| Compton scattering is a means of probing electron momentum distributions and can be used to evaluate calculations of electron wavefunctions in solids. The need for improved resolution in Compton experiments performed with high energy x-rays has motivated the development of a high resolution spectrometer. Calorimetric x-ray detectors, produced at Goddard Space Flight Center for x-rays around 6 KeV, have been adapted for use in Compton scattering research using synchrotron radiation near 40 KeV. Such detectors are operated below 0.1 K and work by measuring the temperature increase which results from the absorption of a single x-ray photon. Seeking to optimize detector efficiency and response at high energies, a number of materials were investigated as candidates for the overlayer which is affixed to a device in order to absorb the x-rays and transfer their energy to phonons. Mercury-telluride and superconducting foils of rhenium, tantalum, and tin were studied, each producing a detector response very different from the others and from that expected from the Debye heat capacity of the material. Experiments with creating quasiparticle recombination sites on the superconductors to assist the thermalization process produced no measurable change in detector response. Using tin absorbers, a resolution of 90 eV at 32 KeV was achieved.; The apparatus was brought to a wiggler beam line at the Stanford Synchrotron Radiation Laboratory, where Compton profiles of silicon for the (100) and (111) directions were measured. The difference between directional profiles was consistent with the previously measured anisotropy, but no new insights into the electronic structure of silicon were provided, owing to the low number of total counts and to a degradation in resolution experienced during operation at the synchrotron. This experiment illustrated the feasibility of using such a system for Compton scattering research.; It is expected that future improvements to the detectors and to the supporting apparatus will make higher resolution measurements possible. A better understanding of the physics of the thermalization of x-rays in superconductors is required. The dissertation discusses some simple models to explain the observed performance of the superconducting absorbers and outlines a plan for further investigation. |
