Virgo Logbook

	Yesterday, we have measured the throughput power of SIB1.
As shown on the attached picture, we measured the transmitted power out of the INJ Tower with an high power calorimeter and a 1m focal length “lentone” (old Virgo end bench lens).
We have measured 15.7W output power (taking account lens transitivity) for 21.6W measured before the last mirror of the EIB.
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Total throughput losses on SIB1 : <28%
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Losses Budget and SIB1 Throughput:
IMC mismatching: 8.9%
M11 transitivity: 1%
Faraday Isolator Throughput losses 5%
IPC Throughput losses 6% (see log entry 31247)
MC throughput losses : 28.0-20.9 = 7.1%

So, if we are able to recover the previous matching on the IMC cavity about 94%, it should be possible to reach 25% of losses on SIB1 and we hope 30% for all the injection system as expected.