The article discusses various upgrades and improvements made to cryogenic systems at the CHRNS facility, which are crucial for maintaining low temperatures required for quantum experiments.
First, a binary gas analyzer has been integrated into the dilution refrigerator gas handling system. This diagnostic tool allows real-time analysis of the 3He-4He mixture, enabling quick identification and resolution of any issues during experiments, thus saving valuable beamtime.
Second, carbon fiber sample sticks have been introduced as replacements for the current stainless-steel ones in both helium-flow cryostats and top-loading closed cycle refrigerators. These new sample sticks have shown excellent performance, reducing sample change times by 20-30 minutes, allowing experiments to restart sooner and enhancing neutron utilization.
Third, an upgrade has been made to the original helium flow ‘orange’ cryostats by equipping one of them with three heat exchangers instead of the single 1.5 K heat exchanger. This upgrade has resulted in more cooling power and faster preparation and sample changing times, taking under half the time compared to the original setup. The successful test has led to plans to retrofit the suite of helium cryostats, with two more expected to be completed in 2023.
Lastly, the article mentions the development of an Automatic Needle Valve Control System for wet cryostats and magnets, as well as an Automatic Cryogen Refill System for wet cryostats and magnets. These systems are designed to automatically refill liquid nitrogen and liquid helium once the level reaches the lower limit and stop once it reaches the higher limit, providing a more efficient and automated cryogen management system.
Source: https://www.nist.gov/ncnr/ncnr-facility-upgrades-during-unplanned-outage/chrns-cryogenic-systems
Keywords: Refrigerator, Cryostats, Helium-flow, Cooling
