IPAC2012 - List of Authors (Yamada, K.)

Paper

Title

Page

Development of a High-power Coherent THz Sources and THz-TDS System on the basis of a Compact Electron Linac

37

M. Kumaki, K. Sakaue, M. Washio
RISE, Tokyo, Japan
R. Kuroda, H. Toyokawa, K. Yamada
AIST, Tsukuba, Ibaraki, Japan

The high-power terahertz time-domain spectroscopy (THz-TDS) has been developed on the basis of a compact S-band electron linac at AIST, Japan. It is strongly expected for inspection of dangerous materials in the homeland security field. The linac consists of a photocathode rf-gun, two acceleration tubes and a magnetic bunch compressor. The 40 MeV, 1 nC electron bunch is generated and compressed to less than 1 ps. THz radiations are generated in two methods with the ultra-short bunch. One is THz coherent synchrotron radiation (CSR). The other is THz coherent transition radiation (CTR). In the preliminary experiment, it was observed that the focused CTR had the donut profile in a transverse fields due to its initial radial polarization, so that it made Z-polarization. In case of the THz-TDS experiment, CTR was controlled to linearly polarization with the polarizer and focused to an EO crystal to obtain a THz temporal waveform which leads to THz spectrum with Fourier transform. The timing measurement between CTR and a probe laser was realized with OTR using a same optical photodiode. In this conference, we will describe details of our linac and results of the THz-TDS experiment.

Slides MOOBA03 [3.342 MB]

THPPR070

Development of Multi-collision Laser Compton Scattering X-ray Source on the Basis of Compact S-band Electron Linac

4139

R. Kuroda, M. Koike, E. Miura, Y. Taira, H. Toyokawa, K. Yamada, E. Yamaguchi
AIST, Tsukuba, Ibaraki, Japan
M. Kumaki
RISE, Tokyo, Japan

A compact hard X-ray source via laser Compton scattering is required for biological, medical and industrial science because it has many benefits about generated X-rays such as short pulse, quasi-monochromatic, energy tunability and good directivity. Our X-ray source is conventionally the single collision system between an electron pulse and a laser pulse. To increase X-ray yields, we have developed a multi-collision system with a multi-bunch electron beam and a laser optical cavity. The multi-bunch electron beam has already been generated from a Cs-Te photocathode rf gun system using a multi-pulse UV laser. The laser optical cavity have developed like a regenerative amplification including the collision point between the electron pulse and the laser pulse which is based on the Ti:Sa laser with a mode-locked frequency of 79.33 MHz. In this preliminary experiment, the modulated seed laser pulses were generated and leaded to the cavity, so that laser build-up amplification was performed in the cavity length of 3.78 m with two seed pulses. In this conference, we will describe the results of preliminary experiments for the multi-collision system and future plans.

TUOBA02

Beam Commissioning and Operation of New Linac Injector for RIKEN RI-beam Factory

1071

K. Yamada, S. Arai, M. Fujimaki, T. Fujinawa, H. Fujisawa, N. Fukunishi, Y. Higurashi, E. Ikezawa, H. Imao, O. Kamigaito, M. Kase, M. Komiyama, K. Kumagai, T. Maie, T. Nakagawa, J. Ohnishi, H. Okuno, N. Sakamoto, K. Suda, H. Watanabe, T. Watanabe, Y. Watanabe, H. Yamasawa
RIKEN Nishina Center, Wako, Japan
A. Goto
NIRS, Chiba-shi, Japan
Y. Sato
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

A new linac injector called RILAC2* has successfully commissioned at the RIKEN RI beam factory (RIBF). The RILAC2 can accelerate very heavy ions with m/q of 7, such as 124Xe¹⁹⁺ and 238U³⁵⁺ from a 28 GHz superconducting ECR ion source**, up to an energy of 680 keV/nucleon in the cw mode. Ions are directory injected into the RIKEN Ring Cyclotron without charge stripping in order to increase the beam intensity, as well as performing independent RIBF experiments and super-heavy-element synthesis. The key features of RILAC2 are the powerful ECRIS, higher extraction voltage of the ECRIS compared to the voltage of the existing injector linac to reduce the space charge effect, improvement of the rf voltage and phase stability, improvement of the vacuum level to reduce the loss by charge exchange, and the compact equipments yet to be installed in the existing AVF cyclotron vault. The first beam acceleration was achieved on December 21, 2010. After the several beam acceleration tests in 2011, we started to operate the RILAC2 to supply beams for the RIBF experiments.
* O. Kamigaito et al., Proc. of PASJ3-LAM31, WP78, p. 502 (2006); K. Yamada et al., Proc. of IPAC'10, MOPD046, p.789 (2010).
** T. Nakagawa et al., Rev. Sci. Instrum. 79, 02A327 (2008).

