3He melting curve thermometry in a nuclear polarization experiment

Temperature measurement and control are important in brute force polarization experiments. We discuss the installation and use of 3He melting curve thermometers in a cryostat used to polarize a TiH2 target. Comparison is made between the melting curve thermometers and the 60CoCo nuclear orientation thermometer, which is often used in such experiments. The melting curve thermometers provide increased temperature resolution and sensitivity, and were used in a feedback heating system to control temperature to ±5.5 μK at 16.5 mK. The 3He melting curve and the 60CoCo temperature scales are found to agree within 2% at 15 mK. The present status of the melting curve scale and the effect of a magnetic field on melting curve thermometry are also discussed. (orig.)