Recombination processes in high-pressure ionization chambers irradiated with low-LET radiation

Initial and volume recombination in high-pressure ionization chambers were analyzed. The method how to perform corrections for volume recombination of ions is described basing on experimental data obtained with the chambers filled with different pressurized hydrocarbon gases. Initial recombination depends on local ion density within small volumes (with mass of order of one femtogram) of the irradiated medium. For radiations with high LET it can be correlated with L∞. For radiations with LET<3.5 keV/μm the initial recombination decreases slower than it was theoretically predicted. The hypothesis that the initial recombination for low-LET radiations depends on restricted LET with cut-off of about 500 eV is discussed.