J. Kissel

Following the same procedure outlined in LHO aLOGs 9453 and 9079, I balanced the coils on the PUM stage of H1 SUS ITMX. The final balanced gains in the L2_COILOUTF bank are

H1 SUS ETMX
Channel     Balanced COILOUTF Gain
L2 UL            +0.909
L2 LL            -0.965
L2 UR            -1.035
L2 LR            +1.099

The precision to which we could balance the coils was limited by the really windy day ground motion, but we believe the obtained values are good to within +/- 0.5%.

This balancing has reduced the L3 P and Y caused by a L2 pringle excitation at 4 [Hz] by
   DOF                  Reduction Factor @ 4.0 [Hz]
    P                          > 14.6      (peak below the noise, and totally incoherent)
    Y                          > 10.1      (peak below the noise, and only ~45% coherent)
The attachment shows the result from which these values were obtained, comparing the optical lever ASD at 4 [Hz] driven from L2 at the same amplitude for both balanced and unbalanced configurations.