Evaluation of Correction Factors Applied in Photon Calibration of NIS TE Neutron Ionization Chambers

Calibrations of two tissue equivalent (TE) ionization chamber were made in five photon beams (100 kV, 180 kV, 250 kV, Cs and Co) with two different pure gases namely acetylene C2 H2 and carbon dioxide CO2. The different calibration factors were compared both for in-air and in-water phantom, the measurements were performed according to the international atomic energy agency (IAEA) recommendations. For ionization chamber the total absorbed dose can be derived from the charge produced within its cavity employing a number of physical parameters. To discuss the charge produced in the cavity several correction factors which are related to the operational characteristics of the chambers have to be introduced. Information on the operational characteristics of two TE neutron ionization chambers were studied as a function of the effects of the warm-up to 3 hours, polarity, stem scattering, ion recombination, leakage current. Six different caps 1, 2, 3, 4, 6 and 8 mm were used to investigate wall thickness effect. Also, gas flow rate up to 31 ml/min and the radial & axial uniformity were investigated. [A. I. Abd El-Hafez and M. Ezzat Evaluation of Correction Factors Applied in Photon Calibration of NIS TE Neutron Ionization Chambers Journal of American Science 2011;7(3):758-772]. (ISSN: 1545-1003). http://www.americanscience.org.