Deuterium Accelerator and Electro-Static Power Supply

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Dennis P Brown
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Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

Well, as mentioned in the previous post that was restarted (thanks - I think - for reminding me of this type of project!), I have started looking at my old electro-static deuterium accelerator again (Third pic.) The unit is complete but needs an electric field to accelerate and guide the deuterium ions. The extra large Van da Graaff I built I have never bothered to test since at the time, I happened to obtain a fusor grade transformer that could do fusion (alas, a unit I will have to return in the near future ...sigh. Just so grateful they lent it to me!)

Well, here is a pic of the new voltage multiplier (First, second, forth & fifth pics.) The long vertical "rod" (see fifth pic) is two high voltage resistors - one 5G-ohm and a single 1 M-ohm. The first two pics show more details of the stack - since the two cap types have different thicknesses I had to use spacers to help keep the units fairly inline - not the easiest solution but works. This entire system will be under oil (still finishing that new tank.) The resistor stack will serve two purposes: 1) as a bleed resistor to discharge the system when I turn off power 2) As a voltage divider so I can measure the actual voltage (if it does go over 100 kV.) That vertical stack will also have a plastic pipe cover as well as be in oil.

In an air test using a NST (7.5 kV, a few ma at best) driver I did get the output of the VM to read 50 kV (direct measure using my HV probe with a built in meter.) The variac was at 50% and since this was in air I hope when in oil it will do closer to 120kV (my red line for accelerator use.)

A few notes: I use two sets of door knob caps because these things, even surplus, are not cheap - I got a deal on each set so I use both types; each is rated for the same voltage - 20 kV; just an issue of different capacitance values. The diodes can handle 30 kV except for the first one - that is one of my chinese made 20 kV 2 amp models. I was short since I never thought I would have to have this many stages to get + 120 kV. The oil I use is synthetic motor oil - does a great job and is cheap. Removing and allowing the original stack to drip for two hours made the stack fairly dry and no issue to handle. Oil immersion isn't the hassle I thought it might be. Besides adding two more multiplier units (4 caps) I changed out the hardware from plastic to metal - decided the plastic was more trouble than I got from reduced corona issues.

The accelerator design is simple: my turbo and vacuum pump system can reach the low 10^-6 torr; the large SS globe contains a battery operated ionization unit (25 kV) to convert the deuterium gas into ions. A small deuterium tank (see image) feeds a needle valve and allows a very small amount of deuterium gas to bleed into the high voltage needle to be ionized and accelerated. I have electro-static lens along the tube length (in hind-site, way too long a tube and only two lens should have been made - live and learn.) The end target will be either a duetrated plastic or a Ti foil with deuterium. The target is water cooled. That target is electrically isolated so I can read the beam current directly. Also, the target has a reverse field coil near it to stop electron back flow (nasty source of x-rays from the unit.) I do have shielding but it isn't in place.

The VM will be used to provide a +120 kV charge on the globe (like charges repeal.) With the correct deuterium flow, this will produce a deuteron stream hitting the target. This can produce a decent neutron flux (like a fusor including 4pi Steradians directional flux) with a deuterated target or I can activate some types of materials - like boron ... . Assuming all works as planned. This project, compared to a fusor, was a significantly more difficult build - providing the high voltage using a VDG is NEVER worth ones time. Hopefully, I can get the VM to work at the full voltage; take note: VM's do not easily get to these high voltages - these are projects, too (my first attempt using slightly smaller caps never worked for reasons I think were driver/Freq. related but again, these are never simple projects despite what one reads by posters - lol; learning curves can be steep.)

