The Instrumented Baffle at the Input Mode Cleaner of Advanced Virgo Plus: Four years of Successful Operation as a Monitor of Stray Light

The suspended end mirror of the Input Mode Cleaner cavity in the Advanced Virgo Plus interferometer was equipped with an instrumented baffle in Spring 2021, serving as a demonstrator of the technology in preparation for the installation of large instrumented baffles in the main arms of the interferometer. This baffle includes tens of sensors positioned near the mirror to enable monitoring of stray light within the cavity. In this contribution, we assess the stability and performance of the instrument after four years of operation. After introducing the main characteristics of the baffle, we study the distribution of stray light and show that the instrumented baffle can be used to monitor laser stability and alignment within the cavity. Finally, we perform a noise level assessment with data from the final stages of the O4b commissioning and conclude that the baffle does not introduce any additional disturbance to the normal operation of the interferometer.