IPAC2014 - List of Authors (Takatomi, T.)

Paper	Title	Page
MOPRI003	Positron Yield Optimization by Adjusting the Components Offset and Orientation	576
	L. Zang, M. Akemoto, S. Fukuda, K. Furukawa, T. Higo, N. Iida, K. Kakihara, T. Kamitani, T. Miura, F. Miyahara, Y. Ogawa, H. Someya, T. Takatomi, K. Yokoyama KEK, Ibaraki, Japan S. Ushimoto Mitsubishi Electric System & Service Co., Ltd, Tsukuba, Japan
	In order to keep high luminosity beam collision condition at SuperKEKB, low emittance electron/positron injection and flexible pulse-to-pulse switching of these beam modes are essential requirements. While a primary electron beam strikes on a target to generate positrons, an injection electron beam passes through a small hole besides the target. Since the injection electron orbit should be on axis to avoid emittance growth, the target and the flux concentrator for positron focusing have a few millimeters offset from the axis. This offset positron generation gives significant degradation in the positron yield. In this paper, we will discuss positron yield improvement by proper orientation of the cut-in slit of the flux concentrator which yields un-symmetric field distribution and primary electron incident point. With particle tracking simulation taking three dimensional field distribution into account, an ideal positron trajectory giving optimum yield was found.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI003
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRI004	SuperKEKB Positron Source Construction Status	579
	T. Kamitani, M. Akemoto, D.A. Arakawa, Y. Arakida, A. Enomoto, S. Fukuda, Y. Funakoshi, K. Furukawa, T. Higo, H. Honma, N. Iida, M. Ikeda, E. Kadokura, H. Kaji, K. Kakihara, H. Katagiri, M. Kikuchi, H. Koiso, M. Kurashina, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Mimashi, T. Miura, F. Miyahara, T. Mori, A. Morita, H. Nakajima, K. Nakao, T. Natsui, Y. Ogawa, Y. Ohnishi, S. Ohsawa, M. Sato, T. Shidara, A. Shirakawa, M. Suetake, H. Sugimoto, T. Suwada, T. Takatomi, T. Takenaka, M. Tanaka, M. Tawada, Y. Yano, K. Yokoyama, M. Yoshida, L. Zang, X. Zhou KEK, Ibaraki, Japan D. Satoh TIT, Tokyo, Japan
	The KEKB positron source is under the upgrade for SuperKEKB. The previous positron production target and capture section have been removed and the new system is constructed at a location forty meters upstream to have sufficient energy margin for beam injection to the newly introduced damping ring. A flux concentrator is introduced in the new capture section to make an adiabatic matching system. Large aperture (30mm in diameter) S-band accelerating structures are introduced in the capture section and in the subsequent accelerator module to enlarge the transverse phase space acceptance. The beam focusing system of quadrupoles is also upgraded for a comparable beam acceptance to that of the capture section. This paper reports on the status of the SuperKEKB positron source construction and the preliminary positron beam commissioning.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI004
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRI030	Basic Design of a 20K C-band 2.6-cell Photocathode RF Gun	658
	T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai LEBRA, Funabashi, Japan M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan T.S. Shintomi Nihon University, Tokyo, Japan
	Funding: This research was supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). A cryocooled C-band photocathode RF gun operating at 20K is under design at Nihon University. The RF gun is of BNL-type 2.6-cell pillbox cavity with a resonant frequency of 5712 MHz. With high-purity Oxygen-free copper used as the cavity material, the quality factor of the cavity is expected to be approximately 60000 from theoretical prediction of the anomalous skin effect at low temperatures. Considering the cooling capacity, initial operation of the RF gun is assumed at a duty factor of 0.01%. The cavity elements designed for low-power test is in preparation for machining. The low-power test at room temperature is scheduled early spring in 2014 before assembled at KEK by means of diffusion bonding technique. Since it is intended for the basic understanding and measurements of low temperature RF properties, the cavity is not equipped with structures for the photocathode assembling or the RF input coupler. The cavity design and the results of RF properties measured at room temperature before diffusion bonding will be reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI030
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRI039	Ultra-short Electron Bunch Generation using Energy-chirping Cell Attached RF Electron Gun	685
	K. Sakaue, Y. Koshiba, M. Mizugaki, M. Washio Waseda University, Tokyo, Japan R. Kuroda AIST, Tsukuba, Ibaraki, Japan T. Takatomi, J. Urakawa KEK, Ibaraki, Japan
	Funding: Work supported by JSPS Grant-in-Aid for Young Scientists (B) 23740203 and Scientific Research (A) 10001690 We have been developing an Energy-Chirping-Cell attached RF electron gun (ECC-RF-Gun) for generating ultra-short electron bunches. ECC-RF-Gun has extra cell at the end of gun cavity in order to chirp the bunch energy. Such a bunch can be compressed by the velocity difference though the drift space. We have already installed it to our accelerator system and successfully observed a coherent synchrotron/transition radiation at 0.3THz. It is clear that the bunch length was short enough to generate 0.3THz, which corresponds to less than 500fs bunch length was achieved if we assume the gaussian shape. In this conference, the principle of ECC-RF-Gun, the recent results of bunch length measurement and future prospective will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI039
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME133	Bunch Length Measurement with 2-Cell RF-Deflector at Waseda University	3556
	T. Takahashi, Y. Nishimura, M. Nishiyama, K. Sakaue, M. Washio Waseda University, Tokyo, Japan T. Takatomi, J. Urakawa KEK, Ibaraki, Japan
	We have been studying on a system to measure the length of electron bunch generated by a photocathode rf electron gun at Waseda University. We adopted the rf-deflector system which can convert the longitudinal distribution to transverse by sweeping the electron bunch. By using HFSS, we optimized the design of the 2 cell rf-deflector which is operating on π-mode, dipole (TM110-like) mode at 2856 MHz. The fabrication and the tuning of the rf deflector have successfully processed. We have installed the rf-deflector in the accelerator system of Waseda University, and performed the measurement of the bunch length. It is confirmed that this rf-deflector has the temporal resolution of 167fs with 700kW supply when the beam energy is 4.8MeV. This means that our rf-deflector system has possibility to measure the ultra-short bunch length. In this conference, the rf-deflector system in Waseda University, the result of the bunch length measurement, the performance of the rf-deflector and the future plan will be reported. Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 and the Quantum Beam Technology Program of MEXT.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME133
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Positron Yield Optimization by Adjusting the Components Offset and Orientation