Using a high frequency driver for a VM is, of course, the best method. My 60 Hz (really half wave) is an easy build but a poor way to get HV - door knobs are ideal for very high frequency driver circuits so (maybe not so much my one large diode), I really should have bit the bullet and constructed one; water under the gate now. Keep these issues in mind if anyone decides this is a worth while project to pursue - it isn't just get the high vacuum and the rest is easy (but that is another story.)
Attachments
Detail of VM stacks (Caps & Diodes)
Detail of VM stacks (Caps & Diodes)
Detail of base/resistor connection
Detail of base/resistor connection
Electro-Static Deuterium Accelerator (Big Ion Gun)
Electro-Static Deuterium Accelerator (Big Ion Gun)
Voltage-Multiplier - Door Knob Caps with diodes; each unit stack can handle up to 20 kV
Voltage-Multiplier - Door Knob Caps with diodes; each unit stack can handle up to 20 kV
VM-Side View showing resistor stack - top resistor not connected to stack
VM-Side View showing resistor stack - top resistor not connected to stack
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Dennis P Brown
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

Some rather good news on my quest for a Giga-ohm high voltage resistor: turns out I have five special high voltage resistors (rubber encased, over five inches long) that are about 330 Mega-ohms each (a sixth one (colored red) is about half a giga-ohm.)

Using these, I should have no issues adjusting the current output from my positive 150 kV voltage-multiplier/NST system. I had these put away and had forgotten about them - came across them today when I was checking for any old resistor's I might have on hand that were still in "long-term" storage (being a pack rat has advantages- lol); they were designed for electro-static service on accelerators. At the time, I figured I'd buy them and someday, maybe, use them on my small accelerator.

Looks like they are well suited for my HVM; I tested three in series connected to the VM output and they matched a one giga-ohm resistor in voltage response (15 uA when the variac/VM yielded 15 kV; this voltage was determined by my HV probe.) Hence, my determination of their resistance.

Well, maybe this project will move ahead; and possibly, even this weekend, time permitting, I may install and test the accelerator's ability to hold an electro-static charge and determine the max current the VM will supply for three of these in series. Of course, can remove or add resistors as needed to get the desired current on the accelerator's sphere.

Aside: a VM is not an electro-static supply. Not trying to confuse anyone but this title refers to my original attempt to create one and afterward, I decided to move on to a VM or HVM (High Voltage Multiplier.) The HVM/NST system will charge a sphere and that electric field will be used to "accelerate" deuterons in a manner identical to the initial concept.

A rubber enclosed 330 Mega-ohm resistor (Pen for comparison)
A rubber enclosed 330 Mega-ohm resistor (Pen for comparison)

I soldered three together and added end connectors:
A One Giga-ohm chain Resistor
A One Giga-ohm chain Resistor
I will install these and make a test ... .
Last edited by Dennis P Brown on Thu Oct 26, 2017 2:02 pm, edited 1 time in total.
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Re: Deuterium Accelerator and Electro-Static Power Supply

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Well, still wondering if the high voltage multiplier will handle the inevitable voltage loss via the accelerator's sphere; that will be a test that creates issues of believable proof for maintaining the voltage - that is, the voltage needs to be remain sufficient even if I hold enough current (I know the current will hold but very likely, the voltage will collapse for the reasons Richard cited. Numbers do not lie.) I guess I can install a 5G-ohm resistor to the sphere and attempt, via a voltage divider (i.e. my HV probe) a direct measurement on the sphere's voltage but that may or may not be valid - an arc test is a good indicator but again, an unknown but certainly a rough indicator if it works ... . Finally, a field build up by the sphere will offer some idea but is hardly proof.

Richard is likely correct that my caps simply can't handle the huge corona loss by the sphere resulting in a far too severe a drop off in the HVM output voltage but I intend to test this out - will be fun.

The good news for me, in any case, is that if the HVM can't directly charge my accelerator's sphere, it can certainly be used to charge my Van de Graaff's belt with a well over 50 kV or so positive charge (at the base of the VdG's belt); that should help that device overcome its possible issues (not sure the VdG even has issues but of late, how could it not?)

Again, reverting back to old projects but they do need to be tested for closure, I guess. The VdG is huge - the sphere is 2.6 ft in diameter and supporting column is about 3.7 ft - the belt is about 5 inches wide and the entire unit stands just over 5 ft tall.)

This overly large VdG was built before I obtained the fusor grade x-former and created a neutron source via that method. This VdG unit remains untested since its operation, at the time, was not required. It runs fine (motor/belt/pulley all work well togther) but getting it to charge was not done at the time (since its belt system does not create fictional charging (all metal rollers) this necessitates that an external voltage spray be used and is its only real source of charging for the VdG's belt.) That external supply has never been hooked up (the corona spray/pick-up arrays are installed in the VdG.) To date, this device has only been eye candy.

