Accession Number:

AD0770114

Title:

Saturation Characteristics of Miniature Ionization Chambers in Pulsed LINAC Exposures

Descriptive Note:

Technical note

Corporate Author:

ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD

Personal Author(s):

Report Date:

1973-09-01

Pagination or Media Count:

18.0

Abstract:

Theoretical expressions have been derived for the critical applied voltage below which charge collection is incomplete in ionization chambers exposed to pulsed radiation. To test the accuracy of the expressions, a 0.5 cc ionization chamber was exposed to 100 nsec pulses in a 35-MeV electron beam from the AFFRRI LINAC. Several gases with negligible electron attachment coefficients were used. These included argon, carbon dioxide, nitrogen, and a tissue- equivalent mixture of methane, carbon dioxide and nitrogen. It was found that the theory accurately predicted that, with 1000 volts applied, a charge density of 11 esu per pulse could be completely collected. It was also found that, for an air-filled chamber sufficiently small so that negative charge is transported to the anode by electrons, the derived expressions accurately predict the critical voltage.

Subject Categories:

  • Nuclear Instrumentation

Distribution Statement:

APPROVED FOR PUBLIC RELEASE