Alkali halide crystals as integrating radiation detectors

摘要

Three of the alkali halides (LiF, NaCl and KBr) have been used' as integrating crystal detectors for X and cathode rays with energies up to 3 million volts. The dosage measurements were based on the photoelectric and optical absorption characteristics of crystals colored by X-ray and cathode ray bombardment. Doses ranging from 20 to 105 roentgens were measured photoelectrically with the crystal arrangement illustrated schematically in Fig. 1 After the crystal has become colored by photon or particle bombardment, the color centers, electrons trapped at halogen ion lattice vacancies, are released by illumination in the color band while an electric field is applied. The resulting photo-currents, which drop essentially to zero in a few minures due to the space charge which builds up in the crystal, were recorded, and the charge Qc representing the area under the photo-current curve was measured as a function of the X-ray dose, Qc increases with the X-ray dose as shown in Fig. 2 for KBr crystals.