If my direct charging of the accelerator fails via the HVM, then I will use that HVM (adjusted to max voltage supportable (what ever that is)) to charge the belt and see what happens relative to charge build up on the large sphere. That isn't a test I will attempt lightly - if it does work, that sphere can carry an overly large current that might not be something one wants to get hit by.)


This is, of course, a real electro-static generator (or is meant to be one. Except for the sphere, all other components for this VdG were obtained from materials bought at local stores.)
VandeGraaff.JPG


Aside: the motor/lower bearing/frame are all from a cheap mini-table sander; as is the upper bearing/support!
Below is a link to other images of the VdG and its internal components:

viewtopic.php?f=12&t=9384&hilit=Van+de+ ... =20#p70504
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Finn Hammer
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Finn Hammer »

Dennis P Brown wrote: Thu Oct 26, 2017 1:57 pm
The good news for me, in any case, is that if the HVM can't directly charge my accelerator's sphere, it can certainly be used to charge my Van de Graaff's belt with a well over 50 kV or so positive charge (at the base of the VdG's belt);

SNIP

If my direct charging of the accelerator fails via the HVM, then I will use that HVM (adjusted to max voltage supportable (what ever that is)) to charge the belt and see what happens relative to charge build up on the large sphere.
Dennis,

With regard to the function of a VDG, you are drawing some erroneous conclusions.
The charge delivered to the top terminal via the belt is directly determined by the area of belt entering the terminal per time unit. And the charge density on the belt. The charge density is the real limiting factor, because there is nothing you can do to increase it, if you try to, the charge just slips off the edges of the belt.
I can assure you, that you need a very weak supply at the bottom of the belt, only enough to create a corona discharge in the tip of the needles that form the comb.
I have used a simple oscillator driving a TV flyback transformer for this purpose, and with a 120Mohm series resistor to limit current so that the corona does not progress to form an arc.
You need to observe the comb under total darkness, let your eyes adjust over 2 minutes, and then you can clearly see the corona, it is _that_ weak, but it is enough to deliver the charge to the belt, if the distance to the belt is around 5-10mm.
Under these dark conditions, you will also see how the belt is lit up by a layer of corona, yes, the charge lights up on the belt when the charge density is at it's maximum.
Do this, you will be enlightened and you will thank me.
You can arrange an extra set of combs in the top terminal, to induce the same amount of corona on the belt on the down run, and this doubles the current.
A very bright professor down in Brazil, Antonio Carlos M. de Queiroz, who knows everything worth knowing about electrostatic machines, has made a small program to calculate the current you can expect from a VDG, you can download it here:
http://www.coe.ufrj.br/~acmq/programs/elcal.zip

You do not want to use a voltage higher than 10kV at the base of your VDG.

There are also very good online calculators which will reliably predict the output of any Cockcroft-Walton-generator, which is what you are building, There is a nice one here at Blazelabs:
http://blazelabs.com/cw-brm-java.asp

Hope this helps,

Cheers, Finn Hammer
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

I REALLY do appreciate any comments, insights or details (and so will others) on both Van de Graaff operation, techniques and do's/don't and what should be done. Misconceptions like mine do harm and are far too often propagated in articles on the subject. So, any corrections are highly and gratefully appreciated!

Thank you again and I will post results as they become available.

Tried the calculator - if my input numbers are correct (they are close), then I should get (roughly) 200 kV and 37 micro-amps. These are the numbers I do require - so, if this device can operate close to this, then the accelerator should work. Again, will have to test. I will absolutely follow your procedure for the voltage adjustment for the lower "comb". That is an excellent methodology!
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

Following Finn's excellent advice, I assembled a 7.5 kV power supply to use with a variac to function as a high voltage corona spray for my Van de Graaff belt.

I had a 7.5 kV NST (no CFI; 60 ma) on hand, as well as numerous small HV diodes (20 kV, 30 ma) and a cap along with some 50 M-ohm resistors I bought. I built a bridge rectifier along with the HV cap (40 kV, 0.02 uF) to filter the output and this in turn, then runs through three 50 M-ohm resistors in series (so 150 mega-ohm.) All this is mounted on top of the NST using ceramic stand-offs and is enclosed for convenience and prevention of getting a not fun shock - I can often find a way ... why I am hyper careful with my fusor supply and have it shielded and doubly and independently grounded.)

