Isotopers,

We are cleaning and refurbishing the source on our FMAT Delta Plus XL after having some problems with a growing H3 factor and emission. We pulled the source to clean the ion box and plates and noticed that the third quartz insulator was chipped on each side.  We order replacement insulators from FMAT and some of the replacement parts that we received,  much to our surprise, were ceramic and not quartz.  In our MAT 251 we changed out the original ceramic insulators for quartz and have been very happy with faster pump down, lower backgrounds and increased sensitivity.  I thought all new Deltas were supplied with quartz insulators in the source as well.

So my question to the list is how important is it to have quartz spacers in the source of a continuous flow instrument (as opposed to ceramic spacers)? I know that quartz insulators are more fragile than ceramic over the long haul, but less prone to contamination.  I was surprised to see how clean the plates and ion box in the Delta source was after ~75,000 analyses.  But I've been down the ceramic insulator road before, and have been more happy with quartz insulators at least in a static instrument.  I would appreciate comments especially from anyone running hydrogen and carbon monoxide.

Thanks,
Bill

William J. Showers
Dept of Marine, Earth & Atm Sciences
Box 8208
North Carolina State University
Raleigh NC 27695

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