Recombination chambers filled with different gases--studies of possible application for BNCT beam dosimetry

Recombination microdosimetric method (RMM), based on the phenomenon of initial recombination of ions is applied to determine the distribution of the absorbed dose versus linear energy transfer (LET). Usually, the recombination chambers used for RMM are filled with tissue-equivalent gas, but the response of the device can be adjusted to the actual needs by the use of different gases. Using a graphite chamber filled with nitrogen and 10BF3 it was shown that RMM can also be used with chambers containing these gases. This opens the possibility of designing a recombination chamber for the determination of the dose fractions due to gamma radiation, fast neutrons, neutron capture on nitrogen and high-LET particles from the (n,10B) reaction in simulated tissue with different contents of 10B. It was also necessary to improve the method for the determination of initial recombination at low polarising voltages, when volume-recombination and back-diffusion of ions are considerably high.