[Michimura, Kokeyama, Saito, Uchiyama and Komori]
We opened the gate valves close to IXA and IYA, aligned the mirrors and locked the interferometer again.
Firstly, we opend the gate valve close to IXA at 15:27.
Before that, the angle of each mirror and the output of REFL_PDA1_DC were as below.
| Angle | pitch [urad] | yaw [urad] |
| PR3 | -5.9 | -8.2 |
| BS | -28 | 0.0 |
| ETMX | 17.4 | 11.8 |
| ETMY | -19.6 | -9.7 |
|
Output of REFL_PDA1_DC [count] |
max: 4500 min: 900 |
| Visibility | 67% |
| from X arm | ~900 count |
| from Y arm | ~2000 count |
After that, we looked for their best values. They changed as below.
| Angle | pitch [urad] | yaw [urad] |
| PR3 | -12.3 | 13.1 |
| BS | -33.8 | 22.3 |
| ETMX | 18.8 | 11.2 |
| ETMY | -21.9 | -1.7 |
|
Output of REFL_PDA1_DC [count] |
max: 5200 min: 700 |
| Visibility | 76% |
| from X arm | ~1100 count |
| from Y arm | ~2000 count |
Secondly, we opend the gate valve close to IYA at 16:00. They changed as below.
| Angle | pitch [urad] | yaw [urad] |
| PR3 | -14.3 | 13.4 |
| BS | -56.2 | 51 |
| ETMX | 18.6 | 11.1 |
| ETMY | -19.1 | -5.0 |
|
Output of REFL_PDA1_DC [count] |
max: 6100 min: 1400 |
| Visibility | 63% |
| from X arm | ~1100 count |
| from Y arm | ~2800 count |
Laser power reflected on each mirror got increased a little bit after opening each gate valve (X: from 900 to 1100, Y: from 2000 to 2800).
From the above, the wedge angles of the gate valve close to IXA and IYA are roughly estimated as 80 urad and 90 urad respectively.
(Here the refractive index of the gate valve is 1.5.)
Finally, we relocked the IMC and aligned mirrors better, which resulted in the output of REFL to be 6300 at maximum and 1200 at minimum
and the visibility to be 68 %.
The optical gain turned from 2.3e10 [counts/m] (klog #1169) to 3.0e10 [counts/m], and we succeeded in locking the interferometer again.