Canal Ray pictures

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ian_krase
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Canal Ray pictures

Post by ian_krase » Mon Dec 17, 2018 10:19 am

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 » Mon Dec 17, 2018 3:38 pm

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Rex Allers
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Re: Canal Ray pictures

Post by Rex Allers » Wed Dec 19, 2018 3:50 am

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?
Rex Allers

ian_krase
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Re: Canal Ray pictures

Post by ian_krase » Thu Dec 20, 2018 2:13 am

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 » Thu Dec 20, 2018 4:35 am

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.
Rex Allers

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Richard Hull
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Re: Canal Ray pictures

Post by Richard Hull » Thu Dec 20, 2018 5:01 am

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: Canal Ray pictures

Post by Harald_Consul » Sun Dec 23, 2018 7:55 pm

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
Attachments
ebay_experimental_canal_ray_tube.jpg

ian_krase
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Re: Canal Ray pictures

Post by ian_krase » Mon Dec 24, 2018 9:57 am

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 7:56 pm, edited 1 time in total.

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Richard Hull
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Re: Canal Ray pictures

Post by Richard Hull » Mon Dec 24, 2018 6:33 pm

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

ian_krase
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Re: Canal Ray pictures

Post by ian_krase » Mon Dec 24, 2018 7:56 pm

That's not me, that's Thomas Rapp (who has posted here).

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