Re: Re-introduction to the group


Chuck Harris
 

It would be cute, but inexpensive it wouldn't be.

It would essentially need all of the HV and deflection
stuff from an oscilloscope, and then probably a
computer to collect and display the data.

These days, schools are ditching all sorts of experimental
artifacts from yesteryear, and using computer simulations
for everything.

Look at circuits class. The lab is to have the kids sit down
in front of a computer simulated plug board, and stick simulated
packaged parts into the simulated board, and watch the result
of a spice like program. The whole thing is open source if you
want to play with it... though I cannot imagine why anyone would.

A local recycler received tons of discarded equipment from the
physics biology, and EE labs of East Coast schools a few years
back. Microscopes galore, meters and bridges, teaching
demonstrations, chemistry glassware, ... you could start a
major university with all the stuff they got.

I still have a globe from a student physics experiment used to
measure the charge and mass of the electron. I couldn't bear
to destroy it. Its 3 dozen mates went to scrap glass because
they couldn't find a single school that wanted them, or any of
it for that matter.

-Chuck Harris

Brad Thompson wrote:

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--

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