Why operate Turbo - or Vapour Jet Pump during Fusion attempt

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Steven Sesselmann
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Re: Why operate Turbo - or Vapour Jet Pump during Fusion att

Post by Steven Sesselmann » Fri May 26, 2017 3:27 am

David Kunkle wrote:What was the purpose of that effort?
David, there would would be a small but very lucrative market for a turn-key neutron generator without a pumping system. Such a system would be a great replacement for hazardous AmBe sources, used in industry and educational institutions.

Steven
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Re: Why operate Turbo - or Vapour Jet Pump during Fusion att

Post by David Kunkle » Fri May 26, 2017 3:47 am

In that case, cool idea. Too bad they couldn't get it to work. Essentially, you would have this little closed system, then all you do is hook it up to a power supply?

What was the main problem?

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Steven Sesselmann
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Re: Why operate Turbo - or Vapour Jet Pump during Fusion att

Post by Steven Sesselmann » Fri May 26, 2017 4:46 am

David Kunkle wrote:In that case, cool idea. Too bad they couldn't get it to work. Essentially, you would have this little closed system, then all you do is hook it up to a power supply? What was the main problem?
AFAIK the main problem was getting it to perform consistently for any length of time, although I saw the machine demonstrated once, I never worked on it so I don't have a clear understanding of what the precise problem is.
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Re: Why operate Turbo - or Vapour Jet Pump during Fusion att

Post by Andrew Seltzman » Fri May 26, 2017 5:02 am

Sealed neutron generator tubes (beam on target) are widely produced without issue. It probably requires superb cleanliness and possibly a deuterium reservoir(like a metal hydride) or a a deuterium reservoir separated by a heated(to allow diffusion) platinum membrane.
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Finn Hammer
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Re: Why operate Turbo - or Vapour Jet Pump during Fusion att

Post by Finn Hammer » Fri May 26, 2017 1:36 pm

Dennis P Brown wrote:
I am very interested in Van de Graaff's since I have built one that stands slightly over five feet tall and has a nearly three foot diameter dome. Would like to find out what you know about those - specifically designs of a high voltage spray (design, and details on the needle array) at the base of the belt; also, pick up needles for the top - location, number, design for both types and belt materials. For instance, return feed polarity spray in the top and best arrangement for wiring in the top relative to the pick up array and return wiring (if any.) Issues of improving performance (excluding a dry box) would be welcome. I have a rather large electro-static deuterium accelerator that I'd like to get working. Built the VdG and a large 60 kV voltage multiplier (for its belt spray - the VdG must have a positive polarity.)
Dennis,
See attachments for details of my latest and by far the best VdG. Notice the construction of the top roller support, by lowering the knurled brown support screws, the belt slacks, and the roller assembly can be pulled out sideways, which is nice when the belt needs changing.
Udklip.JPG

The button on the top corresponds with a switch via an insulating stick, so that the subjects can turn the VDG on themselves:
finalvdg.jpg
The combs are made from a strip of FR6 PCB material, the needles are pin needles like the ones used to hold cloth in position prior to sowing it together, and they are just stuck through holes in the PCB material, soldered on the needle head side. Spacing is 10mm, and 15mm from the edge of the belt.
The comb at the bottom is identical, you need 3 combs in total.
One at the bottom, connected to the spray supply, one in the terminal, just before the belt reaches the roller, and one at the top of the belt.
The spray supply is a ~10kV dc supply, I use a solid state oscillator with variable frequency, to tune it for the resonance frequency of the TV flyback transformer. this oscillator drives a half bridge of small fets, and around 10 turns on the free leg of the flyback core. Nothing fancy. Current is limited with around 180Mohm.
The top pickup comb is connected to the roller as well as to the terminal through an 180Mohm resistor. The voltage drop on the resistor effectively places the terminal et a lower potential than the roller, and since the last comb, the downcharging comb, is connected directly to the terminal, corona is created on it's tips. 10KkV is enough to create the corona, and Microamperes will do the trick.
Run the machine in total darkness, allow a couple of minutes for your eyes to adjust, and you will see the corona clearly, as a fine glow on the tip of each individual needle.
See this diagram for complete datails of charging circuit:
http://laplace.ucv.cl/Cursos/TrabajoTit ... -04-05.gif

