Linear deuterium Accelerator-Ion Gun Issue

For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.

Re: Linear deuterium Accelerator-Ion Gun Issue

Postby Dennis P Brown » Sat May 14, 2016 6:23 pm

Well, the power supply works well; 5-8 amps max and 0 - 20 or 0-40, or 0-60 volts DC (can be pos or neg.) Can't believe how much trouble building this was but I did learn a good bit about transformers and diode bridges and issues both about grounding and filtering - as Richard says, build it.

I have been studying ZVS (zero voltage switches) oscillators and if my new one causes problems again (shouldn't since I have a stable and accurate power supply now) I will build my own; turns out I have 90% of the key components it is just a matter of creating a proper circuit board. Making a high current 30-50 kHz low voltage supply using an existing 60 Hz supply is rather easy or so it is claimed (lol.)
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Re: Linear deuterium Accelerator-Ion Gun Issue

Postby Dennis P Brown » Sun May 15, 2016 5:32 pm

Finish the 0-60 volt DC power supply; realized the issue with the ZVS - it had no marking for the ground and pos inputs which ended up damaging the unit since I didn't know this used polarized caps! So after tracing the circuit determined the correct polarity and realized this was the real issue. Replaced the destroyed cap with a far larger/higher voltage one and replaced a bad resistor. The device works well now.

My flyback is too large for the power supply - 6 amps just isn't enough and the unit tops out at 28 volts creating an extremely low 5 kV from the flyback. Guess I need a better supply - guess I might as well just use my monster 60 - 120 amp, 50 volt transformer (a very big - read heavy - unit. Uses, of course, 220 v)

Glad I am getting some experience with real circuits and able to do some elementary repairs. Also, guess I will hookup my oscilloscope and look at the output frequency later this week.

Below are images of the ZVS freq. converter and a high voltage probe measuring through a HV diode connected to the flyback. Below that image, the entire system.

I installed a variac in the supply so I could free up my large variac. Also, I used a scrap panel meter for the voltage readout; to get it operating I just had to determine the correct resistors to add to get the meter linear over the range. The system works very well (but is, unfortunately, still underrated!)

In any case, this rather long effort resulted in me building from scrap/non-working junk a rather nice variable output pos/neg DC power supply; some interesting theory on ZVS converters and even the chance to repair one. All this just to begin building a alternate 100+ kV supply ...still, learned a good bit (far, far more to go) but has been a rewarding experience through a bit aggravating one ... .
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Re: Linear deuterium Accelerator-Ion Gun Issue

Postby Dennis P Brown » Sun Jun 19, 2016 6:01 pm

Hate to preempt the really great post here but just need to update on my accelerator.

I have made a new belt for my Van de Graaff (VdG) - after removing the metal tape on the rollers (caused the belt to short out from getting metal on the inside surface; that was a surprise. Guess the people who recommend that never tried it) - I made a new belt (same plastic material) but have rectangular squares of conductive silver epoxy every 2.5 cm (each about 1 cm "high" and 8 cm wide) along the entire belt (outside only! Otherwise, the same shorting issue would quickly occur!) In this way I have a "metal" link belt without the need to create a chain system (very difficult.) The belt is 10 cm wide so with a 7 kV spray, I hope this belt can charge the dome rapidly enough to create enough current to power the linear accelerator.

Still, pointless to test the unit until I build the room de-humidifier - otherwise, I know the system will short to air most the charge on the dome and prove nothing.

Still, not really counting on this design to work but it will prove the basic idea of the "if" of using a VdG and partly show IF such a thing is remotely reasonable. This is a big unit with a big belt so if it can't work, highly unlikely smaller units - especially commercial ones - will function for this purpose. I am not saying these things aren't good for creating extremely low current high voltage; just that an accelerator column creates too large a current draw for their practical use for this specific application.

IF (and only if) this new design works, will I post both pics and details on construction of the belt.

Backup plan one to this, is installing a neoprene belt on the VdG (no metal) with the rubber rollers - this is considered an ideal belt for creating a positive charge. Again, not convinced.

Backup plan two is to finish the tested and proven voltage multiplier and add the last two stages to get the 120 kV or so; appears to offer a good bit of current. That (see previous posts and images) existing unit is also a rather large monster and needs to be under oil for the last stages to have a chance to develop full voltage. As such, I am holding off on that device final build until the VdG fails.

Really like the previously posted neutron accelerator unit posted here - the VM design they use is a good way to go and most likely, I will end up following that path; I am using a NST since I have big caps and diodes. I did try a ZVS system but it isn't very good (not due to the diodes.) So, will continue with the NST system since it has been very good creating the 50+ kV to date.
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Re: Linear deuterium Accelerator-Ion Gun Issue

Postby Dennis P Brown » Sun Jun 26, 2016 5:47 pm

Cautionary tale:

Well, more progress but not bothering to do too much too fast - really, summer is a humid time of year. Recharged the de-humidifier (used propane) and it works great (very easy to do.) The room went from 61% to 32% but that is its bottom - guess long term drying would be required to get below that threshold.

Still, 32%, I feel, is just too humid to even consider running a Van de Graaff much less perform a "make or break" test on this new and very large unit. Need a fair test before I decide what to do.

So, next step is to seal the VdG and use a drying agent within it. Considered SF6 but just not worth the effort. Might create a small enclosure for the entire system (vacuum, ion gun, VdG) so the de-humidifier only drys that smaller space. Combing both is silly so may steal on one this week to be done next weekend.

