Development of a cryogenic microcalorimeter

The motivation for this project has been to measure {dollar}beta{dollar}-decay using a low background detector which encapsulated the {dollar}beta{dollar} source (4{dollar}pi{dollar} coverage). It was realized that the ideal detector for this measurement was a microcalorimeter (a small cryogenic detector consisting of an absorber, thermistor and thermal link). Presently microcalorimeters are an active area of research and development because of possible applications in weak interaction physics, x-ray astronomy and dark matter searches. The development of such a detector requires an interdisciplinary effort involving nuclear physics, solid state physics, electronics, and statistical mechanics. We have designed, constructed and characterized microcalorimeters employing two types of thermistors {dollar}(Ausb{lcub}x{rcub}Gesb{lcub}(x-1){rcub}{dollar} and P:Si). In the process we constructed a dilution refrigerator, assembled the necessary electronics, and built a data acquisition and analysis system based on networked desktop computers. This stage of the project has concluded by characterizing the performance of the {dollar}Ausb{lcub}x{rcub}Gesb{lcub}(x-1{rcub}){dollar} based microcalorimeters by measuring {dollar}rmalpha s{dollar} and low energy {dollar}rmgamma s.{dollar} The measured energy spectra have been compared to theoretical predictions, and the linearity of the devices has been tested. Future work will permit these devices to be used to measure {dollar}beta{dollar} spectra.