Flow cryostat

liquid nitrogenstainless steel

This floor-standing cryostat uses a continuous flow of liquid nitrogen from a storage dewar for cooling, and a resistive wire element for heating. The system consists of four separated parts: a cylindrically shaped vacuum chamber, with a liquid nitrogen vessel on top, both integrated into a floor-stand; a temperature control unit; a turbomolecular pump; and a self-pressurized dewar. The exterior of the vacuum chamber is made of stainless steel, while the interior is made of copper. The inside of the vacuum chamber, which contains the wire heating element and a tailored sensor fixture and sample holder, is accessed via releasing the bolt-connections on its top side, and thereafter pulling the cylindrical chamber wall downwards. The sensor cable feedthrough is on the top side, bypassing the liquid nitrogen vessel, and terminating via a hermetic feedthrough. The temperature of the vacuum chamber can reach down to -195°C (78 K), while the temperature stability is ±0.1°C (±0.1 K). The cryostat is intended to be used with our Kapton- or Teflon-insulated Hot Disk® or Hot Strip sensors with our thin-diameter silicone-clad cables, to minimize heat leaking into the vacuum chamber through the sensor leads. The initial vacuum pumping of the vacuum chamber, followed by turning on the nitrogen flow from the dewar to the nitrogen vessel, is done manually. The temperature of the vacuum chamber is thereafter controlled by the wire heating element, which is done automatically by the Hot Disk Desktop App over USB communication. The Hot Disk Desktop App can be programmed to automatically perform a series of measurements with the Hot Disk instrument at multiple chamber temperatures.