Lens inside Cathode?

For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.
DaveC
Posts: 2346
Joined: Sat Jun 30, 2001 5:13 am
Real name:

Re: Lens Musings

Post by DaveC » Sat Oct 15, 2005 8:52 am

Carter -

The field lines and potential contours tell some of the tale, but not all. It is a rule of thumb that electrons above about 10keV increasingly do not follow the field lines set up by electrodes. They are moving too fast to immediately redirect their paths as the fields change direction. They ARE influenced by the fields, however. Ions being far more massive, behave the same at much lower velocities. So one must do some careful modeling to have an idea how to shape the fields near the inner grid so that the D2 ions will miss the wires. There is, however, another issue that does not get discussed much here. And that is, that the glow around the inner grid at the higher pressures, is mostly the cathode fall glow of a simple gas discharge. This is a fairly low voltage, (low energy ) but often high current (lots of ions involved) activity. It is where most of the fusor enregy dissipation takes place. Evidence for this is that the grids melt, are sputtered onto the walls and viewports and insulators, within. Clean this up and the fusor power consumption for doing practically nothing useful, goes to nil.

But if the speculations are correct that the fusions occur out in the volume of the fusor and not at the center, then it would seem to say that trying to have a nice well focused "poissor" or star, may be entirely irrelevant to having high Neutrons/sec numbers.

If the outer regions are where the bulk of fusion occurs, then we do not want collisions in the center, UNLESS they are essentially elastic collisions.

It has always seemed to me that having a low density plasma everywhere except in the dead center, was the way to get low losses. But maybe the law of averages works more strongly in our favor than the concentrating effect of a central focus.

We probably need some more definitive experiments in this area.

Dave Cooper

longstreet
Posts: 165
Joined: Sun Aug 07, 2005 5:35 am
Real name:
Contact:

Re: Lens Musings

Post by longstreet » Sat Oct 15, 2005 8:07 pm

I read the UoW paper on reaction location. They're conclusion was that this is because ions become neutral coming out of the core retaining their high velocity. I don't think this is good because a neutral definatly cannot recirculate. If 2/3 of the fusion is from these neutrals then I think that speaks to just how much energy is lost to neutrals flying out to heat the walls. Imagine how many fast neutral's didn't undergo fusion for every neutral fusion event, and then imagine if every one of those had stayed ionized?

I don't think it's usefull to try and increase the effect, but I also have no idea how to stop it. This is one of the reasons I would like to stop electron emmisions from the inner grid (be dielectrical insulation), to perhaps decrese the recombination effect. But there is still electron exchange with the surrounding gas. I suppose there's not much you can do with that short of trying to operate in a lower vacuum, or ionizing 100% of the gas in the chamber.

However, managing to focus the ion collisions better, I would hope anyway, works to increase fusion between ions before they become neutral, which is really the whole design of the fusor. If you wanted to increase the neutral fusion you would probably abandon the spherical design and just accelerate stuff linearly.

Thanks,
Carter

User avatar
Richard Hull
Moderator
Posts: 11535
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Lens Musings

Post by Richard Hull » Mon Oct 17, 2005 5:53 pm

That we can certainly work for and actually achieve improved operation of the fusor is a virtual given (once the inertia of doing nothing is over come). A ten fold reduction in input losses from a 300 watt heating fusor would in theory imply that only 30 watts is in the crapper and 270 of our watts are no longer lost or heating anything. Are those watts fusing??!! Even at just break even, I hope not or the operator is dead!


Of course not!. Those watts still are not fusing they are still and will always be heating watts as misses are demanded by cross sectional limitations and these misses ARE HEAT, whether deuterons or neutrals or electrons or anything. Focusing and fusing 270 watts worth of deuterons on a kitchen table would really be undesirable from a longevity standpoint. If you actually did this, the first fusion power producing reactor using your principles would certainly bear your name. (posthumously, of course.)

I think what we ARE actually capable of doing is going from .00000001% efficiency to maybe even a 100 or even 1000 fold improvement per unit watt expended to maybe .000001% efficiency. This is the doable process that we might apply ourselves to.

The idea of turning even 10 watts of the 300 watts input into fusion energy is rather ludicrous.

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.

longstreet
Posts: 165
Joined: Sun Aug 07, 2005 5:35 am
Real name:
Contact:

Re: Lens Musings

Post by longstreet » Mon Oct 17, 2005 6:29 pm

If I stated somewhere that this is some kind of breakthrough I stand corrected. But I am fairly sure I never said such a thing. I think your opinion on the matter is fairly documented Mr. Hull, and your continuous pessimism is getting on the nerves.

