A few nights ago I attended a lecture by an MIT geologist on geochronology (dating of rocks). He spent a fair amount of time discussing analytical dating methods based on mass spectrometry but he had some micrographs of zirconia taken using cathodoluminescence (CL).
I think most everyone is aware that certain minerals will glow under electron bombardment, much like they do under UV. Phosphors are another example of excitation by electrons.
I did a bit of research into CL and found that there are two main methods. One uses a vacuum stage with optical window. A vacuum pump exhausts the stage and a side mounted electron gun (hot or cold cathode) bombards the sample with electrons. A microscope is used to view the sample. This is optical CL.
The other uses a stage that is placed within a SEM. A photodetector picks up optical radiation from the sample as it is scanned.
The equipment for optical CL seems to be straightforward enough for amateur construction. (Commercial stages with the associated power supplies seem to be in the $20k and up range.)
Follow this link to a drawing of the Luminoscope's stage:
http://serc.carleton.edu/images/research_education/geochemsheets/coldcathodeclsystem.jpgBasically the beam is established in a discharge tube where the electrons exit an aperture and come into the viewing chamber parallel to the stage. A pair of magnets are positioned on the top of the stage and are moved around until the beam deflects 90 degrees with some uniformity and are then clamped in place. In this one, the samples are brought in through the side. A photo can be found at
http://mineralsciences.si.edu/facilities/cl.htmYou can see the two magnets that are clamped to the top surface.
CITL has a similar cold cathode device but the gun is positioned at maybe a 30 degree angle from the plane of the stage. Not sure if there's further deflection - it may be ok for polished samples. The manual is at
http://www.citl.com/manualsetc/cl5manubeta1.pdf.
Page 8 of the manual has a picture of the gun. It's basically a throwback to the cold cathode guns of the late 1800s.
In making up one I was thinking of using an old KF50 adapter that I have kicking around. I could mount it on a flat plate and use an optical window for the viewing side along with a modified KF50 center
ring. Atmospheric pressure would hold it in place. The gun would be mounted to one side port and the vacuum manifold (pump connection and needle valve) to another. It might be easier to use electromagnets with pole pieces that come into the chamber on either side of the ebeam.
