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Photodiodes improvement for the Advanced Virgo+ gravitational wave detector.

LAPP offers a Master 2 internship in order to participate in the upgrade of the photodiodes electronics for Advanced Virgo+. The internship student will participate in the design phase of the new electronic boards by simulating the expected noise performances and the expected response to an input signal. The student will also participate in the characterization of the modified electronic boards, by measuring their noise levels and transfer functions.

The Virgo gravitational wave detector, installed in Pisa, works on the principle of a laser interferometer with 3 km long arms. In 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 coalescences of compact binary systems (notably black holes). Since 2020, the Virgo detector has entered a phase of modifications and improvements (upgrade Advanced Virgo +) with the goal of entering a new observation period in December 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 transmission of the kilometer arms, for example). These benches house optical elements and light sensors (photodiodes, quadrant photodiodes, cameras, etc.) which have the role of extracting the signals useful for the detection of gravitational waves and for the control of the position of the interferometer mirrors. In particular the photodiodes are divided into two groups : the high-quantum efficiency photodiodes used for the readout of the gravitational-wave signals which must be very sensitive in the 10Hz – 10kHz bandwidth, and the high bandwidth photodiodes which must be able to extract control signals up to 100 MHz. In the context of the Advanced Vigo+ upgrade, the photodiode electronics is being improved in order to reduce the electronics noise of the high quantum efficiency photodiodes and to better adapt the dynamics of the control photodiodes to the RF signals present in the interferometer. LAPP offers a Master 2 internship in order to participate in the upgrade of the photodiodes electronics for Advanced Virgo+. The internship student will participate in the design phase of the new electronic boards by simulating the expected noise performances and the expected response to an input signal. The student will also participate in the characterization of the modified electronic boards, by measuring their noise levels and transfer functions. Using these simulations or measurements, the student will check that the new photodiode electronics is compliant with the needed dynamics, and will then study the impact of the electronic noise on the Virgo sensitivity. To this purpose the student will have to study the noise coupling mechanisms through the various control loops of the interferometer. Depending on the progress of the project, the student will have the opportunity to proceed with the installation and the tests at the Virgo site.

Optional information on a possible PhD subject : :

This internship can lead to a PhD subject on the study of the Virgo instrumental noises and the improvement of the sensitivity of the Virgo detector during the next data-taking run O4 (2023), as well as the preparation and the implementation of the upgrades that will improve further the Virgo sensitivity for the future data-taking run O5 (2025).

Supervisors : Raffaele Flaminio, François Frappez, Romain Gouaty Contact : gouaty@lapp.in2p3.fr Phone : 04 50 09 55 19