Hello Wolfram,

Thank you for your assistance.

We did consider an issue with the power coming into the lab but it is routed through a UPS and as far as we can tell the UPS is fine.  That said, if we have an issue with one of the batteries in the UPS it might show up at the mass spec.  We can test this theory by bypassing the UPS.

That said, we found another issue last night.  After the source tripped off in early Dec we tested the Source parameters (e.g., Trap Voltage, Extraction Symmetry at min and max positions) as we were shown in the training course and everything looked OK.  However, yesterday they were not.  The X-deflection min and max positions were normal but when set to the tune position of 4 the value was zero.  There was also some strange behavior in the X-deflection when Y1 and Y2 were fiddled with.  Our current working theory is that there is a short in the source (…possibly one of the leads coming off the x-deflection plates).  However, it is also possible that the board that controls the x-deflection has issues.  And now that I think about it both possibilities maybe correct.  A short in the source could have taken out the board.

We will be taking the source out today and having another look at it.  We are also shutting down the other DeltaPlus and will be playing a game of “musical boards”.  Wish us luck.

Bye for now,

P.S. Your story about the first IRMS lab reminds me of a X-ray diffraction lab I once ran.  The instrument as water cooled and everyday at about 1 pm it would turn itself off because of low water pressure.  The cause … all those toilets flushing as people came back from lunch.

Jennifer McKay
Assistant Professor (Senior Research)
Stable Isotope Lab Manager
CEOAS, Oregon State University
Corvallis, Oregon 97331

On Jan 17, 2018, at 3:02 AM, Wolfram Meier-Augenstein (pals) <[log in to unmask]> wrote:

Hi Jennifer,
You are right, it could be something to do with the source such as two connecting wires being too close or even touching occasionally (thus tripping the source).
BTW, a loss / reduction of signal after source maintenance can occur if the source flange does not sit dead-centre resulting in a partial eclipse of the gas inlet.
However, that doesn’t really explain the “jumpy” beams.  One possible culprit could be a dodgy part on the source control board. Another could be the power supply unit, and yet another could be the power supply to your lab.  Would you happen to know how the power supply to your  lab fits within the bigger picture of the building where lab is housed?  Conversely, if everything was fine prior to December, was there any work down to power supply and the way power is routed in your building that might affect voltage and how free of spikes / brown-outs the power is in your lab?
My first IRMS lab got its power (initially) from a line that also fed the lifts (elevators) and some other heavy-duty users in the building. The effect on our instruments was such we could not run samples during normal working hours.  Beam intensity over time scans looked like recordings of earth tremors.
Prof. Dr W Meier-Augenstein, CChem, FRSC
Stable Isotope Forensics & Analytical Sciences
School of Pharmacy & Life Sciences
The Sir Ian Wood Building
Garthdee Road
AB10 7GJ
From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Jen McKay
Sent: 17 January 2018 00:40
To: [log in to unmask]
Subject: [ISOGEOCHEM] Stability Issues
Hello Everyone,
Once again my EA-DeltaPlusXL system is giving me problems and I’m not sure why.  An iffy power supply is one possibility but I’m not convinced.  Here is the sequence of events … note that the source keeps tripping off:
Late November to early December we cleaned the source, changed pump oil, cleaned the Penning gauge, and fixed an EA problem.
Dec. 10 the source tripped off overnight (voltage off, emission on).  It turned back on OK but no beams.  Played around with the tuning and got my beams back but the sensitivity did not recover until the next day.
Stabilities were fine so I ran some N-only samples for a few days.
Dec. 17 the nitrogen backgrounds and reference gas signals were too low.  Decided to rebuilt the source using all new ceramics and replace one of the x-deflection half plates because it had a dent (…not sure how you dent one of these but that’s what it looked like).  Made darn sure there were no bits of metal stuck to the source magnets.
Dec 27 sensitivity and stability were OK.
Jan 3 noticed that the water background was really low and beams were a bit jumpy.  Started a run of tests any how.  Sadly this run failed because the source tripped off (…as it did on Dec. 10 prior to the source clean)
Jan 4 the source turned back on OK.  Stabilities looked good even though the beams were jumpy and water was still low (...but not as low as it had been because I had bypassed the He purifier).  Restarted the run of test samples and the results looked fine.
Jan 5 and 6 was able to run some N-only samples .  No problems.
Jan 7 the sensitivity was low so I retuned.  Beams still jumpy.
Jan 12 the stability has gone to “heck”, beams really jumpy.  Retuning (increasing Extraction Symmetry and decreasing X-deflection) seems to help but it only lasts a few minutes.
Jan 15 the source tripped off again but turns back on as per the last two times.
Jan 16 same problems as the 15th but in the process of troubleshooting I turned the source off and on and lost my beams.  Found them again by changing from CO2 to N2.
My best guess is that I have charging in the source.  Anyone have other ideas?  If not, I’m pulling the source out again.
Bye for now,
Jennifer McKay
Assistant Professor (Senior Research)
Stable Isotope Lab Manager
CEOAS, Oregon State University
Corvallis, Oregon 97331


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