Abstract:
I checked the max value of K1:DAS-RANGE_BNS when OMC ADS was performed with upper/lower sidebad.
Though I don't check if the statistic is enough or not, the sensitivity seems high when OMC alignment was performed with upper sideband.
Detail:
Current LSC_LOCK guardian performs the OMC alignment with RF sideband evey time when lockloss happens, so the alignment to OMC can basically keep the good condition.
However, current guardian doesn't check if the RF sideband is upper one or lower one, and we have known that somehow upper sideband and lower sideband has a difference in power.
Therefore, I checked the difference in terms of the sensitivity when OMC ADS was performed with the upper/lower sideband.
I checked max value of K1:DAS-RANGE_BNS in each lock when LSC_LOCK guardian was at the OBSERVATION state after 0:00 JST of June 6, 2025.
Followings are the summary of how many times the max value of K1:DAS-RANGE_BNS reached to certain values when OMC ADS was performed with upper/lower sideband.
| K1:DAS-RANGE_BNS max | All | Upper | Lower |
| 5.3 | 1 | 0 | 1 |
| 5.4 | 0 | 0 | 0 |
| 5.5 | 1 | 0 | 1 |
| 5.6 | 2 | 0 | 2 |
| 5.7 | 1 | 1 | 0 |
| 5.8 | 5 | 4 | 1 |
| 5.9 | 7 | 1 | 6 |
| 6 | 6 | 3 | 3 |
| 6.1 | 2 | 1 | 1 |
| 6.2 | 6 | 5 | 1 |
| 6.3 | 8 | 8 | 0 |
| 6.4 | 6 | 6 | 0 |
| 6.5 | 3 | 3 | 0 |
| 6.6 | 2 | 2 | 0 |
According to the table, high sensitivity seems to achieve when OMC ADS was performed with upper sidebands.
So, it might be good to modify the guardians to select the upper sideband for OMC ADS during the lock acquisition.
Note:
I used the data when SR2 oscilated, so it might be better to check the similar thing again by only using the data after SR2 was recovered.
