Behavior of Space Charge in Diamond Crystal Counters under Illumination. I

Abstract

The development of a technique is described whereby alternate electric field pulses and white light flashes are used to overcome the difficulty of the formation of space charge in a diamond crystal counter when subjected to bombardment by $\ensuremath{\beta}$-particles. Using the method, a study is made of the behavior of the space charge field when the electric field strength and flash intensity are varied. The manner in which the space charge grows and decays with time depending on the conditions of the experiment is described. It is shown how, under suitable conditions, steady counting-rates can be obtained and in particular, how the behavior of the counter under space charge free conditions can be investigated. Qualitative results are also given concerning the effect of illumination of the counter with red and infrared light instead of white light.Preliminary experiments on the effect of temperature on the counter suggest the possibility of permanently preventing the formation of space charge by keeping the temperature of the counter sufficiently high. It is also indicated how experiments at different temperature could yield information concerning the distribution of trap depths in the crystal and the mean lifetimes of trapped electrons and holes.A new approach to the problems of solid state physics has thus been developed. The great advantage that it possesses over luminescence methods is that it does not require the emission of light in order to study the electron transitions between trapping states and the ground state and consequently, radiationless transitions can be investigated.