CYCLOTRONS 2010 - List of Authors (Sakamoto, N.)

Paper

Title

Page

Stable Operation of RF Systems for RIBF

186

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

At RIKEN RI-Beam Factory (RIBF), heavy ion beams are accelerated up to 345 MeV/u by using the RIKEN heavy ion linac (RILAC) and four ring cyclotrons. In order to provide high intensity beams up to 1puA, all the RF systems must be stable enough for a long term (a few weeks), within ±0.1% in voltages and ±0.1 degrees in phases. For a stable operation of RIBF, we have started to monitor for the RF voltages and phases for all the RF systems, and beam intensity and phases using lock-in amplifiers. We have investigated a degree of stability of the RF systems. Then, we have performed several improvements. The Automatic Gain Control units for RILAC were replaced for a better stability. It was found that the stability of RF systems was considerably affected by the fluctuation of reference signals. The fluctuation was mainly caused by the temperature dependence of power dividers used for a reference signal distribution. Therefore, we have changed the distribution method. The reference signal is first amplified to 40 dBm and divided by directional couplers, and they are delivered to low level circuits. The present degree of stability of the RF systems will be presented.

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.

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.

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
MOPCP068	Stable Operation of RF Systems for RIBF	186
	K. Suda, M. Fujimaki, N. Fukunishi, M. Hemmi, O. Kamigaito, M. Kase, R. Koyama, K. Kumagai, N. Sakamoto, T. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan
	At RIKEN RI-Beam Factory (RIBF), heavy ion beams are accelerated up to 345 MeV/u by using the RIKEN heavy ion linac (RILAC) and four ring cyclotrons. In order to provide high intensity beams up to 1puA, all the RF systems must be stable enough for a long term (a few weeks), within ±0.1% in voltages and ±0.1 degrees in phases. For a stable operation of RIBF, we have started to monitor for the RF voltages and phases for all the RF systems, and beam intensity and phases using lock-in amplifiers. We have investigated a degree of stability of the RF systems. Then, we have performed several improvements. The Automatic Gain Control units for RILAC were replaced for a better stability. It was found that the stability of RF systems was considerably affected by the fluctuation of reference signals. The fluctuation was mainly caused by the temperature dependence of power dividers used for a reference signal distribution. Therefore, we have changed the distribution method. The reference signal is first amplified to 40 dBm and divided by directional couplers, and they are delivered to low level circuits. The present degree of stability of the RF systems will be presented.

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.

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.

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]