Continuing on from yesterday's work.

    SCRN0001.jpg and SCRN0002.jpg show the power noise from the 70W amplifier, with the ISS
on and off.  In both cases there are four relatively narrow peaks at ~19 kHz, ~38 kHz, ~54 kHz
and ~73 kHz.  They are present whether or not the ISS is on or off, and when both the ISS and
the AOM driver is off.  In the case that the AOM driver is off, there are a sharp accompanying
higher frequency peaks.

    SCRN0003.jpg shows the output of the front end.  SCRN0004.jpg shows the output of the front
end with the AOM driver on and off.  There is a small difference between the two but oddly
enough with the AOM driver off, there is a broad peak between ~40 kHz and 50 kHz.  The broad
peak around 20-25 kHz is from the NPRO, as shown in SCRN0005.jpg.  In SCRN0005.jpg features
are present irrespective of the condition of the noise eater.

    The power noise from the 70W amplifier seems to be quite sensitive to vibrations.  For
example dropping a screw on the table surface, or tapping the the table surface results in a
number of peaks appear in the spectrum.  It just might be possible that the cooling lines
are vibrating causes the four narrow peaks.  At present the cooling lines are merely drawn
over a metal plate which is fastened at one end.  The more rigid mount for holding the cooling
lines might be more appropriate.  However the peaks do not appear to diminish when the cover
of the amplifier is pushed down upon.  Failing that it would be worth looking at the output
spectrum of the pump diodes.