Hi All--

One other item, sometimes "wiggling" the source helps, as mentioned on 
isogeochem earlier.  Apparently the bushing can stick a little, and then 
you don't get a good seal on the inside wall.  Of course if you put the 
spring on backwards, as I am prone to do...but it slides in easier...

take care

gerry

Nabil Saad wrote:
> Andy,
>
> 1- you can use a gold ring more than once, but you need to apply 
> additional and incremental torque beyond the first time use. We used 
> ours twice and it works fine. Beyond the second use, you can double 
> two old ones. You can also buy gold rings from SIS for a fraction of 
> the price that you'd pay for it from Th.... (Will be happy to provide 
> an SIS part #, upon request)
>
> 2- Unprecedented increase in sensitivity in the instance you 
> mentioned, should be commensurate with "unprecedented" high vacuum 
> level. What is the high vac level that person is operating at and What 
> is your 253 High Vac reading now?
>
> 3- Sensitivity/signal intensity depends on the tuning parameters. 
> Thermo recommends setting al parameters at 50% of their max value 
> except for extraction voltage (80%) and then run the . However, you 
> can double your signal intensity by running a manual tune. It requires 
> some patience on your part but it's quite rewarding :)
>
> 4- Also, you might want to turn your CO2 ref gas on and slowly adjust 
> the sulfur window (ion source variable conductance) until you maximize 
> your signal intensity.
>
> 5- The only problem that  the quartz tube connector that channels the 
> flow into the source is when it's cracked. It will definitely turn the 
> 253 "tight source" into an open one and you will lose sensitivity for 
> sure. There is no sweet spot I am aware of, except that the filament 
> has to be well aligned with the window, hence the variations from 
> filament to filament.
>
> Hope this helps,
>
> Nabil
>
> Nabil Saad
> Kinemed, Inc
>
> On Tue, Apr 1, 2008 at 9:57 AM, Andrew Schauer 
> <[log in to unmask] <mailto:[log in to unmask]>> wrote:
>
>     I have been fighting a low signal intensity on our continuous
>     flow, carbon and nitrogen, MAT253 for some time. The source is
>     clean, the filament is new, the capillaries are freshly cut and
>     not crimped, the reference gas pressures are normal, background
>     N2, O2, Ar, H2O signals are low and at a "no leak" level. The two
>     variables I am wondering about both could potentially mis-align
>     the gas inlet port with the stainless steel bush / quartz tube
>     source inlet. One is the gold ring compression after repeated
>     source removal and installs. Two is the rotational "play" of about
>     2 mm in the source once installed into the appropriate keyed spot.
>     I have heard of one instance where two gold rings (one old and one
>     new) were installed and the user obtained unprecedented (very
>     high) signal intensities.
>
>     1) How many times should one use the gold ring?
>
>     2) Do you think the gold ring compression can mis-align the gas port?
>
>     3) Does a "sweet spot" exist within the ~2 mm of rotational movement?
>
>     4) Any other ideas for MAT253 signal degradation?
>
>     Thank you.
>
>     andy
>
>
>     Andrew Schauer
>     ISOLAB
>     Department of Earth and Space Sciences
>     University of Washington
>     Seattle, WA 98195
>
>     206.543.6327
>     [log in to unmask] <mailto:[log in to unmask]>
>
>