Application of a silicon micro-sensor for measurement of nuclear heating

The heating performance of the inboard-blanket design of the International Thermonuclear Experimental Reactor (ITER) was experimentally investigated at a neutronic mock-up. The energy deposition, dominated by gamma interactions, was measured with a silicon micro-sensor at two positions within the bulk assembly consisting of steel and Perspex. The sensor has a very compact layout as needed for in-core measurements. A hybrid circuit includes Si-pin-diode, charge-sensitive preamplifier and discriminator. The measured pulse-height spectra were experimentally corrected for events induced by neutrons. Then, energy scale and sensitive detector volume were calibrated with sources of monoenergetic gamma-rays in combination with Monte Carlo simulations of the detector response. By this procedure also the contribution of events with pulse-height below the detector threshold was determined. The gamma-heating values obtained by the Si-sensor are compared with both energy depositions measured with thermo-luminescent dosimeters and data from measured gamma flux spectra multiplied by KERMA factors. Finally, they are discussed in context with the gamma heating calculated for the two positions in the blanket mock-up.