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# Dosimetry and Measured Differential W Values of Air for Heavy Ions

Tatsuaki Kanai, Toshiyuki Kohno, Shinichi Minohara, Michio Sudou, Eiichi Takada, Fuminori Soga, Kiyomitsu Kawachi and Akifumi Fukumura
Vol. 135, No. 3 (Sep., 1993), pp. 293-301
DOI: 10.2307/3578867
Stable URL: http://www.jstor.org/stable/3578867
Page Count: 9
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## Abstract

Heavy-ion irradiation systems were designed and constructed at two cyclotron facilities in Japan for use in various fields of radiation physics and radiation biology. A 135 MeV/u carbon beam as well as 12 MeV/u carbon and helium-3 beams were first used in experiments. We have established a systematic method for heavy-ion dosimetry at both high and low incident energies involving measurements of fluences. We also obtained differential W values (w) of air for those beams by comparing the results of fluence measurement dosimetry with ionization chamber dosimetry. The differential W values of air were found to be 36.2 ± 1.0, 34.5 ± 1.0, and 33.7 ± 0.9 eV for 6.7 MeV/u carbon ions, 10.3 MeV/u ${}^{3}{\rm He}$ ions, and 129.4 MeV/u carbon ions, respectively. The w value for high-energy heavy ions approaches the W value for high-energy electron or photon beams. In ionization chamber dosimetry for a heavy-ion beam, we found a track-size effect. A difference in the track sizes of heavy ions in the gas and solid phases affected the output current of the ion chamber in the case of high-energy heavy ions.

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