Cryogenics in the ultra-low temperature range of 1-2 K and below will provide the necessary working environment for the rapidly developing quantum science and technology. The achievement of 1-2 K is crucial, as it forms the foundation of cryogenics for practical applications and it is the major challenge for further moving towards the sub-Kelvin and the mK temperature range. The theoretical and technical difficulties involved have remained at the cutting-edge of cryogenics for two decades.
 

Based on the successful development of a four-stage high-frequency 3.3 K pulse tube cryocooler, we innovatively adopted a hybrid cryocooler by coupling a four-stage high-frequency regenerative cryocooler with a throttling cryocooler. This achieved an extremely-low temperature of 1 K, promoting the development of compact, lightweight, and long-life hybrid cryocoolers.

The related theoretical and experimental verification results have been published in the international journal CRYOGENICS and IEEE Transactions on Applied Superconductivity.

Fig. 1. Schematic of set-up of the developed hybrid cryocooler.



Fig. 2. Linde-Hampson cycle of JTC in P-h thermodynamic plane.



Fig. 3. Steady state thermodynamic cycle of last stage CHEX, JT valve and evaporator in P-h plane.



Fig. 4. Deviation factor as a function of inlet stagnation pressure and temperature with a logarithmic abscissa.



Fig. 5. A prototype of a 1 K compact, lightweight and long-life hybrid cryocooler.