IPAC2011 - List of Authors (Honda, Y.)

Paper

Title

Page

Extreme High Vacuum System of High Brightness Electron Source for ERL

979

M. Yamamoto, T. Honda, Y. Honda, T. Miyajima, Y. Saito, Y. Tanimoto, T. Uchiyama
KEK, Ibaraki, Japan
H. Akimichi, H. Yoshida
AIST, Tsukuba, Japan
H. Kurisu
Yamaguchi University, Ube-Shi, Japan

A compact test accelerator for Japan’s future light source based on energy recovery linac (ERL) is under construction in KEK, aiming to demonstrate key technologies such as a high-brightness photocathode DC-gun and superconducting RF cavities. A DC-gun using GaAs-type photocathode which has a negative electron affinity (NEA) surface is employed. The NEA surface plays an indispensable role to extract electrons from conduction band minimum into vacuum. It assures high quantum efficiency of the photocathode and very low intrinsic emittance of the extracted beam. However, the NEA surface is extremely delicate against residual gas in vacuum. In order to extract mA-level beam currents continuously for more than several tens of hours, the pressure should be lower than the order of ·10^-10 Pa to avid the backbombardment of positive ions produced by the collision of accelerated electrons with residual gas molecules in the beam path. Recent achievements in the development of a 500-kV photocathode DC-gun and in the fundamental studies of its extreme high vacuum system will be presented.

Slides TUODB02 [1.606 MB]

TUPC119

A Comprehensive Study of Nanometer Resolution of the IPBPM at ATF2*

1296

Y.I. Kim, H. Park
Kyungpook National University, Daegu, Republic of Korea
S.T. Boogert
Royal Holloway, University of London, Surrey, United Kingdom
J.C. Frisch, D.J. McCormick, J. Nelson, T.J. Smith, G.R. White, M. Woodley
SLAC, Menlo Park, California, USA
Y. Honda, R. Sugahara, T. Tauchi, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Funding: Work supported in part by Department of Energy Contract DE-AC02-76SF00515.
High-resolution beam position monitors (IPBPMs) have been developed in order to measure the electron beam position at the focus point of ATF2 to a few nanometers in the vertical plane. To date, the IPBPM system has operated in test mode with a highest demonstrated resolution of 8.7 nm in the ATF extraction line during 2008. After expected noise source calculations there still remains 7.9 nm of noise of unexplained origin. We summarize the experimental work on the IPBPM system since this measurement and outline the possible origins of these sources. We then present a study plan to be performed at the ATF2 facility designed to identify and to improve the resolution performance and comment on the expected ultimate resolution of this system.

TUPC161

Cavity Beam Position Monitor System for ATF2

1410

S.T. Boogert, R. Ainsworth, G.E. Boorman, S. Molloy
Royal Holloway, University of London, Surrey, United Kingdom
A.S. Aryshev, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
F.J. Cullinan, N.Y. Joshi, A. Lyapin
JAI, Egham, Surrey, United Kingdom
J.C. Frisch, D.J. McCormick, J. Nelson, T.J. Smith, G.R. White
SLAC, Menlo Park, California, USA
A. Heo, E.-S. Kim, Y.I. Kim
KNU, Deagu, Republic of Korea

The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a future high energy lepton linear collider. The ATF2 beam-line is instrumented with a total of 41 high resolution C and S band resonant cavity beam position monitors (BPM) with associated mixer electronics and digitizers. In addition 4 high resolution BPMs have been recently installed at the interaction point, we briefly describe the first operational experience of these cavities in the ATF2 beam-line. The current status of the overall BPM system is also described, with a focus on operational techniques and performance.

TUPO012

Stable Planner Type Four-mirror Cavity Development for X-ray Production as Basic Development of Quantum Beam Technology Program

1470

H. Shimizu, Y. Higashi, Y. Honda, J. Urakawa
KEK, Ibaraki, Japan

As the development of quantum beam technology program, a facility to produce a semi-monochromatic X-ray via inverse Compton scattering with an electron beam accelerated by a superconducting RF cavity and a fiber amplified high power laser stacked in an external optical cavity system are now under construction. To achieve high brightness of Compton X-ray, we introduced a chicane with about a 1m-long zero dispersion straight section that includes IP. Head on collision scheme improves the yield of X-ray, but to do so, a huge and stout external optical cavity system must be needed. According to this demand, we develop a quite tolerable planner type four-mirror cavity with movable mirror mount system. In this paper, results obtained by the cavity construction and also laser development activities are described.

