Photonicinduction + XRAYS

[Sionyn]

photon wonders if his 'experiments'  are making xrays

[Gall]

Of course. High voltage (>20 kV) + vacuum = X-ray, always.

[c4757p]

Of course. High voltage (>20 kV) + vacuum = X-ray, always.

Why? I mean, I sort of know how it works, but why is it so much more pronounced in a vacuum? I thought it was caused by the deceleration of the electrons when they hit the anode, but air doesn't magically make them not need to decelerate. I noticed that even the light bulb (slightly lower pressure than 1atm, right?) produced a bit - he called it "nothing", but IIRC from watching the video this morning, it went up 20-30 nSv or so.

[Sionyn]

that's what i thought xray tubes emit electrons through thermionic emission then attract them to a target with high potential. hitting the target made from a material of atoms with a high atomic number. 1% of the energy generated is emitted/radiated, usually perpendicular to the path of the electron beam, as X-rays. The rest of the energy is released as heat. There another action were by the electrons can also knock electrons out of the anode material (forget its name).   

[SeanB]

In a vacuum the electrons get up to a high velocity before hitting a target, in air they have a very short travel before hitting an atom of air.

[houdini]

no there are not always x rays.  Also if the voltage gets a lot higher could you produce gamma rays with few million volts in a vacum?

[grumpydoc]

no there are not always x rays. 

high energy electrons hitting a target = x-rays, look up "Bremsstrahlung".

Also if the voltage gets a lot higher could you produce gamma rays with few million volts in a vacum?

Probably not with a vacuum tube - it's difficult to get those past a few hundred kV (they get rather warm!).

For higher energy stuff the electrons are accelerated in a microwave bean (which is what a linear accelerator does).

Also, technically there's no real difference between "x-rays" and "gamma rays" - the latter are just shorter wavelength x-rays.

[Sionyn]

yeah that's what i thought they have to hit a target and loose energy = xray photons
still would like to be his neighbour now he 'experimenting' with xrays 

[G7PSK]

X rays are emitted by electrons and gamma rays from the atomic nucleus you also have hard and soft X rays depending on the Kev involved with hard X rays from above 5 Kev and soft below only hard X rays are any good for imaging as soft X rays are absorbed by air and water too easily.

[c4757p]

still would like to be his neighbour now he 'experimenting' with xrays

I'm sure he won't be doing this for long. At the distance his neighbors would be at, they probably received about ten seconds of a commercial airline flight's worth of radiation if they were plastered to the window trying to figure out what he was doing. Probably less than working in a business next door to a dentist.

[grumpydoc]

only hard X rays are any good for imaging as soft X rays are absorbed by air and water too easily.

Although this is true if you define "hard" as above 5keV (a 5keV photon is a fairly wimpy thing) exactly what energy depends a bit on what you want to image - for instance if you want to image the human body really high energy x-rays are actually pretty useless because they whizz through without interacting very much and anything above 1MeV just produces very low contrast images.

For diagnostic radiography it's best to use x-rays with an energy of 30-250keV (though the top end in practice is about half that). At these energies interaction with matter is mainly by the photoelectric effect. This has the (useful) property that the absorption by a material depends on the atomic number to the fourth power - this gives good contrast between soft tissues which are mainly oxygen(in water) and carbon and bone which has a lot of calcium in it.

You are right about the traditional distinction between x-rays and gamma rays but these days linear accelerators can easily produce x-rays with the same ranges of energies as gamma rays so it's not all that useful a distinction in practice. They're all just photons anyway, if you could catch one and examine it you wouldn't know whether it came from a nucleus or not. Radiotherapy used to be given by using Cobalt-60 as a source of high energy photons - these "gamma rays" have an energy of approx 2MeV but these days we use linear accelerators to produce x-ray beams in the range 6MeV to 30MeV (typically most units use 6 and 15MeV beams).

[Gall]

Of course. High voltage (>20 kV) + vacuum = X-ray, always.

Why? I mean, I sort of know how it works, but why is it so much more pronounced in a vacuum? I thought it was caused by the deceleration of the electrons when they hit the anode, but air doesn't magically make them not need to decelerate. I noticed that even the light bulb (slightly lower pressure than 1atm, right?) produced a bit - he called it "nothing", but IIRC from watching the video this morning, it went up 20-30 nSv or so.

The principle is simple: in vacuum an electron does accelerate ant then impacts something. In air the electron impacts an atom before it accelerates enough to produce X-rays. It is technically possible to produce some X-rays even at 1 atm if the voltage is very high but the output would be very low. In vacuum this is so easy that every HV rectifier tube turns into a dangerous X-ray source.

If the electron is accelerated enough, it can cause characteristic X-ray emission. This is caused by internal electron transitions in an atom and may be easily observed at energies about 50 keV or higher. The intensity of this sort of X-ray is much higher. It is virtually impossible to achieve these energies in air.

[Gall]

but these days we use linear accelerators to produce x-ray beams in the range 6MeV to 30MeV (typically most units use 6 and 15MeV beams).

And sometimes even GeV range!

[grumpydoc]

..but these days we use linear accelerators to produce x-ray beams in the range 6MeV to 30MeV (typically most units use 6 and 15MeV beams).

And sometimes even GeV range!

Yes, indeed - I didn't mean that's as high as linacs go, but that's as high as the ones in clinical use go.

[Hydrawerk]

The guy called Photonicinduction is an evil man. I do not like his videos since he destroyed his analog oscilloscope with a hammer.

[Hydrawerk]

The video is here. Watch from time 3:55.  Ignore the name of the video.

The evil man is good at destroying things. 

[c4757p]

Eh, I had the same scope and wanted to whack it a few times myself. I can handle sacrificing one for show. Now, if it were a Tek... 

[Hydrawerk]

I have a crap scope, too. It is a soviet H313. But I will never crash it.

[Nirios]

The guy called Photonicinduction is an evil man. I do not like his videos since he destroyed his analog oscilloscope with a hammer.

And funny.  In another video of his, he uses a Dyson to vacuum burning petrol and says "look it still doesn't loose suction". 

[c4757p]

It's test equipment, not a religious artifact. Many more where that came from. I wouldn't go destroying my stuff, but I won't cry sacrilege on someone who does. It's all a show.

[smashedProton]

Dude, the wanky scope that he destroyed has a function generator integrated.     Must be a biatch for noise.

[c4757p]

Yes it is. Got rid of mine a long time ago, so I couldn't tell you precisely how bad it was, but there was definitely noise. I ended up yanking the power to the generator. Stupid piece of crap. Deserved Photon's 'ammer, and a good ass-kicking to whoever thought that was a good idea... 

[hans]

This sounds like the same 'Oh my god did he just did that?' response to the smash-my-' xbox360', 'playstation 3', 'wii', 'apple product'-stunts. It's a show about messing about and blowing stuff up with electricity. What do you expect? He also busted some multimeters in his time, that's what he does, get over it.

I have respect for this man in terms of his courage to undertake these 'projects' in his own house, with remarkable amounts of woods, carpet and flames.

[SeanB]

Don't forget his bovva boots fire extinguisher. Works a treat, though the gas it generates can peel the varnish off of the furniture. He is not stupid, just acts the clown, and is pretty good at doing so while still doing it with little risk.

[Hydrawerk]

Well, I prefer other type of non-destructive humour. https://www.youtube.com/user/Deirones/videos?query=energy