Canal Ray pictures

Current images of fusor efforts, components, etc. Try to continuously update from your name, a current photo using edit function. Title post with your name once only. Change image and text as needed. See first posting for details.
Harald_Consul
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Re: Canal Ray pictures

Post by Harald_Consul » Tue Dec 25, 2018 10:53 am

In Thomas Rapp's canal ray accelerator experiment either the target and also the detector are place within the canal ray tube.

Would it be possible to design a canal ray tube with an beryllium window at the end, so that the ion-beam would be delivered outside the canal ray tube (and thus ion beam generation and the target could be separated)?

Or would the ion-beam burn off the beryllium window? I am aware, that beryllium can get fissioned by alpha-radiation (thus most probably in general also by certain fast ions). However, due to beryllium's cross sections this would only happen at certain ion speeds, right? (Which might be avoided by a clever design.)

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Dennis P Brown
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Re: Canal Ray pictures

Post by Dennis P Brown » Tue Dec 25, 2018 7:17 pm

Possibly yes for electrons, but no for protons - especially deuterium based ones. If you calculate the mean-free path for a proton, you'll see the ion energy in fusors is far too small to enable even protons to go through any window that can hold up to the vacuum difference (I've done that calculation; you'll need to do the one for an electron.)

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Re: Canal Ray pictures

Post by John Futter » Tue Dec 25, 2018 9:56 pm

Electrons get stopped much quicker due to the lower mass.
We use external proton and alpha beams at work and they go through various windows to the outside world depending on acceleration
mylar aluminium and beryllium are the favoured (note we do not use external dueteron beams due to neutron production). Minimum energy from the accelerator is 500keV max is 3MeV we used to have a 12MeV accelerator but that has been scrapped where i did post on this site a 12MeV 5uA beam into air showing the Cherenkov radiation and massive neutron production that destroyed a brand new colour camera 5 metres away that was videoing the beam

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Richard Hull
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Re: Canal Ray pictures

Post by Richard Hull » Wed Dec 26, 2018 5:22 am

Yes, there is a point where Quantum tunneling at low energies is not the thing anymore, as in our fusors. At those massive 12 MeV energies you are just totally ripping nuclei to pieces and producing a blast of nucleons. those which are neutrons are not stopped like protons and remnant nuclei.

The good old Oppenheimer-Philips reaction takes over from tunneling fusion in deuterium at about 1.2MeV and simple neutron striping predominates above 2MeV.

Our world at 40-60keV in fusors is nothing like that at or above 4MeV.

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Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Harald_Consul
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Re: Canal Ray pictures

Post by Harald_Consul » Wed Dec 26, 2018 7:15 pm

But it is not possible to generate 12 MeV protons by a canal ray tube, or is it?

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Re: Canal Ray pictures

Post by ian_krase » Wed Dec 26, 2018 7:47 pm

I think that it's not. 1 million volts is about the limit for a static accelerator and that needs massive equipment. You would rather need a cyclotron or other dynamic accelerator (which have been built by hobbyists.)

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Re: Canal Ray pictures

Post by John Futter » Wed Dec 26, 2018 8:04 pm

Yes our 3 MeV accelerator is single ended and uses an Rf powered ccp in a canal type ion source
ion source runs at around 2-3kV but this is on top of 3 million volts generated by the van der graff and then accelerated by the voltage gradient down the acceleration tube whose bottom section is earthed. The Ion source is helped by an external electromagnet to provide the cross field so that a good dense plasma is created it is the cross field that differentiates the electron acceleration systems and the ion acceleration systems. Without the cross field (orthogonal magnetic and electric fields)ion source efficiency is seriously compromised, expect ion output 1000-10,000 times less but you all knew that of course

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Re: Canal Ray pictures

Post by ian_krase » Thu Dec 27, 2018 4:33 am

Explaining what that means,

"RF powered CCP" = radio frequency power (complication, money) is used to boost ionization in a kanal tube ion source.

Kanal ray sources are not normally accelerators all by themselves -- rather they are used to supply ions to a separate particle accelerator which can be any voltage.

You can probably make any fusor work better at higher voltage, lower current, and lower pressure by adding a kanal ray source to the gas input line.

3 MV is probably doable with an extremely expensive, carefully maintained industrial-grade system. I think the most any fusioneer has ever worked with is around 150 kV, much less.

Dynamic accelerators such as bevatrons, cyclotrons, and linacs use a lower voltage drop multiple times, so they don't have the extreme voltage needs of static accelerators.

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Dennis P Brown
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Re: Canal Ray pictures

Post by Dennis P Brown » Thu Dec 27, 2018 3:08 pm

Electrons penetrate further through materials (less energy loss for a given depth) than do protons for identical energies under about 500 MeV; I did calculations for 100 kV protons and these are stopped in microns for most metals (Like Al. Most of us do not use or have access to Be.) Again, for the trivial energies in your cathode ray tube, no window material that can pass those extremely low energy ions will survive the pressure differential. Not happening.

The primary reason for this is that it is the electron cloud (very, very large compared to the nucleus) of atoms that is most effective in stopping protons due to their massive interaction. Electrons being of identical charge are not as affected by this cloud since they are repealed rather than attract by this "large" volume within the atomic/lattice structure of any material; thus they undergo less momentum transfer and tend to penetrate deeper.

See: graph for silicon below.

The mass issue is significant relative to scattering within materials and that certainly can cause a very different absorption volume effects but does not dominate beam depth as does charge polarity.

As for generating beam energies above what a typical Van de Graaf can create, not likely such a machine can be built by most people. As for 12 MeV, that is getting into real accelerator energies. No cathode ray tube will ever do that.

Protonvselectron.jpg
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Re: Canal Ray pictures

Post by John Futter » Thu Dec 27, 2018 7:26 pm

CCP = capacitively coupled plasma
ICP = Inductively coupled plasma

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