Title page for ETD etd-04262010-020346


Type of Document Master's Thesis
Author Leyland, Walter A
URN etd-04262010-020346
Title A Bf3 Fast Neutron Dosimeter (Long Counter)
Degree Master of Science
Department Physics
Advisory Committee
Advisor Name Title
thesis, none found in Committee Chair
Keywords
  • Dosimeters.
Date of Defense 1960-09-03
Availability restricted
Abstract

A BF3 fast neutron dosimeter or long counter is constructed and calibrated for use with the Cockcroft-Walton accelerator and UTR-IO reactor at Virginia Polytechnic Institute. The counter consists of a paraffin cylinder 8 inches in diameter, having a BF3 proportional detector on the axis and a set of holes around the detector to improve the low energy response. External shields of paraffin, 3 inches thick, and boron-trioxide, 1/2 inch thick, enclose the paraffin cylinder. These shields serve to reduce the background effect and improve the high energy response.

Calibration of the counter is accomplished using as neutron sources: plutonium-berylliwn and the induced reactions H2(d,n)He3 and H3(d,n)He4. Long counter efficiencies for both a 1 inch and 1/2 inch BF) tube yield a flat response over the energy range, 2.5 to 4 Mev whereas an approximately 60% decrease in efficiency is observed for a 14.1 Mev neutron.

Count rate of long counter is expressed as a function of the incident neutron flux. Neutron fluxes, ranging from 0 to 1100 neutrons/cm2-seeond are monitored with the counter.

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