Q (K. Mitev):
Have you studied the influence of the pressure (for a given detector system and
for a given gas mixture) on aging? If you have made such studies, is there a
correlation between the concentration of the impurities in the working gas
(outgassing, silicon contamination, other possible contaminants) and the
working pressure?
A (M. C.):
No studies for different pressures. We have always performed the material tests
and irradiated the detectors at atmospheric pressure.
Q (J. Va'vra):
A small comment on your excellent talk. People involved in RICH detectors
used gas systems compatible with the semiconductor industry cleanliness
requirements. (RICHes either at DELPHI or SLD). Perhaps people planning future
experiments should contact people involved in construction of the RICH
systems. There was a wealth of knowledge. It appears that the needs are
becoming similar (stainless steel tubing, VCR fittings, bellows valves, filters etc.)
Note: of course the RICH experiments did it because of the use of TMAE, i.e. not
because of aging. However, the new experiments seem to be drifting into
the same direction.
A (M. C.):
I agree completely on the fact that knowledge has to be transfered in
this case, based on the experience of the existing RICH detectors.
It should be taken into account that at least for ATLAS/TRT, we are
also concerned by the price of the material, so we are trying to find
semiconductor quality at reasonable prices. We have found that
American companies seem to offer equipment at lower prices.
Q (G. Passaleva):
How significant is an accelerated outgassing test considering the final
detector operating conditions may be different?
A (M. C.):
Honestly, the scaling factor is unknown.
Q (G. Passaleva):
There are many sources of pollution but probably not all of them are
relevant for the different detectors, radiation conditions, gas mixtures etc. Are
there systematic studies on what pollution source is relevant for which
detector or class of gas mixtures, etc.?
A (M. C.):
Well, most of the results presented in my talk were carried out with a
particular goal: assembly materials for MSGC's under Ar-DME, others for the
assembly of straw tubes for ATLAS, which will run under
Xe-CF4-C02. So some
statistics for some particular cases do exist.
A clear example of pollution relevant for a detector, is data presented for
DME and the effect of < ppm pollutants on aging.
