NUKLEONIKA 2007, 52(1):7-12
Michał A. Gryziński1, Natalia Golnik2, Mieczysław Zielczyński3
1 Institute of Environmental Engineering Systems,
Warsaw University of Technology,
20 Nowowiejska Str., 00-653 Warsaw, Poland
2 Institute of Precision and Biomedical Engineering,
Warsaw University of Technology, 8 Saint A. Boboli Str., 02-525 Warsaw, Poland
3 Institute of Atomic Energy, 05-400 Otwock-Świerk, Poland
Data on the initial recombination of ions are needed for designing recombination chambers, used in
mixed radiation dosimetry in order to obtain information about radiation quality. Nevertheless,
experimental data for pressurized gases are scarce, whereas reliable theoretical models are absent.
The paper provides experimental data on the initial recombination in hydrocarbon gases (methane,
ethane and propane) depending on gas pressure up to 1.8 MPa. The data were derived from the measurements
of saturation curves of a tissue equivalent recombination chamber of an REM-2 type, in reference
radiation fields of 137Cs and 239Pu-Be sources. Ion recombination due to volume
recombination and back diffusion of ions was subtracted from the measured values of ion collection
efficiency. The values of gas parameters needed for the subtraction procedure were determined by
measurements of saturation curves of the chamber at several dose rates for each gas pressure.
The important practical rule resulting from the experiments is that in the first approximation the
initial recombination does not depend on the kind of the hydrocarbon gas but only on its density
in the chamber.