J. Kissel, D. Hoak

We needed some more damping of the highest vertical and roll modes of the QUADs this evening using DARM as the sensor and the Top Mass (M0) as the actuator. We re-used the same parameters for ETMY vertical at 9.7305 [Hz] (see LHO aLOG 16673). We also tried commissioning some ITMX and ETMX vertical damping toying around with similar filters and gains but were ... inconsistently unsuccessful: I explored the gain and phase parameter space but was either unable to convincingly change the amplitude of the mode, or it broke the lock. 

We did however pioneer roll damping at 13.81 [Hz] on ETMY. It took us a while to find a sensor (besides DARM) that could help us identify which test mass was rolling -- but L2-stage OSEMs saw ETMY's roll mode loud and clear. Dan designed the filters to have similar affect as the vertical, 9.7 [Hz] filters with a relatively wide band pass surrounding 13.9 [Hz] in FM4, and two trial filters that add or subtract 60 degrees of phase at the 13.9 [Hz] in FM1 and FM2 respectively:
FM1  "+60deg"  zpk([0],[3.26459+i*18.5144;3.26459-i*18.5144],1,"n")gain(0.0523988)
FM2  "-60deg"  zpk([0],[1.75001+i*10.3531;1.75001-i*10.3531],1,"n")gain(0.0911865)
FM4  "bp13.9"  butter("BandPass", 4, 13.3, 14.5)gain(120, "dB")
These have been loaded into every QUAD's H1:SUS-?TM?_M0_DARM_DAMP_R bank, but only ETMY's R banks have been commissioned to the point that damping is successful and repeatable (which is the same for V as well).

We found that, for ETMY, the +60 deg filter (FM1), (and FM4, obviously), plus a negative gain (we can get as high as -200 or -300), reduces the amplitude of the mode within a minute or two while in the "DARM WFS" ISC_LOCK state, with CARM and TR CARM, DARM is on AS AIR. Also, we could only get any action with the TOP MASS coil drivers in State 1 (LP OFF, or in its highest range mode). 

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Directions to commission further test masses' loops:
- Check that the TOP mass coil driver is in high-range mode -- preferably *before* you're locked, so you can switch it if you're not (I broke the AS AIR, RF DARM lock when transitioning ETMY's M0 drivers from State 2 to State 1).
- Try to identify *which* test mass' mode has rung up. Vertical modes appear in M0 OSEMs if rung up particularly bad, and so far I've been able to see roll modes in L2 OSEMs.
- Start with only the band pass filter (FM4) on, and gradually increase the gain (with a 5 or 10 [sec] ramp) in the positive direction until you either get close to saturating the DAC, or you start seeing amplitude change on the mode in question. Start with a gain of 1.0, and increase by factors of 2 to 5, depending on how above you are from the normal LF and RT output signals, how close you are to DAC saturation, and how bold you feel today.
    - If you don't see any change, rotate the phase by 60 degs (i.e. turn on FM1), and increase the gain. Rinse and repeat until you see some action (+120 [deg] = negative gain, and FM2 on, +180 [deg] is negative gain, with no FM1 or FM2 on, etc. etc.)
    - If you see an amplitude increase, then flip the sign of your gain.
    - If you see an amplitude decrease, and its slow, try rotating an additional 60 [deg].
    - If you see an amplitude decrease, and it's fast, then you've won!
Notes:
- The definition of "slow" vs. "fast" is that "fast" is that the amplitude noticeably decreases between each average of a 0.1 [Hz] resolution, 70% overlap, 3 exponential overlap, log-scale ASD. "Slow" means you can see it decreasing, but you don't have the patience to wiat for another 30 minutes while it decreases enough that you're happy.
- We've had only a few data points, but we've found that ETMY vertical damping signs between using ALS DIFF for DARM, and any red on DARM. This may just have been that particularly bad day though.