Matt Jennie Mayank TJ Sheila
We wanted to estimate whether we were clipping on the scraper baffle of PR2 so we moved the PR3 YAW sliders during single bounce quite a bit to get an idea of when were clipping, using the AS_C_NSUM to gauge whether we were starting to clip.
Most of the steps are the same in Sheila's previous alog, expect we are in single bounce and we are therefore not looking for the ALS beatnotes, instead we are looking at the AS_C_NSUM value. You want to take ISC_Lock to PR2_SPOT_MOVE so that the guardian will adjust the IM4, PR2 yaw sliders while you adjust PR3 sliders so that most everything stays aligned. You will have to adjust the pitch every once in awhile due to the cross couplings in IM4 and PR2.
Steps taken in this measurement:
We think the yaw offset value that puts the spot on the center of PR2 is around -230 urad (we started here around 09:00 PST)
3. By going in steps to -900 in yaw offset, while pitching PR3 every so often to keep everything centered, we were able to move across PR2 to the left edge of the baffle, clipping about 10% of the power at the ASC-AS_C QPD (finished 09:45 PST).
4. Then we reset the sliders to their starting values and follwed the above steps going to the right (we stopped at +440 yaw offset). Here we recorded around a 10% loss on the right edge of the baffle (finished 10:44 PST).
Mayank has some plots he will comment analyzing the results of this.
Useful ndscopes
We modeled the PR2Baffle beam clipping
Matt Jennie Mayank TJ Sheila Keita
We extracted the beam path and geometry for the PRM-PR2Baffle-PR2-PR2Baffle-PR3 leg of the input light from the following documents, D1200573, D1102451 (cookie cutter), D0901098, D020023 etc.
The angle of PRM-PR2Baffle beam with respect to X axis was changed from about -0.1 radian to 0.1 radian (over and above the existing value of 0.339 Degrees) such that the
PR2 Beam spot moves from approximately -25mm to 25 mm. The PR2 yaw was adjusted such that the PR2-PR3 beam always hits the same spot on PR3.
This ensures that the beam spot on PRM and PR3 remain unchanged while the beam spot on PR2 changes.
Attachment 1: Shows the overall modelled geometry
Attachment 2: Zoom view around PR2Baffle along with the beam paths.
Attachment 3: Python script.
Attachment 4: Experiment_Data_ 19Feb2025.
Attachment 5: Experiment_Data_ 5July2025.
Plot 1 shows the PR2 beam spot motion with respect to the angle.
Plot 2 shows that following distances vs the PR2 beam spot location
a) PRM-PR2 beam and the Lower edge of the PR2Baffle (D1 distance)
b) PR2-PR3 beam and the Upper edge of the PR2Baffle (D2 distance).
Plot 3 shows the transmission of the beam with respect PR2 beam spot (As the beam comes closer to the baffle edge, some of the beam power is blocked by the baffle edge and hence the transmission decreases)
Plot 4 shows the net transmission for the beam (multiplication of Upper edge and Lower edge transmissions)
It also shows the experimentally measured data above.
The two curves do not match exactly however they differ in position by around 2 mm. It seems PR2_Baffle is approximately at the right place. It may not be necessary to move the PR2_Baffle.