Development of a cryogen-free dilution refrigerator

Abstract

With thermal fluctuation strongly suppressed, low temperature environment is essential for studies of condensed matter physics and developments of quantum technologies. Ultra-low temperature below 20 mK has demonstrated its importance and significance in physical sciences and information techniques. Dilution refrigeration is by far the best feasible and reliable method to generate and keep lattice temperature in this range. With a potential shortage of helium supply, cryogen-free dilution refrigerator (CFDR), eliminating the necessity of regular helium refill, becomes the main facility for the purpose of creating ultralow temperature environments. Here we describe our successful construction of a CFDR which reached a base temperature of around 10.9 mK for continuous circulation and 8.6 mK for single-shot operation. We describe its operating mechanism and the designs of key components, especially some unique designs including heat switch and alumina thermal link. Possible improvements in the future are also discussed.

Predicting novel atomic structure of the lowest-energy Fe n P13–n (n = 0–13) clusters: A new parameter for characterizing chemical stability

“…These findings indicate that neutral Fe 12 P 1 and Fe 7 P 6 are ferromagnetic, whereas Fe 13 and P 13 clusters are not magnetic. In order to reveal the electronic orbits that have made substantial contributions to magnetism of Fe-P clusters, we had also plotted the curve diagram of the partial density of states of electrons, such as s, p, and d orbitals [27] in Fig. 7(b).…”

Development of 400-μW cryogen-free dilution refrigerators for quantum experiments

“…In the first generation of our DR, we reported on a composite type of heat switch. [11] Above the still stage cold plate, a mechanical heat switch was used. While below the still stage, thermal connection and insulation were achieved by relying on the change in thermal conductivity of aluminum rods from room temperature to low temperature, which was referred to as a passive heat switch.…”

“…1. Schematic diagram of a cryogen-free DR. [11] The dilution unit is the core functional module of DR that can achieve some important processes, from helium liquefaction to dilution refrigeration. It mainly includes JT condenser, flow impedance, still, CHE, SHE, and MC.…”

“…The detailed structure and principles of these components were introduced in our early paper. [11] In the following text, we will only introduce some key components or technologies in this development.…”