The invention relates to the technical field of extremely low temperature, in particular to a passive thermal switch, a rapid cooling
dilution refrigerator and a rapid cooling method.The passive thermal switch comprises a
graphite rod body, a hot end connecting piece and a cold end connecting piece, and the
graphite rod body is of a
solid rod-shaped structure; the hot end connecting piece is arranged at one end of the
graphite rod body and used for being connected with a hot end
flange. The cold end connecting piece is arranged at the other end of the graphite rod body and used for being connected with a cold end
flange. According to the passive thermal switch, the graphite material has very high
thermal conductivity in a high-temperature area and very low
thermal conductivity in an extremely low-temperature area, so that rapid cooling in a low-temperature area and good
thermal isolation at extremely low temperature can be realized, and compared with a traditional active thermal switch, the passive thermal switch has the advantages that the graphite material is directly used as the thermal switch due to the thermophysical property of the graphite material; compared with the prior art, a complex structure and a complex technological process are avoided, the switch ratio is higher, the thermal response speed is higher, and meanwhile the risk of
heat leakage at extremely low temperature is smaller.