MixD壁電離箱によるベータトロン電子線の測定

概要

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Dosimetry by means of ionization chamber has been widely used in conventional Roentgen and Cobalt-60 gamma ray therapy. Measurement of absorbed dose of Cobalt-60 gamma rays using the cavity ionization chamber has been already well established. When the ionization is measured in an air-filled cavity placed at a point in the irradiated medium, the absorbed dose in the medium may be estimated from the Bragg-Gray relationship. In order to measure the cavity ionization, a thimble ionization chamber has been developed at our center. The cavity wall is made of the MixD, the thickness is 1.8 mm, and the cavity volume is 3 mm φ×7.5mm. The collecting electrode is made of 0.6mm φ sized acrylic resin wire, which are coated by Aquadag. The response of the Radocon Roentgen-dosimeter has been investigated, and the R, -rad conversion factor is calculated by both the absorbed dose which was measured by this chamber at a point in the water exposed to electrons and the data measured by Roentgen-dosimeter. The obtained conversion factor for the Radocon 602 probe of the ratio was ca. 1.02-0.89 at 4 to 26 MeV, as for 606 probe of the ratio was ca. 0.91-0.8 at 8 to 26 MeV.
公益社団法人日本放射線技術学会の論文
1972-01-20