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Kurashima, Satoshi; Miyawaki, Nobumasa; Okumura, Susumu; Ishibori, Ikuo; Yoshida, Kenichi; Kashiwagi, Hirotsugu; Fukuda, Mitsuhiro; Nara, Takayuki; Agematsu, Takashi; Nakamura, Yoshiteru
JAEA-Review 2005-001, TIARA Annual Report 2004, p.349 - 351, 2006/01
A flat-top acceleration system using fifth-harmonic frequency for the JAERI AVF cyclotron was developed to minimize the energy spread of an ion beam mainly for microbeam formation with a spot size of 1 micron in diameter by focusing with a set of quadrupole magnets. A single-turn extraction is an indispensable condition to reduce the energy spread without significant beam loss by the flat-top acceleration. In order to save time for the single-turn extraction tuning over measuring time distribution of the beam bunch, a deflector probe has been developed to observe the turn separation and the radial beam width. In this paper, we report the single-turn extraction technique with the deflector probe. As a result of beam developments, the single-turn extraction can be achieved in one or two hours and radioactivity of the deflector electrode can be also reduced in the acceleration of a high energy proton beam.
Yokota, Wataru; Sato, Takahiro; Oikawa, Masakazu*; Sakai, Takuro; Okumura, Susumu; Kurashima, Satoshi; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Fukuda, Mitsuhiro
JAEA-Review 2005-001, TIARA Annual Report 2004, p.291 - 292, 2006/01
no abstracts in English
Nakamura, Yoshiteru; Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; Kurashima, Satoshi; Fukuda, Mitsuhiro; Okumura, Susumu; Yokota, Wataru; Yoshida, Kenichi; Miyawaki, Nobumasa; et al.
Proceedings of 17th International Conference on Cyclotrons and Their Applications (CYCLOTRONS 2004), p.157 - 159, 2005/00
The AVF cyclotron system at JAERI Takasaki has been smoothly operated for 13 years since 1991. This system continues to deliver various ion species with very frequent alterations of operational conditions. In order to provide a heavy ion beam with energy spread of 0.02 % required for microbeam production, we have developed a flat-top acceleration system, an additional buncher driven by saw-tooth wave, and improved the central region of the cyclotron. An old gradient corrector of passive type was replaced by a new gradient corrector with an active coil inside to obtain complete matching between the trunk beam line and extraction trajectory from the cyclotron. A compact ion source with a set of movable permanent magnet was designed to produce mainly light ions, which will be replaced the existing multi-cusp ion source in future.
Okumura, Susumu; Miyawaki, Nobumasa; Kurashima, Satoshi; Yoshida, Kenichi; Fukuda, Mitsuhiro; Ishibori, Ikuo; Agematsu, Takashi; Nara, Takayuki; Nakamura, Yoshiteru; Arakawa, Kazuo
Proceedings of 17th International Conference on Cyclotrons and Their Applications (CYCLOTRONS 2004), p.410 - 412, 2005/00
A simple analyzing system has been developed to measure the energy spread of the beam extracted from the JAERI AVF cyclotron with an energy resolution of dE/E = 0.001%. The high analyzing power can be obtained with an existing deflecting magnet system in the transport line by installing three sets of slits with a minimum width of 0.01 mm and a beam intensity monitor with a Faraday cup and semiconductor detectors. These new instruments have been compactly designed to fulfill the geometrical condition of the existing beam diagnostic chambers, which are located at the object and image positions. Installation of the analyzing system was completed and a preliminary test has been carried out. This system will be used for optimization of the flat-top acceleration system to achieve the energy spread of dE/E = 0.02%, required for microbeam production.
Kurashima, Satoshi; Miyawaki, Nobumasa; Fukuda, Mitsuhiro; Okumura, Susumu; Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; Yoshida, Kenichi; Nakamura, Yoshiteru; Arakawa, Kazuo
JAERI-Review 2003-033, TIARA Annual Report 2002, p.310 - 311, 2003/11
The JAERI AVF cyclotron provides a variety of ion beams especially for the research in biotechnology and materials science. Several cyclotron technologies such as cocktail beam acceleration, a uniform irradiation in a wide area and beam pulsation have been developed so far. A flat-top acceleration system for the JAERI AVF cyclotron has been designed to minimize the energy spread mainly for a microbeam production. The flat-top acceleration using fundamental and fifth-harmonic frequencies for an acceleration voltage is an excellent technique to reduce the energy spread.
Ishii, Yasuyuki; Isoya, Akira*; Kojima, Takuji; Arakawa, Kazuo
Nuclear Instruments and Methods in Physics Research B, 211(3), p.415 - 424, 2003/11
Times Cited Count：17 Percentile：72.63(Instruments & Instrumentation)A beam width measurement system has been developed for keV submicron ion beams of 0.1 
m or less in width assuming a round shape beam. The system enables to measure beam current change as a function of knife-edge position by cutting a beam focusing point (beam spot) with the sharp edge within a spatial resolution of 0.02 m. The width of 30 keV order submicron 
ion beam was estimated by fitting current change curves based on three different ion density models: uniform, flat-top and Gaussian. Among these models, the flat-top model provide the most reasonable beam width of 0.56 m interpreting contribution of halo around the beam spot to beam width estimation. The beam width measurement system with the high spatial resolution and the data analysis based on the flat-top ion density model should contribute to accelerate developments of submicron ion beam production technologies.
Fukuda, Mitsuhiro; Kurashima, Satoshi; Okumura, Susumu; Miyawaki, Nobumasa; Agematsu, Takashi; Nakamura, Yoshiteru; Nara, Takayuki; Ishibori, Ikuo; Yoshida, Kenichi; Yokota, Wataru; et al.
Review of Scientific Instruments, 74(4), p.2293 - 2299, 2003/04
Times Cited Count：14 Percentile：58.58(Instruments & Instrumentation)A combination of the fundamental- and the fifth-harmonic voltages is ideally suited for flat-top acceleration in a variable-energy multi-particle cyclotron for energy-spread minimization. The flat-topping of the energy gain distribution using the fifth-harmonics has the advantages of minimizing an amplifier power, reducing power dissipation in a resonator and increasing the energy gain per turn. The flat-top acceleration system of the JAERI AVF cyclotron was designed to reduce the energy spread to 0.02 
, required for microbeam production. Tolerable fluctuations of acceleration voltages and the magnetic excitation were 2.0
10
for the fundamental voltage, 1.010
for the fifth-harmonic voltage, and 1.910
for the magnetic field. In order to enhance compactness of the flat-topping cavity and to make a substantial saving of the amplifier power, optimum geometric parameters of the flat-topping cavity were determined by a cold model test and a calculation using the MAFIA code.
Nakamura, Yoshiteru; Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; Tamura, Hiroyuki; Kurashima, Satoshi; Yokota, Wataru; Okumura, Susumu; Fukuda, Mitsuhiro; Arakawa, Kazuo
AIP Conference Proceedings 600, p.129 - 132, 2001/00
The AVF cyclotron system at JAERI Takasaki has been smoothly operated without serious troubles since the first beam extraction of 50 MeV 4He2+ in March 1991. A yearly operation time is about 3200 hours on an average for past several years. In last three years, we performed some improvements and developments as followings: stabilization of the cyclotron beam, renewal of the control computers and basic programs, installation of a new ECR ion source and reconstruction of the rotary shutter. Furthermore, cocktail beams of series M/Q=4 and M/Q=2 have been developed continuously. Now we are modifying the RF cavity for the flat-top acceleration by the addition of 5th harmonic frequency.
