Hi Greg

Sounds that you might have a trap to source short or there is some 
resistance between the two.
Can you check with the source OFF, the resistance between pin 1 electron 
collector (Trap) and pin 2 the source block (Box) on the outside source 
feed-through flange?
On the 253 here it is giving an open circuit so if you are seeing a low 
resistance you could get a maximum trap current.

Regards

John


John Hill
Mass Spectrometry Facility
University College London
Chemistry Dept.
20 Gordon St
London
WC1H 0AJ


kpesil wrote:
> Hi All,
> 
> A bit of a freak accident took place last week on one of our 253s. A
> loose nut on the needle valve allowed a sudden rush of atmosphere into
> the source while everything was on. It was only for a couple of seconds,
> but now my Box and Trap values are 0 and 2.00 mA respectively, where
> they were 0.7 and 0.8 previously. At first thought, I'm thinking the
> cathode has been damaged in some way. So I've changed that with a new
> one from Thermo, and refocused everything, yet still those same funny
> box and trap values remain.
> 
> I can't say this has ever happened to me. Any thoughts out there as to
> what might be happening?
> 
> Cheers
> 
> Greg
> 
> 
> Gregory Cane
> Laboratory Manager
> KPESIL-Keck Paleoenvironmental & Environmental Stable Isotope Laboratory
> University of Kansas, Dept. of Geology
> Multidisciplinary Research Building
> 2030 Becker Drive, RM 130
> Lawrence, KS
> 66047
> Tel: 785-864-7750
> Fax: 785-864-1906
> 
> 
>