576

L. Zang, M. Akemoto, S. Fukuda, K. Furukawa, T. Higo, N. Iida, K. Kakihara, T. Kamitani, T. Miura, F. Miyahara, Y. Ogawa, H. Someya, T. Takatomi, K. Yokoyama
KEK, Ibaraki, Japan
S. Ushimoto
Mitsubishi Electric System & Service Co., Ltd, Tsukuba, Japan

In order to keep high luminosity beam collision condition at SuperKEKB, low emittance electron/positron injection and flexible pulse-to-pulse switching of these beam modes are essential requirements. While a primary electron beam strikes on a target to generate positrons, an injection electron beam passes through a small hole besides the target. Since the injection electron orbit should be on axis to avoid emittance growth, the target and the flux concentrator for positron focusing have a few millimeters offset from the axis. This offset positron generation gives significant degradation in the positron yield. In this paper, we will discuss positron yield improvement by proper orientation of the cut-in slit of the flux concentrator which yields un-symmetric field distribution and primary electron incident point. With particle tracking simulation taking three dimensional field distribution into account, an ideal positron trajectory giving optimum yield was found.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI003

Export •

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

MOPRI004

SuperKEKB Positron Source Construction Status

579

T. Kamitani, M. Akemoto, D.A. Arakawa, Y. Arakida, A. Enomoto, S. Fukuda, Y. Funakoshi, K. Furukawa, T. Higo, H. Honma, N. Iida, M. Ikeda, E. Kadokura, H. Kaji, K. Kakihara, H. Katagiri, M. Kikuchi, H. Koiso, M. Kurashina, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Mimashi, T. Miura, F. Miyahara, T. Mori, A. Morita, H. Nakajima, K. Nakao, T. Natsui, Y. Ogawa, Y. Ohnishi, S. Ohsawa, M. Sato, T. Shidara, A. Shirakawa, M. Suetake, H. Sugimoto, T. Suwada, T. Takatomi, T. Takenaka, M. Tanaka, M. Tawada, Y. Yano, K. Yokoyama, M. Yoshida, L. Zang, X. Zhou
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan

