At the end of October 2019, in the experimental hall of the Northern Mirror of the VIRGO interferometric gravitational-wave antenna (IGA VIRGO), the second Precision Laser Inclinometer (PLI) was installed. From now on, the two inclinometers are operating at VIRGO, and their task is to investigate angular noise from the Earth surface inclination caused by surface microseismic waves. These are the precision laser inclinometers, that made the detection of the noise of this kind possible. The second inclinometer enables the research of additional noise resulting from the operation of both the mirror seismic stabilization system and the equipment at IGA VIRGO.

The monitoring of angular motions of the Earth surface indicated the necessity of PLI within the angular seismic stabilization system of the VIRGO gravitational-wave antenna, which lessens the noise of angular microseisms, improves the stability of the mirror position, and, therefore, refines the antenna sensitivity in the frequency range in which merging of both black holes and neutron stars can be observed.

The long-term cooperation of EGO CERN and JINR is planned in order to provide the angular seism isolation of sensitive devices of IGA VIRGO with PLI. For this purpose, the next-generation PLI is being developed in a smaller size, higher sensitivity and better stability to temperature changes. This next-generation inclinometer will be able to detect signals directly at the mirrors’ suspension base, which can decrease parametric excitation of intrinsic vibration of the suspension and its displacement depending on the Earth surface inclination.

Mikhail Lyablin (DLNP JINR), Beniamino Di Girolamo (CERN) and Ivan Bednyakov (DLNP JINR) participated in the installation of the second PLI. For more information about the installation of the first inclinometer at IGA VIRGO, click here.