How an electron gun works

A description of the working principles of an electron gun, plus a few demonstrations.

[@kari548]

That god you are the person that I have been looking for because no one else has made a video on an electron or when they did it was an animation but this totally opened my mind.

[@rodrigofreitas3288]

Inventors, scientists and engineers from the 20th century were literally wizards.

[@benruniko]

Man I miss New Pepco mana potions

[@johnenalstos4821]

Wow, fantastic explanation and a wonderful setup. This is so educational, as I am trying to understand exactly how an electron microscope works for the first time. Now I am just thinking with your knowledge and skills, you might be a great person to explain exactly how the electron microscope works! ;-).

[@EricDalgetty]

Thank you, I'm glad you liked the video! I'm working on a bigger and better electron gun for the next videos!

[@jawaharbabuadapa]

thank you for making these videos available

[@selektor2567]

Thanks so much! This helped a ton when writing my assignment.

[@69iqtutorial]

Wait.. are you the iridocyclitis guy?

[@selektor2567]

@@69iqtutorial iridocyclitis. I-r...

[@icwiz]

Bravo! I was looking for a video of someone who had done this. Quite impressive. The 1 bar gun with the foil is crazy! I didn't know that was even possible. subbed!

[@miinyoo]

That was more fun than I expected.

[@Green_Lept]

Eric, I know this is a little old but I’m really curious if you could recreate the double slit experiment with electrons using this?

[@EricDalgetty]

Cool idea! I'm working on a better electron gun now, so that might be a fun experiment to try

[@guy0lan]

@@EricDalgetty be great to see it in KZbin.. I think you will be the first to do so

[@redneckrevolt1]

I’m the double slit experiment, how do they know they’re shooting only ONE electron at a time that interferes with itself? Then you measure the electron before that slit and that just takes one electron away?

[@jacenkun2931]

I wonder how much light or electrons are going through my arc welder.

[@GUNVALKERIE]

Very similar to the ion thruster clip I saw... electrons being attracted by copper pipes a DYSONs fan of sorts only this version does not have any moving parts literally

[@tgrey_shift..mp334]

Also, I was wondering, would you like to hear a invention concept I plan to build with an Electron Gun?

[@boring11010]

Yes please share

[@blackburgundy1659]

"Congratulations sir, u have created a new element"

[@chydedelaplace8947]

Why does it have to be in a vacuum? Nice video.

[@EricDalgetty]

Cylde Dellafish The vacuum allows the filament to get extremely hot without burning by preventing contact with oxygen. The lower pressure also allows the elctrons to travel in a straight path without bumping into air particles.

[@chydedelaplace8947]

Eric Dalgetty Thanks.

[@heroinmel]

It also helps the electrons from being bombarded by other atoms that would be in the air

[@skepticalopen-mind4031]

tHIS IS THE VERY FIRST THERMOIONIC VALVE OR VACUUM TUBE

[@tgrey_shift..mp334]

Does the object have so many electrons, it could work even after our lifetime?

[@agustincruz]

Hi. Thanks for your video. Is very simple and illustrative. I have a question. Did you bought the tungsten filament with the V shape or did you bend the filament by yourself?. Many thanks

[@EricDalgetty]

I'm glad you liked the video! I bent the filament myself, it is not too difficult. You can buy very thin tungsten wire on eBay (I think the one here is 0.3 mm)

[@cryora]

Are there safety hazard to worry about? High voltages means the possibility for capacitors to be charged to high levels and can inadvertently discharge if shorted. My PhD advisor would never let me use a high voltage source on my own unless I give him detailed descriptions of how I plan to use it and his express permission.

[@richardtwinn357]

Is this similar to how they fire a neutron to start a nuclear reaction in a uranium fuel rod? Seen loads of videos of how nuclear fission works but none thay explain how they start the reaction and where the singular neutron comes from!

