Today I did a quick tune-up of the PSL FSS alignment, as the TPD had been trending down and remote alignment wasn't bringing it back to its usual level (an indication an on-table alignment tweak is needed). I began by taking a quick power budget of the FSS beam path:
- FSS In: 288.5 mW
- AOM In: 286.3 mW
- AOM Out, Single-Pass: 215.8 mW
- Single-Pass Diffraction Effeciency: 75.4%
- AOM Out, Double-Pass: 148.2 mW
- Double-Pass Diffraction Effeciency: 68.7 %
- EOM Out: 148.3 mW
The single-pass diffraction efficiency is roughly where it normally is, but the double-pass diffraction efficiency is lower than usual. To correct this I slightly tweaked mirror M21 to tweak the double-pass alignment. After the tweak:
- AOM Out, Double-Pass: 157.8 mW
- Double-Pass Diffraction Effeciency: 73.1%
While not as high as we've seen in the past, this is close enough to where we generally run so I began recovering the RefCav. The alignment was far enough off that I had to lock the RefCav manually (this generated an SDF diff for H1:PSL-FSS_TEMP_MANUAL, which I accepted), then used the picomotors to tweak the alignment. In then end, I ended up with a RefCav TPD of 0.961 V. Finally, I adjusted the alignment into the RefCav RFPD and took locked and unlocked measurements for a quick visibility calculation:
- Unlocked: 1.311 V
- Locked: 0.215 V
- Visibility: 83.6%
I then left the enclosure and turned on the ISS. With the enclosure environmentals off and the ISS on, we now have a RefCav TPD of ~0.980 V. I've attached a screenshot of the accepted SDF diff from the manual RefCav locking; only the highlighted SDF difference was accepted, the other two differences are due to the RefCav being unlocked with the ongoing CER power supply work, which took down the RF distribution system and unlocked the PMC and RefCav. They will go away once the RefCav is locked at the end of maintenance. This closes WP 11201.
When re-locking the RefCav after RF was powered back on, I had to do it manually at first. It would catch, but then oscillate and would not stop and the autolocker would not engage the temperature loop. Once I re-locked manually and manually engaged the temperature loop, the oscillations stopped. The manual re-locking necessitated a change in H1:PSL-FSS_TEMP_MANUAL again, with corresponding SDF diff, so I acccepted it and attach a screenshot here. Will keep an eye on the RefCav to see if this behavior with the autolocker continues.
