High resolution thermometers for ground and space applications

Abstract High resolution thermometers with a resolution of 3 × 10 −10 K/√Hz have been flown on a space shuttle for studies of the phase transition of helium near the lambda point (2.1768K). This resolution was found to be degraded by a factor of 2.5 in space due to random heating by cosmic rays. Here we give a report of our program to understand and improve the noise performance for ground applications and to minimize the cosmic ray effects for space applications.