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Fukuda, Mitsuhiro; Kurashima, Satoshi; Miyawaki, Nobumasa; Okumura, Susumu; Kamiya, Tomihiro; Oikawa, Masakazu*; Nakamura, Yoshiteru; Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; et al.
Nuclear Instruments and Methods in Physics Research B, 210, p.33 - 36, 2003/09
Times Cited Count：4 Percentile：33.69(Instruments & Instrumentation)A heavy ion microbeam with energy of hundreds MeV is a significantly useful probe for research in biotechnology. A single-ion hitting technique using a 260 MeV 
Ne
microbeam is being developed at the JAERI AVF cyclotron facility for biofunction elucidation. Production of a microbeam with a spot size of one micro-meter in diameter requires reducing the energy spread of the beam to 0.02 % to minimize an effect of chromatic aberrations in focusing lenses. The typical energy spread of the cyclotron beam is around 0.1 % in an ordinary acceleration mode using a sinusoidal voltage waveform. The energy spread can be reduced by superimposing the fifth-harmonic voltage waveform on the fundamental one to generate a flattop waveform for uniform energy gain. We have designed an additional coaxial cavity to generate the fifth-harmonic voltage, coupled to the main resonator of one-fourth wavelength coaxial type. In a power test we successfully observed the fifth-harmonic voltage waveform by picking up an acceleration voltage signal.
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：58.66(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.
Kurashima, Satoshi; Fukuda, Mitsuhiro; Nakamura, Yoshiteru; Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; Tamura, Hiroyuki; Yokota, Wataru; Okumura, Susumu; Arakawa, Kazuo; et al.
AIP Conference Proceedings 600, p.303 - 305, 2001/00
A flat-top acceleration system for the JAERI AVF cyclotron has been designed. The fifth harmonic of the fundamental frequency is used to obtain uniform energy gain. To determine optimum parameters of the flat-top system, a cold model test was carried out and flat-top waveforms of the voltages were observed successfully in the whole range of the fundamental frequency. An rf power required for generating a flat-top dee voltage of 30 kV was estimated to be about 1 kW. The design of the flat-top cavity is being modified using the MAFIA code.
