Good Electron Beam Generator Source?

I've seen electron guns salvaged from old television CRTs re-used as a source of electron beams, however, this is not usually something that an amateur is equipped to accomplish.

I'm sure that you already realize that the mean free path of even a very energetic electron beam in air is amost negligible, hence you need a high vacuum environment to generate, focus, deflect and contain the beam. Typically in addition to a practical working knowledge of electronics and physics, this requires combined skills and equipment for glass blowing, machining, and high vacuum technology to produce just about any electron beam generation and experimentation apparatus.

Certainly some amateurs have accomplished this (see the 1950s Scientific American "The Amateur Scientist" columns for some examples of home constructed ion and electon beam apparatus. I'm not aware of much on the subject being published in the popular literature much after that era.

If you enjoy a good technical challenge, and have the time available (sometimes measured in years) to pursue, home construction of ion or electron beam apparatus could be an interesing hobby.

A simple alternative for experimenting with electron beams would to purchase a surplus 3-5" electrostatic deflection CRT (such as those used in early oscilloscopes. CRTS like the 5BP1 or 5BP4 are still readily available from specialty dealers at relatively small cost. These offer the added advantage of having a luminescent phosphor that allows you to observe and study the effects electrostatic or magnetic deflection and focusing have on the beam.

Hope this helps.

Harry C.

News2020 seems to have plenty to say on the subject. :o)

well you did say "All Replies Welcome" !!!!!!!!

Tom

Greetings.

A trifling comment regarding your recent post:

On 30 Jan 2004 13:57:28 -0800, snipped-for-privacy@yahoo.com (Harry Conover) wrote: [snip]

[snip]

Apparently not. While I'm wholly unqualified to debate the properties of electrons with you, I am aware of the infamous Therac-25. (See

The Therac-25 was alleged to be the most deadly medical radiological device ever, and the first device with literally deadly software bugs (although the hardware was pretty pathetic too, AFAIK). Since its modus operandi was to fire an intense electron beam at randomly selected patients, apparently electron beams will travel some distance in air: certainly farther than some patients would have preferred. :-( Of course, the Therac-25 just might have been more powerful than your typical 5" 'scope CRT, so the points you raised are doubtlessly valid.

Cordially, Richard Kanarek

Agree, but even with the Therac-25's 25 million volt electrons, the mean free path of its electrons in air was only a few inches. Ion beams, with their comparatively massive particles, are quite another issue.

Harry C.

Tom, I read and post using Google. This "New2020" must have his posts set to "no archive" because they never appear here. Am I wrong in taking this to be a good thing? :-)

Harry C.

Just an afterthought: Methinks that you are selling yourself a bit short.

As a physicist/engineer that began his career in the design of high energy particle accelerators, I find things like the basic physics of electron and ion beams to be simple compared to the design of a complex analog electronics circuit or the proper way to configure a network!

The difficulty of penetrating air with an electron beam stems from the incredibly low mass of an electron. Consequently the momentum of an electron, unless accelerated to nearly stellar energies, is generally incapable of doing anything but scattering when it collides with a molecule of the elements comprising air. Its a bit like trying to play pool using spec of sand as your cue ball, but more extreme!

By contrast, in a vacuum there are few molecules available to impede the electron beam. For this reason, most practical electron beams exist in a high-vacuum environment such as in a CRT, a vacuum system, or even space.

Harry C.

On 31 Jan 2004 08:18:05 -0800, snipped-for-privacy@yahoo.com (Harry Conover) Gave us:

Hahahahahaha..... Yeah... it's a good thing.

I think you, Mr. Conover, are being far to generous in your estimation of others (certainly me, any), and too conservative in your appreciation of your own accomplishments. Since being overestimated is a new, different, and not entirely offensive experience for me, I shall not complain.

Cordially, Richard Kanarek

On 31 Jan 2004 08:36:48 -0800, snipped-for-privacy@yahoo.com (Harry Conover) wrote: [edited for space]

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