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electron beam detection

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Zak28

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Is there a simple method to detect or even measure an electron beam in free air? Preferably without circuitry - however Im sure attaching some electrode to a FETs gate is the only simple method.
 

I assume you mean off-axis detection? Because electron
beams are used to provoke semiconductor sensitivities,
if you hit them with it. Not the kind of energies normally
encountered by sane people, but still.

Electron beams in air do not have much range. I imagine
you might be able to pick up phosphorescence signatures
at N, O excitation wavelengths (see this being employed
for explosives detection, although they use UV source -
LINAC being a bit not-portable). Narrowband optical
filter and photodetector, then.

How much signature you can get, and whether you can
discriminate a random-time-of-arrival signature in the
same way as those detection folks can with their co-
situated pulsed source and detector (you can take a
baseline before the pulse, if you know when the pulse
is coming, and do a sample-sample subtraction and/or
zero the front end).
 

...pick up phosphorescence signatures...

Can calcite or some other phosphorescent mineral light up with a beam incident to it? Would be a neat and simple indicator.
 

In free air (under normal pressure and temp) an electron beam may travel only a few mm (if the energy is in the MeV range, then perhaps 4-5 mm max). The beam will be a mess (cannot be called a beam) because of scattering. After that it will attach to some air molecules and produce negative ions. Detecting free electrons in air will be tricky if not impossible.
 

When I think 'electron beam' I think of a crt. The beam is visible when it hits the phosphor layer.
There are Youtube videos which demonstrate experiments making or playing with a crt. I see a visible bluish beam.
To detect it should be possible with a light sensor which responds at the wavelength of the electron beam.

I also think of lightning since it's a flow of electrons. The path is ionized air so it's not necessarily a beam, but it's easy to detect. Methods include visual, magnetic, rf. Maybe electrons traveling in air causes the air to light up. Anyway it's a way to consider the idea that may lead to other ideas.
Sparks and arcs also make electron flow visible. And by suspending something in the air (gas, particles, phosphors), you might detect an electron beam the same way it lights up gas tubes.
 

In free air (under normal pressure and temp) an electron beam may travel only a few mm (if the energy is in the MeV range, then perhaps 4-5 mm max). The beam will be a mess (cannot be called a beam) because of scattering. After that it will attach to some air molecules and produce negative ions. Detecting free electrons in air will be tricky if not impossible.

But considering under a vacuum with many Mev, the rock/mineral would turn phosphorescent?
 

the rock/mineral would turn phosphorescent?

Perhaps yes. But remember that all rocks are not same and the fluorescence or phosphorescence observed is mostly due to traces of impurities.

Try some rare earth nanoparticles: or something similar to the ones used in CRT tubes. With MeV energies, the rock or the phosphor will rapidly die (perhaps a few seconds if the beam is nicely focused) because the compounds will decompose.
 

...I also think of lightning since it's a flow of electrons. The path is ionized air...

You really mean ozone is indicative of an electron beams presence also?

In that case i suppose turning off the lights and searching for glowing atmospheric gasses would also indicate an electron beam.
 

searching for glowing atmospheric gasses would also indicate an electron beam...

You may have to try hard because most of the glow will be in the UV range but a photodetector can work well...
 

It's hard to be sure which we see, whether electrons, or their effect on substances, when we look at lightning, St Elmo's fire, electron beams, coronal discharge, accelerated electrons, plasma, tesla coils, and related phenomena.

Homemade corona arc discharge:


Homemade cathode ray tube:

https://youtu.be/5-Bco8KRpmU

https://youtu.be/nwRBlyZcNso

The narrator refers to a pinkish color in the bottle due to residual air. Soon this fades and the blue color of the electron beam becomes obvious.
 

Still unanswered / unclear:

detect by being the target, or detect at a distance (off axis)?

An electron beam will create a magnetic field by its current.
This could be detectable at higher beam currents and short
distances. Of course many electron beams are created and/or
focused by significantly higher magnetic fields than the beam
would induce, itself. But if you were sensing far from the beam
head and just a skosh off axis, maybe you could see the start
and stop if you could zero to ambient beforehand.
 

Homemade cathode ray tube:

I saw the two videos: they are not, even remotely, cathode ray tubes. Old TV tubes and old scopes have CRTs. They have an electron gun (three for color TVs) and when the electron beam hits the phosphor on the other end, it produces phosphorescence. The vacuum inside is high and the electron beam reaches the other end without encountering a single collision.

These ones seen in the videos are simply discharge tubes and you cannot get a high vacuum with a simple one state pump...
 

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