CYCLOTRONS 2010 - List of Authors (Goto, A.)

Paper

Title

Page

Review of High Power Cyclotrons for Heavy Ion Beams

9

A. Goto
RIKEN Nishina Center, Wako, Japan

Since heavy ion cyclotrons for use in radioactive beam sciences were built in laboratories worldwide in 1980's, a lot of efforts on the upgrade of many such cyclotrons have been made in terms of beam intensity as well as beam energy. This talk describes an overview of such cyclotrons that provide heavy ion beams with the power in kW range or higher. Some technological issues related to high-power heavy ion beams are also discussed based on the experiences of those cyclotrons.

Slides MOM2CIO01 [8.469 MB]

MOPCP025

Construction of New Injector LINAC at RIBF

102

K. Yamada, S. Arai, M. Fujimaki, T. Fujinawa, N. Fukunishi, A. Goto, Y. Higurashi, E. Ikezawa, O. Kamigaito, M. Kase, M. Komiyama, K. Kumagai, T. Maie, T. Nakagawa, J. Ohnishi, H. Okuno, N. Sakamoto, K. Suda, H. Watanabe, Y. Watanabe, Y. Yano, S. Yokouchi
RIKEN Nishina Center, Wako, Japan
H. Fujisawa
Kyoto ICR, Uji, Kyoto, Japan
Y. Sato
KEK, Ibaraki, Japan

A new additional linac injector called RILAC2 has been constructed at the RIKEN Nishina Center so that RIBF experiments and synthesis of super-heavy element can be carried out independently. The RILAC2 consists of a 28-GHz superconducting ECR ion source (SC-ECRIS), a low-energy beam transport with a prebuncher, a four-rod RFQ linac, three drift-tube linac tanks (DTL1-3), a rebuncher between the RFQ and DTL1, and strong quadrupole magnets that were placed between the rf resonators for the transverse focusing. Very heavy ions with mass-to-charge ratio of 7, such as ¹³⁶Xe²⁰⁺ and ²³⁸U³⁵⁺, are accelerated up to an energy of 680 keV/u in the cw mode and injected into the RRC without charge stripping. The rf resonators excluding the pre-buncher are operated at a fixed rf frequency of 36.5 MHz, whereas the pre-buncher is operated at 18.25 MHz. The basic design of the RILAC2 was finished in 2006 and the construction has started since the budget was approved at the end of FY2008. The SC-ECRIS is installed in a new room, and other equipments are placed in the existing AVF-cyclotron vault. This contribution mainly presents the details of the construction of linac part.

MOPCP043

Modification of the Central Region in the RIKEN AVF Cyclotron for Acceleration at the H=1 RF Harmonic

138

S.B. Vorozhtsov
JINR, Dubna, Moscow Region, Russia
A. Goto
RIKEN Nishina Center, Wako, Japan
V.L. Smirnov
JINR/DLNP, Dubna, Moscow region, Russia

Funding: JINR/DLNP, Dubna, Russia, and RIKEN, Wako, Japan
A highly advanced upgrade plan of the RIKEN AVF cyclotron is under way. The study is focused on the formulation of the new acceleration regimes in the AVF cyclotron by detailed orbit simulations. The extension of the acceleration energy region of light ions towards higher energies in the existing RF harmonic equal to 2 and the modification of the central geometry for the RF harmonic equal to 1 to allow an acceleration of protons at several tens of MeV are considered. The substantial redesign of the central electrode structure is needed to accelerate protons with reasonable values of the dee voltage. The new inflector geometry and the optimized central electrode structure have been formulated for the upgrade.

MOPCP094

Consistency in Measurement of Beam Phase and Beam Intensity Using Lock-in Amplifier and Oscilloscope Systems

245

R. Koyama, M. Fujimaki, N. Fukunishi, A. Goto, M. Hemmi, O. Kamigaito, M. Kase, N. Sakamoto, K. Suda, T. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan

The RIKEN RI beam factory (RIBF) consists of four ring cyclotrons (RRC, fRC, IRC, and SRC) and two injectors (RILAC and AVF) which are all connected in cascade. RILAC, AVF, and RRC began operation in the 1980s, and fRC, IRC, and SRC were installed in 2006. Phase probes (PPs) are installed in all cyclotrons and beam transport lines of RIBF, and the beam-bunch signals that are detected nondestructively by these PPs are used for tuning of isochronous magnetic field of cyclotrons and for monitoring the beam phase and beam intensity. We mainly use a newly developed system that incorporates a lock-in amplifier (LIA; SR844, SRS) for those tuning and monitoring; however, in AVF and RRC, a conventional measurement method using an oscilloscope system (OSC; DSO6052A, Agilent) is used. In this study, we investigated the consistency in the measurements carried out using LIA and OSC systems by Fourier analyzing the observed data. Additionally, we investigated the resolution and measurement uncertainty of LIA and OSC.

