JPS57100366A - Radiation detector - Google Patents

Abstract

PURPOSE:To suppress the output level range on the upper limit side and decrease the bit number necessary for indicating data number within the upper and lower limit range of output signals by using mixed gases of a rare gas and a gas forming negative ions as a packing gas. CONSTITUTION:In an ionization chamber type radiation detector of parallel flat plate type, its output electric current (i) is i=(1-1/6Xalpha/ek1k2Xqd<2>/V<2>)qd (where d: the spacing between electrode plates, V: applied voltage, e: the electric charge of electron, q: ionization density, alpha: a recombination constant, k1: the mobility of negative ion, k2: the mobility of positive ion). The device of this invention uses a mixture of a rare gas and a gas for forming negative ions, for example, gaseous nitrogen, as a gas to be packed into the radiation detector. In this case, the gas for forming negative ions generates negative ions in correspondence to the does of incident rays and therefore the amt. of their recombination with positive ions increases, thereby increasing the term of the recombination in the equation. Hence, as the ionization density (q) increases, the output current (i) deviates from a straight line and provides a non-linear output characteristic.