Canal Ray pictures

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ian_krase
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Canal Ray pictures

Post by ian_krase »

Here's a quick little demo I whipped up of Canal Rays. I suspect many people who have worked only with fusors won't be familiar with this, because a fusor-type chamber simply isn't really set up to demonstrate this phenomenon.

Canal Rays (or Kanalstrahlen in Science German) are useful for making ion guns.


My pump (and a throttle valve) are at the bottom, and are grounded. Going from the bottom up, there is then the shorter glass tube, a metal connector that is also grounded, and which has a metal screen closing the aperture of the tube, then above that another glass tube, and at the very top is the electrode which my power supply is connected to. As such, the area in the lowermost tube is a free "drift" area where there's no discharge and no electric field, so plasma can flow there from elsewhere if forced, but won't be formed there and won't be driven there by itself.

Pressure for both pictures is somewhere in the 20 to 100 micron range.

IMG_20181216_222248.jpg
With the topmost electrode negative, electrons are emitted from the top and stream downwards, while gas ions fly upwards. No visible glowing plasma passes through the screen into the lower glass tube.

IMG_20181216_222102.jpg
When the topmost electrode is positive, electrons are emitted from the center electrode and stream upwards, while gas ions are attracted to the middle electrode and accelerated downward... and through the screen. A visible glow is seen in the lower glass tube.

If the screen were replaced with a "washier" having a small hole, there would be a narrow beam going downward rather than a diffuse glow.
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Richard Hull
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Re: Canal Ray pictures

Post by Richard Hull »

I actually have a formal, manufactured Canal ray demo tube. These were sold by Cenco, Welch and other scientific supply houses for many years to high school and college classrooms. I have the classic electron beam tube, the paddle wheel tube, Maltese cross shadow tube and the demo x-ray tube. A friend of mine has virtually all such tubes ever sold of this type classroom demo tubes. For a very few years they sold what they called a demo atom smasher. (van de Graff accelerator with internal accelerator target system). Ultimately, it was taken out of their catalog due to x-ray issues.

Sadly, my paddle wheel tube needs to be re-pumped and sealed as the exhaust seal tip is broken off. I just haven't got around to doing the glass work.

Richard Hull
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Rex Allers
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Re: Canal Ray pictures

Post by Rex Allers »

Interesting, Ian. I don't think I had seen that setup before.

A couple of side questions about your equipment in the pictures.

The metal connections to the glass tubes look to be some king of compression fittings. Were these meant for vacuum or are they made from home plumbing fittings? Clever, if the latter.

What's the thing in the lower left that looks to have a protective net wrapped around it?
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ian_krase
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Re: Canal Ray pictures

Post by ian_krase »

Yes. They are 1.5 inch kitchen sink drain fittings (made of brass, chrome or nickel plated) brazed into standard KF fittings. They are sealed with viton o-rings and each has a metal internal stop ring.

They work... Sort of. For a fraction the cost of Ultratorr which would be the proper way to do this.

The "mesh covered item" is an Ionization Gauge, for measuring pressure from less than 0.1 micron to Lower Than You Can Afford To Go. It's covered in mesh since it's large, thin-walled glass. Connected by cables to a gauge controller. Obviously the Ionization Gauge is not in use in this picture.
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Re: Canal Ray pictures

Post by Rex Allers »

Thanks for the details, Ian. Both are what I thought.

Good work on adapting the much cheaper plumbing. Unfortunately, I think this metal stuff is getting a bit harder to find as much being sold is going to plastic.

I had guessed that the other thing was a sensor for serious vacuum and assumed it would only be used for some other higher vacuum application.

Nice experiment. Thanks for sharing.
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Richard Hull
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Re: Canal Ray pictures

Post by Richard Hull »

The canal ray demo tube in the image below is the exact tube I have. (The photo was grabbed on-line)
Looking at the base it sits on, it might be a CENCO tube. (Central Scientific Co.)

Richard Hull
Attachments
canal_ray.jpg
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Harald_Consul
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Re: Canal Ray pictures

Post by Harald_Consul »

As canal ray tubes can be used to produce ion guns, I am interested in
  1. What are typical keV speeds of the ion?
  2. Are there also smaller canal ray tubes, especially for assembling in an experiment?
The only experimental canal ray tube I have seen on ebay so far is this one:

Ebay Canal Ray Tube
Image
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ebay_experimental_canal_ray_tube.jpg
ian_krase
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Re: Canal Ray pictures

Post by ian_krase »

A kanal Ray tube for use as an ion gun is probably gonna be homemade out of glass tube and parts.

Here: http://www.rapp-instruments.de/Beschleu ... neugen.htm is an example of a canal Ray tube being used for fusion. This site is by Thomas Rapp, who has posted here as "Rapp Instruments".
Last edited by ian_krase on Mon Dec 24, 2018 2:56 pm, edited 1 time in total.
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Richard Hull
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Re: Canal Ray pictures

Post by Richard Hull »

Nice report on the canal ray accelerator/ion source. This is a nice little linear accelerator/beam on target machine. At 50kv at 500ua you seem to get about 10e5 n/s. All glass has certain advantages when high voltages are used. The glass to metal seals are always an issue in vacuum systems. The more seals, the more issues can exist. Of course, this is true in any vacuum system regardless of sealing method.

I have thought about the little GM tube wrapped in Silver. The issue for me would be the X-radiation which would certainly enter the count scenario unless you had the affair in a box line with lead of sufficient thickness. There are work-arounds, of course. A lower voltage will produce so few and weak x-rays that even a small amount of fusion might be detected in air versus deuterium runs. Silver is so wonderful against the Russian tube as it activates fast and produces mostly hard betas which are detected with great efficiency in such a tube. A better tube would be a Victoreen 1B85 as it has a much larger volume and a bit thinner aluminum shell.

a very thick wrap of silver would do away with the x-ray issue to some degree at high voltages.

A test would be to place a tube behind increasing thicknesses of silver sheet/plate until no significant x-radiation was noted in air runs. Wrap the tube in this thickness and run with D2. There always remain certain ways to detect neutrons on the cheap provided you are careful not to count x-rays provided you have enough fusion going on. In rank amateur hands, any GM counting system for neutrons must always be looked at with jaundiced eyes.

Thanks again for the fine report.

Richard Hull
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
ian_krase
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Re: Canal Ray pictures

Post by ian_krase »

That's not me, that's Thomas Rapp (who has posted here).
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Re: Canal Ray pictures

Post by Harald_Consul »

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 »

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 »

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 »

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.

Richard Hull
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Harald_Consul
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Re: Canal Ray pictures

Post by Harald_Consul »

But it is not possible to generate 12 MeV protons by a canal ray tube, or is it?
ian_krase
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Re: Canal Ray pictures

Post by ian_krase »

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 »

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 »

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 »

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.

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John Futter
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Re: Canal Ray pictures

Post by John Futter »

CCP = capacitively coupled plasma
ICP = Inductively coupled plasma
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