LOW-TEMPERATURE THERMOMETRY IN HIGH MAGNETIC-FIELDS

The calibration and reproducibility of va various commercial and homem ade thermometers have been investigated over a temperature range from 20 mK to 4.2 K and magnetic field strength from 0 to 16 Tesla. The per formance of resistance thermometers made of different materials varies widely as a function of magnetic field. One type (Scientific Instrume nts RO600) is found to have a relatively small magneto-resistance, whi ch a's predictable to better than 1% down to 100 mK, making calibratio n in a magnetic field unnecessary for many applications. This was not true of homemade ruthenium oxide and Cernox (Lakeshore Cryotronics). A new type of sensor, thin film doped germanium on a GaAs substrate, wa s also investigated and found to be useful at higher fields and low te mperature.