TUM2CIO01

Status of RIBF Accelerators at RIKEN

286

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

Recent developments and upgrade program in the near future at RIKEN RI-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 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. We are, therefore, constructing a new injector linac for the RIBF, consisting of a superconducting ECR ion source, RFQ, and DTL, which will be commissioned in this fiscal year. By using this injector, we also aim at independent operation of the RIBF and GARIS facility for super-heavy element synthesis.

Slides TUM2CIO01 [4.914 MB]

WEM2CCO02

Operating Experience with the RF System for Superconducting Ring Cyclotron of RIBF

338

N. Sakamoto, M. Fujimaki, A. Goto, O. Kamigaito, M. Kase, R. Koyama, K. Suda, K. Yamada, S. Yokouchi
RIKEN Nishina Center, Wako, Japan

Since December 2006, Superconducting Ring Cyclotron (SRC) has been operational. Up to now, the beams of ²³⁸U, ⁴⁸Ca, pol-d, N, ⁴He have been provided for nuclear physics experiments. The SRC consists of 6 superconducting sector magnets, 4 accelerating cavities and one flattop cavity. Designed value of the acceleration voltage is 2 MV/turn. The gap voltage of 600 kV is excited with 130 kW rf power in the accelerating cavity. The cavities have been installed at four valley regions of 6 sector magnets and are exposed to a strong stray field of superconducting magnets. The strength of the magnetic field is as large as a few kilogauss. It is found that the condition of multipactor depends drastically on the strength of the stray field. How to treat the multipactor is one of the most important issues for stable operation of the SRC. This paper will discuss on our efforts to settle the problem concerning the cavities. By improving the vacuum, cooling, surface treatment and so on, we finally succeeded to minimize the break time due to the rf break down of the SRC cavities during experiments.

Slides WEM2CCO02 [9.291 MB]

Paper	Title	Page
MOM2CIO01	Review of High Power Cyclotrons for Heavy Ion Beams	9
	A. Goto RIKEN Nishina Center, Wako, Japan
	Since heavy ion cyclotrons for use in radioactive beam sciences were built in laboratories worldwide in 1980's, a lot of efforts on the upgrade of many such cyclotrons have been made in terms of beam intensity as well as beam energy. This talk describes an overview of such cyclotrons that provide heavy ion beams with the power in kW range or higher. Some technological issues related to high-power heavy ion beams are also discussed based on the experiences of those cyclotrons.
	Slides MOM2CIO01 [8.469 MB]

MOPCP025	Construction of New Injector LINAC at RIBF	102
	K. Yamada, S. Arai, M. Fujimaki, T. Fujinawa, N. Fukunishi, A. Goto, Y. Higurashi, E. Ikezawa, O. Kamigaito, M. Kase, M. Komiyama, K. Kumagai, T. Maie, T. Nakagawa, J. Ohnishi, H. Okuno, N. Sakamoto, K. Suda, H. Watanabe, Y. Watanabe, Y. Yano, S. Yokouchi RIKEN Nishina Center, Wako, Japan H. Fujisawa Kyoto ICR, Uji, Kyoto, Japan Y. Sato KEK, Ibaraki, Japan
	A new additional linac injector called RILAC2 has been constructed at the RIKEN Nishina Center so that RIBF experiments and synthesis of super-heavy element can be carried out independently. The RILAC2 consists of a 28-GHz superconducting ECR ion source (SC-ECRIS), a low-energy beam transport with a prebuncher, a four-rod RFQ linac, three drift-tube linac tanks (DTL1-3), a rebuncher between the RFQ and DTL1, and strong quadrupole magnets that were placed between the rf resonators for the transverse focusing. Very heavy ions with mass-to-charge ratio of 7, such as ¹³⁶Xe²⁰⁺ and ²³⁸U³⁵⁺, are accelerated up to an energy of 680 keV/u in the cw mode and injected into the RRC without charge stripping. The rf resonators excluding the pre-buncher are operated at a fixed rf frequency of 36.5 MHz, whereas the pre-buncher is operated at 18.25 MHz. The basic design of the RILAC2 was finished in 2006 and the construction has started since the budget was approved at the end of FY2008. The SC-ECRIS is installed in a new room, and other equipments are placed in the existing AVF-cyclotron vault. This contribution mainly presents the details of the construction of linac part.

