TANSTAFL.

Electrostatic Inertial Plasma Confinement

Study of Ion Microchannels and IEC Grid Effects Using SIMION Code

Development of an IEC Neutron Source for NDE

So the cage is now unwired from the electrical feed-through. Fundamental laws of topology and conflict with the replacement of the seals on the feedthrough... The main chamber seal still isn't closed until I get the cage reconnected to the electrical feed through. But since I have to use the hoist to do that, I'll leave that task until tomorrow night.

Still, all these gaskets in the system created a large area of out-gassing Viton. Replacing this Viton with Teflon can only be a very, very good thing. I also should remember to get some Everclear to clean up the few fingerprints on the cage. Since I'll have the chamber open and all. . .

Moving forward, at least. :)

There's been a couple of things that have happened that I didn't blog about. On the left is the cage as mounted in the chamber. Click on the image for a larger picture. The magnets are all mounted, and the ceramic stand-offs have been attached. I actually got the detachable electrical connection to the feed through completed as well. Now all that awaits is the actual connection of the wires and a test of first plasma.

Well, that and a lot of work on electron guns and ion guns. From my simulations, I found that just the addition of the magnets on the charged cage is enough to increase the orbits of the ions by an order of magnitude at least. I say "at least" because my simulation is slightly asymmetric. Due to the chopping of space by cubes, the fields aren't as symmetrical as I think the actual cage I constructed are.

In any event, the magnets do an excellent job of changing the momentum of the ion at the physical cage boundary. As you can tell from the potential field diagram, due to the inverse square law nature of electrical fields, there are huge wells leading right into the cage structure. The magnets, which have a field strength of 1.2 Teslas, provide just enough kick to the ions so that there momentum is changed just enough to avoid plunging down the potential gradient and grounding out on the cage structure.

Very cool.

Anyways, I got all the old site moved over, and the various pages linked in. Google should have these indexed and such so that queries for the documents won't find the old site location.

On the right is the cage with magnets and stand-offs, sans chamber. Click on the image for a larger picture. It's actually quite the pretty thing to look at. All shiny from the electropolishing n' such...

The guys at Heat Wave labs still haven't gotten back to me. Likely think I'm a wanker and they don't want to waste their time with me... Oh well, I'll have to phone them and talk to the guy in charge of their electron guns and cathodes.

Will have the old site transfered here soon...

It's clear that a lot of the chaos I saw in the previous model was a Tiffin phantasm of the way the equations were solved.  Which is pretty good news.  On the right is the electron trajectories resulting from injecting electrons in one of the pentagon faces.  The view is the same isometric vantage point as the above field image.  The injection point is just inside the actual radius of the cage.  The energy of the electrons is 7.71 keV, directed along the X axis.  The potential contours are nice and smooth and regular.  I believe that I'll have to have some directional focusing to capture the majority of the electrons, but a simple Pierce reflector should be sufficient to focus the beam.  It's the direction that's hard to get accurate without deflectors.

The injection energy is 10 keV or less in the pentagon faces, and that means the electron guns will be a lot simpler to construct.  I also found that the ideal grids that SimIon allows will give a reasonable approximation of the virtual grid formed by the electrons.  Too ideal...  But it's a good first approximation.

What's nice to have confirmed is that it doesn't take much of a change in momentum to push the electrons into the right contour.  For example, a difference 10's of volts on a base of 7,000 is enough to shift the electron's trajectory into reverse.  The addition of the magnetic array should add just the right kicks to keep these beasts caged for a significant number of orbits before becoming power losses.

On to the magnets.

I have only modeled the electrostatics.  I have yet to add the magnets to the simulation.  I must say that you can see the symmetry bias quite clearly.  First, SimIon represents 3 dimensional space via small cubes.  So the icosi-grid structure has some significant aliasing.  Nothing really horrible, but certainly noticeable.  It becomes even  more noticeable when you plot the potential contours for the beast (shown on the right).  I know it's a really complicated contour plot, but it is using the same isometric view of the cage shown above.

The immediate thing that stands out from the field is the one great circle that happens to lie on the Y-Z plane.  This is the only great circle that lies on the icosi-grid which aligns with the 3 ordinal planes of the cubic system of SimIon I might add.  Why am I even mentioning this?  Well, technically, all 6 great circles that make up the icosidodecahedron are the same great circle - just in 6 different orientations.  This should result in a five fold symmetric figure - i.e. all 6 great circle's should have identical fields.  But such is not the case because all I have to divide up the space with is cubes.  Cubes results in an aliasing of the space partition, and thus the imposition of symmetries not in the original model.

