Capacitance thermometer for use at low temperatures and high magnetic fields

We report on the development of capacitance thermometers that are independe nt of magnetic field, can be made with large capacitances (500-150 000 pf), have a small thermal mass, are temperature sensitive from 300 K to 20 mK, and are relatively easy to fabricate from thin sheets of insulator and meta llic foils. Furthermore, we demonstrate that we can move the position of th e minimum in capacitance with respect to temperature and vary the sensitivi ty of the device by changing its construction parameters. Measurements have demonstrated that the thermometers are insensitive to high magnetic fields up to 18 T in the temperature range 20-420 mK. (C) 2001 American Institute of Physics.