Modifying the tel-x-ometer to take better radiographs.
By Leslie Wright
Safety.
X-rays, are downright dangerous! Read this guide first!
The Tel-x-ometer.
I managed to aquire quite cheaply, a used Tel Atomic `Tel-X-Ometer" lab x-ray machine. This is about as safe as you can reasonably expect an x-ray machine to be, as the maximum kVp of the tube is a mere 30kV, and the beam current is around 50uA.
The top cover is manufactured from Chlorinated plastic, and reduces the radiation to undetectable levels.
The reason I bought this, was I thought it would be fun to try and make
some radiographs with it. I had already surmised that the exposure
times would run into multiple minutes.
The first radiograph I took was somewhat dissapointing, as at almost 8
inches from the tube, the beam is only 1 inch in diameter, and the
exposure time was on the order of 55 minutes, to produce a visible
image!.
Of couse, moving the film to aroud four inches, should reduce the exposure time, by a factor of 4 (inverse square law), but the beam would be far too small to be useful, for all but the smallest subjects!
As the instrument, is designed to be used as an x-ray spectrometer, the beam is collimated, and thus the diameter is reduced to about 2mm, by a heavy copper instert, glued into the lead glass shield surrounding the tube. Since I wanted the instrument to still function as a spectrometer, I decided that the collimator, should be replaceable after my modification.
First of all, the lead glass dome was carefully removed. It is released from its base by means of two locks, which can be opened with a screwdriver. The collimator is glued in there very well, but with a combination of attacks with varoius solvents, and some careful levering, I managed to extract it. I did manage to crack the lead glass dome though, which was unfortunate, but it was carefuly glued back together, and the radiation leakage from the joins, is undetectable.
When the dome is reinstalled, the aperture is now ~10mm, and the beam diameter at 8 inches is a much more useful 4 inches, the collimtor, once cleaned of surplus glue, is still able to be inserted into its original hole, if need be.
Next, since I will be using raw film in the device, it is necesarry to eliminate the light from the filament, and lamps. The dome was removed again, and repeatedly sprayed with several layes of flat black paint, and the aperture was covered with a thin layer of black light tight plastic, and re-installed. The two bulbs, for power on, and x-rays on, were also removed. The machine was then switched on in total darkness, to detect and correct any other light leaks (mostly from the base of the lead glass dome)
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Copyright © 2007, Leslie Wright, All Rights Reserved.