IPAC2011 - List of Authors (Kashiwagi, S.)

Paper	Title	Page
MOPC014	RF Processing of L-band RF Gun for KEK-STF	92
	M. Kuriki, H. Iijima, Y.M. Masumoto HU/AdSM, Higashi-Hiroshima, Japan H. Hayano, H. Sugiyama, J. Urakawa, K. Watanabe KEK, Ibaraki, Japan G. Isoyama, R. Kato ISIR, Osaka, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan Y. Takahashi Sokendai, Ibaraki, Japan
	Funding: This work is supported by MEXT Quantum Beam Technology Program, KEK Promotion of collaborative research programs in universitie. KEK STF (Superconducting Test Facility) is established for developing super-conducting accelerator technology for ILC (International Linear Collider). At KEK-STF, accelerator operation with a beam loading is planned in 2013. An electron injector based on L-band Photo-cathode RF gun is now being developed. A L-band RF gun designed by DESY and fabricated by FNAL has been placed in KEK-STF and RF processing was carried out. The results of the RF processing and status of STF injector will be presented.

TUPC059	Study on Energy Compensation by RF Amplitude Modulation for High Intense Electron Beam Generated by a Photocathode RF-Gun	1132
	Y. Yokoyama, T. Aoki, K. Sakaue, T. Suzuki, M. Washio, T. Yamamoto RISE, Tokyo, Japan H. Hayano, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan R. Kuroda AIST, Tsukuba, Ibaraki, Japan
	Funding: Work supported by JSPS Grant-in-Aid for Scientific Research(A)10001690 and JST Quantum Beam Program. At Waseda University, we have been studying a high quality electron beam generation and its application experiments with a Cs-Te photocathode RF-Gun. To generate more intense and stable electron beam, we have been developing the cathode irradiating UV laser which consists of optical fiber amplifier and LD pumped amplifier. As the result, more than 100 multi-bunch electron beam with 1nC each bunch charge was obtained. However, it is considered that the accelerating voltage will decrease because of the beam loading effect. So we have studied the RF amplitude modulation technique to compensate the beam energy difference. The energy difference will caused by transient accelerating voltage in RF-Gun cavity and beam loading effect. As the result of this compensation method, the energy difference has been compensated to 1%p-p, while 5%p-p without compensation. In this conference, we will report the details of energy compensation method using the RF amplitude modulation, the results of beam experiments and the future plans.

WEPC036	Coherent Synchrotron Radiation Source Based on an Isochronous Accumulator Ring with Femtosecond Electron Bunches	2085
	N.Y. Huang NTHU, Hsinchu, Taiwan H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, F. Miyahara, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, Research Center for Electron Photon Science, Sendai, Japan W.K. Lau NSRRC, Hsinchu, Taiwan
	A compact isochronous accumulator ring has been studied as a source of coherent synchrotron radiation (CSR) at a wavelength region from THz to GHz. Since the thermionic rf gun is substantially stable in general, we anticipate a bunch train of very short electron pulses can be provided satisfactorily by means of velocity bunching. Careful numerical simulations show possibility of the bunch length of much less than 100 fs with a bunch charge of 20 pC, which will contain sufficiently large form factor for production of CSR at the wavelengths longer than ~ 0.1 mm. The coherent THz radiation of high average power will be achieved if the short bunches can be circulated in the accumulator ring without bunch lengthening. This paper will describe the optimization of thermionic injector to produce femtosecond bunches in addition to study of the lattice designing of complete isochronous optics for the accumulator ring.

THPS090	Development of the Pulse Radiolysis System with a Supercontinuum Radiation using Photonic Crystal Fiber	3645
	K.B. Ogata, R. Betto, Y. Hosaka, Y. Kawauchi, K. Sakaue, T. Suzuki, M. Washio RISE, Tokyo, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan R. Kuroda AIST, Tsukuba, Ibaraki, Japan
	Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 In usage of radiation, it is important to study the process of chemical effects of ionizing radiation in a material. Pulse radiolysis is a method to trace these rapid initial chemical reactions by ionizing radiation. As a pump beam, we are using 5MeV electron beam produced from the S-band photo cathode RF-Gun. In nanosecond timescale pulse radiolysis, it is required the stable probe light of a broad spectrum. And especially in picosecond timescale pulse radiolysis, probe light should have short pulse width to use stroboscopic method. Therefore, in order to develop a wide range of timescale experimental system, we have been developing a Supercontinuum (SC) light as a probe light, which is generated by nonlinear optical process of short pulse IR laser in photonic crystal fiber (PCF). As a result, the SC light spectrum is broad enough to use as a probe light. Then we tried to measure the absorption spectrum of hydrated electron by SC light, we successfully observed good signal-noise ratio data both nanosecond and picosecond experiment with unified pulse　radiolysis system. In this conference, we will report details of these results and future prospects.