<sigh>  That's okay.  The simulation is far better than required to do some serious engineering with, however!

BTW, the simulation took up 270 megabytes of grid memory alone!  It took SimIon to calculate the potentials for the seven electrodes (six great circles on the icosi-grid plus the spherical chamber ground) about an hour or so on my 1.7 GHz P4 laptop.  Non trivial calculation times.

Right now, the simulation is a solid ground potential spherical shell surrounding the the icosi-cage electrode in the center of that sphere - held at -30,000 volts potential.  To make this more accurate, I'll need to poke the holes in the sphere that approximate the actual geometry of the vacuum chamber.  It will significantly change the field - that much is clear.  So it's necessary.  I can also try to rotate the entire icosi-cage before calculating the fields, removing the aberration of the Y-Z great circle.

I ran some electron trajectories using this set up, and they were very promising.  As I said, more than good enough to do some real engineering.  On the right is a view of one of the runs.  Click on the picture for the full size picture.

The grid and vacuum chamber are not shown in the picture, but roughly the same orientation is used as the previous graphics on this page.  The electrons were shot into the open pentagram of the icosi-cage, sharing the X-Axis of the model view.

What I was hoping to happen has indeed shown to work - at least in simulation.  The electrons are shot into the icosi-cage with a potential of 15,429 volts.  As you can see, they actually penetrate to the center of the cage and spin out - tracing the field contours shown above.  There was some question as to whether one could really inject electrons into the negative potential inner grid.  Since the grid is mostly empty space, there field isn't uniform.  So only 15.5 kV is needed to inject the electrons using an electron beam.

I found that if you inject the electrons on the same radius as the icosi-cage - i.e. an electron emitter sitting right in the open pentagon at the same radius of the cage, you can inject electrons with only 1.5 kV of potential.  Pretty nifty - if true.  Far easier to build an electron gun that only requires 10 keV or less.  And what I think I can show with more simulations is that I can simply use the electron gun equivalent of a flood lamp - i.e. an unfocused electron source.

This vastly simplifies the complexity of this hair brained idea I have.

What's also interesting from the electron trajectories I have modeled so far is the very nice spiraling and symmetric splitting around another axis.  Obvious from looking at the field contours, and obvious in hindsight, but pleasing to see none-the-less.  I think once I add the magnetic circuit of the icosi-cage, I'll have a very nice electron trap.  A very nice one indeed.

The magnets are going to alter the momentum of the electrons.  They don't provide a conservative force, rather an orthogonal force via the cross product.  But the whole point of the icosi-cage is to provide an advantageous geometry for making use of these cross-product forces.  The way that I see the electron trajectories bouncing around, the addition of magnets should be more than enough to push the electrons into a nice bouncing orbit around the insides of the icosi-cage.

I did a few ion simulation runs, and they were pretty fun, too.  The trajectories are much more chaotic.  The focusing of the beam is much more important.  And I can't effectively simulate the space charge of the virtual grid of electrons...  Once I get the magnets in, and assuming that the structure actually is an effective electron trap, I can simulate some of that in SimIon.  I was thinking of using some point electrodes (pixels) to simulate the space charge as well.  Hope that works.  Should provide a good approximation...

In any event, it'll be interesting to find out.  Next step is to add the magnetic circuit and see if there is the effect I believe it will.

In more real news (as opposed to simulated news), I got the electro polished cages back.  They're absolutely gorgeous.  The stresses in the cages have also evened out nicely, so they look very symmetric - not a lot of irregularities.  Very nice.  I also built the ceramic insulator standoffs.  I used the vacuum grade epoxy and constructed 9 of them.  I need 10, but I only ordered enough parts for 10 and I broke one of the cylindrical standoffs when I was trying to drill a venting hole.  Can't really drill fired ceramic without special equipment.  As the standoffs have screw holes, and I epoxy'd a ceramic ball on top of one of these holes (I'll be posting pictures later), I may have a virtual leak situation.  I'll have to see.  Hope not.  The epoxy forms a tight seal...  Fingers crossed.

I tried to come to grips with the wiring of the grid from the electrical feed through.  Got a little bit ugly, but I think I may have a way to do it simply.  We'll see.  I have to drill out a hole on those electro polished pieces of beauty...  Then I have to mount the insulators, then mount the magnets.  Joy of joys.  The magnets are always fun to have flying about :)  So, still lots to do.  Hopefully I'll have more time soon.

