# VIRGO

# Collaboration:

- Italy: Firenze, Lab. Naz. Frascati, Napoli, Perugia, Pisa, Roma1, Urbino (Firenze)
- France: ENS (Lyon), ESPCI (Paris), LAL (Orsay), LAPP (Annecy), OCA (Nice).

Laboratory: EGO Cascina

National Responsible: F. Vetrano (Urbino/Fi)

Home page of the experiment: http://www.virgo.infn.it/

1. Goal of the experiment

The scientific goal of the experiment, after the end of the construction and the commissioning of the interferometric gravitational antenna Virgo (a suspended Michelson interferometer, with 3 km Fabry-Pérot cavities as orthogonal arms), is to reach sensitivity enough, to take data, to develop analysis strategy, in order to be able to detect gravitational waves from astrophysical and/or cosmological sources, provided their amplitudes are those predicted by currently accepted theoretical models.

more on the experiment...

The Virgo groups are also involved in some R&D activities, considered and managed as sub-projects aiming at insuring that projected sensitivity of Virgo will be reached and preserved, or else to improve Virgo sensitivity by reducing the noise. From this point of view, Virgo R&D is presently the most powerful effort to improve the performances of ground-based interferometric gravitational detectors at short- and medium –time.

more on the experiment...

2.

Activities during 2002

Virgo experiment is beginning its activity in 2002, but it was preceded by a long Special Project (1994-2001), which was entirely devoted to the construction of the antenna with all related infrastructures. The commissioning of the Central Interferometer (a suspended 6 m Michelson interferometer without Fabry-Pérot cavities) has been ended in the Summer 2002, and many engineering runs have been performed: analysis of the produced data is now completed and furnished fundamental information about locking strategy to be followed for the 3 km detector too. The Assembly and Integration of the overall antenna is almost completed, even though for ending tower some activity on (final) test masses will be finished at the beginning of 2003. For what concerns R&D activities, LF Facility concluded a first run: acquired data are now being analyzed. The CRYSTAL sub-project received good financial support only during last summer: the hardware structure is just started and will be completed when all components will be delivered from companies. The UVVV activity has been unfortunately stopped due to problems on the laser: we are now ending all tests and we’ll be able to recover the delay reaching full operating state in the first half of 2003.

It is to be underlined that despite the lack of funds for calculus, some fundamental tests for distributed calculus have been performed on the clusters of FI/Ub-PG-NA-RM1 Sections.

The Collaboration is now involved in detailed Plan for the Commissioning of Virgo 3km.

The following achievements have been obtained:

- Completion of the towers at the end of the interferometer (90 %)
- Debugging of the Central Interferometer (100 %)
- Full planning of the interferometer Commissioning (80 %)
- Conclusion of the tests for distributed calculus on the FI/Urbino- PG-NA-Roma1 clusters for Virgo data analysis (60 %) (only partially funded)
- Data taking and PSD for thermal noise of the LFF tower (90 %)
- Completion of the hardware structure for monocristalline suspension (80 %)
- Set up on Cascina of the UVVV technique (20 %) (see comments above)

Milestones 2003

Tests on catalytic gluing of fused silica-silicon for suspension wires-mirror system | 30-04-2003
Implementation of both classic and adaptive control techniques on isolated mirrors | 30-06-2003
Implementation of non-linear alignment and local control on Virgo 3 km | 31-08-2003
Implementation and verification of final active filtering loops on every SA in Virgo | 15-09-2003
Substitution of the LFF payloads with the final one | 15-09-2003
First full tests on substrates for cold mirrors | 31-10-2003
Final version and related upgrade of the system for measuring opto/mechanical transfer function on the last stage of SAs | 30-11-2003
Run and related analysis on LFF data | 15-12-2003
Stability and performance tests on the prototype for adaptive optics control | 31-12-2003
Preliminary tests on electrostatic pushers and related electronics on a suspended mirror | 31-12-2003
End of debugging and of commissioning crucial phases for Virgo 3 km | 31-12-2003
Ending of Assembly and Integration Virgo 3 km | 31-01-2003

3. INFN contribution to the experiment in terms of manpower

Manpower: 73 researchers (55.1 FTE), 18 technicians (7.6 FTE)

Budget for the Year 2003: 5.7 % of the CSN2 budget for 2003

4. Publications in refereed journals (year 2002): 7

5. Conference talks (year 2002): 6

6. Number of undergraduate and doctoral theses on the experiment: 12

7. Leadership roles in the experiment

- National Spokesperson of the Italian Virgo Collaboration is Flavio Vetrano from Urbino University & Florence INFN Section.
- International Spokesperson of the French-Italian Virgo Collaboration is Adalberto Giazotto from Pisa INFN Section.
- Virgo Detector Coordinator is Carlo Bradaschia from Pisa INFN Section.
- Virgo Coordinator for Data Analysis for signals from coalescing binary systems is Andrea Vicerè from Urbino University and Florence INFN Section.
- For LFF sub-project the leading person is Angela DiVirgilio from Pisa INFN Section.
- For Crystal sub-project the leading person is Mauro Tonelli from Pisa University & INFN Section.
- For ElPu and AOC the leading person is Fabrizio Barone from Salerno University and Napoli INFN Section
- For ViC the leading person is (temporarily) Adalberto Giazotto from Pisa INFN Section

8. Innovative instruments

- inertial sensors (accelerometers) both for translation and rotation, of very high sensitivity under U.H.Vacuum conditions, operating from very low-frequency up to 1kHz
- heat treatment (400ºC, open air) for stainless steel up to an intrinsic outgassing rate lower than 10-14 mbar l/s/cm2
- production of suspension wires with high breaking strength (5 Gpa) and very low internal loss angle (lower than 10-7)
- linear position transducer of very high sensitivity (LVDT)

9. Competing experiments

- LIGO (USA) for Virgo
- TNI (Caltech, USA) for LFF

10. International Committee which has reviewed the experiment

Scientific and Technical Advisory Committee (EGO STAC)