Fast Cooling Techniques for Gravitational Wave Antennas

The resonant-mass technique for the detection of Gravitational Waves may involve, in the near future, the cooling of very large masses (about 100 tons) from room temperature (300K) to extreme cryogenic temperatures (20mK). To cool these detectors down to cryogenic temperatures an exchange gas (helium) is used, and the heat is removed from the antenna to the cold reservoir by thermal conduction and natural convection. With the current technique, cooling times of about one month can be obtained for cylindrical bar antennas of 2.5 tons. Should this same technique be used to cool a 100-ton spherical antenna the cooling time would be about 10 months, making the operation of these antennas impracticable. In this work we study the above-mentioned cooling technique and others, like thermal switching and forced convection from room temperature down to liquid nitrogen temperature (77K) using an aluminum, 19kg-25cm-diameter, truncated icosahedron.