The Virgo site

As the curtain is being raised on today's generation of gravitational wave (GW) detectors, the individual project teams met to consider future detectors and the goal of running the global ensemble of instruments as a single array. For this purpose, the annual Aspen Meeting on Advanced Gravitational Wave Detectors descended from its traditional Colorado, US, venue and was held at La Biodola on the Island of Elba, close to the Virgo interferometer site. The Gravitational Wave International Committee sponsors the Aspen meetings, which are usually organized by the US LIGO observatory. On this occasion the meeting moved to Europe to acknowledge the growing international collaboration between all the individual efforts. The meeting drew about 100 scientists from all continents, including representatives from the Germany-UK GEO project, and strong participation from Japan and Australia.
   The theme of the meeting was operating the interferometers as a single machine, echoing an idea from Adalberto Giazotto, one of the fathers of the GW interferometric detector field. The GW interferometers are recognizing the more mature GW bar-detector community, which has already coordinated its data-taking and observations. Bar-community participants at the meeting offered concrete examples of how to build a global collaboration that will include interferometers and bars. No less important was the participation of the nascent space-based interferometric detectors for the detection of ultra-low-frequency gravitational waves.
  

Virgo group

Although the main emphasis was on future developments, the meeting took place as all of the world's present-generation GW interferometers are reaching maturity. This was an occasion to review the extraordinary recent advances of interferometer commissioning by LIGO, GEO, Virgo and Japan's TAMA, and early coincident operation by LIGO, GEO and the Allegro bar in Louisiana. The rapid commissioning and initial data-taking of the new interferometers leads to the challenge of effectively networking them in a single global data acquisition and analysis system.
   TAMA, so far the groundbreaker, reported on a coincidence run between itself and LISM, a pilot underground interferometer in the Kamioka mine, the future site of the projected LCGT kilometre-class cryogenic interferometer. TAMA also announced coincidence data collection with LIGO and GEO that will occur this summer as those two instruments perform their first scientific observation periods. Japanese teams also presented impressive advances on cryogenic techniques for third-generation GW interferometers.
   LIGO reported on its successful commissioning and rapid progression in sensitivity. The three LIGO interferometers, already exercised as an integrated network, are now, together with GEO, at the TAMA sensitivity. This will make the forthcoming GEO-LIGO-TAMA common data-taking even more interesting. GEO presented its advances and reported on the installation of futuristic all-fused silica and low-thermal-noise mirror suspensions.
   Virgo, just finishing the construction of its 3 km vacuum arms, reported on the successes of its Central Interferometer with its advanced low-frequency seismic attenuation chains and its hierarchical mirror control system. Virgo plans to commission its long arms as early as the end of this year. Once Virgo operates as a complete detector it will lead in sensitivity below 50 Hz. Virgo and LIGO are already exchanging environmental data and preparing to integrate the Virgo data in the global network as soon as the complete Virgo is operational.
   All the groups are gearing up to treat the data that starts being produced by the interferometers. All the groups are attaching growing importance to simulations for understanding the instruments and the data. Several challenges ahead were discussed, ranging from the development of advanced suspension and seismic isolation systems, and sensors for Newtonian noise estimation, to theoretical thermal-noise issues. Everybody left Elba feeling they had participated in an extremely productive event.

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