This klog refers to yesterday afternoon's work.
%%%%
 I worked on the improvement of the performance of the blending strategy at EY.
Below are some details of the work.
To have the oplev in their linear range, I request the Align state to Guardian. Keeping this state, I measured the spectra of the IP, BF, and TM when the following control schemes were ON:
- IP LVDT control;
-IP LVDTSC control;
-IP blending at 80 mHz along L and T direction (See Pic1). Blending at 150 mHz along the Y direction (See Pic2).
Pic3, Pic4, and Pic5 show the spectra of the IP compared to the CL noise and rms. It is possible to see that by changing from LVDT control to ID control the rms, and the re-injection of the seismic noise via LVDT are reduced, but there are still some rooms to improve the situation by reshaping the blending and control filters.
As a second step, I reshaped the 80 mHz blending filters so to reduce a bit more the re-injection of the seismic noise in the region [0.12, 0.350] (Pic.6) in L and T, and I moved the blending frequency from 159 mHz to 110 mHz in Y (see Pic7). I closed the loops with the same UGF and measured the spectra again. And as the last step, I reshaped the control filters along L and T and increased the UGF at 1 Hz.
Pic.8 and Pic 9 show the IP spectra in these new configurations. The rms along the 3 DOF are reduced.
In addition to this, I measured the spectra of both H4 (out-of-loop sensor on the IP), BF (L, T), and TM (L, P, Y) in the same configurations.
Pic10 shows the spectra of IP acquired by the out-of-loop sensor H4. Here It is possible to see that changing from LVDT control to ID 80 mHz new and UGF 1 Hz, the suppression of the micro-seismic noise is about a factor of 8 in terms of rms.
Pic11 and Pic12 show the BF spectra along L and T directions. Also here it is possible to see the benefits of the new strategy: a factor of 3 of reduction in terms of rms in the frequency region [0.120-0.350]
Pic13, Pic14, and Pic15 show the TM spectra along L, P, and Y directions. Here it is possible to see that the Pitch motion is suppressed. No evidence of re-injection of geophone noise below 0.1 Hz has been detected.