In the context of the installation of new stable recycling cavities foreseen for the next Advanced Virgo+ phase 2 upgrade scheduled in 2025-2027, a new telescope will be developped and installed on the optical bench used to detect the interferometer output beam. In order to help identifying the best design for this telescope, a test campaign is being carried out on the scatter meter at LAPP to test refractive and reflective optics and quantify the contribution to back-scattered light of each type of considered telescope configurations- those with low-incidence curved mirrors or a simple telescope with lenses. This article will introduce this backscatter meter, show preliminary results obtained with this experiment and give some perspectives for the backscatter meter experiment.
Sayah et al. (2026) studied this question.