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Pick-off beams in the central Interferometer of Advanced Virgo. Stefan Hild January 2009. Creation points of Pick-off beam. All Anti-reflex coatings potentially cause secondary beams. Pick-off beams have about 10 to 20mW (6ppm x 2.7kW)
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Pick-off beams in the central Interferometer of Advanced Virgo Stefan Hild January 2009
Creation points of Pick-off beam • All Anti-reflex coatings potentially cause secondary beams. • Pick-off beams have about 10 to 20mW (6ppm x 2.7kW) • Pick-off beams are of similar size as the main IFO beam (LARGE!) • These 15 (18) beams should either be detected or properly dumped 2 beams 4 beams 3 beams from PRC (+3 beams from SRC) 4 beams 2 beams January 2009
Why more pick-off beams than in Virgo? January 2009
Input mirror AR coating • Can an Etalon (A) be control-led well enough with the CP so close by? • C should be avoided, because of scattered light. • D: one beam is strongly divergent. January 2009
Pick-offs from the CPs • CP is probably primary pick-off for ISC. • For ASC it might be important to have no overlapping beams (distributing the secondary beams in 3D). • Divergence of CP pick-offs depends on IM backsurface (lens or not). • If we get the CP pick-offs to work for ISC, we can probably dump the B5 beam. January 2009
Secondary reflections from BS • 3 beams from within PRC needs to be dealt with for AdV. • What to do about the 3 beams from within the SRC (in contrast they are not differential)? • Do we need B5 or can it be dumped? Currently not dumped beam January 2009