Hi all,
We are trying to find a better compromise for the filament
lifetime/sensitivity on the MAP215 at Caltech. To get high He sensitivity,
the filament has been run with the trap current regulated at 500 microA for
the last 5 years (2.5 - 2.6 A on the filament); however, this has
necessitated changing the filament every 12 months or so. This is fine for
running just He, but is not an effiecient way to run for Ne as it can take
3 months to get CO2 down to operating levels.
I would be interested to hear the experience of the Noble gas network re:
filament operating conditions and the lifetime of the filament. If
listmembers could email me (NOT the list) to save repetitious emails
flinging around, I promise I will summarize the info and re-post it to the
list. Please send me details of how long your last filament lasted, the
approximate filament current, the regulating trap current, and whether it
was a homemade filament or supplied by VG/Micromass/MAP. And any other
information you might have that could relate to the filament lifetime (e.g.
construction, wire type etc) will also be good. I'm primarily interested in
Nier-type sources, but will collate the info from Baur-Signeur sources for
the benefit of the list.
Pete
______________________________________________________________________________
Dr Pete Burnard
Division of Geological and Planetary Sciences,
California Institute of Technology MS100-23
Pasadena CA91125
USA
Tel: 626 396 3872 Fax: 626 683 0621 Website:
http://www.gps.caltech.edu/~peteb
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