The international g.w. observatory


Five resonant bar detectors of gravitational waves are currently in operation; of these, AURIGA (at LNL, Padova, Italy) and NAUTILUS (at LNF, Roma, Italy) are cooled to about 0.1 K, while ALLEGRO (at Baton Rouge, Louisiana, USA), EXPLORER (at CERN, Geneva, Switzerland) and NIOBE (in Perth, Western Australia) are operated at liquid Helium temperatures, i.e. in the range 25 K. These detectors constitute a worldwide observatory dedicated to the search of impulsive gravitational waves, the International Gravitational Event Collaboration IGEC.

Other detectors of gravitational waves based on different principles of operation are been developed, in particular the interferometric detectors.

Two large projects for interferometers of 3-4 Km long arms, LIGO (at Hanford WA and at Livingston LA, USA) and VIRGO (at Cascina, Pisa, Italy), plan to start operation within a few years. A smaller prototype of 300m long arms TAMA300 (in Tokyo, Japan) recently demonstrated to operate for some consecutive hours close to the expected performances. Another interesting interferometric project GEO600: this will be a 600m long interferometer where innovative optical techniques (as the signal recycling) are implemented.

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