Slides TUOBA02 [9.947 MB]

WEPPC018

Design of a Spoke Cavity for RIKEN RI-beam Factory

2245

L. Lu
RIKEN, Saitama, Japan
O. Kamigaito, N. Sakamoto, K. Suda, K. Yamada
RIKEN Nishina Center, Wako, Japan

Designs of a CW superconducting rebuncher tri-spoke cavity for uranium beams with β = 0.303 has been studied. The estimated peak voltage is rather high as 3 mega-voltages (MV). The resonator frequency was chose as 219MHz which is 12 times of the foundational frequency. The buncher would be settled in a location between two booster cyclotrons (RRC: K = 540MeV, fRC: K = 570 MeV). In this cavity design, a flat E field distribution on beam axis was designed based on the Microwave Studio (MWS) simulations. The cavity parameters, detail designs and some simulated results will be reported in this paper.

MOPPD029

Recent Achievements and Upgrade Programs at RIKEN Radioactive Isotope Beam Factory

430

H. Okuno, T. Dantsuka, M. Fujimaki, T. Fujinawa, N. Fukunishi, H. Hasebe, Y. Higurashi, K. Ikegami, E. Ikezawa, H. Imao, T. Kageyama, O. Kamigaito, M. Kase, M. Kidera, M. Komiyama, H. Kuboki, K. Kumagai, T. Maie, M. Nagase, T. Nakagawa, M. Nakamura, J. Ohnishi, N. Sakamoto, K. Suda, H. Watanabe, T. Watanabe, Y. Watanabe, K. Yamada, H. Yamasawa
RIKEN Nishina Center, Wako, Japan

Recent achievements and upgrade programs in the near future at RIKEN Radioactive Isotope Beam Factory (RIBF) are presented. The beam intensity and available ion species are increasing at RIBF, owing to the continuous efforts that have been paid since the first beam in 2006. So far, we accelerated deuteron, helium, nitrogen, oxygen, aluminum, calcium, krypton, and uranium beams with the world's first superconducting ring cyclotron, SRC*. The extracted beam intensities reached 1,000 pnA for helium and oxygen beams. From the operational point of view, however, the intensity of the uranium beam should be much increased. Therefore we constructed a new injector system for the RIBF, consisting of a 28 GHz ECR ion sources, RFQ and DTL, which was successfully commissioned in the end of 2010. Furthermore we developed low-Z (low atomic number Z) gas stripper** alternative to standard carbon foil stripping, which will be reliable and efficient charge stripping scheme for such high-power uranium beams.
* H. Okuno et al., IEEE Trans. Appl. Supercond., 18, 226 (2008).
** H. Okuno et al., Phys. Rev. ST Accel. Beams 14, 033503 (2011).

MOPPD030

Present Status of RIKEN Ring Cyclotron

433

Y. Watanabe, M. Fujimaki, N. Fukunishi, H. Hasebe, Y. Higurashi, E. Ikezawa, H. Imao, T. Kageyama, O. Kamigaito, M. Kase, M. Kidera, M. Komiyama, H. Kuboki, K. Kumagai, T. Maie, M. Nagase, T. Nakagawa, J. Ohnishi, H. Okuno, N. Sakamoto, K. Suda, H. Watanabe, T. Watanabe, K. Yamada, S. Yokouchi
RIKEN Nishina Center, Wako, Japan
T. Aihara, S. Fukuzawa, M. Hamanaka, S. Ishikawa, K. Kobayashi, Y. Kotaka, R. Koyama, T. Nakamura, M. Nishida, M. Nishimura, T.O. Ohki, K. Oyamada, J. Shibata, M. Tamura, N. Tsukiori, A. Uchiyama, K. Yadomi, H. Yamauchi
SHI Accelerator Service Ltd., Tokyo, Japan

The RIKEN Ring Cyclotron (RRC K540) has been in stable operation over twenty-five years, and supplying many kinds of heavy-ion beams to experiments. Since 2007, it has also been supplying beams to the RIBF four Ring cyclotrons including the Super-conducting Ring Cyclotron (SRC K2500). Now the RRC has three kinds of injectors, one is K70 AVF cyclotron for light ions, the second is the variable-frequency linac for heavy ions, and the third is the RILAC2 for using the high intensity very heavy ions like U and Xe. The many combinations of accelerators are possible, and in any acceleration modes, the RRC should works as a first energy booster. A total operation time of the RRC is more than 5000 hr in every year. The present status of the RRC operation will be reported.

