Development and field testing of thermoluminescent personal α-dosimeter for measuring exposure to radon and thoron daughters

An active thermoluminescent personal alpha dosimeter for measuring exposure to radon and thoron daughters has been developed. The TL-chips mounted in the dosimeter are ultra-thin CaSO4· Tm chips which are more sensitive to alpha radiation than those used in the other radon daughter do simeters. The response of the chip to gamma radiation is decreased to such a level as 0.8 counts/mR, so the lower detection limit is reduced to 1.04 μJm-3h (0.05 WLh) (γ background 1 mR/h; sampling period 6 hrs). Exposures to radon daughters and to thoron daughters can be determined separately by mounting three of those chips in the sampling probe of the dosimeter. The compact sampling pump, without flow regulator, features a satisfactory flow-resistance characteristics. The prototype usits have been subjected to a series of tests in laboratory and fields since 1981. The testing results are summarized in the paper