I do have some good news.  I ordered a copy of "High Voltage Laboratory Technique" from AstroLogos books.  They apparently have the copyright on this book and reproduce it for a fee.  It wasn't that expensive, and this is a classic work that I really wanted to have.  Unfortunately, that was three months ago.  Seriously.  I ordered this Nov 21, 2002 and it still isn't here.  Now, granted that they have to perform blood rituals to get this 1954 classic printed, but geez...  The lesson is, NEVER ORDER ANYTHING FOUR DAYS BEFORE THANKSGIVING.  I mean, I see this all the time.  Every place I've worked has always scheduled a release in November-December.  Guess what?  It's non-stop holiday madness for the entire two months of November and December.  People don't get over their new year's hang over until at least January 15th.  So anything that has to be done during these three months just isn't going to get done.  But humans in America still labor under the illusion that stuff actually can get done during this time.  I'm one of the hapless fools that believe this, obviously.

But in theory, the long awaited tome will be here next week.  It was sent Thursday...  Let's hope it will show up.

Anyways, the HV cable should show up for the Bertan here pretty soon.  I'm going to have the gas line spur removed, hopefully this week.  I'm ordering some 2.75" nipples and I have some 2.75" blanks lying around.  I'm going to talk to the good folks at Heat Wave Labs to get some dispenser cathodes so I can start playing around with some ion and electron guns.  Everybody seems to be building them these days <g> so I should get with the program and start building some of my own hair brained designs. 

So, lot's to do.  Not much time to do it, of course.  We had two people quit at work - for good reasons.  One has his fiancé in France, another has his wife in Dallas, TX.  But we'll still miss them very much.  So, more workload for me - in addition to the extra load of interviewing replacements.  <sigh>  I really, really, REALLY hate this economy.  It sucks something fierce.

In any event, I've been getting much better at organizing my time, despite all this madness.  Sorry to harp...  I'll get back to work :)

So we connected one of the resistors and cranked up the supply to 15 kV, which is the rated voltage for these resistors.  It was fun.  But not half as fun as listening to the crackle of the setup.  Brent had gotten the HV probe from EBay I think, but it didn't actually come with the tip.  So one of the hardware trips was coming up with a screw of the correct size to replace the tip.  Well, actually, the original intent was to use the screw to pull out (Brent theorized) the connector so he could screw in the tip he had ordered.  He had the wrong tip, so nothing we could do - short of destroying the probe - would allow that tip to work.  <heh>

So we just used the screw as the probe.  The vast pointy area of the screw threads make a wonderful corona producing surface, but what the heck.  At 25 kV we couldn't see any corona even in the dark - heck it was only half a mA max anyway.  Hardly anything to write home about.  But we managed to crank up the supply to most of its rated values.  To the right is a picture of the load we came up with.  Nothing exciting to those seasoned veterans of high voltage experimentation, but we were pleased any way.

I was especially pleased that Brent didn't seriously injure himself.  Mind you, Brent is no dummy when it comes to electricity.  He works with it a lot, and is quite the safe guy.  But in the first test, Brent went and tried to put his hand near the one resistor to see if it was heating up.  Something that you'd feel perfectly safe doing at 50 volts and below.  It's not like anything around this potential level going to arc out and bite you.  After all, air is a pretty decent insulator, and this is a DC voltage.  Not some high frequency stuff from some Tesla coil or something.

But 30 kV is a different thing entirely.  It does jump out and bite you.  Hard.

It was a very stupid thing to do.  Brent has a lot of habits picked up from his years of working with electricity.  Some of the ones that are okay for low voltages are really bad in the realm of high voltages.  It's just a completely different world when you're beyond the breakdown voltage of air.  You simply don't have to physically come in contact with a conductor to get bitten.

We did observe something that we couldn't adequately explain, however.  If you look at the picture above and to the right, you'll see a green wire connecting the two resistor bundles.  When we got the voltage cranked up to 15 or 20 kV, the green wire on the right of the terminal block started vibrating.  At first, when I mentioned this, Brent said that it was his hand shaking.  I couldn't see any other vibration in the system, and I was looking intently.  So we shut everything down.  Removed Brent from the system (i.e. no probe) and tried the experiment again.  The wire started vibrating again.  So now Brent was convinced that something unexpected was going on.

Note that this side of the resistive load was connected to the negative 30 kV side of the supply.  The system is symmetric, so the other green wire - on the ground side - wasn't vibrating at all.  There was a metal bar under the table.  Brent thought it might have something to do with it.  So we moved the load away from it, and tried it again.  Same result.  Then we turned off the lights to see if there was any corona that might help explain it.  No such luck - certainly to our eyes.  And it's pretty dark down there with the lights turned off.

