F-Centres in Metaphosphate Glass
A NUMBER of investigators1 have shown that glass on exposure to radioactive and X-radiation becomes coloured. Sheline, Sharp and Arner2 suggested that this may be due to F-centres similar to those produced in alkali halides when bombarded by X-rays and cathode rays. Yokota3 found that F-centres could be created in fused silica and α-quartz by X-irradiation. He further showed that alkali silicate and borate glasses become coloured on X-irradiation due to formation of F-centres4. Przibram5 showed that F-centres could also be created in borate glass by β- and γ-irradiation from radium.
Dosimetry of X‐Rays and Gamma‐Rays by Radiophotoluminescence
The effects of high energy radiation on the luminescence properties of solids are surveyed. Of the four effects considered—radiophotoluminescence, radiophotostimulation, radiothermoluminescence, and the ``killing'' of luminescence by x‐rays or gamma‐rays—the first effect is shown to have advantages in principle over the others as a basis for dosimetry.The absorption, excitation, emission, sensitivity, energy dependence, and stability characteristics of a radiophotoluminescent Ag‐activated phosphate glass are described. It is shown that dosage measurements can be made with this material, employing a simple fluorophotometer, from 10 roentgens to a few thousand roentgens of gamma‐rays. By proper shielding, such a dosimeter element can be made reasonably independent of energy. The dosage indication obtained is quite stable with time and is not seriously affected by exposure of the glass to visible or ultraviolet light or to temperatures in the range of −70° to +100°C. Because of its sensitivity range and its ...
Some Optical Properties of Lead-Activated Sodium Chloride Phosphors
Absorption and luminescence phenomena in NaCl:Pb phosphors have been found to be rather complex. Melt-grown NaCl:Pb has an asymmetrical, 2730A-peaked absorption band. The variation of emission spectrum with wave-length of excitation within this band shows that it consists of two poorly resolved absorption bands, one peaking at 2730A and the other at 2900A. At low Pb concentrations, irradiation into the first of these causes a near-ultraviolet emission peaking at 3200A; irradiation into the second causes a visible emission peaking at about 4500A. At high Pb concentrations, irradiation into the first band gives a second near-ultraviolet emission band peaking at 3850A in addition to the one peaking at 3200A. Precipitated NaCl:Pb shows all the above phenomena, and in addition, has an excitation band peaking at 2600A, producing simultaneously a 3300A-peaked emission and a visible emission. The NaCl:Pb phosphors are unstable, deteriorating after a few days at room temperature and more rapidly at 130°. X-irradiation of these phosphors destroys the above absorption and emissions, and gives a print-out effect due apparently to the formation of colloidal Pb. The x-rayed material can be excited by near ultraviolet to give a red emission, peaking at about 6100A. Some suggestions concerning the interpretation of the above phenomena are given.