[@EricDalgetty]

Not quite, but I had always wondered that, too! They actually use a neutron source, like a mixture of plutonium and beryllium. The alpha particles from the plutomium have a reaction with berrylium and produce enough neutrons to start the reactor. You might check out the wiki article for "neutron source"

[@fickrymuhammad9207]

hello sir, i'm need for wiring diagram for connection component, please give me wiring for the system electron gun, thanks a lot

[@jmg9509]

1. After accelerating the electrons into a vaccuum, can the electrons be stored there indefinitely? 2. If no to question 1, can they be stored there indefinitely using a magnetic bottle? (using regular magnets, not electromagnets)

[@EricDalgetty]

Hi, good question! I'm not a physicist, so I don't want to use the word "indefinitely", but there is something called a penning trap and something called a cyclotron, both have ways of keeping electrons in an orbit, but I'm not sure that they will stay there forever.

[@jmg9509]

Thanks for replying so soon, i'll check them out.

[@Bunicutaintelectuala]

Nice work!

[@samuelmoss7001]

Great video. I am making my own electron gun at home, and the tungsten vaporizes/smokes excessively. I am using a 6v battery as the current source to the tungsten filament. How do you keep your filament from smoking?

[@EricDalgetty]

That sounds like there is too much oxygen around the filament, are you running it in a vacuum? And are you able to measure the pressure around it?

[@samuelmoss4014]

@@EricDalgetty Eric, thanks for the quick reply. I do have it in a vacuum, but I am using an old mini fridge compressor which only is allowing me to get to -16 Hg. Which means it is about little more than halfway to a perfect vacuum. I am assuming that the tungsten needs a perfect vacuum to work effectively. Did you use a two-stage vacuum compressor to get your vacuum chamber perfect?

[@EricDalgetty]

That's definitely going to be tough to keep the filament alive at those pressures. Generally I would guess that you need

[@samuelmoss4014]

@@EricDalgetty Thanks, I will definitely change out the pump or use a sorption pump. I will let you know how it goes, as I am using this for a tabletop experiment for a new confinement method for fusion. For the tabletop, I only want to test the electron confinement capabilities. I created a website on the new concept called fusionandgravity.com, feel free to check it out, and thanks for your help and advice on the vaporizing tungsten issue.

[@alexanderrydberg6118]

@@samuelmoss4014 That seems really interesting

[@DevinBates]

I would like to build this. How did you make the vacuum? What is that Pyrex bowl, how do you create the vacuum with the wires? What's the seal under the plate?

[@EricDalgetty]

So the vacuum in this video was generated by a cryopump, which is very out of reach for most people. Probably the easiest way that you could achieve a vacuum of this pressure is with a diffusion pump and a roughing pump. The pyrex glass is something called a bell jar, and I bought mine used, they can be quite expensive. The wires enter the vacuum chamber through an electrical feedthrough, in this case a ceramic one. The seal for the bell jar is a gasket made for that bell jar, but I've seen people use a silicone mat to create the seal as well. Hope this helps!

[@courcol_jean2462]

awsome video!I have a question though: in the second experiment is the electric potential between the copper and the foil or between the heater and the copper?

[@EricDalgetty]

Thanks! The potential is still between the copper anode and the filament.

[@chrisdeerleg975]

Very nice, would you explain how you build the phosphor screen ? I try to build a SEM and try to proof the electron beam.

[@EricDalgetty]

Sure! You can order a chemical called "Zinc Sulfide" online, I bought mine on eBay pretty cheaply. Make sure that the zinc sulfide is made to glow in the dark. I usually add water to make a paste and then paint it onto a surface. Hope this helps!

[@poojasharma-sc1dc]

hindhi MA bhi explain kijiye

[@rafs6045]

good job! keep it up!

[@MikeFougnie]

How is the filiment active and held at a low potential?

[@EricDalgetty]

It is possible to have both AC current flowing through the filament, and to have a high voltage potential on the filament at the same time. You can see this in the design of some vacuum tubes. You can google the circuit diagram of a vacuum tube diode. I hope this helps.

