CYCLOTRONS 2010 - List of Authors (Yokota, W.)

Paper	Title	Page
MOPCP019	Present Status of JAEA AVF Cyclotron Facility	87
	T. Yuyama, I. Ishibori, T. Ishizaka, H. Kashiwagi, S. Kurashima, N. Miyawaki, T. Nara, S. Okumura, W. Yokota, K. Yoshida, Y. Yuri JAEA/TARRI, Gunma-ken, Japan
	The JAEA AVF cyclotron provides various ion beams mainly for research in materials science and biotechnology such as estimation of radiation hardness of space-use devices, and plant breeding by ion beams. We have been developing ion sources, the cyclotron, and beam irradiation techniques to meet requirements from users. In order to stabilize the beam intensity, power supplies for magnets were improved by installing a digital-to-analog converter (DAC) unit with a Peltier device for coil current control. As a result, coil current stability of main magnet of ± 5 × 10^-6 has been obtained by the renewed DAC unit which guarantees temperature control within 1°C at 30°C. Initially, it took about eight hours to form a heavy-ion microbeam, so it was impractical to change the microbeam ion species in an experiment. However, the microbeam of a 520 MeV 40Ar¹⁴⁺ has been successfully changed to the one of a 260 MeV ²⁰Ne⁷⁺ within 30 minutes using a cocktail beam acceleration technique. A beam profile uniformization system using multipole magnets are being developed to enable uniform irradiation of a large sample at a constant particle fluence rate.

MOPCP090	Progress in Formation of Single-Pulse Beams by a Chopping System at the JAEA/TIARA facility	233
	S. Kurashima, I. Ishibori, T. Nara, W. Yokota JAEA/TARRI, Gunma-ken, Japan M. Taguchi JAEA/QuBS, Takasaki, Japan
	The intervals of beam pulses from a cyclotron is generally tens of ns and they are too short for pulse radiolysis experiments which require beam pulses at intervals ranging from 1 μs to 1 ms (single-pulse beam). A chopping system, consisting of two types of high voltage kickers, is used at the JAEA AVF cyclotron to form single-pulse beam. The first kicker installed in the injection line generates beam pulses with repetition period of 1 μs to 1 ms. The pulse width is about a cycle length of the acceleration frequency. The other kicker in the transport line thins out needless beam pulses caused by multi-turn extraction. We could not provide single-pulse beam stably over 30 min since the magnetic field of the cyclotron gradually decreased by 0.01 % and the number of multi-turn extraction increased. The magnetic field was stabilized within 0.001 % by keeping temperature of the cyclotron magnet constant. In addition, a new technique to measure and control an acceleration phase has enabled us to reduce the number of multi-turn extraction easier than before. We have succeeded to provide single-pulse beam of a 320 MeV carbon without retuning of the cyclotron over 4 h, as a result.

Paper

Title

Page

Present Status of JAEA AVF Cyclotron Facility

87

T. Yuyama, I. Ishibori, T. Ishizaka, H. Kashiwagi, S. Kurashima, N. Miyawaki, T. Nara, S. Okumura, W. Yokota, K. Yoshida, Y. Yuri
JAEA/TARRI, Gunma-ken, Japan

The JAEA AVF cyclotron provides various ion beams mainly for research in materials science and biotechnology such as estimation of radiation hardness of space-use devices, and plant breeding by ion beams. We have been developing ion sources, the cyclotron, and beam irradiation techniques to meet requirements from users. In order to stabilize the beam intensity, power supplies for magnets were improved by installing a digital-to-analog converter (DAC) unit with a Peltier device for coil current control. As a result, coil current stability of main magnet of ± 5 × 10^-6 has been obtained by the renewed DAC unit which guarantees temperature control within 1°C at 30°C. Initially, it took about eight hours to form a heavy-ion microbeam, so it was impractical to change the microbeam ion species in an experiment. However, the microbeam of a 520 MeV 40Ar¹⁴⁺ has been successfully changed to the one of a 260 MeV ²⁰Ne⁷⁺ within 30 minutes using a cocktail beam acceleration technique. A beam profile uniformization system using multipole magnets are being developed to enable uniform irradiation of a large sample at a constant particle fluence rate.

MOPCP090

Progress in Formation of Single-Pulse Beams by a Chopping System at the JAEA/TIARA facility

233

S. Kurashima, I. Ishibori, T. Nara, W. Yokota
JAEA/TARRI, Gunma-ken, Japan
M. Taguchi
JAEA/QuBS, Takasaki, Japan

The intervals of beam pulses from a cyclotron is generally tens of ns and they are too short for pulse radiolysis experiments which require beam pulses at intervals ranging from 1 μs to 1 ms (single-pulse beam). A chopping system, consisting of two types of high voltage kickers, is used at the JAEA AVF cyclotron to form single-pulse beam. The first kicker installed in the injection line generates beam pulses with repetition period of 1 μs to 1 ms. The pulse width is about a cycle length of the acceleration frequency. The other kicker in the transport line thins out needless beam pulses caused by multi-turn extraction. We could not provide single-pulse beam stably over 30 min since the magnetic field of the cyclotron gradually decreased by 0.01 % and the number of multi-turn extraction increased. The magnetic field was stabilized within 0.001 % by keeping temperature of the cyclotron magnet constant. In addition, a new technique to measure and control an acceleration phase has enabled us to reduce the number of multi-turn extraction easier than before. We have succeeded to provide single-pulse beam of a 320 MeV carbon without retuning of the cyclotron over 4 h, as a result.