An Electrostatic Apparatus for Measurement of Thoron in Breath

An apparatus based on an electrostatic method for thoron in breath measurement (TIBM) is described. Details of the electrostatic chamber, its performance optimisation, calibration and use for TIBM are given. The collection efficiency of the chamber was measured for different concentrations of thoron drawn from a standardised thoron calibration chamber. The achievable efficiency of the system is observed to be appreciably better than that reported for similar systems used elsewhere. Experimental results demonstrate that it may be possible to measure as little as 14 mBq of 224Ra that emanates thoron at the mouth with a 5% error using this apparatus. (author)