Carter

DaveC
Posts: 2346
Joined: Sat Jun 30, 2001 5:13 am
Real name:

Re: Lens Musings

Post by DaveC » Tue Oct 18, 2005 12:37 am

I stand with Richard on this as I do on most things. We should at this juncture, be looking for increases in yield efficiency, not breakeven schemes. And huge levels of output. That will make for obituaries. Besides, most scientific progress is in the form of small steps, once the direction is shown.

As for me, I am not sure I have a clue about that "direction", although I have a few ideas about what I might try, next. But just getting an electrostatic lens from the arm waving concept to an actual piece of hardware, that works as planned, is a fairly involved task. And to do "focus" on a sub nanometer scale...!!! This is not trivial stuff. For example, how could you tell if focus is achieved. Testing for more output, of course is one way, but that actually only tests for.... more output, not better focus. So the experiments are increasingly sophisticated, and the prep time gets longer, and the instrumentation might get a bit more demanding...etc.

But not wanting to discourage anyone, systematic evaluation of what methods work - consistently and predictably, with amps, volts, neutron counts, and all relevant data... is the way to find the trail.

But I don't think there are any "breadcrumbs" on this trail, yet, because no one has been on it. So it could be a strange an wonderful direction. But it will definitely involve principles already known, mostly, and possibly something new, and as yet unforseen.

Dave Cooper

longstreet
Posts: 165
Joined: Sun Aug 07, 2005 5:35 am
Real name:
Contact:

Re: Lens Musings

Post by longstreet » Tue Oct 18, 2005 2:30 am

I really don't understand you people's fixation on breakeven. WHO is talking about breakeven? Electrostatic lensing in IEC is the basis of it's operation, and I haven't even proposed any new scheme's; I mearly observed why Hirsch's outer grid increased transparency. Why do you have to warn me ten times in a posting about how it's such a long and hard road to breakeven?

Q
Posts: 200
Joined: Mon Jan 12, 2004 10:45 pm
Real name:

Re: Lens Musings

Post by Q » Tue Oct 18, 2005 3:07 am

carter,
the breakeven goal seems to be one of the main objectives in a lot of theoretical discussions. perhaps that's why breakeven even came up.
now, i'm not one of the brightest on this board, so perhaps i missed it, but i didn't really understand why you proposed the lensing. i realize you want to finely focus the ions, but is this to try and increase the reaction rate?

Q

longstreet
Posts: 165
Joined: Sun Aug 07, 2005 5:35 am
Real name:
Contact:

Re: Lens Musings

Post by longstreet » Tue Oct 18, 2005 3:46 am

You can use lensing, as Hirsch did, to decrease collisions with the grids. If for nothing else increase the lifetime of operation. However, getting the ions closer to the center of the inner grid spacings mitigates the defocusing effect near the grid wires (which I showed in the origional thread). This would increase the number of ions you actually have travelling to your target, which is the center of the fusor. If more ions are passing through the same region of space, ideally this would increase the number of high energy collisions.

Thanks,
Carter

LeePalmer
Posts: 1
Joined: Tue Jun 26, 2007 7:41 pm
Real name:

Re: Lens inside Cathode?

Post by LeePalmer » Tue Jun 26, 2007 8:01 pm

Hi Carter-

Farnsworth had a similar thought, with regard to a 3D version of an Einzel lens, see his older fusor patent number 3258402, embodiment number two, and the drawings on page five and six: http://www.google.com/patents?id=6VBkAA ... +discharge

The idea of creating a potential well using a 3D analog of an Einzel lens is a good one, I think, because it opens up the possibility of getting rid of grids all together. I wonder how deep of a potential well it is possible to create this way?

Farnsworth's original idea was similar to Bussards current idea, just confine the electrons, and use this to create a virtual cathode that will attract positive ions, I think. He gave up on it because of excessive electron losses to the grids, I think, maybe.

What software are you using for your plots, by the way?

longstreet
Posts: 165
Joined: Sun Aug 07, 2005 5:35 am
Real name:
Contact:

Re: Lens inside Cathode?

Post by longstreet » Wed Jun 27, 2007 7:01 am

I think Bussard is on the right track about magnetic electron confinement. Using only electric grids is a dead end if you're trying to make power. Magnets maybe too but it has promise.

Post Reply