A quick test showed the system reached a 7.5 kV (max) positive output (the negative side of the bridge is grounded.)

I will closely follow Finn's method tonight and adjust the lower corona spray needle array (for the belt.) I will also install a micro-amp meter to the dome and out put this meter to ground - this will let me see what the VdG can put out (via the belt) and keep the dome from charging while I do all of this (not interested in getting zapped if this all works according to plan.)


I have already tested the operation of the VdG motor/belt system and it works well.


Corona High Voltage Supply with Van de Graaff
Corona High Voltage Supply with Van de Graaff

Corona Supply
Corona Supply
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Finn Hammer »

Dennis,
Sounds good.
With 150Mohm in series, you will be good. I hope you will get a dark night, where you can see the corona on the tips of the comb. I wonder how the silver paint on your belt is going to influence the operation, but am very interested in hearing about your observation of the corona on the belt in darkness.
Although it glows as bright as phosphorescence in the sea, where the water around the boat can light up a meter out, and the dolphins appear to swim in a sea of light, it is too dim to photograph, even with a very sensitive camera, the eyes are a wonderfully sensitive transducer, and I really hope you get to see it.

Good luck,

Cheer, Finn Hammer
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

Thanks for the help; I may need to replace the belt - what material do you use?
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Finn Hammer »

I will have to look it up, It is a transport belt used in the food industry, you know, to get the cookies and bisquits from the oven to the packing machine.

The company that produces it is called Habasit and the product number is F-2EQWT.
Not sure they are in business anymore. But any thin polyurethane white belt from the food industry, without antistatic measures, will be fine.

You might like to read this thread about the first VDG i built:
http://4hv.org/e107_plugins/forum/forum ... hp?26708.0

Cheers, Finn Hammer
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

That is your first VdG! That is interesting because that is the design that I first looked at to get answers on how to "how to build a Van de Graaff"! LOL. That is an extremely sophisticated device, and the most technically advance VdG that I have seen.

As for observing the corona, no luck - I even set up a single needle to the power supply to enhance the effect and that didn't work, either - I confirmed that the supply reached 7 kV and was working current wise (I could get a small arc from the supply.)

I will do a search for that type of belt material today. I will also do more work on the power supply and try to determine why the corona (lack there of) is such an issue; are your power supplies high frequency, maybe? Operating 60 Hz might be the issue. I might have a higher frequency unit somewhere.
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Finn Hammer »

Dennis,

Sorry to hear you missed the corona at the tip of the needles. I was wondering about the possible difference between the 60Hz you are using, and the 24kHz that I am using, but thought better about mentioning it beforehand. It shouldn't really matter, since the supply is rectified, but who knows?
The bottom pulley is made of metal, and grounded, right?
Mine is, and I have covered it in electrical tape, to avoid the alluminium smearing on the back side of the belt, which you also have experienced.
Cheers, Finn Hammer
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

Hello Finn, and I will soon see if the applied frequency matters using another supply I happen to have on hand (again, being a bit of a "pack-rat", pays off.) Using this I can perform the test you outlined (my preliminary day-light test tends to indicate it does): this "supply" consists of a ZVS (Zero Voltage Switch; a very nice Chinese built unit) which is a high frequency driver (supplied by a simple 12 - 30 VDC high current supply; luckily, I have such a DC supply.) I use this ZVS to drive a flyback - also, fortunately, this outputs a positive 35-50 kV (my charging unit must be positive.) While it tends for higher voltage (even when driven in the ZVS's lower operating voltage range), I will put it though my 150 M-ohm resistor series and see what this can do via a corona discharge tonight. My lower VdG's corona needle assembly is a few inches above my lower bearing but has a "grounding" plate across from that - the belt is between these two "electrodes".

A quick bench test using my HV probe as a grounding point on the flyback's output lead yields a strong corona field of 12 kV about 5 mm from the HV probe's pickup point; one can really hear the high frequency corona "buzz" as the probe gets close. A good indicator of what you are describing - not dark currently, so that test will be later.