[@MikeFougnie]

@@EricDalgettyAwesome, thank you.

[@reviewexpert4111]

What about coolent? As the sheet absorbs a lot of energy it might melt right?

[@EricDalgetty]

You're correct, in high power systems like an X-ray tube, you definitely need coolant to stop the target from melting. In this system the power was only a few watts, so the target likely wouldn't have heated up very much.

[@artkoala1243]

can i use just normal LED that i can buy in thrift stores? or a special one? sorry😅 i don't really know much about those stuff but im interested into building one... if that's possible 😅 great video BTW😀

[@EricDalgetty]

Thanks, I'm glad you enjoyed the video! Yes these are just regular LEDs, other loads work as well. I have also powered a small motor with this set up

[@adiliraliyev5882]

Is your red wire connected to your anode?

[@EricDalgetty]

The red wire is connected to ground and the LEDs positive lead

[@huangvincent6549]

I am very interesting you science video. Could you provide the circuit diagram of electron gun in this video?

[@paulmoity1318]

Eric, What is the name of the material (white board) all this sits on? Thanks in advance Paul

[@EricDalgetty]

Hi Paul, this is a piece of UMHW polyethylene. I'm not sure that it's a great material for vacuum but it seems to have held up okay

[@paulmoity1318]

@@EricDalgetty Thank you for the response & love the videos.

[@habbokoreiapix]

The formula you used to calculate the electrons' speed is considering just one electron? So the filament only emits one electron "per time"?

[@EricDalgetty]

The number of electrons won't matter for that formula. Any number of electrons in that electric field will all be accelerated to the same velocity

[@habbokoreiapix]

But is there a way to know how many electrons are being emitted? I got curious about the quantity of them

[@EricDalgetty]

@@habbokoreiapix The number of electrons is directly related to the beam current of the electron gun. There are 6.242E18 electrons in one Ampere, so at a beam current of 0.5 milliamps, there are roughly 3E15 electrons in the beam. I hope this helps!

[@habbokoreiapix]

@@EricDalgetty thx! It helps a lot

[@jmg9509]

Hey man, I've decided to look into building and electron gun for an idea I have in mind. Do you have any plans or a viable site I can get the plans for the device from? Thanks

[@EricDalgetty]

I watched Applied Science's videos to help me when I started building the system (there's a reason my chamber looks similar :) ). My advice is to go through eBay and find the materials that you can cheaply. The vacuum chamber ends up being the much more difficult task than the electron gun, I think. Good luck! Ask me if you have any specific questions, maybe I can help.

[@jmg9509]

Ironically I just started watching the disassembly of a cathode ray tube as I saw this message from Applied science. I just learned that the old tvs used cathode ray tubes to generate a picture, one of which I have in my house so I'm going to attempt to take it a part tomorrow to see if I can use the electron gun in that for the experiment. Will keep you updated!

[@younessking9874]

good job

[@ricardocasimiro6424]

great job! how vaccum you are using?

[@EricDalgetty]

This was probably about 1E-6 torr, but anything lower than 1E-4 should be enough to keep the filament from burning.

[@user-hv7pc6ju8g]

Can it use for welding 😊

[@EricDalgetty]

Probably not with such low power, but I'd really like to build an electron beam deposition system!

[@HomeDistiller]

what are you using as the screen?

[@EricDalgetty]

Zinc sulfide. Its a glow in the dark powder, you can buy it very cheaply on eBay. I've found MgO also works, but it is not as bright

[@tanishkulkarni7958]

now i got to understand the gun

[@pici24]

nice, ty !

[@JinghuiWang]

Supper cool!

[@EricDalgetty]

Thank you!

[@reviewexpert4111]

Did it generate any EM waves?

