[RASMB] intensity issues

[Borries Demeler]

Dear Colleagues,

I have an issue with an XLI at FSU - it has a strange problem with
intensity. First, it is very low, and second, it has a regularly spaced 
intensity oscillation. Please see the attached image. It was generated
by scanning a channel containing just water in intensity mode and 
averaging the intensity in the flat region over all points. The plot
shows the average intensity of the scans over a number of scans. The
entire run shows this consistent intensity fluctuation, and it is 
apparent in all cells. The run was done at 50,000 rpm. Does anyone
have a good suggestion as to what flaw in the XLI could potentially
cause such a pattern? Is this a lamp firing issue, or a voltage issue
with the PM tube or flash lamp? The machine was just newly installed
and configured by Beckman service, and this is the pattern it produces.

Thanks, -borries
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