I really need to replace my belt but frankly, sites are all over the map with what works and what's available (yes, the company you mention does appears to have been sold to a Chinese's company and their web sight does not appear to support English.) Guess I may end up ordering various materials and trying them.

Aside: I should not have gotten back to this old project because now, frankly, I am a bit angry at it for not working. So, I guess I will keep at it. That attitude worked well for my fusor and neutron generation/detection efforts, and even the very recent HV multiplier rebuild (my goal was 150 kV and it appears that I did achieve that (to no avail - the unit didn't have enough power)) but I did achieve that voltage, so I can cross that goal off my left over project list - lol.
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

Well, the good news, when I used a super sharp needle and this ZVS driven (high frequency) flyback system, a corona discharge was easily visible even in just low light. That settles the frequency question very clearly; 60 Hz is not going to work very well at all compared to high frequency supplies.

Strange that two or three people on the web have written extensive articles on sources and did not examine this issue and discus it. I know these people suggested 60 Hz NST systems but then again, I've only seen them talked about in theory, not necessarily used by them. But then, they might have decent belts and then, even a system that yields no visible corona might still charge a good belt material enough to give satisfactory results. Still, I have no doubt that the brighter the corona from the needles/pins, the more charge is being deposited upon the belt.

The bad news for my real device test, is that on the Van de Graaff, all I was getting was about one micro-amp current transported from the dome.

Again, most likely the belt material is the primary issue here. To a lesser extent, I noticed the ground plate for the corona is not in the correct position at all (an oversight when building) and that is not easy to address (but will be. Also, I will install the ZVS/Flyback in the unit as well) Still, some tenable but none-the-less, real progress.

So, getting and making a new belt is priority #1; it is just finding a material that will really work. Anyone with a source, please weigh in. Thanks!
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Finn Hammer »

Dennis,

Great news on the corona issue. The Habasit site looks like a dead end to me, it looks like the company has folded, and is just holding on to the URL for future reasons. Just plain impossible to get to a place where you can place an order, or even get material descriptions.
Come to think of it, the last batch of belts I ordered might be from another company, but from the same distributor. It may take some time to find the name, I will have a look for it tomorrow, have to dig the old invoice out of files.
The belt is important. Some people use rubber, some rubber bands used by physio therapists, and it works of course. But if you want to run fast and long, then nothing beats there conveyor belts. I had mine running at 6000rpm on a 4" pulley, that is 36 Km/hour and the only limiting factor here was the lack of ability to increase the revolutions of the motor. The top roller running op to 12000rpm might become a problem in the long run, though.
I hope I can get some info on the belts.

Cheers, Finn Hammer
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

Thank you again Finn. I ordered some white transport belt grade material from a source recommended by someone else that builds VdG's.

For entertainment, I repaired my high voltage multiplier (of course I cracked the seam and oil was leaking) and connected it to my "accelerator" sphere (10 ich diameter.) I manage to get a stable charge up to around 100/120 kV by indirect measurement via the electric field on the HV probe; that is, when the probe read/achieved 25 kV when it was set four centimeters away (this was based/loosely calibrated on a previous run without the sphere and I had the HVM at near zero load and then I read the variac scale to determine the real voltage. Aside: 20% full scale is directly measured as 50 kV on my HV probe.)

In any case, I measured the sphere's voltage more directly via air insulation break down - an arc 5 cm long occurred (so this indicates about 100 - 150 kV depending on humidity.) This arc went to one of the accelerator's focus lens (a bit confused why that conducts since it is way out on a ceramic tube so not exactly grounded to anything directly.)

Finally, I did do a direct voltage measurement upon the sphere with a voltage divider (5 G-ohm to 1 G-ohm and got a 25 kV reading on the HV probe before break down resulting in voltage loss. Again, supports this high voltage of 125 kV. (scale of variac was about 35%.)

All in all, far better performance than I would have suspected considering the cap limitations - looks I might be close to 140/150 kV upper range I hoped for and worse case, at least over a 100 kV.

