On the Feasibility of Designing a Small-Sized X-Ray Calorimetric Dosimeter Using a Thermopile Temperature Sensor

Calorimetric dosimetry is based on exposing an absorbing body to a radiation field. The energy deposited in the absorber is determined by measuring the absorber temperature rise. We explored the feasibility for obtaining measurable dose rates by using a thin ( $240 \, \mu $ m) lead Pb plate, a sixfold aluminum/silicon thermopile, and a tungsten W anode 70–125-kV X-ray source. The plate/thermopile thermal coupling was based on a thin layer of thermal grease. Response signals were measured for different current and voltage operations of the X-ray tube at different distances; the 20- $\mu $ V signal was measured for 125-kV, 20-mA tube operation at a distance of 22 cm. The obtained signals were, however, consistently smaller than expected by about an order of magnitude. We suggest that improved thermal insulation between the lead plate plus thermopile, and the other device constituent elements, would allow obtaining much higher response signals, making it a worthy candidate for X-ray dosimetry.