CRYOGENIC ASPECTS OF COOLING LARGE MASSES TO MILLIKELVIN TEMPERATURES - APPLICATION TO A 100-TON 10-MK SPHERICAL GRAVITATIONAL-WAVE DETECTOR

Large metallic cylinders of several tons of mass have been cooled to liquid helium temperatures and recently have been cooled to T similar to 100 mK leading to the most sensitive gravitational wave detector (NAUTILUS). The sensitivity is still not enough to detect waves from distances so large that the number of events would be several per year. Cooling spherical detectors of mass around 100 ton to temperatures around 10 mK could achieve this goal giving rise to a new astronomy.