A New PC Based Semi-Automatic TLD Badge Reader System For Personnel Monitoring

Personnel monitoring of more than 40,000 radiation workers in India is being carried out routinely using a Bhabha Atomic Research Centre (BARC) made thermoluminescent dosimeter (TLD) badge based on CaSO4:Dy phosphor embedded in Teflon discs [1], and a photographic film badge. Till recently the TLD badges were read using the manual type TLD badge reader system with an external interface unit for connection to a PC for glow curve storage and dose evaluation [2]. The film badge is being replaced by the TLD due to the operational convenience and the low cost of the latter resulting in a very significant increase in the number of persons being monitored using TLD. A new PC based semiautomatic TLD badge reader system with a number of design improvements for faster processing of the TLD badges with reduced man power has been developed. The new reader has features such as non contact N2 gas heating, reproducible temperature profile of the gas, built-in safeguards against gas flow, heater and EHT failures, dark current compensation, background subtraction, auto ranging, automatic switching of EHT to a lower value when high TL output is encountered to enable a wide range of measurement with high sensitivity to lower levels of TL, etc. An elaborate software is written in ‘C’ language for storage and recall of glow curves, evaluation of doses and printout of dose reports.