Summary of the stylus data

The motions of the wire measured by the stylus at various places
relative to the wire oscillation amplitude

    conditions                 x(stylus)/x(wire at middle)
   ------------               ---------------------------
On BK7 prism with groove        9.5 x 10^-3  @ 292 Hz
no aluminium prism

On wire 1cm below BK7 with
groove, no aluminium prism      4 x 10^-3    @ 292 Hz

just below grooved 
Sapphire prism with 
aluminium prism                 1 x 10^-3    @ 293 Hz

grooved sapphire prism, 
just above aluminium prism      8 x 10^-4    @ 293 Hz

grooved sapphire prism,
just below aluminium prism      5 x 10^-5    @ 293 Hz


This is the relevant data that shows:

1) The double prism arrangement reduces the
coupling of motion to the test mass by a factor
of about 80 in amplitude.


2) Not shown in the table but seen in the figures, 
the up conversion above the wire drive frequency 
is about 10^-4 (x(f)/xrms drive(delta B) ~ 2 Hz)
between the test mass and the prism when there is
no aluminium prism. With the sapphire and aluminium
prisms in place the up conversion measured on the wire 
between the test mass and the aluminium is not visible,
x(f)/xrms drive ~ 10^-6 or smaller.

Note: If one wants to compare the up-conversion to the
actual wire motion at the middle the numbers are even
smaller. For the case without the second al prism
x(f)up-conversion/xrms wire < 10^-7 deltaB = 2 Hz
For the case with the sapphire prism and the alumnium
prism  measured between the aluminium prism and the test
mass
x(f) up-conversion/xrms wire < 10^-9