GRAIL - A 10 MK, 100 TON SPHERICAL GRAVITATIONAL-WAVE ANTENNA

Massive metallic spheres cooled to millikelvin temperatures could reach quantum-limited sensitivities high enough to detect gravitational waves from supernovae explosions up to 100-200 Mpc which would include millions of galaxies. They could provide sensitivity (in the frequency range above 700 Hz) and directionality, superior to the large interferometer arrays presently under construction, which will be better at lower frequencies and can have a larger bandwidth. World wide gravitational wave observatories will probably use both types of detectors. In this paper we give a brief overview of the problems involved in making a resonant spherical gravitational wave detector of very large mass working in the low millikelvin range.