Helium Pot System for Maintaining Sample Temperature After Cryocooler Deactivation

摘要

A system for maintaining a sample at constant temperature below 10 K after stopping the cooling source is demonstrated. In this system, the cooling source is a 4 K GM cryocooler that is joined with the sample through an extension that consists of a helium pot and a resistive medium. Upon deactivating the cryocooler, the power applied to a heater located on the sample side of the resistive medium is decreased gradually to maintain an appropriate temperature rise across the resistive medium as the helium pot warms. The sample temperature is held constant in this manner without the use of solid or liquid cryogens and without mechanically disconnecting the sample from the cooler. Shutting off the cryocooler significantly reduces sample motion that results from vibration and expansion/contraction of the cold head housing. The reduction in motion permits certain procedures that are very sensitive to sample position stability, but are performed with limited duration.