Q (A. Krivchitch):
You reported that no aging effect was observed up to 20 C/cm at 5
muA/cm. According to our data, under these conditions the gas gain in
the center of the irradiated zone drops more than 10 times compared to
the nominal gas gain (25000) you need. Haven't you made an optimistic
statement in your talk?
A (A. R.):
It is correct that at 5 uA/cm the gas gain is much less at the middle of
the irradiation area. But the goal of the tests with such a current was
to make the comparison between different wires as fast as possible.
We actually see the largest wire damage at the edge of the irradiation zone.
This area was used for comparison.
On the basis of these tests we have chosen the best wire candidates.
We don't think that it is a very important issue for such a kind of test
because if we don't see gold damage at high current at the edgges of the
irradiated area we don't see it at any current.
But anyway, the final validation has been carried out at different conditions
including tests at 1 uA/cm.
Q (H. Kolanoski):
Did you make aging tests (gold etching) at water contents as low as 20 ppm?
Did you see an effect at this water concentration?
A (A. R.):
Yes, we have done tests in a wide range of H2O concentrations between 20
and 2000 ppm. No gold damage was found up to 10-20 C/cm.
Q (J. Vavra):
1) Since it appears that the wire damage happens due to an interaction
of CF4 & H20, did you try to run without
CF4?
2) From your curve it would appear that the small high-rate tests
would always "prefer" etching and therefore they would offer more
optimistic results than low rate tests. (especially for the real detectors)
A (A. R.):
1) It was our plan to do these tests but they were not performed because of lack
of time.
2) Yes that is absolutely true, particularly for CF4 containing gas mixtures.
Q (M. Capeans):
On the CF4 etching-polymerization balance: It not only
depends on the gases accompanying CF4, but you suggest that this
balance depends on the ionisation current. How can you control this
balance in a real experiment, where the ionization current is not
uniform over the full area of the detector?
A (A. R.):
This balance is not what we should rely on in a real experiment. I would
think that we should keep the Si-concentration below the limit at which polymerization
appears.
Q (M. Hohlmann):
Do you have some understanding of the differences in wire production by
different manufactures that produces the difference in etching and peeling
behaviour of these wires?
A (A. R.):
I hope, yes. The most important issues are quality of the gold adhesion,
gold thickness (>0.5 mu m), no Ni substitute for gold, no damage of gold
plating.
Q (M. Titov):
What was the largest irradiation area or wire length, which stayed under strong irradiation
up to 10 or 20 C/cm?
A (A. R.):
Up to 2.5 cm.