Belt material, I have had good results with certain belts from the food industry, be sure to not get the ones that come with conductive material in them. A production line in a cookie factory can easily become quite electrified!
Habasit make a product called F-2EQWT, that is what I use.
http://www.habasit.com/en/index.htm

There is a build thread here If you like, of the first design I made:
http://4hv.org/e107_plugins/forum/forum ... 26708.post
VDG2.jpg
VDG1.jpg
Dennis P Brown wrote:
Gate valves have marginal use with a fusor (see the use for a DP but they are generally all or nothing) - having a throttling valve between a DP/turbo and the chamber is far and away the most useful method to control a fusor for real work.
Having read a lot, but not all, in this forum, I gathered the impression that the connection from DF pump to chamber should be full diametre and as short as possible, so that is what I did, but I can still regroup, and take another half shell, if the gate valve is a waste of time.
In that case, I would appreaciate if you could point me in the direction of a suitable throttling valve
Dennis P Brown wrote:
Issues relative to getting a high enough power/voltage transformer should be something you could help a lot of people here! So, feel free to post on that subject especially how you decide to address that issue!
The only real problem is sourcing a suitable transformer core, winding the coils is easy enough, although it takes a lot of patience.
Here is a picture of a 20kV, 300mA transformer I wound for a Medium sized Tesla coil, it has done museum duty for over 15 years now:
trafo.jpg

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Dennis P Brown
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Re: Why operate Turbo - or Vapour Jet Pump during Fusion att

Post by Dennis P Brown » Fri May 26, 2017 4:48 pm

Search ebay with the words butterfly vacuum valve or similar. Here is one result:

http://www.ebay.com/itm/VAT-612-Series- ... SwjqVZB0U7

It is stepper motor controlled unit but converting to a manual is just adding a knob; 4 inch throat so would work for many chambers; rather cheap, too for that type of valve.

Here is a much cheaper one also 4 inch throat and has a nice motor system!

http://www.ebay.com/itm/Butterfly-Gate- ... SwiLdV7gJj

There were other units on more pages but I didn't bother to view them. This unit appears rather nice for its size - yes, one would have to have matching o-ring face plates to seal.

A plasma pressure does not really follow a simple law like a gas at normal pressure since it is being ionized but for my chamber when its high voltage is off and having a 5 micron pressure to start and then applying high voltage results in ...5 microns pressure (when my system is clean, of course.) The throttle valve is closed - in any case, when in the 10^-3 torr range, temperature and pressure do not follow such a simple equation.

I have seen a paper on a neutron sources via deuterium acceleration in sealed systems from the 1930's (the deuterium was from a titanium source if memory serves.)

A 20 kV 300ma power supply can do fusion; a bit low on the voltage but would produce neutrons (and really heat the cathode - might melt it ... ) - would most likely require a rather good detector system to prove it is doing fusion. If one can make a x-former that puts out 25 -30 kV with 20 ma or more (my x-former can do 32 kV with up to 60 ma) the fusion neutron rate should be detectable with any average neutron detector system. The system MUST be negative voltage; so an AC system must be rectified.

Your shop skills are far and away beyond mine (LOL!) But I see the collector pickup pin locations for you isn't an issue that matters except for fitting it in conveniently (?) or has that position been proven to be best - also, belt direction for the image? I've read that being farther down the belt works better.

I will add a 150 M-ohm resister to my top collector and run it to the dome; I assume the return wire (connected to the same point as the collector wire) is necessary or just a nice feature?

An aside: I haven't tested my new belt but I added 1.5 cm by 4 cm silver conductive epoxy strips spaced every 2.5 cm (the strips are horizontally orientated on the vertical belt - the belt is 8 to 10 cm wide) around the entire belt - hope to mimic a chain drive system so the spray voltage couples more effective from the base to the dome ...maybe a bad or just ok or even could work idea in your opinion?
Last edited by Dennis P Brown on Fri May 26, 2017 5:20 pm, edited 3 times in total.

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Rich Feldman
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Re: Why operate Turbo - or Vapour Jet Pump during Fusion att

Post by Rich Feldman » Fri May 26, 2017 5:14 pm

Thanks for sharing pictures of your museum work, Finn!

>> Completely sealed off was my first thought. But then I thought that can't be it, sounds ridiculous and how could that work? Apparently it doesn't.
>> What was the purpose of that effort?

