Abstract Cryogen-free (“dry”) cryostats are widely used to achieve as low as mili-K scale temperature, a common environment for neutron scattering experiments. In top-loading dry cryostats, the samples are usually held in a sample can or sample plate at the bottom of a long sample probe, and the sample space is filled with low-pressure helium exchange gas. The cooling of the sample relies on the natural convection of the helium gas, which is eventually cooled by a cryocooler. The inherent inefficiency of this cooling mechanism, as well as low cooling power of cryocoolers, causes up to 8 hours of cooling time from room temperature to base temperature, with typically more than 50% (or even 87%) of this time spent for cooling from room temperature to around 80 K, leading to time-consuming sample change process and waste of high-cost beam time. Here, a sample probe with embedded two-phase nitrogen cooling for top loading cryostats is presented. A 1/4” tube is implemented to a conventional 3/4” (diameter) sample probe for nitrogen transport. A full-scale prototype was fabricated and tested. Cooling from room temperature to around 80 K was achieved in less than 10 minutes due to the efficient two-phase cooling mechanism.
Zou et al. (Tue,) studied this question.