MOPCP043	Modification of the Central Region in the RIKEN AVF Cyclotron for Acceleration at the H=1 RF Harmonic	138
	S.B. Vorozhtsov JINR, Dubna, Moscow Region, Russia A. Goto RIKEN Nishina Center, Wako, Japan V.L. Smirnov JINR/DLNP, Dubna, Moscow region, Russia
	Funding: JINR/DLNP, Dubna, Russia, and RIKEN, Wako, Japan A highly advanced upgrade plan of the RIKEN AVF cyclotron is under way. The study is focused on the formulation of the new acceleration regimes in the AVF cyclotron by detailed orbit simulations. The extension of the acceleration energy region of light ions towards higher energies in the existing RF harmonic equal to 2 and the modification of the central geometry for the RF harmonic equal to 1 to allow an acceleration of protons at several tens of MeV are considered. The substantial redesign of the central electrode structure is needed to accelerate protons with reasonable values of the dee voltage. The new inflector geometry and the optimized central electrode structure have been formulated for the upgrade.

MOPCP094	Consistency in Measurement of Beam Phase and Beam Intensity Using Lock-in Amplifier and Oscilloscope Systems	245
	R. Koyama, M. Fujimaki, N. Fukunishi, A. Goto, M. Hemmi, O. Kamigaito, M. Kase, N. Sakamoto, K. Suda, T. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan
	The RIKEN RI beam factory (RIBF) consists of four ring cyclotrons (RRC, fRC, IRC, and SRC) and two injectors (RILAC and AVF) which are all connected in cascade. RILAC, AVF, and RRC began operation in the 1980s, and fRC, IRC, and SRC were installed in 2006. Phase probes (PPs) are installed in all cyclotrons and beam transport lines of RIBF, and the beam-bunch signals that are detected nondestructively by these PPs are used for tuning of isochronous magnetic field of cyclotrons and for monitoring the beam phase and beam intensity. We mainly use a newly developed system that incorporates a lock-in amplifier (LIA; SR844, SRS) for those tuning and monitoring; however, in AVF and RRC, a conventional measurement method using an oscilloscope system (OSC; DSO6052A, Agilent) is used. In this study, we investigated the consistency in the measurements carried out using LIA and OSC systems by Fourier analyzing the observed data. Additionally, we investigated the resolution and measurement uncertainty of LIA and OSC.

TUM2CIO01	Status of RIBF Accelerators at RIKEN	286
	O. Kamigaito, S. Arai, T. Dantsuka, M. Fujimaki, T. Fujinawa, H. Fujisawa, N. Fukunishi, A. Goto, H. Hasebe, Y. Higurashi, K. Ikegami, E. Ikezawa, H. Imao, T. Kageyama, M. Kase, M. Kidera, M. Komiyama, H. Kuboki, K. Kumagai, T. Maie, M. Nagase, T. Nakagawa, M. Nakamura, J. Ohnishi, H. Okuno, N. Sakamoto, K. Suda, H. Watanabe, T. Watanabe, Y. Watanabe, K. Yamada, Y. Yano, S. Yokouchi RIKEN Nishina Center, Wako, Japan
	Recent developments and upgrade program in the near future at RIKEN RI-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 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. We are, therefore, constructing a new injector linac for the RIBF, consisting of a superconducting ECR ion source, RFQ, and DTL, which will be commissioned in this fiscal year. By using this injector, we also aim at independent operation of the RIBF and GARIS facility for super-heavy element synthesis.
	Slides TUM2CIO01 [4.914 MB]

WEM2CCO02	Operating Experience with the RF System for Superconducting Ring Cyclotron of RIBF	338
	N. Sakamoto, M. Fujimaki, A. Goto, O. Kamigaito, M. Kase, R. Koyama, K. Suda, K. Yamada, S. Yokouchi RIKEN Nishina Center, Wako, Japan
	Since December 2006, Superconducting Ring Cyclotron (SRC) has been operational. Up to now, the beams of ²³⁸U, ⁴⁸Ca, pol-d, N, ⁴He have been provided for nuclear physics experiments. The SRC consists of 6 superconducting sector magnets, 4 accelerating cavities and one flattop cavity. Designed value of the acceleration voltage is 2 MV/turn. The gap voltage of 600 kV is excited with 130 kW rf power in the accelerating cavity. The cavities have been installed at four valley regions of 6 sector magnets and are exposed to a strong stray field of superconducting magnets. The strength of the magnetic field is as large as a few kilogauss. It is found that the condition of multipactor depends drastically on the strength of the stray field. How to treat the multipactor is one of the most important issues for stable operation of the SRC. This paper will discuss on our efforts to settle the problem concerning the cavities. By improving the vacuum, cooling, surface treatment and so on, we finally succeeded to minimize the break time due to the rf break down of the SRC cavities during experiments.
	Slides WEM2CCO02 [9.291 MB]