Deterioration of Boron Trifluoride Counters Due to High Counting Rates

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Abstract
Twenty‐two boron trifluoride counters were run at counting rates of about 106 counts per min in the proportional region until they had all lost their plateaus of voltage versus counting rate. This occurred in from 108 to 109 counts. The pulse heights decreased to the point at which maximum sensitivity of the circuitry failed to record more than 103 counts per min, although many more small pulses could be detected on an oscilloscope. Raising the voltage did not restore the pulse heights. The counters did not recover after inactive periods of up to four months. Gas samples from several of the counters were analyzed on a mass spectrometer. A theory is proposed which would explain the deterioration on the basis of a negative ion sheath which is formed when the BF3 dissociates.

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