Ushiba (remote), Akutsu
Summary
Now the input beam to IMC is P polarization. The input power to IMC is reduced to 80~70 mW.
Details
In order to check the global alignment of each mirror relevant to IMC (MCi, MCo, and MCe), we would like to let the IR beam pass through these mirrors in air. We would like to avoid accidental optical resonance of IMC in s polarization, which should be high finesse and will damage each mirror coatings in dusty air. We tried to repeat the way shown in 20336.
The procedure was:
- Confirm the laser hazard; Kimura-san confirmed (in place of Uchiyama-san) required treatment was done for claiming the laser hazard. Ushiba-kun annnounced laser hazzard to start.
- Put a dump between MCi and PSL room in- between MCi and MCo; the height of the anticipated beam or the centers of these mirrors and the dump were confirmed with a laser level. The "beam dump" here was, this time, just a self-standing small black target, which I had used frequently for this purpose in the beginning of 2021.
- Open the PSL shutter; and reduce the PSL output power by rotating the relevant (other) HWP (by Ushiba-kun remotely) so that we can safely put the S-P HWP concerned across the beam line without being burned on the optical table in the PSL room. Note that the power meter can measure the power only when the shutter is open. At the power meter, the input beam to IMC became 70-80mW.
- I locate the S-P HWP; firstly the one used in the past was gone, so I collected the HWP and its post. Then somehow adjusted the height, but I am not so confident. Then somehow adjusted the horizontal position of the S-P HWP location with looking at IMC REFL RF DC (relevant to MCi reflection) counts to be maximized. Then somehow adjusted the roll of S-P HWP so that the IMC REFL RF DC counts to be minimized. Itelate the last two procedure.
- I tried to check its polarization with a polarizer that should be stocked in the MCF clean booth metal shelf but lost. It is so expensive and useful, but gone. So sad. Anyway, as the reflection of MCi got minimized, it would mean the transmission of MCi might be maximized, which would be a certain evidence of P-pol, so I left it.
Surprisingly I did not take much relevant photos... I may add them tomorrow. The only one is Fig. 1.
Note
- When I tried to locate the HWP on the PSL optical table, I found that an IR beam was being accross the place. It was very unuseful. Anyway, I somehow put the HWP at the side of this beam. See Fig.2.
- As explained, the input power to IMC is reduced to 70-80 mW in purpose. Please do not increase it without letting us know.
- The S-P HWP was not fixed; it has just a magnet pedestal, so please do not touch it.
