A new LHe-free cryostat for the heterodyne SIS receiver for the Leighton Chajnantor Telescope.

The article focuses on the design, fabrication, and testing of a new liquid helium (LHe)-free cryostat for the heterodyne superconductor–insulator–superconductor (SIS) receiver of the Leighton Chajnantor Telescope (LCT), an international collaboration among Caltech, Shanghai Normal University, and Universidad de Concepción. This upgrade addresses the high cost and operational challenges of the previous LHe-based cooling system used at the Caltech Submillimeter Observatory by employing a two-stage Gifford–McMahon cryocooler to achieve stable temperatures below 4 K without liquid helium. Mechanical and thermal analyses confirmed that the cryostat meets the telescope’s pointing accuracy and thermal requirements, with measured steady-state temperatures of approximately 34.5 K and 3.1 K for the first and second stages, respectively. The LHe-free cryostat is expected to enhance the receiver’s sensitivity and reliability for high-resolution submillimeter spectral observations at the new high-altitude site on the Chajnantor Plateau in Chile.