Fast neutron and pion interaction data from low pressure proportional counter measurements

Low pressure proportional counters can be used to measure absorbed dose and kerma for penetrating radiation with relatively low uncertainty applying the cavity chamber principle. Simultaneously, pulse height spectra are measured which represent the ionization yield spectra of the charged particles released in interactions of single primary particles and traversing the cavity. The measured spectra and the comparison with calculated distributions provide the possibility of analysing total kerma in terms of contributions by different types of secondary particles and of drawing conclusions on interaction data. The method can be successfully applied to improve the obviously inadequate knowledge of kerma factors and basic interaction data for high energy neutrons used at the new generation neutron therapy facilities. Principal and practical aspects of the method are described and some results for neutrons with energies between 14 and 20 MeV and proportional counters with walls made of A-150 plastic, graphite, aluminium and magnesium are presented. First experiences in measurements with negative pions are also reported. (author). 30 refs, 10 figs, 2 tabs