硫化亜鉛螢光体の重陽子線による放射線損傷

抄録

An investigation has been made of the effects of 2 MeV deuteron bombardment by means of cyclotron on the following optical properties of copper-activated zinc sulfide phosphor, i.e. the luminescent brightness, growth and decay of luminescent emission at room and near liquid air temperatures, and glow curve, under the excitation both in the copper absorption band and in the fundamental absorption band of ZnS host crystal (called “ copper excitation “and” host excitation”, respectively).
Deuteron bombardment gives rise to the following effects. The color of the phosphor becomes pale brown, and the luminescent brightness is lowered very much. Principally, the growth of lumines-cence becomes slower, while the decay becomes faster, than with an unbombarded sample. At low temperatures, however, these tendencies are not so remarkable as at room temperature; they seem to die out under the host excitation. Both growth and decay at low temperatures are generally slower than at room temperature. The glow curve of an unbombarded sample has three peaks located at about 320° (called “A” peak), 270° (“B” peak), and 200° K (“C” peak). For a bombarded sample, the “A” peak becomes very small and the “B” peak sharp and small, both shifting to lower temperatures. The “C” peak shifts to a lower temperature and several small peaks are created on its high temperature side. If samples which had different degrees of bombardment are compared with one another, it is shown that the more the sample is irradiated, the smaller the light sum shown by glow curves becomes. The effect of annealing on bombarded samples has been examined, and it is found that the damage can fairly well be removed by annealing the samples at 550°C.
The following conclusions can be drawn from the experimental results. 1) Decomposition of zinc sulfide is scarcely produced. 2) Displacement of ions strongly induced by bombardment will produce various types of traps. Most of the aforementioned changes of optical properties caused by bombardment are attributed to these new traps, and moreover many of these traps, especially deep ones, act as killers.