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Author Topic: How slow can electron go?  (Read 3789 times)

Offline madus

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How slow can electron go?
« on: 22/10/2012 06:15:31 »
Hello. Please understand while any opinion is welcome I can only accept published experimental measurements as definite answer. Let me also make it clear I am not interested in "drift velocity" or speed of electric potentials or waves in conductors or crystals and such, but only the speed of FREE individual electrons or electrons in electron beam.

Ideally the experiment would be set up like double-slit experiment, that is electron gun is emitting single electrons or bursts of electrons towards detector. The time of emission and the time of detection is recorded and so the speed is determined directly with v= s/t.

Can anyone point any such, or similar, published measurements?


I was told over at physicsforums there can exist such thing as slow electron that would need whole second to travel 10 meters across the room (v= 10m/s), but they could not point anyone ever actually published any such measurements, then they banned me and deleted the whole thread, so I am sceptical. Heh. And curious, did I stumble over some amazing mystery, or conspiracy? What's going on?

Thank you.


 

Offline CliffordK

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Re: How slow can electron go?
« Reply #1 on: 22/10/2012 07:51:51 »
There are Electron Traps as well as Positron Traps.  while potentially not at zero velocity, the electrons or positrons in the trap are not colliding with anything within in the trap, or with the walls of the storage container.

BTW:
I am not aware of your issues on other websites, but I would encourage you to keep the discussions civil.  This is, of course, a website hosted in Britain where high ranking politicians resign for merely calling police officers commoners. 
 

Offline madus

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Re: How slow can electron go?
« Reply #2 on: 22/10/2012 08:42:17 »
There are newbielink:http://en.wikipedia.org/wiki/Electron_beam_ion_trap [nonactive] as well as newbielink:http://positrons.ucsd.edu/positron/buffergas.html [nonactive].  while potentially not at zero velocity, the electrons or positrons in the trap are not colliding with anything within in the trap, or with the walls of the storage container.

Yes, but it doesn't seem any velocity is actually measured in such experiment, rather it is deduced or assumed indirectly via energy input, or something. Right? The experiment I am looking for must measure the time of travel and so directly measure the speed according to v= s/t.

If there is such thing as electron gun that could emit electrons with velocity as small as few thousand meters per second, or slower, such experiment should be easy (cheap) to set up, I would think, but I can't google anything conclusive about it.

 
Quote
BTW:
I am not aware of your issues on other websites, but I would encourage you to keep the discussions civil.  This is, of course, a website hosted in Britain where high ranking politicians resign for merely calling police officers commoners.

I have no idea.
 

Offline yor_on

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Offline madus

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Re: How slow can electron go?
« Reply #4 on: 22/10/2012 12:36:23 »
newbielink:http://www.mpq.mpg.de/cms/mpq/en/groups/hommel/homepage_cms/projects/microwave_guiding1/index.html [nonactive]

- "In our experiment we have for the first time successfully confined electrons in a planar guide driven at microwave frequencies. Slow electrons with energies of several electron volts are directed along a curved electrode structure."


Unfortunately, it seems, when they say "slow electron" they are only really talking about energy. I really need it to be velocity measured directly by measuring the *time* of flight over some distance: v= s/t.

Their experiment reminds me of bubble chamber. From their description I gather it is not "easy" to confine or slow down electron. It's like there need to be constant input of energy to generate magnetic fields just to "deflect" electron path, rather than slow it down and then let it drift slowly in a straight line on its own through some vacuum tube. Is that possible? That's my question.
 

Offline JP

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Re: How slow can electron go?
« Reply #5 on: 22/10/2012 14:35:20 »
Madus, as a heads up: copy/pasting your question to multiple forums is against our site rules.  I'll leave this thread up, but please don't do so again.

Thanks,
JP moderator
 

Offline madus

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Re: How slow can electron go?
« Reply #6 on: 22/10/2012 15:01:05 »
Madus, as a heads up: copy/pasting your question to multiple forums is against our site rules.  I'll leave this thread up, but please don't do so again.

Thanks,
JP moderator

You must mean cosmoquest forum since the question was removed from physicsforums. I'm surprised you even know, or care. More people know more, that was on my mind. -- Ok, I hear you, thanks.
 

Offline yor_on

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Re: How slow can electron go?
« Reply #7 on: 22/10/2012 20:05:35 »
The magnetism expressed in a permanent magnet is assumed to be a property of the electrons 'spin'. That is a property that if treated as a speed would exceed the speed of light, so? It's not what we normally call a motion. But this spin must always be existent, as the spin is, and so the magnetism expressed.
 

Offline CliffordK

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Re: How slow can electron go?
« Reply #8 on: 22/10/2012 20:19:39 »
Of course, you could say that if you take a hydrogen atom, then while the electron is orbiting, it is confined to an area of 1 cubic .
In a block of frozen hydrogen, one could easily confine the movement of the hydrogen atoms.
 

Offline Bored chemist

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Re: How slow can electron go?
« Reply #9 on: 22/10/2012 20:54:22 »
Not quite the same thing, but some of the earliest measurements of velocities of ions in air were done with, in effect, a pendulum clock.

A good sprinter would certainly leave them behind.
 

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Re: How slow can electron go?
« Reply #9 on: 22/10/2012 20:54:22 »

 

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