THPC034

Post-earthquake Recovery of PF Ring and PF-AR

2984

T. Honda, T. Aoto, S. Asaoka, K. Endo, K. Haga, K. Harada, Y. Honda, M. Izawa, Y. Kobayashi, A. Mishina, T. Miyajima, H. Miyauchi, S. Nagahashi, N. Nakamura, T. Nogami, T. Obina, T. Ozaki, C.O. Pak, H. Sakai, S. Sakanaka, H. Sasaki, Y. Sato, K. Satoh, M. Shimada, T. Shioya, M. Tadano, T. Tahara, T. Takahashi, R. Takai, Y. Tanimoto, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, M. Yamamoto
KEK, Ibaraki, Japan

When the unprecedented scale of earthquake occurred in Japan on the afternoon of March 11, 2011, PF ring and PF-AR, two synchrotron light sources in KEK, also suffered various damages. At PF ring, a formed bellows in a wall current monitor was broken, and atmospheric air rushed into the beam duct. At PF-AR, which is installed in the underground tunnel, the alignment of the ring magnets seemed to be disordered to an order of ten mm. At both rings, a lot of electronics racks and toolboxes in the control rooms or in the experimental halls were tilted or tipped over. It was extremely fortunate that the user operation had just been stopped on the morning of that day, and all the gate valves in the rings and to the beam lines had already been closed for the scheduled shutdown. A wide area blackout took place at the big earthquake, and the electric power for the accelerator was interrupted over the next two weeks because of temporal shortage of the electricity in the eastern part of Japan. In April, we could start detailed investigation of machine damages and repair works towards recommissioning of the rings before the summer and resumption of the user operations in the autumn.

TUPO002

High Flux Polarized Gamma Rays Production: First Measurements with a Four-mirror Cavity at the ATF

1446

N. Delerue, J. Bonis, I. Chaikovska, R. Chiche, R. Cizeron, M. Cohen, P. Cornebise, R. Flaminio, D. Jehanno, F. Labaye, M. Lacroix, Y. Peinaud, L. Pinard, V. Soskov, A. Variola, Z.F. Zomer
LAL, Orsay, France
T. Akagi, S. Miyoshi
Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima, Japan
S. Araki, Y. Funahashi, Y. Honda, T. Omori, H. Shimizu, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
E. Cormier
CELIA, Talence, France
T. Takahashi
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan

Funding: ANR, IN2P3
The next generation of e+/e^- colliders will require the production of a very intense flux of gamma rays to allow polarized positrons to be produced in sufficient quantities. To demonstrate that this can be achieved a four-mirror cavity has recently been installed at the Accelerator Test Facility (ATF) at KEK to produce a high flux of polarized gamma rays by inverse Compton scattering. A four-mirror non-planar geometry is used to ensure the polarization of the gamma rays produced. The main mechanical features of the cavity are presented. A fibre amplifier is used to inject about 10W in the high finesse cavity with a gain of 1000. A digital feedback system is used to keep the cavity at the length required for the optimal power enhancement. First preliminary measurements show that on some beam crossings the interactions produce more than 25 photons with an average energy of about 24 MeV. Several upgrades currently in progress are described.

Paper	Title	Page
TUODB02	Extreme High Vacuum System of High Brightness Electron Source for ERL	979
	M. Yamamoto, T. Honda, Y. Honda, T. Miyajima, Y. Saito, Y. Tanimoto, T. Uchiyama KEK, Ibaraki, Japan H. Akimichi, H. Yoshida AIST, Tsukuba, Japan H. Kurisu Yamaguchi University, Ube-Shi, Japan
	A compact test accelerator for Japan’s future light source based on energy recovery linac (ERL) is under construction in KEK, aiming to demonstrate key technologies such as a high-brightness photocathode DC-gun and superconducting RF cavities. A DC-gun using GaAs-type photocathode which has a negative electron affinity (NEA) surface is employed. The NEA surface plays an indispensable role to extract electrons from conduction band minimum into vacuum. It assures high quantum efficiency of the photocathode and very low intrinsic emittance of the extracted beam. However, the NEA surface is extremely delicate against residual gas in vacuum. In order to extract mA-level beam currents continuously for more than several tens of hours, the pressure should be lower than the order of ·10^-10 Pa to avid the backbombardment of positive ions produced by the collision of accelerated electrons with residual gas molecules in the beam path. Recent achievements in the development of a 500-kV photocathode DC-gun and in the fundamental studies of its extreme high vacuum system will be presented.
	Slides TUODB02 [1.606 MB]

TUPC119	A Comprehensive Study of Nanometer Resolution of the IPBPM at ATF2*	1296
	Y.I. Kim, H. Park Kyungpook National University, Daegu, Republic of Korea S.T. Boogert Royal Holloway, University of London, Surrey, United Kingdom J.C. Frisch, D.J. McCormick, J. Nelson, T.J. Smith, G.R. White, M. Woodley SLAC, Menlo Park, California, USA Y. Honda, R. Sugahara, T. Tauchi, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	Funding: Work supported in part by Department of Energy Contract DE-AC02-76SF00515. High-resolution beam position monitors (IPBPMs) have been developed in order to measure the electron beam position at the focus point of ATF2 to a few nanometers in the vertical plane. To date, the IPBPM system has operated in test mode with a highest demonstrated resolution of 8.7 nm in the ATF extraction line during 2008. After expected noise source calculations there still remains 7.9 nm of noise of unexplained origin. We summarize the experimental work on the IPBPM system since this measurement and outline the possible origins of these sources. We then present a study plan to be performed at the ATF2 facility designed to identify and to improve the resolution performance and comment on the expected ultimate resolution of this system.

