My goal for tonight was to lock PRMI,
grasp the current situation by my eye,
and capture some images using Sensoray.
They are done, but what are we going to do to solve the problem? The beam looks terrible than I had expected.
What I did:
1. DC output of POP55 PD was plugged out from 1Y2 rack, so we plugged it in.
2. Aligned POP beam to POP25 PD and moved POP camera position at ITMX table.
3. Mis-aligned PRM and SRM, aligned both arms, aligned FPMI as usual.
4. Mis-aligned PRM and ETMs, aligned MI and locked MI.
5. Aligned PRM, and carrier locked PRMI. PRM alignment was not saved since June 7, so slider values which give good alignment was pretty much drifted (~0.4 in C1:LSC_PRM_(PIT|YAW)_COMM).
6. Took some images of POP, REFL, AS during PRMI lock.
PRMI commissioning plan:
From the beam shape at POP, REFL, and AS, the problem clearly comes from the mode-matching, including clipping, longitudinal mismatch, and alignment mismatch. Koji's idea of flipped-PRM seems reasonable, so I think we should better measure something to prove this.
To prove this,
1. Simulate what the beam look like in POP, REFL, AS if PRM was flipped. Compare them with actual captured images. I need to study on unstable cavities.
2. Calculate power recycling gain and compare.
3. Misalign PRM and capture the image of primary, secondary, ... reflections like Koji did in elog #6421. Measure the beam sizes of these reflections using some image analysis(Python Imaging Library? Is there anyone good at this?) and calculate PRM curvature.
4. Can we do come characterization by making PRM-ITMY cavity? ITMX will be mis-aligned, BS will be the loss port to PRC.
5. Beamspot on POP, REFL, AS looks woblby when PRMI is locked. Why?
6. Open the vaccum chamber and see PRM. Simple.
Any other ideas? I have to lock PRFPMI, at least, by July 13!