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Study of scattered light in the Virgo gravitational wave detector.

The Virgo gravitational wave detector, installed in Pisa, works on the principle of a laser interferometer with 3 km long arms. In August 2017, the first joint observation of gravitational waves, detected by the LIGO and Virgo detectors, from the coalescence of a binary neutron stars system, and a gamma-ray burst, followed by the observation of an optical signal, opened a whole new chapter in multi-messenger astronomy. A period of joint observation of LIGO (in the United States) and Virgo detectors followed from April 2019 to March 2020, allowing the weekly detection of coalescence of compact binary systems (notably black holes). Since May 2020, the Virgo detector has entered a phase of modifications and improvements (upgrade Advanced Virgo +) with the goal of starting a new observation period in 2022. Several optical benches, suspended and placed under vacuum, are used to extract the laser beam in different locations (at the output of the interferometer, but also in the transmission of the kilometer arms, for example). These benches host optical elements and light sensors (photodiodes, quadrant photodiodes, cameras, etc.) which have the role of extracting the signals used for the detection of gravitational waves and for the control of the position of the interferometer mirrors. These elements can diffuse part of the incident light or generate parasitic reflections. This unwelcome light can recombine with the main beam, and by interference generate variations in the laser power measured on the main photodiodes, variations which are interpreted as the passage of a gravitational wave.

LAPP offers a Master 2 internship in order to participate in the characterization of the light scattered on the suspended optical benches of the Virgo interferometer.

o Level : Master 2 internship, can be followed by a PhD

o Date of the internship : spring 2021

o Supervisor : Romain Gouaty

o Phone : 04 50 09 55 19

o e-mail :

o Team members : R. Bonnand, D. Buskulic, R. Flaminio, R. Gouaty, F. Marion, T. Regimbau, L. Rolland, E. Tournefier, D. Verkindt, M. Was

Detailed description :