craig.cahillane@LIGO.ORG - posted 16:02, Thursday 11 August 2022 - last comment - 16:57, Friday 12 August 2022(64446)
IM4 Trans centered
Because of high measured jitter coupling from alog 64372, we are interested in the IM4 Trans input beam jitter witness. We also recently engaged a stage of whitening to avoid ADC noise, but found we are dark noise limited on this diode alog 64371. I moved the PICO B (HAM 2 + oplev) motor 2 (IO IM4_Trans QPD centering) down and to the left, relative position change from (X = 0, Y = 0) to (X = 3700, Y = -3880) This increased the witnessed power on IM4 Trans by 0.4%. We don't want this to overwrite our IM4 calibration from alog 63812, so I adjusted the Input beam power incident on PRM calibration (IM4 Trans NSUM FM10 gain) from 4.624 to 4.606.
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IM4 segments after realignment posted, for comparison to alog 64378. Some strange shelf is occurring around 7 Hz here, obscuring the peak Evan's spectra saw, may be spectral leakage. Forest of peaks at 13 and 18 Hz appear again. We can grab a long spectra from today's lock to resolve these peaks and limit leakage.
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Uploaded finer resolution spectrum.
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