Masters Theses

Date of Award

3-1987

Degree Type

Thesis

Degree Name

Master of Science

Major

Electrical Engineering

Major Professor

J. M. Rochelle

Committee Members

T. V. Blalock, G. W. Hoffman

Abstract

Small beams of radioactive ions are often used in the study of nuclear physics. Monitoring the profile of these beams is important for a number of reasons. This work describes an ion beam profile monitor designed to measure the profile of beams with intensities of a few pA. This profile monitor uses a rotating wire probe which intercepts less than 1% of the ion beam. Also, the charge is collected on a stationary, biased surface, thus reducing microphonic noise. The preamplifier is positioned in the vacuum vessel very near the charge collector to limit the possibility of triboelectric effect noise compromising the signal. This preamplifier has a transimpedance gain of 160 db and an output noise spectral density in the midband region of 1.95 X 10-12 v2/Hz. Because of a circuit used to compensate for capacitance changes between the wire probe and the charge collector, a profile signal with a signal-to-noise ratio of one occurs for a beam intensity of 1.8 pA.

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