Ultra-low temperature noise thermometry and its applications at ISIS neutron and muon source

The ISIS neutron and muon source undertakes approximately 100 experiments per year at temperatures below 1 K. At these temperatures, there is a clear need for accurate, precise, and well-calibrated thermometry, which is resilient to the challenging sample environments found in large science facilities. In this work, we look to improve the use of low temperature resistive sensors in the high-throughput environment of an operational large-scale facility. By installing the MFFT-1 SQUID thermometer into a dilution refrigerator, we were able to create a methodology for the rapid calibration of cheap commercial resistors. This provision also enables us to characterize the behavior of both SQUID and resistance-based thermometers in the extreme environments found at neutron and muon sources. Lastly, we use these tools to understand the effect of “beam heating” upon samples placed in our neutron instruments.