In any event, we think it's just related to having a potential of 30 kV on that wire.  The air in the lab is pretty humidified, being so close to the Pacific ocean.  It's not like it's the national institute of standards down there.  Lousy grounds are still grounds, and we do have the ground return to the supply in close proximity - so I wouldn't be surprised if it was just attracted to that.  But we had never witnessed this effect, so it was kind of cool to see.  I'm sure it's no mystery to HV veterans, so I'd love to hear the real explanation - love to check my theories. Kinda cool to see.

Naturally, after we had played around with the home made load, the real HV test load I had snagged off of EBay for a steal showed up.  The next day.  On the left you can see it in all it's strange glory.  The unit stands about 18 inches high and is about 7 inches in diameter.  The resistors are the blue columns in the picture, and they are about 1.1 inches in diameter.  The top is aluminum, nicely curved structure - not a doughnut.  We don't have a clue as to what potential its rated for, but the resistor columns are 15 inches in height.  So we're guessing about 75 kV or so.  I think 30 kV, which is all I can output anyway, will be pretty safe.  I think, judging from the sheer size of the resistors, that the thing can handle a kilowatt for short periods.  I mean, the resistors are just simply massive.  In any event, I think I can use it to test the Bertan when the cable comes sometime in the next week or two.

Oh, on Monday, the 90 kV supply showed up.  Well, that was fun.  It was shipped in two packages.  One contained the power control and supply and the other the voltage multiplier.  The package containing the multiplier was soaked in oil - obviously insulation oil from the multiplier.  Hmmm.  What to do?  The poor UPS guys give me a choice.  Accept the shipment, or decline.  Well, not knowing if this insulation oil was hazardous, I said "decline, please", and they drove off with the packages.  The control system and main supply package was also soaked in oil, from the runoff of the multiplier.  I just wasn't prepared to store something that may have PCBs in it downstairs...

I once had several 7 kilo Joule capacitors (yow!) that were in my garage for several years.  They had PCB insulation, and I eventually had to get rid of them at a toxic waste facility in the county.  Not fun.  Kinda terrifying to have around.  Not immediately dangerous, but something always gnawing at the back of your mind.  So I wasn't in any mood to deal with this.  I'm still talking with the guys who sold it to me.  It was insured, so the money will all work out in the end.  But I have to wonder.  First, what in the heck is UPS doing to these packages?   I mean, I'm assuming the people who sold me this supply shipped it in good faith.  I severely doubt it was leaking when they packed it.  This is a company which seems to be on the ball, and they would be just completely insane to do something like that.  So I believe it was in good shape and pretty well packed.

But it was in a card board box, weighing in at 174 pounds.  So that wasn't probably the best packaging scheme.  Especially with fluids.  Got to have a hard container because people who ship things are pretty rough on stuff...  Likely they were moving it and BAM!  It falls on the edge, or something falls on it, or its dropped 4 feet off the back of some truck, or falls off a conveyor belt.  It likely bursts a seal or something, and then the inevitable leak starts.  God only knows how this will work out.  Definitely entertainment, though...

So I got some DB 15 connectors and some shielded 25 wire cable.  I just have to make up a connector, wire it to the lab jack, and I should have a controller for the Bertan supply.  The Spellman seems to have some remote controls and monitors, so I should be able to drive that as well.  But I don't have the schematic or pin outs yet from that unit...  But they should be here soon.  But I'm getting the hang of LabVIEW's programming language and should have something measurable from the LabJack on the voltmeter and be able to measure a supply input from a test input.  That'll be fun.  Automation is always cool.  Then I'll have to see if I can drive the hydrogen mass flow controller.  I've got the pin outs and signals needed for those, and they look really straight forward.  No big mystery there.  So that'll be fun, too.

Since Brent is out of work, he's volunteered to do some leg work for various things that need planning and pre-positioning.  That's useful.  Hopefully he'll lose his temporary unemployment, and he won't have this wonderful stretch of free time that he's enjoying now.  But until then, he is going to be doing some useful stuff on various fronts.

In any event, I know it's not much to report, but it was the best I could eek out this weekend.  Nothing too exciting, but fun none-the-less.

Yesterday I got the 40 kV wire, the LabJack and the ceramic high voltage stand offs.  SmallParts back ordered the ceramic balls - figures.  So I spent the day trying to decipher and learn LabVIEW...  Man, what a frickin' complicated program.  But I'm coming along okay.  It takes some getting used to, being dataflow and graphical.  Normally I despise graphical programming languages, but it really makes sense with LabVIEW.  We'll see.

