- The vacuum chambers have been vented.
- The north heavy door of the BS chamber has been opened by Genie (not by the crane).
It was replaced by the light door. The door is currently closed.
- The MC has been locked with 20mW incident and aligned. MC REFL was left unchanged but lock was able to be achieved.
- The optics before MCT CCD and MCT QPD have been adjusted for the low power operation.
- The first HWP for the variable optical attanuator (HWP/PBS/HWP pair) was set to be 86deg from the maximum transmission at 126deg.
The incident power of 19mW has been measured.
- The PSL mechanical shutter has been manually opened. Two other beam blocks has been removed.
- I found the MC was totaly misaligned with no resonance.- I tried to align it based on the previous OSEM values but in vain.
• How to align the MC mirrors from the scratch
- MC1 has been aligned so as to maximize REFL PD and DC signal of WFS QPDs.
- MC3 has been aligned by looking at the scattered light on the MC2 frames. The spot is centered on the MC2 approximately.
- MC2 has been aligned so that any resonance is seen in MC_F.
• Modification of the MCT optics
- The ND filter before the MCT was removed.
- The Y1-45S mirror before the MCT CCD, which is also used to steer the beam to the MCT QPD path, was replaced to BS1-50-45P.
The reason I used 45P is to obtain higher reflectivity. Because S has higher reflectivity than P in the each layer, I expected to have higher reflectivity for S than 50%.
- The MC REFL path has not been untouched.
• Modification of the servo
- The lock was attempted after alignment of the mirrors. Here how to lock the MC is described below.
1. Run script/MC/mcloopson
2. Open the MC Servo screen in MEDM
3. Change the input gain from 6dB to 22dB.
Change offset from 0.78 to -0.464 (such that the length output has no offset).
Change VCO Gain from 3dB to 21dB
Change MC Length path Gain from 0.3 to 1.6