TUPC161	Cavity Beam Position Monitor System for ATF2	1410
	S.T. Boogert, R. Ainsworth, G.E. Boorman, S. Molloy Royal Holloway, University of London, Surrey, United Kingdom A.S. Aryshev, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan F.J. Cullinan, N.Y. Joshi, A. Lyapin JAI, Egham, Surrey, United Kingdom J.C. Frisch, D.J. McCormick, J. Nelson, T.J. Smith, G.R. White SLAC, Menlo Park, California, USA A. Heo, E.-S. Kim, Y.I. Kim KNU, Deagu, Republic of Korea
	The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a future high energy lepton linear collider. The ATF2 beam-line is instrumented with a total of 41 high resolution C and S band resonant cavity beam position monitors (BPM) with associated mixer electronics and digitizers. In addition 4 high resolution BPMs have been recently installed at the interaction point, we briefly describe the first operational experience of these cavities in the ATF2 beam-line. The current status of the overall BPM system is also described, with a focus on operational techniques and performance.

TUPO012	Stable Planner Type Four-mirror Cavity Development for X-ray Production as Basic Development of Quantum Beam Technology Program	1470
	H. Shimizu, Y. Higashi, Y. Honda, J. Urakawa KEK, Ibaraki, Japan
	As the development of quantum beam technology program, a facility to produce a semi-monochromatic X-ray via inverse Compton scattering with an electron beam accelerated by a superconducting RF cavity and a fiber amplified high power laser stacked in an external optical cavity system are now under construction. To achieve high brightness of Compton X-ray, we introduced a chicane with about a 1m-long zero dispersion straight section that includes IP. Head on collision scheme improves the yield of X-ray, but to do so, a huge and stout external optical cavity system must be needed. According to this demand, we develop a quite tolerable planner type four-mirror cavity with movable mirror mount system. In this paper, results obtained by the cavity construction and also laser development activities are described.

THPC034	Post-earthquake Recovery of PF Ring and PF-AR	2984
	T. Honda, T. Aoto, S. Asaoka, K. Endo, K. Haga, K. Harada, Y. Honda, M. Izawa, Y. Kobayashi, A. Mishina, T. Miyajima, H. Miyauchi, S. Nagahashi, N. Nakamura, T. Nogami, T. Obina, T. Ozaki, C.O. Pak, H. Sakai, S. Sakanaka, H. Sasaki, Y. Sato, K. Satoh, M. Shimada, T. Shioya, M. Tadano, T. Tahara, T. Takahashi, R. Takai, Y. Tanimoto, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, M. Yamamoto KEK, Ibaraki, Japan
	When the unprecedented scale of earthquake occurred in Japan on the afternoon of March 11, 2011, PF ring and PF-AR, two synchrotron light sources in KEK, also suffered various damages. At PF ring, a formed bellows in a wall current monitor was broken, and atmospheric air rushed into the beam duct. At PF-AR, which is installed in the underground tunnel, the alignment of the ring magnets seemed to be disordered to an order of ten mm. At both rings, a lot of electronics racks and toolboxes in the control rooms or in the experimental halls were tilted or tipped over. It was extremely fortunate that the user operation had just been stopped on the morning of that day, and all the gate valves in the rings and to the beam lines had already been closed for the scheduled shutdown. A wide area blackout took place at the big earthquake, and the electric power for the accelerator was interrupted over the next two weeks because of temporal shortage of the electricity in the eastern part of Japan. In April, we could start detailed investigation of machine damages and repair works towards recommissioning of the rings before the summer and resumption of the user operations in the autumn.

TUPO002	High Flux Polarized Gamma Rays Production: First Measurements with a Four-mirror Cavity at the ATF	1446
	N. Delerue, J. Bonis, I. Chaikovska, R. Chiche, R. Cizeron, M. Cohen, P. Cornebise, R. Flaminio, D. Jehanno, F. Labaye, M. Lacroix, Y. Peinaud, L. Pinard, V. Soskov, A. Variola, Z.F. Zomer LAL, Orsay, France T. Akagi, S. Miyoshi Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima, Japan S. Araki, Y. Funahashi, Y. Honda, T. Omori, H. Shimizu, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan E. Cormier CELIA, Talence, France T. Takahashi Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
	Funding: ANR, IN2P3 The next generation of e+/e^- colliders will require the production of a very intense flux of gamma rays to allow polarized positrons to be produced in sufficient quantities. To demonstrate that this can be achieved a four-mirror cavity has recently been installed at the Accelerator Test Facility (ATF) at KEK to produce a high flux of polarized gamma rays by inverse Compton scattering. A four-mirror non-planar geometry is used to ensure the polarization of the gamma rays produced. The main mechanical features of the cavity are presented. A fibre amplifier is used to inject about 10W in the high finesse cavity with a gain of 1000. A digital feedback system is used to keep the cavity at the length required for the optimal power enhancement. First preliminary measurements show that on some beam crossings the interactions produce more than 25 photons with an average energy of about 24 MeV. Several upgrades currently in progress are described.