Ushiba, Washimi, Akutsu
Summary
Did finalization including relocation of some beam dumps and treatment of some cables.
Beam dumps inpection and relocation
Read first carefully posts 15970, 16565, 16593, where you will find detailed discussion on the ghost beams (GBs) in the MCF chamber. Today we only used P-pol 1 W input from PSL room.
Around MCi:
| GB names in Fig. 1 and 3 | GB names in JGW-E2112790 | Power w/ 100W (assumed) injection | Description |
| K, L | MCF_GB5, 6 | 100 mW | The relevant (single) beam dump was once relocated in 16565, but today we re-inspected the relative location of the dump and the GBs, and re-located the beam dump. See Fig. 4 |
| N | MCF_GB1 | 30 mW | No relocation; nice catch! See Fig. 5 |
| J | MCF_GB2 | 30 mW | The relevant beam dump was once relocated in 16565, but today we re-inspected the relative location of the dump and the GB, and re-located the beam dump. See Fig. 6 |
Around MCo:
| GB names in Fig. 2 | GB names in JGW-E2112790 | Power w/ 100W (assumed) injection | Description |
| a | MCF_GB3 | 30 mW | No relocation; nice catch! The beam dump is the center one in Fig. 6. |
| f | MCF_GB7 | 18 uW | No dedicated beam dump, but the shield plate catches it. At lease with P-pol it can be clearly seen. According to the record, it cannot be seen with S-pol the other day (15970). |
The other treatment
- The free swinging cables from picomotors on POM1 were tightened on its pillar with PEEK ties (Fig. 8). The counterpart cables were disconnected at the inner BNC connectors, and taken out of the MCF chamber (Fig. 9).
- There was a clamp left... maybe used for clamping the white-ish flat vacuum-compatible cable. We simply removed the clamp, and left the flat cable as is.
Note
- The post 16565 reported GB "R" was seen with 30 mW P-pol beam, while post 15970 reported it could not be seen with unknown-watt S-pol. But In fact I guess this GB would be hard to be seen, according to a simple estimation: This GB is generated by double AR reflection. The AR is of a very high quality window (cat-A; JGW-D1402644); each AR reflection is <0.1% at 1064 nm. So the double AR reflection would be 1e-6. Even inputting 1 W, this corresponds to 1 uW, which would be hard to be seen with a sensor card. Note that the incident angle of the input beam to the window is almost 0 deg, so independent on S- or P- pol choice. This time we gave up to put a beam dump for this GB.
