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Pure and magnesium-doped LiF crystals have been implanted with mainly magnesium and argon ions of 100 keV energy. Fluences were in the range of 6*1015-1*1017 ions cm-2. Changes in optical absorption during thermal annealing are reported. The magnesium colloid band at 280 nm and the lithium colloid band at 520 nm are identified. Some cases of anomalous colloid growth are observed. Hidden structural factors such as dislocations are thought to produce this anomalous annealing behaviour. Magnesium colloids develop in doped crystals after the implantation of rare gas ions. The responsible mechanism is thought to involve the interaction of F centres with impurity-vacancy (IV) dipoles. We find that the dopant has little effect on the concentration of F and F2 colour centres or on their thermal stability in ion-implanted samples.

The effects of pre-irradiation annealing on the thermoluminescence glow curves of gamma irradiated alpha-Al2O3:C have been studied for measurements between 30 and 500 degrees C. In particular, the response of the main dosimetric peak has been studied for gamma irradiation doses between 0.1 and 440 Gy and that of a subsidiary higher temperature glow peak for doses between 0.1 and 200 Gy. The response is observed to be linear only at low doses in agreement with previously reported data. The type and density of defects that may contribute to the observed dose response at various stages of the growth curve are discussed.

Measurements of the efficiency of electromagnetic detection and generation of ultrasonic shear waves in superconducting tin are presented. Theoretical calculations of the'generation efficiency are given, based upon a model by Quinn. Similar calculations are made for the radiation (detection) efficiency by adapting the Pippard model for ultrasonic shear wave attenuation, and lead to an identical temperature dependence as that predicted for the generation efBciency. Excellent agreement with this predicted behavior is found for experimental observations of the radiation efBciency for an electropolished (001) surface in tin at 15.3 MHz, using a single adjustable parameter. This parameter corresponds to a value of the London penetration depth XL(0) = 253 + 25 A, in agreement with values found in the literature. The experimental generation efficiency is found to be strongly power dependent and is described theoretically by adapting the theory to the case of the intermediate superconducting state established at the surface by the rf magnetic field. Experimental radiation eNciencies are also found to be very sensitive to surface damage, a fact which is attributed to collision drag of the electrons by the lattice in the damaged layer. The theory, modified to allow for surface damage, gives reasonable agreement with experimental radiation eNciencies for etched and spark-planed surfaces.