CHARGE COLLECTION AND THERMALIZATION IN A COMPOSITE CALORIMETRIC AND IONIZATION X-RAY-DETECTOR

A combination calorimetric and ionization x-ray detector has been made by attaching a silicon p-i-n diode to a monolithic silicon microcalor imeter. We were able to measure a charge signal in the absence of appl ied bias on the diode at a temperature as low as 0.1 K, demonstrating that the junction potential is sufficient to drift the ionized charges to the contacts. A fraction of the electron-hole pairs created became trapped, as was manifested by excess broadening in the measured therm al signal. The fraction of charge trapped was determined from the vari ation of the thermal signal magnitude with reverse bias. The ability t o collect charge without applying a bias is an encouraging result in t he development of high resolution combination thermal and ionization d etectors. At higher biases high resolution is precluded, but the enhan cement of the thermal signal due to the work done on the ionized charg es can lead to a low detection threshold. With an applied bias of -25 V, we achieved a detection threshold of 8 eV, based upon energy scalin g of the 1sigma value of the baseline noise distribution.