Jennie W, Sheila D, Rahul K
Summary:
I guess the summary for yesterday is we improved the input alignment to JAC but are not sure why it was lower relative to last Thursday.
And that we have aligned into the IMC with steering mirrors after JAC on HAM1 and now get TM00 modes flashing on the IMC TRANS camera but are not sure why our on-table references (IMC REFL WFS) and in-chamber iris are not aligned with this beam.
Before we went into chamber today we checked the fringes in the JAC cavity transmission to see if we had the same power in the TM00 modes as Friday (when it was ~ 0.15). From the image you can see that the level on the JAC-TRANS_A PD is now around 0.1, and it looks as though the 01 mode could be near the size of the TM00 mode.
This implies the input alignment (which we recovered on Thursday to 0.22) has been drifting.
In chamber Sheila found that the JAC cavoity was locking on a 01 mode (two vertical lobes).
She tried moving the JM1 mirror and found the base was slightly loose in the mount. Not sure if this is enough to really explain the mis-alignment fully.
She tweaked up the alignment of this mirror and I tweaked up the alignment using PSL PZT periscope mirror until the beam went up to 0.22 on the JAC TRANS A PD.
We checked the power in chamber right before the input coupler to JAC and it is now 93 mW.
The power measured after JAC (right before mirror JM2) is 58 mW.
The power measured on IOT2L after the bottom periscope mirror is 44mW.
After continuing tweaks to the input alignment we got 0.28 on the JAC TRANS A PD 0.28 with input alignment changes.
We maximised the power onto the table by moving JM2 and JAC-M3 and looking at the IMC REFL PD.
We have 76mW power after bottom periscope mirror and
a 0.96 - 1.2 level on MC REFL PD.
Still have 0.28 level on JAC trans out.
We started to notice fringing (see image) on the IMC TRANS camera and on MC2 TRANS QPD NSUM.
I did a quick check of the mode-matching and it looks like our mis-match is now about 11% (for the second highest mode in the scan).
We therefore switched to using these as our metric while we optimised the alignment into the IMC with the same two mirrors JAC_M3 and JM2.
Eventually Sheila and Rahul discovered clipping on the last iris before the beam leaves HAM1 so marked the height with a C clamp and took it out. This was our reference for the original beam into HAM2 before the JAC install was started.
Continued to optimise with these two mirrors.
At the end of the day we placed new iris after output periscope and moved iris on IOT2L in reflection of first table steering mirror to mark the placement of the beam.
Since we still are not aligned to our references on the table - ie. the WFS, the iris placed at the HAM1 output before JAC was installed, we will double check the MC mirrors position relative to our most recent in-air lock and the last in vacuum lock.
Compared to the 19th December 00:25 UTC, the position of MC3 M1 DAMP INMON has increased by 6 uradians in pitch and has not changed in yaw.
Compared to the 19th, the position of MC2 M1 DAMP INMON has decreased by 10 uradians in pitch and has decreased by 1 uradian in yaw.
Compared to the 19th, the position of MC1 M1 DAMP INMON has decreased by 3 uradians in pitch and has increased by 3 uradian in yaw.
Cursors show current values in this ndscope plot.
Jeff also did a check here (alog #88895).
