Date: Wed, 15 Sep 93 16:03:26 CDT
Subject: Re: Beam allignment
From: "Ray Guillemette"

John,
I believe that the problem Will discussed with John Valley was indeed the
support limiter assembly problem that I told you about last spring. We have had
earlier,much less serious problems that have affected our column alignment. The
various causes of these were at different times:
- an improperly seated graphite column liner tube (with aperture at base)
- an improperly seated anode cap (cap fitted so tightly that it could not be
seated properly, resulting in the aperture below the anode cap being slightly
out of center; this was fixed by sanding the base of the anode cap assembly)
- the lower of the 2 apertures in our original (factory-shipped) regulation
assembly was inverted

These problems generally caused us to have difficulty in getting "gun auto"
to work properly in aligning the gun. I could usually obtain a satisfactory
(although not perfect) alignment by manually adjusting the gun controls to
maximize beam current.

I had not heard that Dave Pierce at UC Santa Barbara was working on getting
an SX50 users group organized. I would definitely be interested in being an
active part of that group.
Regards,
Ray

FYI: I should also be reachable via e-mail at my internet alias of
microprobe@tamu.edu


Dr. Renald N. Guillemette (rng5840@geopsun.tamu.edu)
Electron Microprobe Lab
Dept. of Geology
Texas A&M University
College Station, TX 77843-3115