From CRT to Electron Gun

6 10 2011

This post is dedicated to Steve Jobs. Hero, and inspiration to all.

All photos.

I bought a second CRT; broke the vacuum by drilling an unused pin; scored it and smashed it!

Now we have an electron gun:

I installed it in the chamber and wired it up:

Here you can see down the beam line to the hot cathode.

I taped a piece of broken phosphor screen on the viewport so I can see the electron beam:

But something is not working, no beam.

Time to troubleshoot.

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Date : October 6, 2011
Categories : Electron Gun

11 responses

6 10 2011: kcdodd (20:29:52) :

Look up oxide-coated hot cathodes, which are sensitive to being exposed to air.

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6 10 2011: Mark Suppes (20:40:38) :

The cathode was not heated in air.Although it was exposed to air at room temp.

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6 10 2011: yonemoto (20:45:45) :

Taped to the inside or the outside? You sure those electrons are getting through the viewport?

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6 10 2011: Mark Suppes (20:47:10) :

It’s attached so the electrons would directly hit the phosphor powder.

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6 10 2011: yonemoto (20:51:49) :

is the phosphor powder oxygen senstive? This guy uses fluroescent lamp powder:

http://www.sparkbangbuzz.com/crt/crt6.htm

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6 10 2011: yonemoto (20:47:57) :

oh nm, it’s obvious from the pics.

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6 10 2011: Steve (21:56:52) :

You need a positive connection to the phosphor, It has a conductive coating, otherwise the coating / conductor charges negatively and repels the incoming electrons. Perhaps copper tape would make the best connection.
Steve.

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7 10 2011: tomschuring (04:00:08) :

i always thought the front of the screen ‘pulled’ the electrons to it via a grid once the were focussed by the electron gun.

on the inside of the screen there should be a conductive grid, and the holes in the grid is what you see on a tv screen as ‘pixels’
not 100% sure though

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7 10 2011: MikeH (18:48:09) :

I was curious about this problem so i did some websurfing. While I didn’t find an answer your quandary, I did find an interesting website, which I am passing along in case you didn’t know about them. No idea of the $ involved in having a electron gun made for your application, but maybe an engineer at the firm would be willing to help you troubleshoot your improvised solution.

http://www.kimballphysics.com/electron-gun-systems/technology/product-overview

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13 10 2011: Remy Dyer (20:16:26) :

Hmm. What vacuum are you getting?

I’m not sure about the exposed insulation and heat shrink – might they outgas enough to add a virtual leak?

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5 12 2011: Just Look at this Print « Prometheus Fusion Perfection (19:20:07) :

[…] I tesed out the electron gun and I didn’t see a beam on the phosphor. I wanted to rule out the possibility that there WAS […]

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