The attached files contain recent results of tension measurements on
cathode foils.

FOIL02DL.PS -

    I realized that I can use my pressure vs time data to calculate the
foil
deflection directly without reference to the tension in the foil.  The
only
assumption made is that the shape of the deflected foil is a paraboloid.

The volume under a paraboloid is given by: V = (b(Pi)r^2)/2 where b =
deflection at center.  Since gas compression is minimal (~ 0.1%), this
must
be equal to the volume of gas flowed into the foil clamp at all times
(assuming no leaks).  Thus we get:  b = (2Ft)/((pi)r^2)  where Ft = flow
X
time flowed = volume.

 I flowed the gas into foil02 at a much lower rate (10 cc/min) and was
able
to get a measured (pressure,deflection) data point at 55 microns
deflection.  The attached file "foil02dl.ps" shows the plotted
deflection
vs pressure for this test.  The result gives me confidence that we can
safely imply the deflection at ~ 10 mTorr from data taken in the range 0
-
500 mTorr.

FOIL02PT.PS -  Shows measured pressure vs time curves over several days
for FOIL02.
    Before March 22, measurements of foil tension and/or deflection
consistently showed decreasing tension (increasing deflection) with the
passage of time.  It appears that the tension in the foil relaxes over
periods of days.   Subsequent measurements on March 24, 26 indicate that
the relaxation ceases after ~ 5 or 6 days, and tension remains constant
thereafter.
    It should be noted that measurement errors are of the order of  2 or
3%, so this tension relaxation is just noticeable above the error
limits.  Also note that higher tensioned foils seem to relax more than
lower tensioned foils.
    These tests will continue over the next few weeks.

FOIL03PT.PS - Shows measured pressure vs time curves for FOIL03.
    This foil initially had a leak rate of ~ 6.3 cc/min which is clearly
visible on the Press vs Time plot.  The leaks (due to insufficient glue
on one of the G-10 cathode rings) were subsequently repaired, and the
final Press vs Time curve on March 26 indicates the leak has been
plugged.

TSTSUM.PS - A tabular summary of all foil tension tests to date.


Robert

Filename: foil02dl.ps

Filename: Foil02pt.ps

Filename: Foil03pt.ps

Filename: Tstsum.ps

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