J. Kissel

Here, I make further corrections to the HSTS actuator noise budgeting -- an update from TAKE 2 (LHO:65317). The details of what I fixed and how I found it, are outlined below, but in short -- I found another error in the actuator noise calculations that caused more over estimation of the DAC actuator noise. 

However, the error caused more egregious over-estimation of the M2 and M3 stage actuator noise than the M1 stage, so the conclusion from TAKE 1 (LHO:65247) and TAKE 2 (LHO:65317) of remain the same: the HSTS top mass (M1) 18-bit DAC noise projected to the optic still is either roughly equal to or dominates over residual seismic and sensor noise re-injection contributions to overall optic motion below 2.5 Hz.

I post three, 3-page comparisons again. As a reminder the differences between the three SRM, SR2, and FC1 models are:
    (1) The H1 SUS SR2 model, which uses 
        - The H1 HAM5 ISI performance model,
        - 18-bit DAC noise for the M1 stage, 
        - 20-bit DAC noise for the M2 and M3 stages BUT 
        - both the M2 and M3 stages have the modified TACQ driver,
    This is currently like LHO's PRM, PR2, SR2, and SRM.

    (2) The H1 SUS SRM model, which uses 
        - The H1 HAM5 ISI performance model,
        - 20-bit DAC noise model all three M1, M2, and M3 but
        - only the M2 stage has the modified TACQ driver,
    This is currently like LLO's PRM, PR2, SR2, and SRM. Comparing with (1) suggests that LHO should revert their M3 coil driver to the low range unmodified TACQ driver.
 
    and,
    (3) The H1 SUS FC1 model, which uses 
        - The H1 HAM7 ISI performance model,
        - 20-bit DAC noise model all three M1, M2, and M3 stages and
        - the M2 or M3 stages TACQ drivers are unmodified,
    This is the lowest noise configuration we know how to create with current technology.

%%% WHAT HAD HAPPENED WAS

While updating the HLTS damping loop & noise budgeting design (LHO:65687), while copying over the updates to the actuator noise, I noticed that the hard-coded lever arms in the function used to compute the HSTS actuator noises,
    /ligo/svncommmon/SusSVN/sus/trunk/HSTS/Common/FilterDesign/Scripts/plothstsactuatornoise.m

were an errant copy and paste of the HLTS lever arms. Namely, the lever arms were          
                   %% R    P     Y          % From T1300083 / D070447
    leverArms.hsts = [0.070 0.045 0.080;... % [m] M1         
                      0     0.030 0.105;... % [m] M2
                      0     0.104 0.060];   % [m] M3
and they should be
                   %% R    P     Y          % From G1100968 / D020700
    leverArms.hsts = [0.060 0.030 0.080;... % [m] M1         
                      0     0.048 0.048;... % [m] M2
                      0     0.048 0.048];   % [m] M3
Given that the lower-stage lever arms of the HSTS are half that the HLTS, the HSTS actuator noise estimates from TAKE 1 (LHO:65247) and TAKE 2 (LHO:65317) had over estimated the lower stage actuator noise by the ratio of the two lever arms -- in some cases as large as a factor of 2.