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Reports until 12:06, Monday 25 March 2024
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jennifer.wright@LIGO.ORG - posted 12:06, Monday 25 March 2024 - last comment - 12:29, Monday 25 March 2024(76683)
A2L Steps

Jennie W, Sheila, Camilla

I looked at the results of the A2L tests from the weekend for ETMY, ITMX and ETMX.

For ETMY the steps seem too small / A2L gain changing has little effect on the power recycling (LSC-POP-A and ASC-POP_NSUM), build-ups (ASC-{X,Y}_PWR), range (MPC range channel and BLRMS channels) or optical gain (KAPPA C). See first image.

 

More of a difference can be seen in the arm build-ups and PRG for ETMX. The best value for P2L looks like 4.4 as this maxmises the arm power and PRG, while the best range is for a Y2L of 4.6. See second image.

Y2L gains for ITMX seem to already be at their optimised value in terms of arm build-ups and power recycling, however the range improved slightly when the P2L gain was at  -0.4. See third image.

 

In summary maybe we need to retune ETMX and ITMX A2L gains a bit, but for ETMY it doesn't seem to gain us much.


See comment from Elenna below, we will run these again as per this entry.

 

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elenna.capote@LIGO.ORG - 12:29, Monday 25 March 2024 (76687)

I am not sure the results of these tests are telling us what we think they should. The camera servos were running during this test, not the ADS. Therefore, changing the A2L gains would only change the mirror actuation point, while the camera servo would continue to servo the same offset set by the ADS convergence during lock acquisition. This means that the spot stayed static on the mirror while the mirror actuation point changed. In this sense, the buildups shouldn't really tell us anything, since the spot was not moving. However, the noise may change during this test if we are changing some alignment coupling.

If we truly want to move the spots around to look for better buildups, we should either make a test that adjusts the camera servo offset value, or turn on the ADS when the A2L gains are changed.

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