HI Zac--

Not to have you pull the source again, but...

-- Source magnets???  The can be easy to turn around...
-- One of the feed throughs is caught under a spacer (Delta Series?) 
???  Make sure the source is tight--and it looks like you did that...
-- cleaning include sonication??? (not the magnets) 

take care

gerry

p.s. you may want to try Paul Eby's suggestion (peak jump stability 
thread) and re-do the mass calibration.  Make sure the HV is up where it 
should be before you start.
p.p.s. if you have a high voltage meter, and don't mind electrocuting 
yourself, you could monitor the voltage for the Y-deflection on the 
board-see if it changes when you move across the range.  (be careful)  
They should float on the HV setting, so you could try at a lower HV (say 
0.8KeV) first.

Zachary Atlas wrote:
> Dear Isogeochemers,
>
> We were having problems getting dD in the past but CO2 was OK.  So we 
> just ran CO2 and postponed any hydrogen analyses until we could 
> diagnose the problem.  With this in mind, last week the filament blew 
> and we took out the source which was very dirty and cleaned it. Upon 
> reinstallation we had a number of issues.  1) box and trap currents 
> were mismatched.  We re-adjusted the filament in the ionization 
> housing to be center and this fixed that issue but we still get only 
> ~1/2 the intensities we should get on CO2 (44, 45, & 46) running the 
> gas bench at our normal 1 bar pressure.  Peak centering shows lopsided 
> peaks and focus doesn't fix the low intensity issue.  Ran scans on 
> x-focus, y-deflection, extraction, etc vs. intensity and found that we 
> see no peak on the y deflection 1 (it starts high on 0% and goes down 
> from there).  Y-deflection 2 is near flat line with only very slight 
> increases with %.  Extraction is the same but in the opposite sense 
> (peak top at, near or above 100%).  Pulled out the source 3 times and 
> all looks ok.   Re-adjusted the plates to be in the best alignment my 
> eye could tell, checked all leads and connections but this did not 
> solve our problem.  Did manual tuning and can pull the Y-Defl. peak in 
> somewhat but best focus is still achieved at Y deflection = ~5% or 
> less.  I think this issue has to do with the y-deflection having 
> improper voltages going to the y plates but am unsure of any other 
> possible causes.
>
> We cranked the CO2 pressure up to 2 bar and are able to get 4000 mV on 
> 44, ~4800 on 45 and ~5600 on 46.  Stability is ok but we still have 
> some drift over time.  However sample peak height is still about 1/2 
> what we normally get for CO2.  We suspect this is what was also 
> causing poor results for H analyses and that due to Y-Defl. having to 
> be pulled to one side we may be missing the cup-
>
> Thoughts?  Any assistance is appreciated.
>
> Thanks
>
> Zac Atlas
>
>
> /
> /"Do not follow where the path may lead./
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> /-Wise fortune cookie-/**
> * *
> *Zachary D. Atlas, Ph. D.*
> /Associate Research Scientist/
> /Center for Geochemical Analysis/
> ----------------------------------------------
> University of South Florida
> Department of Geology
> 4202 East Fowler Ave, SCA 528
> Tampa, Florida 33620
> Tel: (813) 974-6419
> Lab: (813) 974-5842
> Fax: (813) 974-2654
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>
> On Apr 24, 2009, at 2:02 PM, Paul Eby wrote:
>
>> Sergey,
>>
>> I had a similar problem recently that I was able to correct with a 
>> fresh mass calibration.
>>
>> Paul Eby
>> University of Victoria
>>
>> At 12:29 PM 4/22/2009, you wrote:
>>> Hello List members,
>>>
>>> I have a question related to poor d18O precision on our TCEA-IRMS 
>>> system. In our
>>> lab the TCEA is hooked to a Delta V and used for water and solid 
>>> samples.
>>>
>>> The del2H and del18O are fine (low drift, low memory effect between 
>>> samples, low
>>> SD) when I run a water sample separately for each element (no peak 
>>> jump). The
>>> first time the syringe injects a sample the software monitors only 
>>> H2.  For the
>>> second injection after the peak centering Isodat monitors only O2.
>>>
>>> When I try to combine both measurements in the same run (with peak 
>>> jump) the
>>> del18O becomes unstable (SD=0.5 and higher). I do not see any 
>>> difference between
>>> the oxygen sample peaks with and without peak jump ­ the same 
>>> backgrounds,
>>> shape, height, area, HV, magnet steps. The peak jump file is fresh. 
>>> The only
>>> difference is 29 mass peak centering and the elimination of the 
>>> cycling of the
>>> electromagnet when I run without peak jump.
>>>
>>> Does anybody have experience with a similar problem or have a 
>>> suggestion for how
>>> to explain/fix this?
>>>
>>> --
>>> Sergey Oleynik, PhD
>>> Dept. Earth and Atmospheric Sciences
>>> Purdue University
>>> 550 Stadium Mall Drive
>>> West Lafayette, IN 47907
>>> Phone: 765-494-3274
>>>
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>