Date of Award

3-1992

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

George John, PhD

Abstract

A channel electron multiplier (cem) detector system was designed and built to provide a signal to a Mossbauer spectroscopy system in an effort to obtain a better signal-to-noise ratio than achievable with a proportional counter system. Three cems are contained in a vacuum chamber built using standard components. Gamma, rays of 14.4-keV energy from a 57Co source enter from outside the chamber through a window and are absorbed by an 57Fe target near the cems. The target emits internal conversion electrons which are collected by the cems and a Mossbauer spectrometer collects the signal. The system produces a usable signal, but the signal-to-noise ratio is unacceptably high. The strongest peak has a maximum count only 2.1% of the total background count. The corresponding peak in a spectrum collected using the proportional detector system is 3.4% of the total background count. One possible cause is that some gamma rays are striking two of the cems, producing ionizations in the detectors. The cems need to be repositioned. A screen should be added in front of the cems and grounded to reduce counting of low energy electrons. These improvements should reduce the background count rate.

AFIT Designator

AFIT-GNE-ENP-92M-9

DTIC Accession Number

ADA248154

Comments

The author's Vita page is omitted.

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