Detection of Radiation Damage in Anthracene Crystals by Space‐Charge‐Limited Current Measurements

Abstract

It is shown that hole traps are induced in anthracene crystals by irradiating the crystals with either gamma or x rays. These traps are detected by measuring the steady‐state current—voltage characteristic of the crystal in the space‐charge‐limited current region. A modified type of Kallmann—Pope cell employing a sodium sulfate solution as one electrode and sodium iodide—iodine solution as the hole injecting electrode was used. After irradiating the crystals with gamma rays or x rays, part of the current—voltage curve shows a square‐law dependence and the current saturation occurs at higher voltages than in the nonirradiated crystals. By applying space‐charge‐limited current theory and interpreting the voltage at which the departure from the square law occurs as the trap‐filled‐limit voltage for the induced deep traps, the density of these traps can be estimated. Using this calculated density it is found that one deep trap is created for every 45 keV of incident energy absorbed in the crystal.