Abstract: In an electron paramagnetic resonance spectrometer, a closed cycle cryocooler is used to cool gaseous helium, which is then circulated around a sample to cool the sample by direct convection. Since the sample is not mechanically connected to the refrigerator, no vibrations are transmitted from the refrigerator to the sample and the sample can be quickly removed and replaced. The cooled helium can be passed through a Joule-Thomson expansion device before circulating the cooled helium around the sample to further cool the helium. In addition, a vacuum pump can be connected to the helium outlet after circulating the cooled helium around the sample to increase the pressure differential across the Joule-Thomson expansion device and further cool the helium. In order to raise the temperature of the cooled helium, a heater can be placed about the cooled helium line upstream from the sample.

Abstract: In an electron paramagnetic resonance spectrometer, a closed cycle cryocooler is used to cool gaseous helium, which is then circulated around a sample to cool the sample by direct convection. Since the sample is not mechanically connected to the refrigerator, no vibrations are transmitted from the refrigerator to the sample and the sample can be quickly removed and replaced. The cooled helium can be passed through a Joule-Thomson expansion device before circulating the cooled helium around the sample to further cool the helium. In addition, a vacuum pump can be connected to the helium outlet after circulating the cooled helium around the sample to increase the pressure differential across the Joule-Thomson expansion device and further cool the helium. In order to raise the temperature of the cooled helium, a heater can be placed about the cooled helium line upstream from the sample.

Abstract: A cryostat includes a thermal interface located at a first end and a cryocooler located at a second end. A thermal link has a thermal connector thermally linking the thermal interface and the cryocooler below a critical temperature. The thermal link is separated from one of the thermal interface and the cryocooler above the critical temperature. A method of operating the cryostat is also disclosed.