Fieldbus in Basic Research
Fibre optic FIP field bus in gravitational wave antenna
One of the most demanding tasks in basic research is the detection of gravitational waves predicted by Albert Einstein. For this so called interferometers are used. Fibre optics and real time communication are first choice in this extremely sensitive equipment.
The detection of those waves is extremely difficult, because their interaction with masses is very weak. Thus huge detectors, mechanically very well insulated from earth generated noise are mandatory. Unfortunately those gravitational wave antennas must be extended over several kilometres.
Currently only five interferometers are operative worldwide. A major project in Europe is named VIRGO . It is financed jointly by the French CNRS (Centre National de Recherche Scientifique) and the Italian INFN (Instituto Nazionale di Fisica Nationale). The interferometer basically consists of two perpendicular arms, each of them three kilometres long. A plurality of research institutes contribute components to the detector situated in Cascina near Pisa in Italy, inaugurated Mai 2007. The University of Paris' Laboratoire de l'Accelerateur Lineaire worked on the ultra high vacuum system, where the large gate valves etc. are operated via FIP I/O networks using fibre optic communication made by Hirschmann .
Project parameters
- Mechanical dimensions:
- Arm length 3km
- Tube diameter 1.2m - Vacuum performance:
- Vacuum residual pressure <10mbar - Laser system:
- Laser frequency stability <10-4 Hz1/2
- Stored laser power 50kW - Interferometer mirrors:
- Diameter 35mm
- Absorption <1ppm
- Micro roughness < 1 Ångstrom - Mechanical performance:
- Seismic attenuation 10-11
- Thermal stabilisation 0.1 K
- Control through high speed real time bus system
- Communication via fibre optics
Solution
- Control system based on FIP I/O
- Industry grade fibre optic converters from Hirschmann
- Line topology alongside the ultra high vacuum tubes
