Thanks for the tips.  I managed to located a couple of leads in the source array that were touching and thus providing a lot more power to the trap than it was supposed to get.  This resulted in the high trap readings.  I think I have it all straightened out now!






From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Tao Sun
Sent: Wednesday, July 14, 2010 12:16 PM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] High box and trap currents


Hi, Christine,

   We had similar ,but opposite symptoms couple weeks ago. We changed a new filament for our MAT253, but the sum of trap and box currents were far lower than the emission, e.g. 0.6mA, 0.4mA-->1.5mA. Days later, things got better that we can have trap+box =emission when we set emission lower than 1.8mA. However, that was under the condition that no sample gas got into the ionization housing. When we load gas in, trap+box do not equal emission! What we did was replacing this filament with old, but working one. Then everything turned back to normal. We request a return of that filament, however, we are still trying to do diagnosis on it. Maybe the positioning of the filament? some deformation of the filament shape? I'll keep you updated if we find out anything.
  Good luck.

Tao Sun

Louisiana State University

On Wed, Jul 14, 2010 at 10:53 AM, France, Christine <[log in to unmask]> wrote:

Hello Isogeochemers,


I recently cleaned the source and replaced the filament on my Delta V Advantage.  The original symptoms included jumpiness and variability in the box and trap over the last couple weeks leading up to a complete loss of emission and a trap value of 0mA.  I pulled the source, cleaned everything, and installed a new filament.


When I turned it on my box reads 1.5mA and my trap also reads 1.5mA.  I am seeing an emission signal, but these values are much higher than the expected 0.7-0.8mA range.  I’ve dealt with issues where my box was 1.5mA and the trap 0 due to a short in the source, but I’ve never seen them both so high.  Could this be due to a similar cause (i.e. a short or leads touching in the source array) or am I dealing with something completely different?  Naturally my vacuum came down quickly and it looks great – I’d hate to break vacuum again unless I absolutely have to.  Any advice would be appreciated.