I have completed initial tests of the "glasscrusher" foil tension/leak
testing device.  This device was designed to allow gas pressure testing of
cathode foils after they have been attached to the glass plates, and after
the anode wires have been strung.  The apparatus consists of 2 aluminum
plates.  The glass plate is placed on an elevated o-ring on the bottom
aluminum plate.  The top aluminum plate is then lowered onto the glass
plate to form an aluminum/glass/aluminum sandwich.  A 5mm thick stepped up
ring on the top plate pushes on the glass directly over the elevated o-ring
on the bottom plate.  Holes in the bottom plate provide gas inlet, outlet,
and pressure measuring ports.

     Two anode planes from the PPP chamber were tested (3DC0, 2DC0).
During the course of the testing both glass plates were cracked.  The crack
in 2DC0 occurred at the location where the aluminized foil is silver
epoxied to the lamel.  The glue is quite bumpy, and unfortunately is
directly under the "pusher" ring of the top plate, where clamping pressure
is applied against the o-ring.  On 3DC0 one of the citals is cracked, and
the glass plate is cracked from that cital to the inside edge of the glass
plate.  There is some excess glue on the glass plate around the edge of the
cital.  It's possible that if the  glass plate was not positioned correctly
in the "glasscrusher", the clamping rings may have been applied across the
glue or even the corner of the cital.  We are currently investigating
modifications that can be made to the "glasscrusher" and to anode plane
assembly procedures to prevent such problems in the future.

  The foils on these plates had both been tested shortly after they were
stretched and glued to the g-10 rings in May 99.  Their initial foil
tensions were ~ 1.9 lb/inch. From long term tests on similar foils, we
would expect the tensions to relax to ~ 1.4 lb/inch.  In mid April, 2000
the measured tensions were 1.13 lb/inch and 1.17 lb/inch for the two foils,
approximately 20% less than expected.
	It's possible that the lower apparent tension is due to flexing of the
g-10 rings and/or the glass plate caused by the applied differential
pressure.  The calculation converting volume flow and resulting
differential pressure to foil tension assumes that all of the "new" volume
created by the differential pressure is due to the flexing of the foil.  In
the initial tests of the foil/g-10 sandwich, the g-10 ring is clamped
around the circumference ~ 1 cm from the inside edge of the g-10 ring.  The
"glasscrusher" clamps the glass plate at a radius ~ 4 cm further out.  If
the glass plate/g-10 were to flex such that the entire circumference of the
foil was raised ~ 50 microns, the calculation would underestimate the
tension by about 20%.

	The leak/diffusion rate of the foils was measured in 2 ways.  First, the
foil was pressurized to ~ 225 mTorr and then isolated from the atmosphere.
The pressure was then monitored for 3 minutes.  For both anode planes no
change in differential pressure (+/- 1 mTorr) was observed.  This indicates
that any leak must be less than ~ 0.1 cc/min.
	In the second test "pure" (12ppm O2) argon was flowed through the chamber
and the oxygen content of the exhaust was monitored.  The oxygen analyser
used in the test typically requires flows >100 cc/min for reliable
operation.  Unfortunately the maximum flows in these tests had to be
limited to ~ 40 cc/min due to the backpressure of the oxygen analyser
causing the cathode foil to expand out into the anode wire plane.  After
several trials, it was confirmed that with sufficient prior purging of the
"glasscrusher" assembly and the oxygen analyser, repeatable O2 measurements
could be made after ~ 5 hours of gas flow at 40 cc/min.  The first anode
plane (3DC0) indicated an O2 diffusion rate of ~ 0.01 cc/min.  The second
anode plane (2DC0) indicated an O2 diffusion rate of ~ 0.003 cc/min. 
     Our previous measurements (TN-6) of helium diffusion through the 25
micron aluminized mylar suggested we would expect a helium diffusion rate
of ~ 0.015 cc/min per foil.  These calculations assumed a 1 atmosphere
helium external environment, whereas our O2 diffusion measurements only
have a 0.2 atmosphere O2 external environment.  All of the tests on each
anode plane were performed again after the cracks in the glass plates were
noticed.  No significant changes in any of the before and after
measurements were observed.  However, it is possible that the plates
cracked during the first sets of tests.

     Fortunately there are no more anode planes available for testing. 

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