A comparison of two methods of rapidly heating thick TLDs

To heat a TLD quickly, the process should be limited only by the thermal characteristics of the TLD itself. One method is to bring the TLD into thermal contact with a metal mass, or anvil at a constant temperature which is approached asymptotically by that of the TLD. An alternative is to supply radiant heat to the TLD, for example from a CO2 laser. If this is done quickly, to minimise heat losses, the TLD temperature will rise linearly with time. Measurements have been made with experimental heaters of both types with the following parameters needed for their comparison: the time needed to heat the TLDs and its reproducibility, and the reproducibility of TLD readings when exposed and unexposed to radiation. With a 5 W CO2 laser, the heating time for a 0.9 mm thick TLD was about 10 s compared with about 6 s for the anvil heater. The heating rate for the laser heater was more consistent than for the anvil heater, but the latter provided more reproducibility in dosemeter readings. The use of the laser reduced the residual signal below a detectable level. The performance of both methods was shown to depend upon the methods of mounting the phosphor and the data analysis. (author)