Saturation Characteristics of Miniature Ionization Chambers in Pulsed LINAC Exposures
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1973
- Accession Number
- AD0770114
Entities
People
- D. W. Shosa
Organizations
- Armed Forces Radiobiology Research Institute