Experimental studies of a large-volume tissue-equivalent proportional counter

The operational characteristics of a 5 inch spherical single-wire tissue-equivalent proportional counter have been investigated to test the suitability of the device for low dose microdosimetric measurements in radiation protection. Gas gain and resolution measurements indicate satisfactory performance although electrical breakdown and discharge in the counter limit the range of simulated diameters (gas pressures) that can be used to measure microdosimetric spectra extending down to cover event sizes of the gamma component of a mixed field. Measurements carried out in mixed fields produced by an Am-Be source and the neutron activation facility of the Department of Medical Physics illustrate the use of the counter for low dose microdosimetry and the ability of the device to yield mean quality factors of acceptable uncertainty in a few minutes measuring time at absorbed dose rates of the order of 1μGy.min-1. (author)