Hi Andrew,

It seems like the heating is making the source gasket seal tighten and the
cooling causes it to loosen and produce a slight air leak.

Mark

-----Original Message-----
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
Of Andrew Schauer
Sent: Tuesday, March 10, 2009 12:35 PM
To: [log in to unmask]
Subject: [ISOGEOCHEM] MAT253 Heater Background interaction

Hi all,

I have observed high backgrounds on our MAT253 for masses 28 and 29 (conflo,
EA) that drop very quickly upon turning the Analyzer heater on. This is the
heater that takes hours to heat the entire block of metal up surrounding the
source. The drop I observe starts seconds after turning the heaters on (NO
OTHER HEATERS TURN ON). On the outside of the metal block, heat is barely
detectable by touch. When no heat as been applied for hours and the entire
flight tube is at room temperature and I heat the same area where these
heaters are located with a heat gun, I observe the opposite. Backgrounds go
up. Here is a jpg of the trace I captured today.

http://depts.washington.edu/isolab/temp/090310_heater_background_drop.jpg

Vacuum doesn't measurably change. The heaters are located toward the magnet
and adjacent to the main turbo. If I leave all heaters on over a weekend,
turn all heaters off and allow the system to return to room temperature, the
background come back up. Any thoughts? Thanks.

 Andrew Schauer
ISOLAB
Department of Earth and Space Sciences
University of Washington
Seattle, WA 98195


206.543.6327
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