Miniature Joule-Thomson cryocooler operating at liquid helium temperatures

A miniature Joule-Thomson cryocooler operating at liquid helium temperatures, comprising an integral structure formed by welding at least three base plates sequentially superposed, wherein an outermost base plate in the at least three base plates is configured as a cover plate and configured to seal the rest of the at least three base plates, the rest of the at least three base plates is configured as a first-stage cooling circulator, a second-stage cooling circulator and a third-stage cooling circulator respectively, the first-stage cooling circulator, the second-stage cooling circulator and the third-stage cooling circulator have a first-stage working fluid, a second-stage working fluid and a third-stage working fluid respectively, the first-stage cooling circulator is configured to precool the second-stage working fluid and the third-stage working fluid through the first-stage working fluid, and the second-stage cooling circulator is configured to precool the third-stage working fluid through the second-stage working fluid;

• and wherein:
• the integral structure is formed by welding seven base plates sequentially superposed;
• in the seven base plates, a first base plate serves as the cover plate, a second base plate and a third base plate form the first-stage cooling circulator, a fourth base plate and a fifth base plate form the second-stage cooling circulator, and a sixth base plate and a seventh base plate form the third-stage cooling circulator;
• a top end of the first base plate is provided with six through holes serving as a first-stage working fluid inlet, a second-stage working fluid inlet, a third-stage working fluid inlet, a first-stage working fluid outlet, a second-stage working fluid outlet and a third-stage working fluid outlet respectively;
• a top end of the second base plate is provided with five through holes serving as a first-stage working fluid inlet, a second-stage working fluid inlet, a third-stage working fluid inlet, a second-stage working fluid outlet and a third-stage working fluid outlet respectively;
• a top end of the third base plate is provided with four through holes serving as a second-stage working fluid inlet, a third-stage working fluid inlet, a second-stage working fluid outlet and a third-stage working fluid outlet respectively;
• a top end of the fourth base plate is provided with three through holes serving as a second-stage working fluid inlet, a third-stage working fluid inlet and a third-stage working fluid outlet respectively;
• a top end of the fifth base plate is provided with two through holes serving as a third-stage working fluid inlet and a third-stage working fluid outlet respectively;
• a top end of the sixth base plate is provided with one through hole serving as a third-stage working fluid inlet;
• the working fluid outlets and the working fluid inlets of the same type are arranged at same positions on the corresponding base plates;
• each of the third base plate, the fifth base plate and the seventh base plate is provided with a high-pressure side passage, a throttle valve and a buffer chamber in sequential communication, and an inlet end of each high-pressure side passage is in communication with the working fluid inlet of a corresponding stage;
• and
• each of the second base plate, the fourth base plate and the sixth base plate is provided with a low-pressure side passage, and each low-pressure side passage has an inlet end in communication with the buffer chamber of a corresponding stage, and an outlet end in communication with the working fluid outlet of a corresponding stage;
• and the low-pressure side passages on the second base plate and the fourth base plate have functions of a heat exchanger, a precooler and an evaporator, and the low-pressure side passage on the sixth base plate has functions of a heat exchanger and an evaporator.