Paper	Title	Page
MOOBA03	Development of a High-power Coherent THz Sources and THz-TDS System on the basis of a Compact Electron Linac	37
	M. Kumaki, K. Sakaue, M. Washio RISE, Tokyo, Japan R. Kuroda, H. Toyokawa, K. Yamada AIST, Tsukuba, Ibaraki, Japan
	The high-power terahertz time-domain spectroscopy (THz-TDS) has been developed on the basis of a compact S-band electron linac at AIST, Japan. It is strongly expected for inspection of dangerous materials in the homeland security field. The linac consists of a photocathode rf-gun, two acceleration tubes and a magnetic bunch compressor. The 40 MeV, 1 nC electron bunch is generated and compressed to less than 1 ps. THz radiations are generated in two methods with the ultra-short bunch. One is THz coherent synchrotron radiation (CSR). The other is THz coherent transition radiation (CTR). In the preliminary experiment, it was observed that the focused CTR had the donut profile in a transverse fields due to its initial radial polarization, so that it made Z-polarization. In case of the THz-TDS experiment, CTR was controlled to linearly polarization with the polarizer and focused to an EO crystal to obtain a THz temporal waveform which leads to THz spectrum with Fourier transform. The timing measurement between CTR and a probe laser was realized with OTR using a same optical photodiode. In this conference, we will describe details of our linac and results of the THz-TDS experiment.
	Slides MOOBA03 [3.342 MB]

THPPR070	Development of Multi-collision Laser Compton Scattering X-ray Source on the Basis of Compact S-band Electron Linac	4139
	R. Kuroda, M. Koike, E. Miura, Y. Taira, H. Toyokawa, K. Yamada, E. Yamaguchi AIST, Tsukuba, Ibaraki, Japan M. Kumaki RISE, Tokyo, Japan
	A compact hard X-ray source via laser Compton scattering is required for biological, medical and industrial science because it has many benefits about generated X-rays such as short pulse, quasi-monochromatic, energy tunability and good directivity. Our X-ray source is conventionally the single collision system between an electron pulse and a laser pulse. To increase X-ray yields, we have developed a multi-collision system with a multi-bunch electron beam and a laser optical cavity. The multi-bunch electron beam has already been generated from a Cs-Te photocathode rf gun system using a multi-pulse UV laser. The laser optical cavity have developed like a regenerative amplification including the collision point between the electron pulse and the laser pulse which is based on the Ti:Sa laser with a mode-locked frequency of 79.33 MHz. In this preliminary experiment, the modulated seed laser pulses were generated and leaded to the cavity, so that laser build-up amplification was performed in the cavity length of 3.78 m with two seed pulses. In this conference, we will describe the results of preliminary experiments for the multi-collision system and future plans.

TUOBA02	Beam Commissioning and Operation of New Linac Injector for RIKEN RI-beam Factory	1071
	K. Yamada, S. Arai, M. Fujimaki, T. Fujinawa, H. Fujisawa, N. Fukunishi, Y. Higurashi, E. Ikezawa, H. Imao, O. Kamigaito, M. Kase, M. Komiyama, K. Kumagai, T. Maie, T. Nakagawa, J. Ohnishi, H. Okuno, N. Sakamoto, K. Suda, H. Watanabe, T. Watanabe, Y. Watanabe, H. Yamasawa RIKEN Nishina Center, Wako, Japan A. Goto NIRS, Chiba-shi, Japan Y. Sato J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	A new linac injector called RILAC2* has successfully commissioned at the RIKEN RI beam factory (RIBF). The RILAC2 can accelerate very heavy ions with m/q of 7, such as 124Xe¹⁹⁺ and 238U³⁵⁺ from a 28 GHz superconducting ECR ion source*, up to an energy of 680 keV/nucleon in the cw mode. Ions are directory injected into the RIKEN Ring Cyclotron without charge stripping in order to increase the beam intensity, as well as performing independent RIBF experiments and super-heavy-element synthesis. The key features of RILAC2 are the powerful ECRIS, higher extraction voltage of the ECRIS compared to the voltage of the existing injector linac to reduce the space charge effect, improvement of the rf voltage and phase stability, improvement of the vacuum level to reduce the loss by charge exchange, and the compact equipments yet to be installed in the existing AVF cyclotron vault. The first beam acceleration was achieved on December 21, 2010. After the several beam acceleration tests in 2011, we started to operate the RILAC2 to supply beams for the RIBF experiments. O. Kamigaito et al., Proc. of PASJ3-LAM31, WP78, p. 502 (2006); K. Yamada et al., Proc. of IPAC'10, MOPD046, p.789 (2010). ** T. Nakagawa et al., Rev. Sci. Instrum. 79, 02A327 (2008).
	Slides TUOBA02 [9.947 MB]

