LIGO Document T0900285-v2
- After completing the commissioning of the L1 HAM ISI, its performance was measured in detail. These pdfs show the performance in amplitude spectral densities (ASD) for each of the 6 degrees of freedom (X, Y, Z, RX, RY, RZ) between 10mHz and 500 Hz, and table / ground coherent transfer functions (TF) for X,Y, and Z between 5 mHz and 50 Hz. Where possible, both ground and table motion were measured by GS-13s above 10 Hz, and STS-2s below 10 Hz, as indicated in the legend.
The .mat file contains the calibrated data shown in the plots.
- The performance shown here is improved over v1 at frequencies between 50 mHz and 1Hz. The improvement was obtained from two changes, both to get rid of excess ADC noise found in the differential vertical geophone signals: (1) adding an analog DC Gain of 10 on the vertical geophones, compensating with a gain of 0.1 digitally, and (2) increasing the crossover frequency on the RX and RY blend filters, sacrificing RX and RY performance to reduce > 500 mHz tilt-horizontal coupling with X and Y (see ilog/pub/ilog.cgi?group=detector&date_to_view=02/04/2010&anchor_to_scroll_to=2010:02:04:13:03:31-kissel>>http://defang_ilog.ligo-la.caltech.edu/-->ilog/pub/ilog.cgi?group=detector&date_to_view=02/04/2010&anchor_to_scroll_to=2010:02:04:13:03:31-kissel> for details on better blend filters).
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