60Coガンマ線による後方・側方散乱線の影響

抄録

It is generally recommended that the ionozation chamber must be calibrated in air using 60Co gamma ray beams. In an ionization chamber having cylindrical shape, the ionization cavity may be surrounded by an adequate thickness of build-up cap for any direction. For some ionization chambers having parallel plate shape, however, the cavity is surrounded by an extra scattering material for back and side directions. The extra scattering as a function of back and side extra volume have been measured for 60Co gamma ray beams. The correction factor for the extra scatter effect was given by an approximate equation with good accuracy.