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Calorimetric determination of the cavity‐gas calibration factor N gas
Author(s) -
Schulz R. J.,
Weinhous Martin S.
Publication year - 1985
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.595758
Subject(s) - electrometer , ionization chamber , calorimeter (particle physics) , calibration , dosimetry , graphite , ionization , absorbed dose , materials science , physics , radiochemistry , nuclear physics , chemistry , nuclear medicine , optics , detector , medicine , ion , quantum mechanics , composite material
In the recently published AAPM protocol for the dosimetry of high‐energy photons and electrons, the response of an ionization chamber is defined as the dose to the gas in the chamber per unit electrometer reading, N gas . Using a graphite calorimeter, N gas has been determined for a Farmer‐type ionization chamber using 4‐ and 25‐MV x rays. The procedure was to measure the dose to graphite using the calorimeter, and then obtain the response of the chamber at the same depth in a graphite phantom. Equation (9) of the AAPM protocol was then used to calculate N gas . The values of N gas determined with the calorimeter are within 1% of N gas calculated according to the AAPM protocol, using the 6 0 Co exposure‐calibration factor.