While Corey and Keita were aligning the TMS, I kept myself busy touching up some of the alignments and clean-up tasks on ISCTEY. The refl path and WFS paths are nominally aligned, and I've observed that without my favorite anthropogenic noise sources in the chamber, the return beam is relatively stable.
I'm working with TMS offsets of PIT 20 urad, YAW 9 urad. Not all that bad.
IR:
I adjusted the polarization on the IR Path from its initial position to something closer to the nominal power given in the ISC End Station manual.
Also, my earlier concerns about the shorted power cable damaging the BBPD appear to be unfounded... that factor of 10 I had to add to the impedance was nicely accounted for by the gain switch on the hardware PD interface, which I had completely forgotten existed.
power | |
Laser output | enough* |
After attenuation | 38.7 mW |
IR mon PD | 310 uW |
BBPD | 18.4 mW |
*this power meter's filter didn't make it into the storage bag, no chance of measuring this one with the tools I have right now.
Green:
PD4 is aligned to the rejected Faraday beam. At this moment, the polarization coming from the laser in relation to the first Faraday appears to be slightly different from EX; I'm consistently measuring ~1.2% power rejected to EX's 1.9%. I've also adjusted the laser current to increase power to the chamber; I'd had it turned down to 0.97 A in an attempt to find the beatnote, and the polarization of the laser wasn't optimal for getting power into the rejection beam (it was initially about ~0.4% of input power). This may be why I was having such a hard time aligning PD4 earlier, there wasn't much there to find.
Also the REFL_A PD might need
power | |
Laser output | 53 mW |
After 1st Faraday | 49.1 mW |
On mon PD | 700 uW |
After 2nd Faraday | 41 mW |
At periscope | 40 mW |
At REFL_A PD | 12.87 mW** |
** at the PD I'm seeing flashes up to ~5 mW. Unclear if this is an alignment or calibration issue, will be tracking this down tomorrow.