ISC Meeting on 2020/03/09 14:00 - 15:00
Participants:
Zoom meeting: https://zoom.us/j/6676627462
Next meeting
TBD
Minutes
Agenda
- We want to know what to do for O4 with birefringence and ITM transmission asymmetry
- Summary of current measurements
X-arm round-trip loss from reflectivity is 86(3) ppm https://klog.icrr.u-tokyo.ac.jp/osl/?r=7307
- Y-arm round-trip loss: NOT MEASURED YET
ITMX and ITMY single bounce has 12% and 15% loss, respectively, including ITM transmission and losses to p-pol. Losses to p-pol measured at POP was 9.4% for ITMX and 4.6% for ITMY. Considering BS reflectivity is different for s-pol and p-pol., this corresponds to 6.1% for ITMX single bounce and 11% for ITMY single bounce. https://klog.icrr.u-tokyo.ac.jp/osl/?r=9314 https://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=10369
Carrier power recycling gain for PRMI was about 3, which corresponds to PRC intra-cavity loss of 25% or so. Considering ITMX and ITMY single bounce losses, this means that Michelson contrast defect is 10% or so. http://klog.icrr.u-tokyo.ac.jp/osl/?r=9300
The mount of p-pol from ITMX is smaller by a factor of 3 with X-arm locked (mode healing effect). http://klog.icrr.u-tokyo.ac.jp/osl/?r=9393
Carrier power recycling gain when PRFPMI is locked is 12 for X-arm and 10 for Y-arm. http://klog.icrr.u-tokyo.ac.jp/osl/?r=12639
X-arm round-trip loss, finesse, and mode healing effect altogether gives X-arm loss on reflection give 86 ppm * ~1000 + 6.1 % / 3 = 11 % loss. So may be PRG of 10-12 for the carrier is reasonable. This is also consistent with X-arm reflectivity measurement done before we are aware of birefringence issue. https://klog.icrr.u-tokyo.ac.jp/osl/?r=7307
- Power recycling gain for the sidebands are
- DRMI on 1f is fine. Lasts 30 min or so
DRMI on 3f lasts 5 min or so. https://klog.icrr.u-tokyo.ac.jp/osl/?r=12535
- List of measurements to be done before the vent for O4
- List of calculations to be done
- Executive summary (tentative)