- found a bit of clipping on ISCT1 popair shutter, moved shutter, 2 inch lens and bs right after lens in -X direction
- Adjusted alignment onto POPAIR B using PRMI flashes at 10W, then MICH bright at 10W we were able to see a small signal to align this diode to.
- Also checked alignment onto REFLAIR A using MICH bright.
| POP A LF | POPAIR B LF | REFLAIR A LF | MICH IN1 (REFLAIR A 45 Q) | PRCL IN1 (REFLAIR A 9I) | POPAIR B RF18 | |
| PRMI O4 | 200-400 | 200 | 2-10 | +/-6000 | +/-600 | 80-100 |
| PRMI now | 100 | 6 | 2.5-4 | +/-20 | +/-100 | 5 |
| PRX O4 | 0.5 | |||||
| PRX now | 0.5 |
- Ran OMC scan to check modulation depth, comparing to 89497. Modulation depth settings are 27dBm for both 9MHz and 45 MHz, as that alog says they should be. Modulation depths are about the same as in that alog, (9MHz peak over carrier peak is 0.01, 45 MHz peak/carrier peak is 0.018). However the carrier peak is about half as large as it should be. AS_C sees 20mW, we have 8.5W at IM4 trans so we expect 18mW entering HAM6 in single bounce, so this seems OK.
- With MICH dark locked, Elenna worked on centering POP X, while I went back to ISCT1 to check alignment onto the diodes. I am sure that the beam is reasonably centered on REFLAIR A, POPAIR B, and POPAIR A (did not check REFLAIR B this time).
In order to fix this alignment issue, Sheila, Keita, and I had some different ideas, and it was hard to determine the best path.
Here is the one we tried:
- Sheila found the alignment slider positions from O4, and noticed that PR3 and ITMX pitch are bother very different now versus then. So is ITMX yaw.
- I suggested we use PR2 spot move to move the PR3-PR2 axis, and see if we can follow with PM1 to better align the beam onto POP LF. Then, we can adjust ITMX and beamsplitter.
- Moving PR3 pitch to the O4 alignment causes the beam to fall off POP X, and it does not go back onto POP A LF. I tried moving the PM1 slider to the "good for POP A LF" setting above, but that does not bring the beam back.
- When in the "good for POP X" setting, PM1 saturates both LL and UR, so it is not obvious if the problem is pitch or yaw.
- I tried moving ITMX around, and PR3 as well, but ITMX moves cause us to fall off ISCT1 refl camera, and PR3 moves do not bring us back on that camera.
- Overall, Keita and I agree that we need to think more about this.
This is the state of the alignment as I am leaving it tonight:
- PM1 is in the "good for POP A LF" state, which means it is not saturating, and there is no beam on POP X
- PR3 alignment (as well as the corresponding IM4, PR2 and PRM alignment) is reverted to where it was before I started this particular adventurew
- ITMX alignment and BS alignment are also reverted.
Screenshot attached of all these settings.
Earlier we did some OMC scans and got weird results. We tracked this down to an incorrect DCPD whitening setting. Keita fixed it, and we reran the scans, the carrier peak heights are now correct compared to the blue reference.
Oli tracked down the problem with MC2. All crossovers are fine now and the mode cleaner locks with normal gain settings. They will alog the details.
Centering on POP X DC with PM1 pulls beam off POP A LF
Right now we have an alignment that can bring the beam to both POP A in vac and to the POPAIR diodes on ISCT1 in a PRMI, or with either PRX or MICH locked.
However, the beam was very far off of POP X WFS DC, suggesting PM1 is not well-aligned. I spent a bunch of time trying to move PM1 while keeping the beam on POP A LF and improving the POP X alignment while we are locked on MICH DARK, which brings a lot of light to the POP port.
I gave up on keeping the beam on POP A and instead did much larger moves of PM1, which brought the beam to all four segments of POP X DC and increased the POP X sum. I finally got the beam well enough aligned that I could engage the DC6 centering loop, which aligns PM1 to POP X.
We are now well centered on POP X, but have lost the beam on POP A. PM1 is also unfortunately close to saturation at this alignment.
Here are the PM1 slider values that put the beam on POP X:
P: -868.5, Y: -2076.5
Here are the PM1 slider values that put the beam on POP A LF:
P: 213.5, Y: -258.5
Assuming the sliders have a decent calibration to urad, this is a 1 mrad difference in pitch and 1.8 mrad difference in yaw.
