illinois Institute of Technology, Chicago, Illinois, USA
	Six normal-conducting, L-band rf cavities have recently been commissioned as part of the upgrade to the AWA facility . The cavity design is a seven-cell, standing-wave, 1300 MHz cavity made with OFE copper and was reported on earlier . In this paper, we present data on: (i) tuning and balancing; (ii) high-power rf conditioning; and (iii) dark current measurements; of the cavities. All six cavities were tuned to 1300 MHz and were balanced to >96% in all cells. They are designed to operate with 10 MW of rf input power but were conditioned beyond this operating point to insure low dark current during operation. During rf conditioning, we recorded the arcing history to better understand the overall conditioning time and the final breakdown rate. Finally, dark current measurements were used to measure the cavity’s surface field enhancement factor, “beta” throughout rf conditioning to record how the condition of the surface evolved during rf conditioning. M.E. Conde et al., see these proceedings. ** J.G. Power et al., in proceedings of IPAC 2010

Paper

Title

Page

A Tunable Energy Chirp Correction

279

S.P. Antipov, C.-J. Jing, A. Kanareykin, P. Schoessow
Euclid TechLabs, LLC, Solon, Ohio, USA
S. Baturin
LETI, Saint-Petersburg, Russia
M.G. Fedurin, C. Swinson
BNL, Upton, Long Island, New York, USA
W. Gai, A. Zholents
ANL, Argonne, USA

Funding: DOE SBIR
Short (subpicosecond) pulses are central to many of the next generation light source initiatives that are based on linear accelerators. Beam compression is performed by means of a chicane utilizing a correlated linear energy chirp. The small energy chirp is kept as the beam goes through the remaining accelerating stage to compensate for wakefield effects. It is necessary to compensate the residual energy spread before the beam enters the undulator stage. We present here a concept for a passive wakefield device- the wakefield silencer- to perform this compensation. We have recently demonstrated a passive energy chirp correction by self-wakefield at the Brookhaven ATF facility. In this paper we present a progress report on development of these tunable chirp correction devices.

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

TUPSM05

Studies of Field and Photo-Emission in a New Short-Pulse, High-Charge Cs2Te RF Photocathode Gun

637

E.E. Wisniewski, M.E. Conde, W. Gai, C.-J. Jing, W. Liu, J.G. Power
ANL, Argonne, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
L.K. Spentzouris, Z.M. Yusof
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: This work was funded by the U.S. Dept. of Energy Office of Science under contract number Agency DE-AC02-06CH11357.
A new high-charge RF gun is now operating at the Argonne Wakefield Accelerator (AWA) facility at Argonne National Laboratory (ANL). The 1.5 cell 1.3 GHz gun uses a Cesium telluride photocathode driven with a 248 nm laser to provide short-pulse, high charge electron beams for the new 75 MeV drive beamline. The high-gradient RF gun (peak field on the cathode > 80MV/m) is a key piece of the facility upgrade (see M. E. Conde, this proceedings). The large Cs2Te photocathode (diameter > 30 mm) is fabricated in-house. The photo-injector generates high-charge, short pulse, single bunches (Q > 100 nC) or bunch-trains (Q > 1000 nC) for wakefield experiments, typically involving dielectric-loaded accelerating structures. Field-emitted dark current from the Cs2Te cathode was measured during RF conditioning. Fowler-Nordheim plots of the data are presented and compared to similar measurements made using a copper cathode in the initial phase of conditioning. Results of quantum efficiency (QE) studies are presented with the cathode operating in both single and bunch-train modes.

WEPMA08

Tuning, Conditioning, and Dark Current Measurements of the 1300 MHz NCRF Cavities at Argonne Wakefield Accelerator (AWA) Facility

996

J.G. Power, M.E. Conde, D.S. Doran, W. Gai, C.-J. Jing
ANL, Argonne, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
E.E. Wisniewski
Illinois Institute of Technology, Chicago, Illinois, USA

Six normal-conducting, L-band rf cavities have recently been commissioned as part of the upgrade to the AWA facility *. The cavity design is a seven-cell, standing-wave, 1300 MHz cavity made with OFE copper and was reported on earlier **. In this paper, we present data on: (i) tuning and balancing; (ii) high-power rf conditioning; and (iii) dark current measurements; of the cavities. All six cavities were tuned to 1300 MHz and were balanced to >96% in all cells. They are designed to operate with 10 MW of rf input power but were conditioned beyond this operating point to insure low dark current during operation. During rf conditioning, we recorded the arcing history to better understand the overall conditioning time and the final breakdown rate. Finally, dark current measurements were used to measure the cavity’s surface field enhancement factor, “beta” throughout rf conditioning to record how the condition of the surface evolved during rf conditioning.
* M.E. Conde et al., see these proceedings.
** J.G. Power et al., in proceedings of IPAC 2010