Two PLIs installed at the VIRGO Gravitational Antenna

News, 08 November 2019

At the end of October 2019, the second Precision Laser Inclinometer (PLI) was installed in the hall of the Northern Mirror of the VIRGO Interferometric Gravitational-Wave Antenna (IGA VIRGO). Now VIRGO has two inclinometers operating simultaneously the task of which is to study the angular noise of the earth’s surface inclination occurring from the passage of surface microseismic waves. The detection of this type of noise has become possible thanks to precision laser inclinometers. The second inclinometer allows studying the impact of additional noises caused by the operation of the system of seismic stabilization of mirrors and equipment used in IGA VIRGO.

Monitoring angular oscillations of the Earth’s surface showed the necessity to use the PLI in the angular seismic stabilization system of the VIRGO Interferometric Gravitational-Wave Antenna. Thus, the impact of angular microseisms is reduced, the stability of the mirror position is improved, and thus it positively impacts the sensitivity of the antenna in the range of frequencies at which merging of black holes and neutron stars is detected.

Long-term cooperation between EGO CERN and JINR is planned to provide seismic isolation of the IGA VIRGO sensing elements using the PLI. For this purpose, at JINR in the frames of the project “Precision laser metrology for accelerators and detector complexes” under the supervision of Julian A. Budagov, a next-generation PLI is being developed that will be smaller and will have a higher sensitivity and better resistance to temperature changes. Such a new-generation inclinometer will be able to register signals right in the area of the suspension base of the mirrors, and this will help to reduce the parametric excitation of natural oscillations of the suspension and its displacement depending on the oscillations of the earth’s surface.

Mikhail Lyablin (DLNP JINR), Beniamino Di Girolamo (CERN) and Ivan Bednyakov (DLNP JINR) took part in the installation of the second PLI. Leader of the project is J. A. Budagov. Information about the way the first inclinometer was installed at IGA VIRGO is available via the link.

Source: DLNP