Not much else going on.  Tomorrow is the peace march in SF - today was Chinese new year, and they bowed out in favor of the traditional celebration.  Millions of people marched all over the world today, though.  Sorry to bring politics in here, but it's something important...  So tomorrow is basically hosed.  Brent is coming over tomorrow night or Monday, so we'll mess around in the lab a bit.  I got some 15 kV 1 G ohm resistors, so we'll crank up the power supplies and do a load test.  Have been thinking quite a bit about the gas subsystem.  Need to think much more. tag:www.mr-fusion.hellblazer.com,2003://4.4056 2003-02-14T01:30:41Z 2008-11-29T16:47:31Z

Me?  Well, I'm still straggling along.  Tonight I'm going to construct a new cage out of the stainless steel pieces I got a while back.  The problem with the mild steel cage I currently have - besides having to keep it in a desiccated environment so it won't rust - is the question of a magnetic circuit.  The mild steel cage forms an incredibly complicated magnetic circuit, which means I don't stand a snow ball's chance in analyzing this short of using Deep Blue - not anything remotely possible.  Secondly, the magnetic permeability significantly changes the magnetic fields which extend outside the cage which are used to bottle up the electrons.  The second follows from the first, but it's significant in that the field flux lines are concentrated in the mild steel, not distributed where I want them.  D'oh!

But I'm still going to use this cage for my first experiments.  I want to see if I can use this cage as a normal, glow discharge fusor, just to see what it can do.  It'll be neat to see if I can produce neutrons from it.  Should be able to, with no problems.  We'll see.

Ordered the high voltage cable for the Bertan power supply.  Geesh.  What a frickin' monster.  One inch thick, 60 kV cable.  Very cool, though.  It'll be here "sometime".  Couldn't get a hard date out of Del, but who knows.  I've got more than enough to do in the mean time.

So...  Off to work after a glass of wine...

If you look at the larger picture, you can tell that there are three bolts on the main 14.5" flange missing above the electrical feed through on the bottom hemisphere.  Directly opposite, where the cold cathode ion gauge is attached, another three bolts are missing.  I can't get the bolts in, due to the flange configuration - something that I thought would happen.  I'll have to see if I can get some double threaded bolts so I can get these puppies bolted down firmly.

In any event, the vacuum test went well.  I got the chamber down to 2x10^-6 torr.  There were a few fits and starts as I tightened the zillion seals on the chamber, but after everything tightened up it dropped like a stone.  I turned off the turbo and the pressure held for about 15 minutes before I had to close down the shop for the night.   The fore line pressure on the roughing pump held at 1 millitorr.  Very cool.  I think this will do quite nicely.

Now the real work will start - building ion guns, setting up the high voltage and gas lines and...

<heh>

So all that delayed the actual testing of the beast for tonight.  It was fun though, putting it together.  Wish I had actually built the chamber itself, but gee - I'm just not that good of a TIG welder at all - certainly not vacuum quality.  Nor do I have a machine shop capable of building the beast to even a semblance of the tolerances that Huntington did.  I went down to Huntington and got a tour of the place from Herb - the gentleman who managed my the building of my chamber.  Ye gods.  100,000 square feet of amazingly cool machinery.  Huge and really cool computerized milling machines that made me physically drool.  Racks and racks of seriously cool raw material just waiting to become pieces of high quality chambers.  Amazing.  If heaven actually exists, it will be much like Huntington for me.

I decided to use viton gaskets on all the conflats.  Yea, I know.  What's the use of conflat seals if you aren't using metal gaskets?  Well, the problem with metal gaskets is their very high price.  Copper is not cheap.  Oxygen free and precision punched.  Not exactly free.  And once used, it's a false economy to reuse them - ever.  However, knowing this, the vacuum industry makes viton gaskets for conflat fittings.  Duniway pre-outgasses these gaskets, and claims they have an outgassing pressure of 10^-10 torr.  Yow.  If this holds true, then I'm going to be one happy camper.  These gaskets are reusable - unlike the metal gaskets.  And since I think that 10^-7 will likely be sufficient for my needs, I think that this will work out so very well.  If these gaskets perform as Duniway advertised, then 10^-9 is not out of the question.  Gee, wouldn't that be just ducky?  Naturally, there's something wrong here.  Has to be.  Otherwise, why would anyone be using metal gaskets at all?  No doubt the hammer of reality will come down and let me know how things really work.  But until then, I'll satisfy myself wrapped in the illusion that 10^-7 is going to work for my experiments.  Knowing all along that I'm just living in fantasy land...  And if the viton gaskets don't get me low enough, I can always switch to copper gaskets.  But by then, I'm sure to have made ample use of the reusable viton gaskets in my exploration.

Anyways, until tomorrow...