Bottom line - while building a very large VdG is easy and rather cheap (under $200 for everything) just getting any VdG to operate is tedious and even then, no guarantee that it will work (current wise.) Still, traveled this far so I am determined to finish this project (the VdG) one way or another. Just herding cats isn't a lot of fun ... .
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Re: Linear deuterium Accelerator-Ion Gun Issue

Postby Richard Hull » Sun Jun 26, 2016 7:12 pm

A good friend, Bill Richards, an old member of TCBOR here, Now passed away, solved his VDG problems in a unique manner.

He bought a junk hair blower from a local trift store. $1.00 He made a duct/plenum to supply blower air to the column containing the belt. He attachted the dryer to a variac and let it heat the air just enough to be rather dry and warm. Now, this will not assist with moisture in the air around the top load. He would always wipe his oblate terminal with a 90 proof alcohol wet cloth to rid it of dust and lint, (major bleed points). It improved his output by 50% in humid summer conditions and made it spectacular in winter.

Running his VDG always demanded a 5 minute cleaning and de-humidifying prep and another 5 minutes of run before it stabilized.

I own the largest VDG that American Science and Surplus ever made (old Morris and Lee), but haven't run it in years.

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.
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Re: Linear deuterium Accelerator-Ion Gun Issue

Postby Dennis P Brown » Mon Jun 27, 2016 6:16 pm

Thank you Richard! These are all great ideas (I can't believe I didn't think of the hair dryer!!!)

Very glad you mentioned this and how this was used.

I will definitely use a hot air dryer and with the room de-humidifier this should give me a good chance to get the air dry enough; I will keep a humidity meter in the unit to both confirm and monitor the air quality.

I use the alcohol trick and it does a good job.

Aside: Jeannette (a senior now at MIT!) is done the reading (research papers) for the project she was hired as a summer intern at the Max Planck Institute and starts today working on a 3 Tesla superconducting magnet for her research job at the Wendalstein 7-X Stellarator. Hope she remembers to remove all metal items before turning the unit on!
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Re: Linear deuterium Accelerator-Ion Gun Issue

Postby Dennis P Brown » Tue Jul 05, 2016 9:14 pm

A bit of updating: the main Van da Graaff box/column/dome are all nearly sealed - a good bit of rebuild. Far slower than I thought!

Once done I will dry the room, add desiccant in the VdG and close the VdG box. I will then wait for the weekend so I can try to see if all my work was worth the trouble. I hope the new belt design with metal conductors will load the dome from my charging system (A NST and voltage multiplier system to make positive 14 kV for the spray system.) Will keep the hair dyer idea ready for further drying if necessary.

I hope the VdG system (inside) gets below 10%. I already know that the room can easily reach 30% using the air drying system I put together. Will need this all to work for a valid test.

Again, not counting on this part of the project but would be nice to have a success with such a major rebuild.
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Re: Linear deuterium Accelerator-Ion Gun Issue

Postby Dennis P Brown » Sun Jul 10, 2016 5:31 pm

Well, the Van de Graaff sealing work is done; had to reduce the width of the new belt. Pictures to show the new belt - the "silver" rectangles are really silver (conductive epoxy: 2-3 ohms across each.) Humidity just isn't low enough in the room - from 70% to 40% just ins't gonna do it. So, will wait. Also, sealed the upper dome, too. When the room is dry enough, will add desiccant to the inside of the VdG (including the dome section.) Installed a humidity meter inside the VdG as well as one outside.

The idea is that the metal surface will accumulate a significant amount of charge from my high voltage "spray" system and transport this to the dome. In this manner I will get a greater charging rate than from simple fictional belt/slippage accumulation. That is the theory, at least. Works on professorial systems but this is very home built - 56" tall and the belt is about 4 inches wide. The dome is about 25 inches across so I am hoping this will create enough current for my needs - that is, if I can get a dry room!
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Re: Linear deuterium Accelerator-Ion Gun Issue

Postby Dennis P Brown » Wed Jul 20, 2016 12:50 pm

A quick update on the status of my deuterium accelerator project: the room humidity, even with my a de-humidifier running all day, is well above 40%; so definitely, this project is on hold until cooler days of autumn (?). However, I did, as posted, build the very powerful high voltage positive 10 kV supply for the lower 'spray bar' that will be used to charge the belt (as can be seen in the photo previously posted the belt has 'silver metal' rectangles to carry extra charge up to the dome) for the Van de Graaff. Can't think of anything else to do for this project but wait for lower humidity conditions.

As such my postings in the "Fusor Power" section I have taken my partly finished fusor out of mothballs and will try to get that into operation now that I have a power supply that can handle the required power/voltage. Unlikely this will provide enough neutrons for my experiment but who knows? Worth trying and is kinda fun.
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Re: Linear deuterium Accelerator-Ion Gun Issue

Postby Dennis P Brown » Sun Jul 24, 2016 5:27 pm

Well, decided to change the "ion gun" assembly yet again on the gun; this requires de-mounting the accelerator and striping it down, "breaking the end seal (never fun)" and then I will do two things; first, add a high vacuum port/valve system so the small deuterium gas tank needs not be removed; this has the added advantage that I can refill the tank anytime without significantly disturbing the system. (Aside. My deuterium tank is stored inside my high voltage hemisphere. In this manner, I don't have gas lines leading to this hemisphere which significantly reduces current lose from the Van de Graaff.)

Second, get rid of the whole existing "ion gun" assembly that is based on ceramic and metal; rather, convert it to all metal. Using metal will improve the seal (decrease possible high vac leakage) and get rid of a highly delicate part that tends to fail if I disturb it in any significant manner. Machining a new part is trivial and I really hate that I didn't do that three builds ago ...learning, even after many years is always an on going experience with high vacuum.

Really might as well do these things since I still have a few months before humidity drops enough that I can run the new Van de Graaff.
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