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Entry  Thu Aug 16 13:49:33 2012, Yaakov, Update, PEM, Transfer functions of seismic stacks, differential motion of test mass 8x
    Reply  Thu Aug 16 20:04:46 2012, Yaakov, Update, PEM, Transfer functions of seismic stacks, differential motion of test mass 6x
Message ID: 7209     Entry time: Thu Aug 16 20:04:46 2012     In reply to: 7204
Author: Yaakov 
Type: Update 
Category: PEM 
Subject: Transfer functions of seismic stacks, differential motion of test mass 

 

 I made the plots a little nicer and added new sensor noises (from Brian Lantz's scripts and measurements). Click to enlarge.

stack_tf.pngstack_tf.figmass_diff_motion.pngmass_diff_motion.fig

 sensor_noises_diff.pngsensor_noises_diff.fig

The last plot shows that these other sensors' noises are lower than the differential ground motion below 1 Hz.  Though 3 seismometers per STACIS is impractical, this shows that such seismometers could be used as feedforward sensors and provide isolation against differential ground motion. At these noise levels, the noise of the high voltage amplifier circuit in the STACIS would probably be the limiting factor.

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