A transportable cryostat

A transportable cryostat was developed for the calibration for thermometers at low temperatures between 20K and 150K. This calibration is easy to handle, transportable, and yet has high calibration precision. Six calibrated Si diodes imbedded in the uniform temperature copper block were used for a check of the uniformity of temperature within the block. The temperature gradient in the copper block was shown to be negligible. Calibration tests of thermometers showed that the calibration precision of the system was within + or - 0.2K. The calibration time for one temperature was about 10 minutes. It was confirmed that an Si diode is a useful and economic thermometer for precise measurements of temperatures near the boiling point of nitrogen and oxygen and this system is useful for the calibration of thermometers at low temperatures.