I have two topics I wanted to mention.

First, I made an LHO elog entry on Sunday about correlations between
the LHO 4k CPU meter and increased AS_Q noise during S2 science mode. We
had tried to eliminate the problem by limiting test points, but, at least
at LHO 4k, we were still running a bit close to the edge and the
microprocessor seems to have stumbled on a couple of occasions.

Second, we may also have been running quite close to AS_Q clipping.
I injected a 14 Hz seismic signal with a shaker over the
weekend and found that I got harmonics and increased GW-band noise in AS_Q
with only a 20% increase in the rms of AS_Q. This data is suspect
since the interferometer may have drifted from its S2 configuration
(we are having locking difficulties), but I second Ranas concerns with distortion.
What about vetoing based on a 5 to 25 Hz AS_Q band? Increases in AS_Q
clipping are likely to be associated with this band since a fractional
increase in this band has a much greater effect on the RMS than
a similar percentage increase in any other band.
We could make sure that we arent vetoing huge in-band GWs by demanding
that the increase in the 5 to 25 Hz band be greater than the increase in the
GW band. John, have you noticed any correlation between increased noise in
the 5 to 25 Hz band and increaseed noise in the GW-band?

Robert