As Andrew and others have said, it would be no big deal if industrial tube-manufacturing technology were accessible. Look at hydrogen thyratrons. Here's one good paper found right away on the Internet: http://www.cdvandt.org/Evolution%20of%2 ... ratron.pdf

Permanently sealed vacuum tubes, with envelopes of glass, ceramic, or metal, have been ubiquitous for about 100 years. Generally they include a getter pump, good for the lifetime of the tube. As do capacitance manometers, aka baratron absolute-pressure gauges.

When you need rarefied hydrogen or deuterium in the tube, the bigger problem is "clean-up" of the good molecules, since they are sticky and chemically reactive. The usual remedy appears to be built-in metal hydride reservoirs that are electrically heatable, for control (or at least buffering) of the gas pressure. Here's a snip from the paper in link above.
thy.JPG
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Finn Hammer
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Re: Why operate Turbo - or Vapour Jet Pump during Fusion att

Post by Finn Hammer » Fri May 26, 2017 6:34 pm

Dennis P Brown wrote:Search ebay with the words butterfly vacuum valve or similar. Here is one result:

http://www.ebay.com/itm/VAT-612-Series- ... SwjqVZB0U7
I snatched this one @40US, should be easy to convert to manual:
http://www.ebay.com/itm/311861839545?_t ... EBIDX%3AIT

Btw, it would appear that much vacuum gear is priced at more than twice the expected price, when "Make offer" is an option, I regularly get "offer accepted" without counteroffer when I bid 50% of asking price.


Dennis P Brown wrote:

A 20 kV 300ma power supply can do fusion; a bit low on the voltage but would produce neutrons (and really heat the cathode - might melt it ... ) - would most likely require a rather good detector system to prove it is doing fusion. If one can make a x-former that puts out 25 -30 kV with 20 ma or more (my x-former can do 32 kV with up to 60 ma) the fusion neutron rate should be detectable with any average neutron detector system. The system MUST be negative voltage; so an AC system must be rectified.
The 20kV 300mA is just an example, thinner wire and more turns would result in higher voltage at less current, but distance to ground becomes an issue even when under oil. So a core with a large window area is needed.
I cannot help thinking about a 3 phase supply, which has inherent low ripple, and if made with both a delta and a star configuration, could have as little as a couple percent ripple with no stored energy, but we will see when I get there.
Dennis P Brown wrote: Your shop skills are far and away beyond mine (LOL!) But I see the collector pickup pin locations for you isn't an issue that matters except for fitting it in conveniently (?) or has that position been proven to be best - also, belt direction for the image? I've read that being farther down the belt works better.
I started out in life as a toolmaker, later shipyard welder, now podiatrist with mad scientist tendencies.
I think I have the best position on all combs, copied from this drawing: (which also gives you belt direction.
vdg.gif
Dennis P Brown wrote: I will add a 150 M-ohm resister to my top collector and run it to the dome; I assume the return wire (connected to the same point as the collector wire) is necessary or just a nice feature?
Just study the drawing carefully, the pulley needs to be at same potential as the electrode (dome) to attract corona from the down charging comb. I use a small ball bearing ball nested in the countersunk hole at the end of the pulley axle, and a small piece of spring hard bronze sheet as contact.
Dennis P Brown wrote: An aside: I haven't tested my new belt but I added 1.5 cm by 4 cm silver conductive epoxy strips spaced every 2.5 cm (the strips are horizontally orientated on the vertical belt - the belt is 8 to 10 cm wide) around the entire belt - hope to mimic a chain drive system so the spray voltage couples more effective from the base to the dome ...maybe a bad or just ok or even could work idea in your opinion?
Well, I don't know about that, sounds to me like an unwanted complication that should not be added before you already have an operating machine. VDG's are finicky.

Cheers, Finn Hammer

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Re: Why operate Turbo - or Vapour Jet Pump during Fusion att

Post by Richard Hull » Sat May 27, 2017 10:53 pm

A perfectly sealed fusor, ( 0.00000 leaks), that is pressurized to fusion pressures with deuterium will fuse just fine until you bury the gas and the pressure drops. I did this with fusor III. Differential pumping is the norm for all amateur fusor efforts.

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Bob Reite
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Re: Why operate Turbo - or Vapour Jet Pump during Fusion att

Post by Bob Reite » Sun May 28, 2017 12:38 am

I believe that Doug Coulter runs his fusor in "batch mode"
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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