CALORIMETRIC SINGLE-PARTICLE DETECTION IN HIGH MAGNETIC-FIELDS AT LOW-TEMPERATURES

High resolution calorimetric detection of single particles in magnetic fields up to 8 T at temperatures (0.1 K is reported. A careful study of heavily doped Si and Ge thermistors reveals an extremely large posi tive magnetoresistance in the variable range hopping conductivity regi me. This phenomenon is used to optimize the impedance and the temperat ure sensitivity of a calorimetric detector. Initial experiments show a n energy resolution full width at half maximum of 800 eV for 62.5 keV conversion electrons and an energy threshold of <400 eV. (C) 1996 Amer ican Institute of Physics.