MMR Probe Station Rebuild with Helium Cryopump

Noah Allen bio photo By Noah Allen

Problem:

Prior to my arrival at Virginia Tech our group acquired an MMR Technologies cryogenic probe station capable of 8 probes. The sample stage is about 1cm2 and is cooled using high-pressure dry nitrogen through capillaries etched into glass or sapphire. High-pressure nigtrogen flows through the capillaries where most of the pressure is dropped under the copper sample stage and then flows through a different path out of the vacuum chamber. This process is known as the Joule-Thomson effect and can cool the sample down to liquid nitrogen temperatures (77K) as long as everything works properly. The glass (or sapphire) stage is fragile and we were looking at ~$5K to replace one that got a short between the input and output capillaries rendering it useless. I had been looking into finding a cryogenic probe station capable of helium temperatures <10K but those were even more expensive so instead I decided to integrate a CTI Cryodyne M22 cryopump into our MMR probe station.

Solution: