[Tanaka, Komori, Dan]
1. CHARD_P
At first, We worked with only the CHARD_P loop mainly engaged, while the other P DoFs were kept weakly locked.
- The CHARD_P filter was created by copying from the DHARD_P filter and modified a little.
- The OLTF was measured and compared with previous results.
OLTF file: /users/Commissioning/data/ASC/2026/0205/OLTF_CHARD_P_20260205.xml
- Brown: updated (measured in the morning)
- Blue: yesterday’s result
- Green: before notch tuning
- Purple: remeasured CHARD_P OLTF
The purple measurement was performed in the RF_LOCKED state, where all other DoF loops were also closed. A large response was observed in DHARD_P signals, suggesting that residual coupling remains from CHARD_P to DHARD_P.
Result: See OLTF_CHARD_P.png (fig001).
2. DHARD_P
Previously, the DHARD_P gain was set to −3 externally. In this work, the gain was incorporated into the filter bank FM6 = HBtest.
After this change, an oscillation appeared around 2 Hz. Therefore, the gain was temporarily reduced from gain(3) to gain(2).
Compared with yesterday’s results, a larger bump around 10 Hz was observed. After repeating the measurements several times, this bump seemed to occur when the alignment was poor. In particular, the bump around 10 Hz was prominent in measurements taken when the transmitted power was low.
OLTF measurements were performed with and without the DHARD_P FM2 (notch filter). After that, the IFO was brought to the RF_LOCKED state, and the same measurements were repeated.
Measurement file: OLTF_DHARD_P_20260205.xml
Result: See OLTF_DHARD_P.png(fig002).
3. ASC GRD update
Based on the above results, the ASC GRD was updated.
- The appropriate filters for DHARD_P and CHARD_P are now automatically engaged.
Filters to be engaged for DHARD_P and CHARD_P:
ASC_filter_after_GRD_change.png (fig003)DC_HARD_P_FB.png (fig004)
VIS MN LOCK filter configuration:
The FM4 = HBtest filter (marked by blue circles in the figure) is now turned ON via GRD instead of the conventional FM9 and FM10.
See VIS_MN_LOCK_FB.png (fig005).
