Thomas Abbott at LLO applied the Pcal beam localization analysis the the LHO ETMY image to calculate the position of the center of the optic in the image from last Friday.

The image below contains lines that indicate the center of the optic using the Pcal image analysis.

Attached is a picture of the original FirstContact (FC) sheet, circa ~Jan 2014, showing the "IAS window" which is a thinner film of FC in the central 3" of the larger sheet.  To me, the shape of the FC window looks similar to the 3" ring showing up in green on the recent optic photo above.  SYS is working with us to get our cleaning game plan together in order to remove the ring.  As well, they are investigating other possible scenarios of where the ring came from if not the window.  Note, there was a full FC sheet re-cleaning in March that apparently did not remove all of the ring that was left behind apon the removal of the first sheet.  To be continued...

I've attached an overlay of (a) the SolidWorks CAD view of ETMy along the PCal camera path and (b) the PCal camera image of H1 ETMy (scaled and rotated). Since SolidWorks does not diffract the image viewed through the ETM optic, I indicate the shift in the ETM Telescope Baffle aperture as well. Three of the 4 bright areas are along the ETM Telescope Input aperture/baffle edge (a coincidence?). (The upper one is red.) One of the 4 bright spots does not correspond to any feature in the CAD image and is likely a spot of residual First Contact.
As subsequently shown by the zoomed in PCal image using the Green Lantern flashlight (green LED) after venting (see entry #15635), it is simply a coincidence that the two prominent bright areas appeared to be along the ETM Telescope baffle aperture edge.

We are repeating the measurement for the ITM. Then the script will try to get a bigger spiral on the ETM.

Please do not unlock the Y arm for the next 200 minutes.

The limiting aperture for an ITM scan is probably the BS baffle. Not sure we can (yet) conclude that these losses come from the ITMY.

Here are the expected clipping losses as a function of offset from the mirror center. This assumes a 62mm radius beam on a 326mm radius optic coating. The pdf shows the clipping loss as a function of offset, and the other attachment is an animation showing the intensity spilled over the edge as the offset is increased (since gifs are all the rage these days).

Years ago, the cleaning crew were wiping down these curtains with some sort of solvent (Acetone?) which caused similar issues.  Could this be happening again?  

Ryan called and walked me through unsticking the green QPD loops at the Y end, which had become railed.

We're leaving the rest of the work for the morning.

I and Alexa looked at the video image of ETMY and ITMY.

We confirmed that the green and the IR are on top of each other on ITMY when the alignment was good-ish for green and IR. There's no particularly bright spot.

We couldn't tell if the green and the IR are on top of each other on ETMY. But there are two bright spots on the ETMY camera that only appear when the arm is locked. See attached images (green was misaligned for these images so you only see IR).

The ETMY camera is looking at the ETMY from HR side. These spots could be something on the HR coating itself, or could be an image of something else (e.g. some scattering and ACB or some unknown ghost beam hitting near by structure?) reflected by the HR coating. This cannot be behind the HR coating, but it's still not impossible that these are some ghost beams from TMS structure taking strange path and coming into the camera at a large angle.

While Dave was walking the beam in PIT, the high spot became brighter or weaker but the lower spot didn't change much (the first three images).

When the beam was moved in YAW the lower spots got brighter (the 4th image).

Update:

This morning I locked green to Y arm without IR, and I can see bright spots on the same position (5th picture), so now it seems more likely that they are on the HR of the mirror.

The sixth picture is taken with green and IR both locked.

If these are on the mirror, the low spot is somewhat low and somewhat to the right  left  to the center of the HR.

Update 2: Is the loss by shmutz big?

To see if the loss caused by the shmutz is significant, Alexa and I moved the beam about +-3cm in YAW on the ETMY without moving ITMY position: (ITMY, ETMY)= (-7.5, +5.88) urad in YAW moves the beam on ETMX to the right, flip the sign to move to the left.

We saw an improvement in both of the cases but it was better when we moved to the left. This is probably because the shmutz is to the right to the center of the mirror.

Alexa will post the StripTools plot, Dave is working on the loss number.

In the attached picure, the first one is when the beam was moved to the right, the next one is when it was moved to the left. Ignore the bright thing at the center of the shmutz as that's just green, look at the halo, and you can see that the IR is indeed dimmer than the last picture from my previous entry.

Keita and I had intentionally misaligned the green PZTs to examine the ETMY and ITMY camera with only the IR beam, and we never realigned it. This is why Evan found the EY green QPDs railed.

Also I found that one of the two IR input pointing WFS had not been cleared, which also explains why the IR beam was not flashing in the cavity.

The above tables lists the positions and the counts on ASAIR. When the IR is not resonanting in the arm, ASAIR reads about 1360 cnts.

In the StripTool I have shown ASAIR_LF_OUTPUT which we are using to measure the power loss, and LSC-Y_TR_A_LF_OUT which measures the IR transmitted power.

At -75 min the IR is flashing in the arm cavity, and ASAIR is about 1360 cnts. Shortly after the IR locks, and then the input pointing WFS engage, as seen by the power build up in IR.

At -70 min we have full IR buildup (TR is about 11 counts), meanwhile ASAIR has dropped to about 1068 cnts. 

At -45 min I begin to move the beam to the right; this is completed at about -40 min. At this point the transmitted power has remained the same and ASAIR is now up to around 1117 cnts

Shortly after we lose lock, and I recover the lock.

At -30 min I begin to move to the left; this is completed at about -20min. Again the tranmistted power has stayed the same, and now ASAIR is at 1129 cnts. Eventually we lose lock again.

Mirror cage outline and guesstimated mirror center line.

Note that we are looking the mirror from the left at a big-ish angle.

Blue lines are inner edges of the cage.

Rick sent us this picture of Pcal camera. We can clearly see bright spots, which I assume is caused by the IR.

Note that pcal camera is looking at the optic from the right.

If beam mis-centering on the TMs is the cause of all the extra loss, it will have to be quite a big mis-centering. I did a quick calculation, and to get 750ppm loss at the ETM, the beam has to be offset from the center by about 6cm (roughly one beam size). The attached plots show the intensity spill over for a 62mm radius beam on a 163mm radius coating, with no offset and with a 6cm offset. The proportions of beam power outside the coating, with no offset and 6cm offset, are 0.991ppm and 762ppm respectively.

Just in case someone wants a plot ...

Dave has a calculation which makes some assumptions about mode-mismatch and sideband power for the X arm.

Suppose the power in the sidebands is 6% of the incident beam, and 15% of the incident carrier doesn't enter the cavity because of mode matching issues; i.e., about 20% of the light is nonresonant. Then the equivalent power reflection is (1155 - 236) / (1180 - 236) = 0.974. This gives a loss of 108 ppm in the X arm.