A Massive Calorimeter for Single-Particle Detection
The compound detector, described here, consists of an absorber with 120 grams of silicon in thermal contact with a paramagnetic sample (about 150 mg) of Tm3A15O12 doped with 0.5% 168Er (nuclear spin zero). With an applied magnetic field B=3 mT, the ground state Kramers doublet of Er exhibits a Zeeman splitting of the order of 10−6 eV. This is the excitation energy for spin-flip processes, which are induced on absorption of energy. The resulting change of the magnetic moment is measured with a SQUID, coupled directly to the magnetic sample .