THPC040	Expected Performance Characteristic of Accelerator-based THz Source at Tohoku University	2990
	H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, School of Science, Sendai, Japan N.Y. Huang NTHU, Hsinchu, Taiwan
	Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003. Sources of coherent synchrotron radiation at THz wavelength region have been constructed at Tohoku University. Bunch train of extremely shorter electron pulse less than 100 fs will be provided by an injector linac employing thermionic rf gun, where the bunch compression will be performed by means of velocity bunching in an accelerator structure. Radiation source under development are a Halbach type planar undulator and an accumulator isochronous ring. The undulator employs large gap and long period length configuration, so that the resonant frequency of 1 THz is achieved when a lower beam energy of ~ 20 MeV. Since spectrum of coherent synchrotron radiation (CSR) is strongly depending on longitudinal bunch form factor, we have calculated CSR spectra for various conditions of the beam to evaluate the performance of the THz source. Numerical simulation with multi-particle system has been carried out to understand the radiation power and angular distribution as well. The beam transport in the undulator is crucial for quality of the radiation because the beam energy is very much low relative to strong focusing power. Characteristics of THz CSR from the undulator will be discussed.

THPC041	Injector System of Test Accelerator as Coherent Terahertz Source	2993
	S. Kashiwagi, H. Hama, F. Hinode, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka Tohoku University, School of Science, Sendai, Japan N.Y. Huang NTHU, Hsinchu, Taiwan F. Miyahara KEK, Ibaraki, Japan
	Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003. A test accelerator as a coherent terahertz source (t-ACTS) project has been under development at Tohoku University, in which a generation of intense coherent terahertz (THz) radiation from sub-picosecond electron bunch will be demonstrated. We will supply a wide-band coherent radiation from bending magnets in an isochronous ring and a narrow-band coherent THz radiation using an undulator in a linac. Stable generation of very short electron bunch is one of the key issues in the t-ACTS project. The injector system is consists of a thermionic RF gun with two independent cavity cells, an alpha magnet and an accelerating structure. A velocity bunching scheme is employed to produce the very short electron bunch. Components of the t-ACTS injector except the accelerating structure have already been installed and we have started a high power RF processing of the gun cavities. The characteristics of electron bunch extracted from the RF gun are measured by varying phase and amplitude of input RF fields for the gun cavities. The status of t-ACTS project will be presented in the conference.

Paper

Title

Page

RF Processing of L-band RF Gun for KEK-STF

92

M. Kuriki, H. Iijima, Y.M. Masumoto
HU/AdSM, Higashi-Hiroshima, Japan
H. Hayano, H. Sugiyama, J. Urakawa, K. Watanabe
KEK, Ibaraki, Japan
G. Isoyama, R. Kato
ISIR, Osaka, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
Y. Takahashi
Sokendai, Ibaraki, Japan

Funding: This work is supported by MEXT Quantum Beam Technology Program, KEK Promotion of collaborative research programs in universitie.
KEK STF (Superconducting Test Facility) is established for developing super-conducting accelerator technology for ILC (International Linear Collider). At KEK-STF, accelerator operation with a beam loading is planned in 2013. An electron injector based on L-band Photo-cathode RF gun is now being developed. A L-band RF gun designed by DESY and fabricated by FNAL has been placed in KEK-STF and RF processing was carried out. The results of the RF processing and status of STF injector will be presented.

TUPC059

Study on Energy Compensation by RF Amplitude Modulation for High Intense Electron Beam Generated by a Photocathode RF-Gun

1132

Y. Yokoyama, T. Aoki, K. Sakaue, T. Suzuki, M. Washio, T. Yamamoto
RISE, Tokyo, Japan
H. Hayano, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
R. Kuroda
AIST, Tsukuba, Ibaraki, Japan

Funding: Work supported by JSPS Grant-in-Aid for Scientific Research(A)10001690 and JST Quantum Beam Program.
At Waseda University, we have been studying a high quality electron beam generation and its application experiments with a Cs-Te photocathode RF-Gun. To generate more intense and stable electron beam, we have been developing the cathode irradiating UV laser which consists of optical fiber amplifier and LD pumped amplifier. As the result, more than 100 multi-bunch electron beam with 1nC each bunch charge was obtained. However, it is considered that the accelerating voltage will decrease because of the beam loading effect. So we have studied the RF amplitude modulation technique to compensate the beam energy difference. The energy difference will caused by transient accelerating voltage in RF-Gun cavity and beam loading effect. As the result of this compensation method, the energy difference has been compensated to 1%p-p, while 5%p-p without compensation. In this conference, we will report the details of energy compensation method using the RF amplitude modulation, the results of beam experiments and the future plans.

