sheila.dwyer@LIGO.ORG - posted 10:59, Friday 13 March 2026 (89497)
9MHz modulation depth was low
Tony, Filiberto, Sheila, Jennie Wright, Oli
This morning we tried to do an OMC scan to check the modulation depths. The OMC high voltage was off, Filiberto found that the supply was powered on but the output disabled, so he enabled it.
We used 10W input power single bounce off ITMX. I compared this to a reference from 65828, it seems as thought the 9MHz is too small.
| April 2022 | this morning (EOM driver 23.4dBm 9 Mz, 27dBm for 45MHz) | now (EOM driver 27dBm 9 Mz, 27dBm for 45MHz) | modulation depth now (calculated by Oli and jennie W) | modulation depth from April 2022 (alog 81816) | |
| 9MHz +/00 peak height | 11.4e-3 | 5.04e-3 | 11.7e-3 | .217 | 0.213 |
| 9MHz -/00 peak height | 11.7e-3 | 5.4e-3 | 11.6e-3 | .215 | |
| 45MHz +/00 peak height | 1.9e-2 | 1.7e-2 | 1.7e-2 | .266 | 0.275 |
| 45MHz -/00 peak height | 1.9e-2 | 1.7e-2 | 1.7e-2 | .265 |
Jennie Wright checked modulation depths in 89456, at that time the EOM driver was set to 27dBm for 9MHz, on 10 am on March 10th it was set to 23.4dBm. This was in SDF as 23.4dBm, but this channel is not monitored and this table is not in SDF revert. ISC_LOCK prep for locking sets these values because they get changed in low noise, I've changed it in lsc params now.
Images attached to this report
