Right after the ALSY laser was adjusted earlier today, IR power went down (right column, 2nd from the top) while the green power went up significantly (left column 2nd from the top) and started drifting significantly. There are times when green Y transmission cannot go more than 0.45 or so even when the arm was free swinging despite the higher green power. It doesn't seem as if the problem is not alignment.
Interestingly, last two times when Y arm locking was good (i.e. green transmission divided by the green laser power was reasonable) were when IR output of the laser peaked and the green output went down to the previous power level.
General Locking notes and other hacks:
ALS Y has been very difficult today, I spent over an hour trying to get a good alignment on Y arm and was never able to acheive better than 0.6. letting Increase flasshes increase the flashes only gets us to 0.6 aswell.
Reverted Y arm to gps time: 1414950519
I was then able to touch up Y-arm Slightly better, but the ALS-C_TRY_A_LF_OUT was still below 0.7 (the threshhold for locking the arm).
Keita then Lowered the Thresh hold to 0.45 which allowed us to lock Yarm in Green arms manual after touching up the Alignment by hand.
H1:ALS-Y_REFL_LOCK_TRANSPDNORMTHRESH -> 0.450
This allowed us to get through Initial Alignment.
The ALS-Y green power was changed today, and the Noise eater has Stopped eating as much noise.
Once locking , I took ISC_LOCK to Green arms manual, Keita lowered the Threshold even further: H1:ALS-Y_REFL_LOCK_TRANSPDNORMTHRESH -> 0.40 which is even lower than initial alignmnet. We did this because the Diff beatnote that we were seeing was -41
We also increased the gain H1:ALS-Y_REFL_LOCK_LOCKEDGAIN from 6 to 12.
Line 921 in ALS_ARM.py was changed:
if ezca['ALS-C_TR%s_A_LF_OUT16'%self.arm] < 0.5: # WAS Changed From 0.5 to 0.3
We then just waited and eventually it went to LOCKING_ALS !
I then reverted all my changes in ALS_ARM.py and save and reloaded ALS-Yarm.
We repeated these steps multiple times, and lost lock in Find IR due to instable Diff IR signal.
But on the 3rd attempt it worked!
