Speaker
Description
Dust deposited on optics and other detector components can become a major source of Scattered Light (SL) if not properly controlled. On the other hand, overestimating cleanliness requirements can result in unnecessary costs for the infrastructure. In the context of the Virgo upgrades, it is important to define cleanliness requirements that can assure satisfying the SL noise limits with minimal costs.
We study how to determine the clean room class and the exposure time as a function of the scattering requirements of exposed surfaces, as quantified by the Bidirectional Scattering Distribution Function (BSDF) and Total Integrated Scattering (TIS). We pay special attention to the case of an impinging beam of limited footprint, highlighting the importance of fully accounting for the statistical spread of the expected scattering, particularly when the Percentage Area Coverage is small. We also discuss the limitations of our models. A few case studies related to Virgo are presented, together with a procedure which can be easily adapted to the Einstein Telescope.