CYCLOTRONS 2010 - List of Authors (Koyama, R.)

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.

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]

WEM2CCO05

Beam Diagnostics for RIBF in RIKEN

351

T. Watanabe, M. Fujimaki, N. Fukunishi, O. Kamigaito, M. Kase, M. Komiyama, R. Koyama, H. Watanabe
RIKEN Nishina Center, Wako, Japan

In the present work, many varieties of beam diagnostics have been played a tremendous role for the RIBF (RI Beam Factory) in RIKEN. During beam user's experiments, it is essential to keep the beam transmission efficiency as high as possible, because the production of RI beams requires an intense primary beam, and the activation of the beam transport chambers induced by beam loss should be avoided. This presentation will include the overview of the Faraday cups, the transverse beam profile monitors, radial probes and phase probes to tune the accelerators and the beam transport line. To realize the stable operation of the accelerator complex, the nondestructive monitoring system of RF fields and beam-phase by using lock-in amplifies are used. Plastic scintillation monitors have been fabricated to evaluate the energy and longitudinal profiles of heavy-ion beams. Furthermore, a highly sensitive beam current (position) monitor with a high Tc (Critical Temperature) SQUID (Superconducting QUantum Interference Device) monitor, has been developed. We will report the present status of the facility, the details of the beam diagnostics and the results of the beam measurement.

Slides WEM2CCO05 [6.855 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.

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]

WEM2CCO05	Beam Diagnostics for RIBF in RIKEN	351
	T. Watanabe, M. Fujimaki, N. Fukunishi, O. Kamigaito, M. Kase, M. Komiyama, R. Koyama, H. Watanabe RIKEN Nishina Center, Wako, Japan
	In the present work, many varieties of beam diagnostics have been played a tremendous role for the RIBF (RI Beam Factory) in RIKEN. During beam user's experiments, it is essential to keep the beam transmission efficiency as high as possible, because the production of RI beams requires an intense primary beam, and the activation of the beam transport chambers induced by beam loss should be avoided. This presentation will include the overview of the Faraday cups, the transverse beam profile monitors, radial probes and phase probes to tune the accelerators and the beam transport line. To realize the stable operation of the accelerator complex, the nondestructive monitoring system of RF fields and beam-phase by using lock-in amplifies are used. Plastic scintillation monitors have been fabricated to evaluate the energy and longitudinal profiles of heavy-ion beams. Furthermore, a highly sensitive beam current (position) monitor with a high Tc (Critical Temperature) SQUID (Superconducting QUantum Interference Device) monitor, has been developed. We will report the present status of the facility, the details of the beam diagnostics and the results of the beam measurement.
	Slides WEM2CCO05 [6.855 MB]