The KEKB positron source is under the upgrade for SuperKEKB. The previous positron production target and capture section have been removed and the new system is constructed at a location forty meters upstream to have sufficient energy margin for beam injection to the newly introduced damping ring. A flux concentrator is introduced in the new capture section to make an adiabatic matching system. Large aperture (30mm in diameter) S-band accelerating structures are introduced in the capture section and in the subsequent accelerator module to enlarge the transverse phase space acceptance. The beam focusing system of quadrupoles is also upgraded for a comparable beam acceptance to that of the capture section. This paper reports on the status of the SuperKEKB positron source construction and the preliminary positron beam commissioning.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI004

Export •

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

MOPRI030

Basic Design of a 20K C-band 2.6-cell Photocathode RF Gun

658

T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai
LEBRA, Funabashi, Japan
M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan
T.S. Shintomi
Nihon University, Tokyo, Japan

Funding: This research was supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
A cryocooled C-band photocathode RF gun operating at 20K is under design at Nihon University. The RF gun is of BNL-type 2.6-cell pillbox cavity with a resonant frequency of 5712 MHz. With high-purity Oxygen-free copper used as the cavity material, the quality factor of the cavity is expected to be approximately 60000 from theoretical prediction of the anomalous skin effect at low temperatures. Considering the cooling capacity, initial operation of the RF gun is assumed at a duty factor of 0.01%. The cavity elements designed for low-power test is in preparation for machining. The low-power test at room temperature is scheduled early spring in 2014 before assembled at KEK by means of diffusion bonding technique. Since it is intended for the basic understanding and measurements of low temperature RF properties, the cavity is not equipped with structures for the photocathode assembling or the RF input coupler. The cavity design and the results of RF properties measured at room temperature before diffusion bonding will be reported.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI030

Export •

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

MOPRI039

Ultra-short Electron Bunch Generation using Energy-chirping Cell Attached RF Electron Gun

685

K. Sakaue, Y. Koshiba, M. Mizugaki, M. Washio
Waseda University, Tokyo, Japan
R. Kuroda
AIST, Tsukuba, Ibaraki, Japan
T. Takatomi, J. Urakawa
KEK, Ibaraki, Japan

Funding: Work supported by JSPS Grant-in-Aid for Young Scientists (B) 23740203 and Scientific Research (A) 10001690
We have been developing an Energy-Chirping-Cell attached RF electron gun (ECC-RF-Gun) for generating ultra-short electron bunches. ECC-RF-Gun has extra cell at the end of gun cavity in order to chirp the bunch energy. Such a bunch can be compressed by the velocity difference though the drift space. We have already installed it to our accelerator system and successfully observed a coherent synchrotron/transition radiation at 0.3THz. It is clear that the bunch length was short enough to generate 0.3THz, which corresponds to less than 500fs bunch length was achieved if we assume the gaussian shape. In this conference, the principle of ECC-RF-Gun, the recent results of bunch length measurement and future prospective will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI039

Export •

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

THPME133

Bunch Length Measurement with 2-Cell RF-Deflector at Waseda University

3556

T. Takahashi, Y. Nishimura, M. Nishiyama, K. Sakaue, M. Washio
Waseda University, Tokyo, Japan
T. Takatomi, J. Urakawa
KEK, Ibaraki, Japan

We have been studying on a system to measure the length of electron bunch generated by a photocathode rf electron gun at Waseda University. We adopted the rf-deflector system which can convert the longitudinal distribution to transverse by sweeping the electron bunch. By using HFSS, we optimized the design of the 2 cell rf-deflector which is operating on π-mode, dipole (TM110-like) mode at 2856 MHz. The fabrication and the tuning of the rf deflector have successfully processed. We have installed the rf-deflector in the accelerator system of Waseda University, and performed the measurement of the bunch length. It is confirmed that this rf-deflector has the temporal resolution of 167fs with 700kW supply when the beam energy is 4.8MeV. This means that our rf-deflector system has possibility to measure the ultra-short bunch length. In this conference, the rf-deflector system in Waseda University, the result of the bunch length measurement, the performance of the rf-deflector and the future plan will be reported.
Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 and the Quantum Beam Technology Program of MEXT.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME133

Export •

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