Saburo Kitamura

Influences of Heat-treatment upon Cadmium Sulphide Single Crystals

Ionization energies and electron trap depths in cadmium sulphide single crystals heat-treated in vacuum or in oxygen were obtained by measuring the dark conductivity as a function of the temperature and the thermally stimulated current, respectively. It was found that, in the case of crystals heat-treated in vacuum, the ionization energies were 0.04 eV, 0.7 eV, 1.0 eV and 1.4 eV, and the major electron trap depth was 0.50 eV below the conduction band, and the dark conductivities and the concentrations of the electron traps were reduced as the crystals were heat-treated in oxygen. And when the crystals were heat-treated in vacuum or in oxygen, it was found that the sensitivity of photocurrent at about 600 mµ was increased.

Calcium Sulfate Activated by Lead and Manganese for Thermoluminescence Dosimetry

CaSO4: Pb, Mn has been found to be free from the serious disadvantage of rapid fading possessed by CaSO4: Mn, the most sensitive thermoluminescence phosphor available so far. A study has been made on the effect of lead and manganese content on CaSO4, and it is concluded that lead in CaSO4 produces new traps for radiation energy, resulting in improvement of the properties of the phosphors for dosimetry. The optimum content of such activator additives was found to be 0.2 mol/0 of lead and 3 mol/0 of manganese. The improved phosphor thus obtained produces glow peaks at 160° and 190°C, and the energy yield of the thermoluminescence is about which is twice that of CaSO4: Mn. The more significant properties of this phosphor from the viewpoint of application to radiation dosimetry include: (1) Linear responce from 50μR to 104R (2) Minimum detectable dose of 50μR±25% by experimental reader (3) Fading rate of 5% in a week