Re: Re-introduction to the group


Brad Thompson <brad.thompson@...>
 

On 2/22/2018 9:52 AM, Chuck Harris wrote:
As was stated earlier, TEM and SEM are abbreviations identifying
two types of electron microscopes: transmission, and scanning.
The fundamental difference is whether the electrom beam passes
through the sample(TEM), or is reflected off of the sample(SEM).
They are exciting combinations of a whole bunch of "boy toys":
<snip.

Hello, Chuck and the group--

If anyone Out There has access to CRT fabrication and has
free time to investigate things, here's an idea (*) for an educational
science gizmo. Please note that I am not a knowledgeable SEM
engineer, and indeed my only contact with an SEM involved getting
images of a cat's whisker (**) ( long story).

Suppose that you built an electron gun and deflection-plate structure
much like what you'd find in a typical CRT. Instead of a phosphor
screen, permanently attach a target (e.g., a coin or metallized biological
specimen). Add a collector surface to the inside of the tube's envelope
and evacuate the tube.

The support electronics comprise beam-focus and intensity controls
and X-Y deflection of the beam.

In operation, the target gets scanned by the CRT and the collector
accumulates electrons reflected from the target at a given beam position.
Image-processing circuitry digitizes and formats the image and presents
video to a display.

The goal would be to create an inexpensive mass-produced teaching aid.
Having a fixed target in a sealed envelope eliminates the need for a vacuum
pump.

Comments of an educational nature are welcome.

73--

Brad AA1IP
(*) Like many ideas, this one's partially baked.

(**) The whisker in question isn't an RF detector. It's a whisker
from an actual cat.

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