Using Rana's excitations last night, we measured the REFL port ASC sensing matrix for YAW at three different times (each measurement last 512 sec ~ 10 mins):
1). gps start: 1229337258; input power: 20 W; POP18: ~62 ct
2). gps start: 1229338980; input power: 23 W; POP18: 56 -> 55 ct (approaching thermal steady state)
3). gps start: 1229316688; input power: 23 W; POP18: ~54 ct (reached thermal steady state)
The response matrix corresponding to the three times are (in order listed above):
| PRC1 | PRC2 | CHARD | CSOFT | |
| RF9_A | 7.5e-2 | 1.6e-1 | 1.2e-1 | 1.5e-1 | 4.2e-1 | 2.2e-1 | 3.6e-1 | 3.5e-1 | 3.6e-1 | 1.3e-1 | 1.8e-1 | 1.9e-1 |
| RF45_A | -1.1e-2 | 4.3e-2 | 3.1e-3 | 2.0e-2 | 2.1e-1 | 1.0e-1 | 2.7e-1 | 3.0e-1 | 3.2e-1 | 1.8e-2 | 6.8e-2 | 6.6e-2 |
| RF9_B | 1.7e-1 | 2.7e-1 | 2.1e-1 | 2.5e-1 | 5.9e-1 | 3.2e-1 | 4.6e-1 | 4.7e-1 | 4.5e-1 | 2.2e-1 | 2.9e-1 | 2.9e-1 |
| RF45_B | 1.8e-1 | 6.2e-1 | 5.9e-1 | 4.6e-1 | 1.7e+0 | 1.1e+0 | 3.2e-1 | 5.4e-1 | 6.5e-1 | 5.4e-2 | 3.7e-1 | 4.9e-1 |
The response matrix can be inverted to get an input matrix. For the two interferometric DOFs PRC2 and CHARD, the input sensing matrix:
| RF9_A | RF45_A | RF9_B | RF45_B | |
| 1.00 | 1.00 | 1.00 | -0.45 | -0.33 | -0.24 | -0.59 | -0.55 | -0.69 | 0.12 | 0.01 | 0.04 | PRC2 |
| -0.94 | -1.00 | -1.00 | 1.00 | 0.61 | 0.39 | 0.49 | 0.45 | 0.60 | 0.00 | 0.02 | -0.01 | CHARD |
The input matrices for both PRC2 and CHARD have some large cancelation between the signal in RF9_A and (RF45_A+RF9_B), and use the residual as the input signal. This indicates a high condition number for the original response matrix. Not sure we could use those matrices as its variation might make the residual signal changes sign...
We also looked at the dithering lines' responses in the TR QPDs.
Here we just focus on two times:
1). gps: 1229337258; input power: 20 W; POP 18: ~ 62 ct
2). gps:1229316688; input power: 23 W; POP 18: ~ 54 ct
The response matrix for the two times:
which can be inverted to the following input matrix:
Such a matrix can be used as the AC part of the HARD/SOFT sensing.
Because the CHARD response was essentially stationary, the combo for CSOFT sensing that decouples CHARD stays also stationary. The soft response changes, yet in neither of the cases we would run into the situation that HARD and SOFT being almost degenerate (i.e., no large signal - large signal in the sensing matrix), thus we could just choose one combo of CHARD input, and even if its decoupling of SOFT would degrade as we went to another power level, the CHARD signal would not accidentally vanish.