Talk:Electron gun

What would happen if one were to cut open a CR or Röntgen tube, turn on the electron beam at normal power, and then point it at various objects? Could, say, a TV be turned into a weapon? This concerns working the tube in and out air, as after letting the air through a large hole in the tube first or cutting only picoscopic holes in the tube to let electrons through but not molecules. lysdexia 10:57, 22 Oct 2004 (UTC)

The mean free path of electrons in atmospheric pressure is very very small. This means that you will not get a sizeable electron beam even a few nanometers away from the source. Don't forget, high energy electrons are simply beta-particles.

To my knowledge, the effective range of beta particles in air is ~1 Metre. —Preceding unsigned comment added by 81.159.66.56 (talk) 00:05, 9 March 2008 (UTC)

Is it possible to weaponize old junkyard electron guns out of CRT monitors into harassment weapons???

I've been hearing strange rumors that a certain group of unethical engineers have been going around and secretly installing the electron guns from out of CRT monitors behind the walls of other people's offices to harass them while working. Is this possible? I realize that CRT's normally have lead glass, etc... but what if they removed it and just used the gun? The office I work in seem to have a strange electronics sound and the feeling of pelted on your skin by something at random times during the day... how would you detect free electrons pinging you from inside a wall? A Geiger counter don't seem to measure electrons below a certain electron — Preceding unsigned comment added by Aloftjunco1 (talk • contribs) 08:37, 15 February 2014 (UTC)

No, it isn't possible. The electron gun from the neck of a CRT isn't worth a thing without the accelerating anode. This is a conductive coating on the inside of the "bell" of the CRT. It is the positive charge from this anode (around 25 to 30 KV in a largish color TV) that accelerates the electrons, and combined with the charge on the focus anode, focuses them so that they come to a spot at the CRT face. That by the way brings up another misconception: The electrons don't really travel in a "beam" all the way from gun to phosphor screen. Rather they sort of bloom out and then come together again. The difference in voltage between the two anodes is what causes that effect. I know that in diagrams of CRTs in popular texts you will see the "electron beam" represented as a narrow beam, but those are what we call "cartoons."

So if you remove the phosphor screen but keep the rest of the CRT, the electrons are just going to fan out again after they pass the plane where the screen was.

All of the above assumes that you're still operating the gun in vacuum. The notion of running an electron gun in open air is complete nonsense. Any old-time TV technician will tell you that a CRT has about the hardest vacuum you'll find in electron tubes, and that even the slightest leakage will render it useless. Running the gun in air at one atmosphere? Forget about it. An electron would, on average, get to travel only about 10 nanometers (10 billionths of a meter) until it ran into a molecule of air.

If you don't believe me and want to try to detect electrons being flung your way, get an electroscope. You can find them on eBay for well under $50. Better yet, find a "static electricity experiment kit" and learn how static behaves (how it can charge pieces of paper, then they will stick to things and then fly away, etc.), because that's what an electron gun would do IF it could work: it would build up a small negative charge on what it was aimed at. As with other electric charges on your body, this would either leak away or discharge suddenly the next time you touched something metal with a sufficiently lower charge, like a doorknob. Jeh (talk) 13:37, 15 February 2014 (UTC)

"An electron would, on average, get to travel only about 10 nanometers (10 billionths of a meter) until it ran into a molecule of air. "

I wouldn't dismiss it so quickly based solely on that. What if you kept pushing huge(!) numbers of electrons along the same line? Wouldn't they be able to (over some time) somehow "clear" that path over an extended distance which would depend on the velocity, focus and intensity of the electron beam and on the density, temperature (the intensity of random particle motion) and composition of the atmosphere / gaseous medium? I have no idea what beam lengths would be achievable with a few hundred watts. A few meters could have practical applications, e.g. for law enforcement or... office harassment (although Aloftjunco1's example also includes effects through walls). Elias (talk) 08:59, 23 April 2021 (UTC)

quantum Electron gun pixel monitor

the electron gun idea is not dead yet, each pixel is constituted by (usually) 3 subpixels: a.reb, b.green. c.blue.

The quantum electron gun pixel, controls the flow of electrons of the three subpixels, each electron has a different speed according to the light beam is purposed to generate while crushing on phosphorus atoms.

pixel electron guns cannot accelerate electrons sufficiently yet except if the pixels become very large.

That technology can work for huge monitors - but consumes more energy than other options.

The goal is to make that technology quantum, but that's what LED does already! — Preceding unsigned comment added by 2.84.216.225 (talk) 10:38, 20 June 2015 (UTC)