In any case, the variac and HVM saturated at 35%-40% of full scale: after that, the voltage would not increase due to severe arcing.
I was surprised to see internal shorting within the metal sphere!? I didn't think that could occur ...well, learn a bit more.

My next step (weekend?) is to get the accelerator tube under moderate vacuum (10^-4 torr or better) and seen what happens when I charge the sphere again. See what breaks down and how and why there is internal arcing in a metal sphere!

In any case, these results indicate I am in the voltage range I feel that would allow me to get the accelerator to work - then again, been fooled before but these measurements, unless one see's issues I'm missing, indicate my measured values are likely valid.

So, anyone want to weigh in and provide better insight/measurement methodology to refute or support my efforts at some really high voltage measurements?
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Richard Hull »

One must remember and realize that a 100kv reading off the spark length is worthless under any true load condition, no matter how minor the load happens to be. The entire charge and, thus, the voltage on the sphere, at break down, instantly disappears from that sphere and it must be charged again. The sphere is the source of the ultimate voltage as an isotropic capacity. How fast the charge and, again, the voltage, can recover is controlled solely by the rate of charge delivery by the belt and its efficient transfer to the sphere.

This is readily seen by moving the discharge, (grounded), ball closer and observing that the spark is more frequent. Amazing isn't it! A real loaded voltage might best be obtained by measuring the spark length that the VDG can deliver at a virtual continuous rate. Can it do this at 1CM?

Even the least interested by-stander can tell that a 10cm spark off a VDG delivered every 10 seconds is white hot and noisey..POW! A s---pot load of current was in that lightning bolt! You bet it was! As the discharger is moved in closer, the spark becomes more frequent and a bit weaker,.... less current. As it comes to a point of close proximity to the big sphere, the spark is almost continuous and the noise from the spark is grossly reduced, as is the current. Under any load actually connected via a wire lead to the sphere the voltage and current plunge even more. Simple physics

Unfortunately, a continuous load, as in an accelerator, might reduce the continuously available voltage, and or current, far below that needed to achieve a specific goal with that accelerator.

Trying to get a VDG to do real scientific work demands far more than getting a hot, snappy, 9cm spark every 8 seconds. Half of all useful VDG work will involve insulation, the other half, a study in rapid electrostatic charge transfer to a large enough and well insulated, isotropic capacity.

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
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Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

Thank you, again Richard. All good points that offer better understanding of the real situation for such systems; not obvious for people like myself with near zero knowledge of high voltage systems. Learning about these very high voltage systems is tricky; issues such as the length of time between arcing is a point I hadn't considered and is rather critical in order to properly determine a valid sustained voltage/charge. Just as I forgot that since the accelerator is under vacuum (10 - 20 torr) it is an excellent conductor (duh; forgetting that is not something I should have done); hence, the internal arcing is rather obvious (accelerator dome/sphere to the internal accelerator tube) and also to the metal electro-static lens 5 cm away from the accelerator's sphere. Also,this arcing, as you point out, eliminates all significant stored charge on the accelerator's sphere and the arcs are causing severe loss of the accelerator''s voltage and charge on the sphere. Your discussion of distance and arc strength/time between arcs was very clear and encompasses the key points I hadn't properly considered.

My method of using a voltage divider was a more realistic measure and I still think the accelerator's sphere is close to the 100 kV value; that is, until the arc over/short does occur. I do get a strong electric field to form (between arcs, that is.) I do believe that the arcing issue can be fixed by reducing the system's vacuum to under 10^-4 torr. Then I will see what sustained voltage/charge can be achieved on the sphere (then again, maybe not.)

Just as in mastering fusor operation and the issue of creating a stable plasma, a learning curve is involved. This necessitates getting feedback from someone familiar with high voltage systems in order to learn the techniques and correct mistakes (both in understanding and execution) to determine a valid charge & voltage that is sustained rather than what I want or just assume.

While my primary focus will, for now, remain repairing and upgrading the Van de Graaf so that it at least functions and provides some realistic charge/voltage levels while isolated - and maybe, with some better design features - in the future can operate the accelerator, I will continue to explore the issues of measuring the high voltage created by my voltage multiplier. More to the point and relative to your post my determining if a significant charge/voltage can be maintained on the accelerator's sphere using that device will be more involved then I suspected.

