The LIGO
Web Newsletter
Front Page Hanford Caltech
Virgo's First Commissioning Run!

Virgo's First Commissioning Run!

- Contributed by Albert Lazzarini

In last month's LIGO Web Newsletter, Barry Barish reported from Cascina, Italy, on the inauguration of the Virgo Project, held 23 July 2003. Barish represented the LIGO Laboratory at this milestone event of the Italian and French experimental gravitational-physics community. The celebration officially ended the construction phase of the Virgo Project, which has now embarked on the exciting journey of commissioning and continued sensitivity improvements. This is an important development for the international gravitational-wave community in that it brings us closer to the day when the various kilometer-scale interferometers will all be in continuous and reliable operation as a phased array or detector network.

Shortly after the inauguration, we received encouraging news that progress towards Virgo's ultimate sensitivity may be moving swiftly. Preliminary results from the first light in the Virgo North Arm were distributed to the international community within one week of the inauguration! The first commissioning run, C0, began on 30 July at 11:00 and ended the following day at 1500. The laser injection system operated with an auxiliary beam (i.e. with the main beam bypassing the mode cleaner cavity), and the beam was transmitted to the north end mirror three kilometers distant. The angular stability was such that the maximum drift recorded was 60 Áradians in one 24-hour period (2.5 Ár/hr). All the suspensions involved in the North Arm operation were under high vacuum, and the seismic superattenuators (both long and short) were operating properly. The systems for global control, data acquisition, vacuum, and detection all worked as expected. By taking advantage of the experience gained during the C0 run, Virgo scientists removed the mode cleaner bypass and were able to continue operating the laser injection with the laser frequency locked to mode-cleaner cavity length. They eventually succeeded in sending the main beam to the north end mirror. A CCD camera snapshot of the beam and its profile are shown in the figure below. Virgo's next goal in September will be to align the north cavity and subsequently lock it.

Snapshot of beam and its profile.