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) : Shosa, D W


Full Text : http://www.dtic.mil/get-tr-doc/pdf?AD=AD0770114


Report Date : Sep 1973


Pagination or Media Count : 18


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.


Descriptors :   *ELECTRON BEAMS, *IONIZATION CHAMBERS, ION DENSITY, LINEAR ACCELERATORS, SATURATION, SPACE CHARGE


Subject Categories : Nuclear Instrumentation


Distribution Statement : APPROVED FOR PUBLIC RELEASE