Jennie W, Rahul K, Jason O, Keita K
Rahul and Jason installed body mode dampers on the JAC, we did not expect it this to change the position of the JAC much.
Thinking of what could have cause this there are two possibilities:
- Installing the body mode dampers moved the JAC.
- The B & K hammering on Tuesday (see alog # 88822) of the input HAM1 periscope somehow shifted its mirrors.
After installation we tried to lock and could not. Checking the output of the JAC we could not see flashes. Lookign at the input coupler of JAC on a card the beam seems high coming into the JAC.
Jason and I recovered the alignment into the JAC somewhat with the PSL persicope PZT and the "JM1" fixed mirror which sits right after the HAM1 input periscope.
We finally managed to lock the JAC (altered the guardian timeout thredhold which checks the power level - I marked what I changed in the code so I can reverse it).
Below I include a comparison of the last time we were locked last Friday 16th, this is nominally in mW but we have not checked the calibration of this PD yet.
Yesterday afternoon we took this image of the locked level and it is worse by a factor of 2, see this image.
Keita suggested we do a scan with the on board PZT while the cavity was unlocked.
Taking the measured hom spacing which Masayuki and I measured in this unit at CIT, 1.75 radians and the FSR, caluclated from 1/time period between TM00 modes, we estimate the 01 mode is 0.75 of the FSR.
The scan of the transmitted beam in blue makes it look like we have two candidates for this 01 mode that are between 70 and 50% of the height of the TM00 mode, so we are most likely mis-aligned. The scan voltage is in red.
Last week we had aligned into HAM2 and out of the viewport that normally delivers the beam to IOT2L. We checked this late in the afternoon and the beam gets through the MC REFL periscope on the table and through one mirror, then clips on BS1.
This makes it likely that our output alignment has not changed badly and so we can go ahead with aligning the output of the JAC.
Our plan today is to spend half an hour checking the JAC is not locking to a HOM and then try and improve the alignment ontpo IOT2L with JM2 and JAC_M3 mirrors in HAM1.
We still have irises at the output of the HAM1 table, one of which was placed at the old output beam position before we installed the input periscope or the JAC cavity, so we will try and improve the line through this iris and onto IOT2L.
Yesterday the EOM arrived midday, Keita and Rahul concentrated on building this in the optics lab, this will continue to be worked on today.
