This sounds a bit like a tuning problem in the Bauer-Signer source. Have
you gone through the entire source tuning procedure (including using the
electron repeller as a trap)?
In <[log in to unmask]>, on 11/21/02
at 04:34 PM, Richard Spikings <[log in to unmask]> said:
>I have developed a problem with peak shapes on our MAP 216.
>The ms was performing well earlier in the year. I then did some servicing
>to the extraction line (during which time the ms was not turned off but
>kept isolated and evacuated) and we started doing blanks etc again this
>week.
>Two strange phenomena are occuring:
>1. Continuously scanning blanks through 1.2 - 1.4 MF units yields a
>peculiar pattern on the multiplier. Some scans are as expected, with
>peaks appearing at the expected MF, with normal intensity. However, other
>scans are extremely noisy, masking out the peaks. There is no regular
>cyclicity to the noisy and clean scans.
>2. Analysis of air-shots produces sharp, flat-topped peaks at 36 and 38
>with expected amplitudes. However, 60% down the 40Ar peak (from max
>value) the peak widens dramatically (hundreds of percent) and spans
>approximately 0.1 MF units, masking the 39Ar peak. The peak is also
>asymmetric and is scewed towards the lower MF side.
>The extraction line has been baked and is sitting at 9E-10 - 1E-9 torr so
>we do not suspect any contamination problems from the line.
>Any comments would be appreciated.
--
Chris M. Hall, Assistant Research Scientist
Dept. of Geological Sciences, University of Michigan
Quando omni flunkus moritati
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