Calibration of a polycarbonate etched track detector

The efficiency of the Karlsruhe etched track detector was determined over a wide range of radon exposures. Sixty four detectors were placed in an airtight chamber. The radon concentration was kept at about 80 kBq.m(-3) by circulating air over a solid radium source. At predetermined times, a group of four detectors was taken out of the chamber. The exposure period varied from a few hours up to several months in order to determine the efficiency curve for low exposure as well as for the region of saturation. The functional form y=a (I -e(-bx)) was fitted to the data. The low exposure range was fitted with only the first six data points. The slope is 0.546 tracks.cm(-2).kBq(-1).m(3).h(-1), which is comparable to the earlier value of 0.55 tracks.cm(-2).kBq(-1).m(3).h(-1). The high exposure rang was fitted with the whole data sec. The two curves intersect at 2700 tracks.cm(-2). At higher track densities the curve based on the whole data set has to be used to convert the number of tracks into an exposure