WEPC036

Coherent Synchrotron Radiation Source Based on an Isochronous Accumulator Ring with Femtosecond Electron Bunches

2085

N.Y. Huang
NTHU, Hsinchu, Taiwan
H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, F. Miyahara, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
W.K. Lau
NSRRC, Hsinchu, Taiwan

A compact isochronous accumulator ring has been studied as a source of coherent synchrotron radiation (CSR) at a wavelength region from THz to GHz. Since the thermionic rf gun is substantially stable in general, we anticipate a bunch train of very short electron pulses can be provided satisfactorily by means of velocity bunching. Careful numerical simulations show possibility of the bunch length of much less than 100 fs with a bunch charge of 20 pC, which will contain sufficiently large form factor for production of CSR at the wavelengths longer than ~ 0.1 mm. The coherent THz radiation of high average power will be achieved if the short bunches can be circulated in the accumulator ring without bunch lengthening. This paper will describe the optimization of thermionic injector to produce femtosecond bunches in addition to study of the lattice designing of complete isochronous optics for the accumulator ring.

THPS090

Development of the Pulse Radiolysis System with a Supercontinuum Radiation using Photonic Crystal Fiber

3645

K.B. Ogata, R. Betto, Y. Hosaka, Y. Kawauchi, K. Sakaue, T. Suzuki, M. Washio
RISE, Tokyo, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
R. Kuroda
AIST, Tsukuba, Ibaraki, Japan

Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690
In usage of radiation, it is important to study the process of chemical effects of ionizing radiation in a material. Pulse radiolysis is a method to trace these rapid initial chemical reactions by ionizing radiation. As a pump beam, we are using 5MeV electron beam produced from the S-band photo cathode RF-Gun. In nanosecond timescale pulse radiolysis, it is required the stable probe light of a broad spectrum. And especially in picosecond timescale pulse radiolysis, probe light should have short pulse width to use stroboscopic method. Therefore, in order to develop a wide range of timescale experimental system, we have been developing a Supercontinuum (SC) light as a probe light, which is generated by nonlinear optical process of short pulse IR laser in photonic crystal fiber (PCF). As a result, the SC light spectrum is broad enough to use as a probe light. Then we tried to measure the absorption spectrum of hydrated electron by SC light, we successfully observed good signal-noise ratio data both nanosecond and picosecond experiment with unified pulse　radiolysis system. In this conference, we will report details of these results and future prospects.

THPC040

Expected Performance Characteristic of Accelerator-based THz Source at Tohoku University

2990

H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, School of Science, Sendai, Japan
N.Y. Huang
NTHU, Hsinchu, Taiwan

Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003.
Sources of coherent synchrotron radiation at THz wavelength region have been constructed at Tohoku University. Bunch train of extremely shorter electron pulse less than 100 fs will be provided by an injector linac employing thermionic rf gun, where the bunch compression will be performed by means of velocity bunching in an accelerator structure. Radiation source under development are a Halbach type planar undulator and an accumulator isochronous ring. The undulator employs large gap and long period length configuration, so that the resonant frequency of 1 THz is achieved when a lower beam energy of ~ 20 MeV. Since spectrum of coherent synchrotron radiation (CSR) is strongly depending on longitudinal bunch form factor, we have calculated CSR spectra for various conditions of the beam to evaluate the performance of the THz source. Numerical simulation with multi-particle system has been carried out to understand the radiation power and angular distribution as well. The beam transport in the undulator is crucial for quality of the radiation because the beam energy is very much low relative to strong focusing power. Characteristics of THz CSR from the undulator will be discussed.

THPC041

Injector System of Test Accelerator as Coherent Terahertz Source

2993

S. Kashiwagi, H. Hama, F. Hinode, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka
Tohoku University, School of Science, Sendai, Japan
N.Y. Huang
NTHU, Hsinchu, Taiwan
F. Miyahara
KEK, Ibaraki, Japan

Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (S), Contract #20226003.
A test accelerator as a coherent terahertz source (t-ACTS) project has been under development at Tohoku University, in which a generation of intense coherent terahertz (THz) radiation from sub-picosecond electron bunch will be demonstrated. We will supply a wide-band coherent radiation from bending magnets in an isochronous ring and a narrow-band coherent THz radiation using an undulator in a linac. Stable generation of very short electron bunch is one of the key issues in the t-ACTS project. The injector system is consists of a thermionic RF gun with two independent cavity cells, an alpha magnet and an accelerating structure. A velocity bunching scheme is employed to produce the very short electron bunch. Components of the t-ACTS injector except the accelerating structure have already been installed and we have started a high power RF processing of the gun cavities. The characteristics of electron bunch extracted from the RF gun are measured by varying phase and amplitude of input RF fields for the gun cavities. The status of t-ACTS project will be presented in the conference.