Measurements of Neutron Contamination in High Energy X-ray Beams from Mevatron

• Published in: Japan Radiological Physics Vol. 2; no. 2; pp. 103 - 115
• Main Authors: KAWASHIMA, KATSUHIRO, HOSHINO, KAZUO, HIRAOKA, TAKESHI, MARUYAMA, TAKASHI, KUMAMOTO, YOSHIKAZU, KATOH, TOSHIO, MURAKAMI, YUKO, KAGAYA, SHINSAKU, KOMATSU, HIROSHI, FERRE, EDWARD, NISHIMURA, HARUYUKI, KUMAGAI, KAZUMASA
• Format: Journal Article
• Language: Japanese
• Published: Japan Society of Medical Physics 01.12.1982
• Subjects: Etch pit; Mevatron; Neutron dosimetry; Protection; Rem-counter
• ISSN: 0288-5506; 2186-9847
• DOI: 10.11323/jjmp1981.2.2_103

In high energy x-ray beams, neutrons are produced due to photo - d isintegration in the target material, beam flattening filter and collimator. Neutron dose equivalents from a Mevatron were measured using two kinds of detectors. One of the detectors was a neutton dose rate meter, generally called a rem counter. The other was a track-etch detector made up of 10B and polycarbonate plates for detecting alpha-track from 10B(n, a) reaction. The track-etch detector as well as BF3 counter of remcounter is mounted inside a moderator. After the irradiation at the level of 2 to 10 mrem, polycarbonate plates are electrochemically etched to record only alpha-track as etch pits. Neutron dose equivalents were measured as a function of the distance away from the isocenter. This relation may be represented by an exponential function. The distances of every 1.3 in and 1.4 m decrease the neutron dose equivalent about one half for 10 MV and 15 MV x-ray beams respectively. It can be concluded that these two dosimetry combination provides a new approach with a number of advantages compared to some other existing techniques for such measurements of neutron dose equivalent in high energy x-ray beams.