[@EricDalgetty]

If you mean like x-rays from the target, i don't believe so. Typically much higher energy collisions are needed to create x-rays. If I put a phosphor, like zinc sulfide, on the target that will glow very brightly at only a few hundred eV

[@tgrey_shift..mp334]

And I have a question, why do you have a collector?

[@EricDalgetty]

[T://Grey_shift.]#.mp3 The collector was used to measure the output of the device, it is similar to a "Faraday cup"

[@ella-gm6bz]

Could anyone explain how the electrons are accelerated? thanks

[@ella-gm6bz]

like how does it gain energy i thought p.d. was when it lost energy

[@EricDalgetty]

Basically, the electrons are in a very strong electric field between the cathode and anode, which produces a force on the electrons. This accelerates them towards the anode (copper loop), but some miss and go through at very high speeds. Applied science has a really good video which can explain in more detail (kzbin.info/www/bejne/kHqtYp1_Zt13nrs)

[@adiliraliyev5882]

Is your anode connected to a different circuit than your led lamp circuit

[@EricDalgetty]

The anode is on the same ground as the LED

[@adiliraliyev5882]

@@EricDalgetty thx, I understand now, it doesn't go to ground right away, instead it flies past that to the plate, but why? Inertia?

[@adiliraliyev5882]

@@EricDalgetty is it because it chooses the leat resistance path through air instead of pushing it self trough coper wire at first, but then gets trapped in a circuit and has to do it anyways after?

[@EricDalgetty]

@@adiliraliyev5882 This is all taking place in a vacuum, so there is no way for the electrons to lose energy except for colliding with something. I think you are correct that it is the electrons inertia that keeps them going. When they are at the cayode, they see the anode as a solid plate because it is so far away. As they get closer, they only experience a net force forwards because they are attracted equally in all directions towards the loop

[@EricDalgetty]

When the pass the anode (copper loop), there is no more force exerted because the entire chamber is grounded. There is no electric field to cause a force.

[@YathishShamaraj]

You are awesome 👍

[@EricDalgetty]

Thank you!

[@user-mw1gk1io7l]

Hi, Eric. I want to get the schematic of this electron gun. Where can I get the schematic??

[@EricDalgetty]

Hello, there isn't really a schematic. Are you wondering about electrical connections?

[@user-mw1gk1io7l]

@@EricDalgettyThank you for your quick answer. Actually yes, i want to know how can i connet those like you

[@EricDalgetty]

@@user-mw1gk1io7l I think this is a useful schematic: qph.fs.quoracdn.net/main-qimg-db083012c51a6e2308b2ac23bcd37d9f

[@user-mw1gk1io7l]

​@@EricDalgettyI saw some schematic about electron gun in the internet, and they used variable resistance and balancing resistance when they heat the filament. You didn't use them, right??

[@user-mw1gk1io7l]

@@EricDalgetty like this. kzbin.info/www/bejne/kHqtYp1_Zt13nrs

[@jujuthehoms5482]

What does Vacc represent at 1:29?

[@EricDalgetty]

The voltage used to accelerate the electrons. I should mention this formula is really only accurate below 10 kev, because after this point the electrons are relativistic

[@jujuthehoms5482]

@@EricDalgetty Thanks!

[@arkohmay]

Can the electron gun function outside of the vacuum?

[@EricDalgetty]

Good question. There are two reasons why the electron gun DOES need a vacuum. The tungsten filament would oxidize and burn out if it was exposed to atmospheric oxygen, and the electrons emitted would only be able to make it a few micrometers before they lost all their energy through collisions with air particles. There is something called a Lenard tube which you might find interesting. It uses a very thin window to allow high energy electrons to pass into the atmosphere.

[@arkohmay]

@@EricDalgetty is it possible to provide high enough voltage, constant or pulse in order for the electron beam to reach greater distances over time? Specifically applying voltage to the accelerating anodes and such?

