stefan.ballmer@LIGO.ORG - posted 22:05, Saturday 25 August 2018 - last comment - 22:09, Saturday 25 August 2018(43661)
Violing damping festival
TVo, Danny, Craig, Stefan We made some progress damping the most offending violin modes - almost all of them on ETMX (presumably since ETMX is driven). We kept updating the Violin wiki page: https://cdswiki.ligo-wa.caltech.edu/wiki/Violin_Mode_Table_v2 The well damping modes are: Mode 2 (507.493Hz) , Mode 6 (511.180Hz), Mode 7 (516.678Hz), Mode 8 (507.36Hz), Mode 9 (516.781Hz), Mode 11 (508.844Hz, currently its monitor is on Mode 1) They all have monitor channels with 20mHz BW. We had problems with Mode 10 (510.714Hz) not convinced he is on the ETM yet... Some additional remarks: - Some guardian currently keeps the ramp time to 0.2 sec. This is too short - it creates a 5Hz-wide buzz, and we see all monitor filters being kicked by it. We should go to 5sec ramp time at least. We left the interferometer running for the night, with all violin damping settings on. Reference time for all the settings: 1219294728 (2018/08/26 04:58:30UTC). Attached are snap shots for the ETMX violin screen.
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The ITMY 501 Hz modes are particularly hard to damp because of the proximity of the modes creates a low frequency beatnote (~ 2 mHz). I made the Mode 3 bandpass very small (also 2 mHz). This means you have to wait a long time before you can tell if your damping settings are good or not. I am leaving ITMY Mode 2 and Mode 3 on with the settings pictured below. It seems like over the past thirty minutes we've been winning, we'll be able to say more in a couple of hours.
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