Investigation of tissue-equivalent proportional counters in mixed neutron-photon fields also applying time-of-flight techniques

The determination of absorbed dose fractions due to photons and neutrons by means of tissue-equivalent proportional counters (TEPC) was investigated in monoenergetic neutron fields with energies of 50 keV, 144 keV and 570 keV. As an extension of the conventional methods applied to the pulse-height spectrum of the detector, time-of-flight techniques (TOF) were used which allow a distinction to be made between photons and neutrons originating from the target on the basis of their different TOF. The pulse-height signals from the detector were simultaneously measured with different amplifications and stored together with the TOF information as correlated events by using a multiparameter system and list-mode data recording. As an additional application this procedure allows the gain ratios of various partial spectra and the electronic offsets on-line to be determined without further calibration. (author)