WEPPC018	Design of a Spoke Cavity for RIKEN RI-beam Factory	2245
	L. Lu RIKEN, Saitama, Japan O. Kamigaito, N. Sakamoto, K. Suda, K. Yamada RIKEN Nishina Center, Wako, Japan
	Designs of a CW superconducting rebuncher tri-spoke cavity for uranium beams with β = 0.303 has been studied. The estimated peak voltage is rather high as 3 mega-voltages (MV). The resonator frequency was chose as 219MHz which is 12 times of the foundational frequency. The buncher would be settled in a location between two booster cyclotrons (RRC: K = 540MeV, fRC: K = 570 MeV). In this cavity design, a flat E field distribution on beam axis was designed based on the Microwave Studio (MWS) simulations. The cavity parameters, detail designs and some simulated results will be reported in this paper.

MOPPD029	Recent Achievements and Upgrade Programs at RIKEN Radioactive Isotope Beam Factory	430
	H. Okuno, T. Dantsuka, M. Fujimaki, T. Fujinawa, N. Fukunishi, H. Hasebe, Y. Higurashi, K. Ikegami, E. Ikezawa, H. Imao, T. Kageyama, O. Kamigaito, M. Kase, M. Kidera, M. Komiyama, H. Kuboki, K. Kumagai, T. Maie, M. Nagase, T. Nakagawa, M. Nakamura, J. Ohnishi, N. Sakamoto, K. Suda, H. Watanabe, T. Watanabe, Y. Watanabe, K. Yamada, H. Yamasawa RIKEN Nishina Center, Wako, Japan
	Recent achievements and upgrade programs in the near future at RIKEN Radioactive Isotope Beam Factory (RIBF) are presented. The beam intensity and available ion species are increasing at RIBF, owing to the continuous efforts that have been paid since the first beam in 2006. So far, we accelerated deuteron, helium, nitrogen, oxygen, aluminum, calcium, krypton, and uranium beams with the world's first superconducting ring cyclotron, SRC. The extracted beam intensities reached 1,000 pnA for helium and oxygen beams. From the operational point of view, however, the intensity of the uranium beam should be much increased. Therefore we constructed a new injector system for the RIBF, consisting of a 28 GHz ECR ion sources, RFQ and DTL, which was successfully commissioned in the end of 2010. Furthermore we developed low-Z (low atomic number Z) gas stripper* alternative to standard carbon foil stripping, which will be reliable and efficient charge stripping scheme for such high-power uranium beams. * H. Okuno et al., IEEE Trans. Appl. Supercond., 18, 226 (2008). ** H. Okuno et al., Phys. Rev. ST Accel. Beams 14, 033503 (2011).

MOPPD030	Present Status of RIKEN Ring Cyclotron	433
	Y. Watanabe, M. Fujimaki, N. Fukunishi, H. Hasebe, Y. Higurashi, E. Ikezawa, H. Imao, T. Kageyama, O. Kamigaito, M. Kase, M. Kidera, M. Komiyama, H. Kuboki, K. Kumagai, T. Maie, M. Nagase, T. Nakagawa, J. Ohnishi, H. Okuno, N. Sakamoto, K. Suda, H. Watanabe, T. Watanabe, K. Yamada, S. Yokouchi RIKEN Nishina Center, Wako, Japan T. Aihara, S. Fukuzawa, M. Hamanaka, S. Ishikawa, K. Kobayashi, Y. Kotaka, R. Koyama, T. Nakamura, M. Nishida, M. Nishimura, T.O. Ohki, K. Oyamada, J. Shibata, M. Tamura, N. Tsukiori, A. Uchiyama, K. Yadomi, H. Yamauchi SHI Accelerator Service Ltd., Tokyo, Japan
	The RIKEN Ring Cyclotron (RRC K540) has been in stable operation over twenty-five years, and supplying many kinds of heavy-ion beams to experiments. Since 2007, it has also been supplying beams to the RIBF four Ring cyclotrons including the Super-conducting Ring Cyclotron (SRC K2500). Now the RRC has three kinds of injectors, one is K70 AVF cyclotron for light ions, the second is the variable-frequency linac for heavy ions, and the third is the RILAC2 for using the high intensity very heavy ions like U and Xe. The many combinations of accelerators are possible, and in any acceleration modes, the RRC should works as a first energy booster. A total operation time of the RRC is more than 5000 hr in every year. The present status of the RRC operation will be reported.