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 l iquid helium temperatures and recently have been cooled to T similar t o 100 mK leading to the most sensitive gravitational wave detector (NA UTILUS). The sensitivity is still not enough to detect waves from dist ances so large that the number of events would be several per year. Co oling spherical detectors of mass around 100 ton to temperatures aroun d 10 mK could achieve this goal giving rise to a new astronomy.