Date of Award
Doctor of Philosophy (PhD)
Gilbert R. Hoy
The research described herein is among the first attempts to test one of the more popular theories for development of a gamma-ray laser. This work is a "marriage" between the Borrmann effect, which is a consequence of the dynamical theory of x-ray diffraction, and time-filtering which comes from time-domain Mossbauer spectroscopy.
Our experiments involved the search for a nuclear Borrmann effect and the subsequent time-filtering effect using 57Fe and 73Ge. In both cases, no nuclear Borrmann effect was observed; however, the methodology and criteria necessary for such an observation with any isotope were documented. The procedures necessary for testing the crystal samples for the ability to support a Borrmann effect, both prior to and after the introduction of the parent nuclei, were derived for both a table-top x-ray system and a synchrotron radiation facility. For the table-top system, energy dispersive photon detectors were used to map the crystals in a computer-controlled goniometer system. At the synchrotron facility, the technique of x-ray topography was used to determine crystal quality. Additionally, a process was developed in which radioactive 73As was introduced into natural germanium single crystals via electro-deposition and subsequent annealing for the nuclear Borrmann effect studies.
The experimental setup and circuitry required for observation of the time-filtering effect were also developed and tested. The processing electronics used in the delayed coincidence circuit were optimized and the resulting configuration documented. Time filtering experiments were performed on 57Fe and 73Ge using both powder and crystalline samples. During these investigations, a new method for studying the time-filtering effect was investigated using the internal conversion channel. This led to the realization that the currently accepted theory explaining time-filtering is incomplete, and requires further study and experimentation.
McDermott, Walter C..
"Gamma-Ray Optical Studies of ⁷³Ge and ⁵⁷Fe"
(1996). Doctor of Philosophy (PhD), dissertation, Physics, Old Dominion University, DOI: 10.25777/dn8q-8683