camilla.compton@LIGO.ORG - posted 16:34, Tuesday 06 December 2022 - last comment - 10:54, Friday 09 December 2022(66179)
HWS Corner Station SLEDs replaced.
WP# 10849 Camilla, Mitchell
Following procedure T1500193 we replaced both HWS corner station SLEDs after reported they have decayed in alog 65847. Previously we had camera sync frequency at 5Hz for both to get enough light on CCD, this strangely doesn't need to change, will investigate. Nominal power out of SLED collimator is max 2.5mW.
| Old S/N | Old Power Output | Age (#61892) | New S/N | New Power Output | |
| ITMX QSDM-790-5 | 06.18.002 | 0.8mW | 21 months | 07.14.255 | 2.2mW |
| ITMY QSDM-840-5 | 11.17.126 | 0.19mW | 10 months | 11.17.127 | 1.9mW |
The noise of Spherical power calculation seems to have decreased after the swap, great! See attached plot. New references could be taken next Tuesday with a cold IFO.
See attached, the power measured by the CCD (HWS_PROBE_TOTAL_PIXEL_VALUE) increased by x3.5 for ITMX and x10 for ITMY, equivalent to the power increase in powers of the new vs old SLEDs as measured by the power meter in measurement above. We checked that no pixels were saturating which means that the previous frame rate of 5Hz should have been lower. We can reduce the frame rate down to 2Hz for ITMX without saturating but the lowest for ITMY is 5Hz. As the data looks good, I'll keep them both at a 5Hz frame rate.