Auttomatic nuclear emulsion scanner.

Abstract

An automatic nuclear emulsion scanner has been designed and constructed to scan the exposed film in personnel radiation monitoring badges. The scanner detects a portion of proton-recoil tracks in the film emulsion caused by incident neutron flux. The scanning speed, at present, is comparable with that of the visual reader and provides about the same statistics. The scanner uses a special closedcircuit TV camera system to view, scan, and count the proton-recoil tracks in a magnified image of a dark-field illuminated nuclear emulsion. The camera video signals are analyzed in a computer that uses two ultrasonic delay lines for signal storage. The computer discriminates against single grains, clumped grains, and unusual antifacts in the emulsion. Tracks are detected on the basis of their contrast against their background and their projected length in the emulsion. Field evaluation tests at Brookhaven National Laboratory indicate that the track count is a linear function of neutron flux. The spectral response curve of the scanner shows a proportionately greater track count at the higher energy levels. In addition, the scanner track count is fail-safe for moderate exposures. Operational characteristics of the automatic nuclear emulsion scanner are discussed. (auth)