Vacuum and Mechanics (VAC)
7000 M3 UNDER ULTRA-HIGH-VACUUM
A giant vacuum system is needed to preserve undisturbed conditions for the critical part of the detector:
- the laser beam propagates inside two 3 km long arms maintained at a residual pressure trillion times less than atmospheric;
- the test masses (the main mirrors) are housed in large vacuum chambers isolating them from acoustic and damping effects and not least preserving the cleanliness of their surfaces.
The Virgo vacuum system is one of the largest ultra-high-vacuum systems ever realized in the world.
The most impressive feature, perhaps more than its volume, is the extension of its exposed surface = 24000 m 2.
We are a team of 8 staff, becoming 9 within 2020 in order to strengthen the effort for maintenance and our contribution to the next generation project .
Within our Dept., different skills are combined in a unique team to accomplish complex and multidisciplinary tasks: running the vacuum apparatus, handling the vacuum laboratory, operating the workshop and finally the mentioned tests facilities. The management of the cryogenic storage plant is included as well.
During the on-site works and the major upgrades of the Virgo apparatus, we often outsource technical manpower to cover high peaks of activities. Contracts follow-up is then another facet of our activity.
Principal collaborations: since the creation of EGO and its Vacuum team, we are in a strong and continuous collaboration with several laboratories of the Virgo community : INFN-PI, INFN-GE, LAL, Nikhef, IFAE, … hosting the scientists that funded and still support our research.
Also, we strive for contacts and cooperation with labs outside our community: the opportunities and topics of our interest are = vacuum technology, LN2 cryogenics, ‘low noise’ vacuum pumps, electrostatic charging (and discharging) under vacuum, in-vacuum dust particles control.
THE VIRGO VACUUM SYSTEM IS COMPOSED BY SEVERAL INTERCONNECTED APPARATUSES AND CHAMBERS:
- 2 arm tubes 3 km long and 1.2 m in diameter, plenty wide to limit the interference between tube walls and photons escaped from the main beam path. Here the residual pressure reaches its minimum, despite their huge extension.
- 10 vertical chambers (towers) housing the principal mirrors and optical benches, including their corresponding ‘seismic’ isolation systems.
- 4 +2 large size cryostats, cooled by liquid nitrogen, providing large pumping speed for water vapor. They are fed by a cryogenic supply system, with a capability of ~ 1000 liters per day.
- 5 smaller chambers, around 5 m3 each, operated in ‘static’ vacuum to house optical benches.
- 2 ‘short’ cavities working in the E-6 mbar range: the Mode Cleaner pipe (150 m long and 300 mm in diameter) and the SQZ filter cavity (300 m long and 250 mm in diameter).
Each system is equipped with a complete pumping system able to operate from 1000 mbar to 1E-9 mbar; this includes equipment such as turbo-molecular pumps, dry compressors, Ion pumps, getter pumps, residual gas analyzers, many gauges and valves.
Remarkably, the pumping units are only a few along the ‘3 km tube arms’ (average speed of ~ 1 liter / s per m2 of surface) while they are concentrated and powerful in correspondence of ‘towers’, given the relatively large ‘outgassing’ from the numerous experimental apparatuses present inside them .
Expertises & facilities
The first duty of the V&M team is the running and the maintenance of the Virgo vacuum system, as well as the study and the improvement of its performances.
Continuous effort is devoted to improve the vacuum system response to the extremely low noise requirements of gravitational waves detector:
- control of the contamination (‘hydrocarbon’ and dust particles) threatening optical surfaces;
- lower acoustic, seismic, and magnetic emissions of vacuum elements degrading the detector sensitivity.
Periodically the vacuum system undergoes ‘major’ upgrades along with the more general ‘chapters’ of Virgo detector: ‘V+’ (first cryostat being adopted); ‘AdV’ (several new chambers, cryostats, ‘towers’ displacement, …) and finally ‘AdV+’ (2 m metal sealed flanges , integration of the ‘squeezing’ vacuum line).
As part of the everyday activities, the team runs a laboratory equipped for testing new vacuum equipment, outgassing measurements and conditioning treatments.
The team’s expertize includes software development, such as the ‘supervisor’ used to monitor and control the about 40 pumping stations are spread along the apparatus: http://olserver135.virgo.infn.it:8081/jchv3/
Mechanics is also a significant part of our business: we supply support to various teams of the collaboration for designing and realizing UHV qualified parts for their needs. These are typically in-vacuum components such as optical mounts, but also large parts or entire systems being integrated during the major upgrade phases.
We manage a small but complete mechanical workshop on site, dedicated to day-to-day production and to guarantee fast response to mechanical needs during major installation phases.
Worth to mention two special facilities present on site: a large 10 m3 UHV chamber, and a pulse tube cooled cryostat (1.x m dia 2.x h mm,) capable of working at temperatures down to 8 K.
Job & internship opportunities
You can find in this area all informations about job opportunity or Internship opoortunity in EGO staff.
All offers are published in different websites and scientific newspaper, a complete description of each position for job or internship offer can be consulted below in pdf format.
For any question or to postulate you can send a email to generic adress, we’ll analyze your CV and motivations and we’ll contact you rapidly in order to exchange about your interest to work in one of the three international Gravitational Waves Observatory.
We analyze also any spontanous candidature.
Thanks for your interest to join EGO staff for these scientific and technological challenges.
You can find in this area a selection of main pictures of realization, simulations and developments of Vacuum & Mechanics Department.