[@EricDalgetty]

@@arkohmay If I understand your question, yes the electrons will travel faster with higher accelerating voltages. This is not a linear relationship, though, because the electrons are traveling at relativistic speeds (speeds which are somewhat close to the speed of light) around 10keV. These higher energy (velocity) electrons can also penetrate further into matter before they are stopped.

[@arkohmay]

@@EricDalgetty Another question if I may ask, but, could you use a nichrome alloy filament instead of tungsten to act as the cathode so that it may function outside a vacuum and not oxidize as quickly as tungsten?

[@EricDalgetty]

@@arkohmay Potentially, but the filament usually needs to get very hot for thermionic emission to take place. But, if there are enough gas molecules you don't actually need a filament. There is something called a "Hollow Cathode" which uses ionized gas to produce the electrons. I think you would need incredibly high voltages if you wanted to make an electron gun that way, like more than 1,000,000 volts

[@alexanderrydberg6118]

Does anybody know if magnets could slow the electrons down just so that the collector isn't as hot? The electrons are going pretty fast so

[@EricDalgetty]

A magnet can only change the electrons direction, it can't make them speed up or slow down. If you wanted to slow them down they would need to pass through an electric field (the reverse direction of how they were accelerated). There is something called a beam degrader, which is some material that the beam has to pass through on the way to it's target. The beam will deposit some of it's energy in the degrader (as heat) so that it has a lower energy when it reaches the target.

[@alexanderrydberg6118]

@@EricDalgetty But what if like instead of a collector you have a powerful magnet? Electrons are charged and they have little kinetic energy, wouldn't they change direction and go backwards

[@EricDalgetty]

It is possible for them to turn around, but it won't change their kinetic energy. You could cause them to hit the collector at different angles which would probably affect how much energy is transferred to the collector vs. how much energy is retained by the scattered electron

[@alexanderrydberg6118]

@@EricDalgetty Thank you! My plan is to have an electron gun and use magnets to keep the electrons in a container and I want to see if I can store a little energy

[@alexanderrydberg6118]

@@EricDalgetty By the way, what transformer so you use/recommend?

[@empiresekiz]

why ? how ? the electron is a wave ? how ? why ? -_-

[@blakefrancis4538]

wowie

[@discoverlight]

A neutron gun works the same way?

[@EricDalgetty]

Generally speaking, neutrons are much more difficult to produce. Because they are not charged, they can't be accelerated by electric fields. A more typical way of producing neutrons is by accelerating protons and having those protons hit a target. You can look up a "spallation neutron source".

[@discoverlight]

@@EricDalgetty ok thanks for that info, I’m not a physician or anything, but I have curiosity about almost everything so lately I’ve been learning about nuclear fission, and I’ve managed to learn a lot of basics, but I still wanted to know how neutrons are shot towards the uranium, since the Uranium is a solid Little Rock (the one used as fuel cells) so I have understood that this solid piece is hit by neutrons. I still have so much to learn btw. 😆

[@EricDalgetty]

Oh so in the case of a weapon, they used something called an "urchin". This is a radioisotope that emits alpha radiation, surrounded by a material like beryllium. When the alpha particles hit the beryllium a small percentage will cause a neutron to be emitted.

[@discoverlight]

@@EricDalgetty ok that makes sense, I’ll check on that urchin thing, I guess the speed of the neutrons is quite high right?

[@EricDalgetty]

@@discoverlight Generally neutrons will be several MeV, unless they are thermalized, like in a nuclear reactor

[@jimhalpert9803]

A quintillion electrons flowing in my phone? Jeez.

[@Bacchian]

But can you use it to take over the world?

[@bigdesignspop]

Are people electron guns ? If our mental focus, or attention, in our minds, creates a similar reaction in this video, within our internal systems of imagination and feelings. If so, that would tie into the slogan, "what we think about, we bring about" ( thru heated up thoughts that electron transfer Into the atmosphere , and they manifest events

[@anonymousshawn9996]

1:37 cowboy hat

[@EricDalgetty]

Haha good catch! That was for a thumbnail that I was making but decided not to