Nuclear Radiation Detection Using a Superconducting Resonant Cavity

Abstract

Nuclear radiation is detected using a superconductingresonant circuit operated at 380 MHz. The technique uses a dopedsemiconductor crystal placed on the stub of a reentrant cavity. The cavity is lead plated and cooled to 4.2°K, such that it becomes superconducting. The cavity then becomes the frequency controlling element for a voltage variable oscillator. Nuclear radiation impinging on the crystal causes a change in the relative dielectric constant, which in turn causes the resonant frequency of the cavity to change. The crystal exhibits a peculiar trap property at 70°K or below, which allows any electron‐hole pairs generated in the crystal to be indefinitely trapped. The output frequency of the resonant circuit is then proportional to the total dose received by the crystal. Frequency shifts of the order of 4.051 kHz/min are observed in CdS, for a 14C source of 1 μ Ci.