craig.cahillane@LIGO.ORG - posted 18:32, Tuesday 04 September 2018 - last comment - 20:28, Tuesday 04 September 2018(43824)
IMC Error Signal Spike at 53.4 kHz
I took an IMC spectrum at the MC servo board while ALS_COMM and CARM have been down today. There's a spike at 53.4 kHz. Not clear to me what's causing this. Edit: It's gain peaking. Attached IMC OLG. AdjustedIMC_power_adjust_func()inISC_library.pyto give 3 dB less gain and put the IMC UGF at around 25 kHz where we have heaps of phase margin.
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I actually brought the IMC servo board IN1 Gain down 6 dB (from 23 dB to 17 dB at 2 watts input power) because there was still significant peaking with a 3 dB reduction. New IMC spectrum/OLG posted. IMC UGF = 21 kHz This low of frequency suppression could have implications down the road, from direct coupling to DARM to vertex LSC noise coupling. More quantitative statements are forthcoming.
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