Again, thank you for both the insights and clarifications - they save me a great deal of trouble and prevent me from wasting a lot of time.
Bruce Meagher
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Joined: Thu May 12, 2011 11:25 pm
Real name: Bruce Meagher
Location: San Diego

Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Bruce Meagher »

Dennis,

Nice to see that you’re continuing your electrostatic accelerator efforts. As Finn mentioned you want to get as much charge on the belt as possible. Belt material (with high surface resistivity), width, speed and comb design will determine how much current your VdG will get to the terminal. Unlike a fusor you’re not going to draw a ton of current. You have your ion source, equipotential resistor divider network, and corona losses. I think of it like a link budget, and as long as your VdG can supply more current than your budget (for a particular voltage) you’ll be in good shape. One key element to continuous stable operation is pulling off extra charge from the terminal. On the pelletron there are adjustable corona needles used to set the voltage and keep the terminal's voltage from breaking down (see attached pics).

You might consider grounding the terminal through a current meter and focusing on improving your charging rate.

Also attached is a paper from the web on a particular Van da Graaff accelerator design from the '70s. It has some useful info if you haven’t seen it already.

Finally, there's a sweet Van de Graaff accelerator for sale right now on eBay! At $10k it might be out of some people’s budget, but it’s a 400KV unit from High Voltage Engineering (the company founded by Robert Van Da Graaff in the late ‘40s). It’d be an excellent setup for high energy physics experimentation. https://www.ebay.com/itm/Small-Van-de-G ... SwjqVZL24Q

Bruce
Attachments
Corona probe on the pelletron
Corona probe on the pelletron
Inside an empty pelletron chamber with corona probe extended
Inside an empty pelletron chamber with corona probe extended
05_chapter 2.pdf
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Last edited by Bruce Meagher on Wed May 20, 2020 8:39 pm, edited 2 times in total.
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Dennis P Brown
Posts: 3147
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Deuterium Accelerator and Electro-Static Power Supply

Post by Dennis P Brown »

First off, I appreciate any comments/help because this project has been waiting for a few years now (obviously from my complaining), only because the Van de Graaff is the issue with my accelerator project (but really, all such projects based on either a VdG or voltage multiplier - people have misrepresented their results in past articles on-line (not a reference for any here.)) Back to the matter at hand, as you mention, current generated vs. the losses in a VdG are the driving concern. That will occupy me and determine success or failure.

Also, by the way, thanks for your post relative to this topic!

The VdG unit you posted is a bit outside my budget constraints (lol.)

I am determined to try and get this accelerator working (if possible.) Yes, to all your points - I have a 0 - 2 and 0-100 micro-amp meters (both analog so ok with the voltage) that I am using to determine output in a manner you suggest. While I solved one serious problem that I had overlooked in the past (and this issue has never really been addressed in the literature, for that matter) and that was the spray supply frequency - that matters a good bit as I discovered in real world testing.

By the way, any source for belt materials that you have experience with or knowledge of would be useful.

I am currently rebuilding my monster Van de Graaf to accommodate the new belt (the new material arrived) - also, I increased the system's drive speed via a larger drive sprocket but now I am having issues with stalling the motor; to address that issue, I need a belt with a good bit less drag (now have) but my motor mounts do not adjust enough to accommodate the slight size change so, back to redesign/rebuild in order to deal with that new issue.

I also have a small VdG and that now is out-of-mothballs, and on my 'to-do' assembly line (currently, that list has my neutron scintillation detector which is currently priority #1 - that scintillation system's wiring and machine work have been a significantly easier but also bigger pain than I thought but is now done. On the plus side, I have discovered a good bit about problems/repairs relative to my entire HV supply/counter/pre-amp systems used for all my neutron detectors (the pain part). Never gets easier ... .)

Having the small VdG should enable me to do some experiments on using this device due to these will be a lot cheaper, faster and easier builds, while I continue (as time windows open) the mod's on the giant VdG.

Mean-while, I have run my fusor and conditioned it - it, at least (unlike my He-3 detector project), is working very well ...but wondering what shoe will fall next, equipment wise.
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