Pulsing in deuterium

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Frank Sanns
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Pulsing in deuterium

Post by Frank Sanns »

Last night, I was in the process of adding an alumina tube to inject deuterium right into the inner grid. This would give a much higher density of deuterium right where it needs to be when the low density ions come streaming in. Of course the deuterium that is being added in is essentially at rest and the ions will hit the deuterium as in a simple spherical collider. What occured to me is that there is a much better way to add the deuterium.

If deuterium were passed over an ionizer (penning, RF, etc.) before entering the chamber, then all of the ionized deuteium would be ready to be accellerated by the inner grid. Instead of bleading in the deuterium into the inner grid, it would be brought in in a group from around the outer grid. Sound familiar from another nuclear application? You would have a shell of ionized deuterium with a clear path right to the fusor center. High mean free path but loads of deuteruim rushing toward the inner grid void en mass. At first it would be rushing in at near the speed of sound from pressure differential alone, but then the grid would go to potential high and the deuterons would be yanked at some fraction of the speed of light toward the inner grid with nothing in thier way all the way to the inside of the inner grid.

The problem is how to get the big chunk of ionized deuterium evenly at the outer grid all in a micorsecond or so. It would require a complex structure much like an implosion device OR the deuterium could be liberated in a fusor shell lined with a suitable material that would liberate the deuterium just before it is needed. I think you can see where I am going with this.

Frank S.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
Frank Sanns
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Re: Pulsing in deuterium

Post by Frank Sanns »

It looks like I am going to shelve my Fusor I and start a new one to test this most recent theoretical approach. Of all of the ideas so far, I am thinking that this one will different enough from all of the others to justify a new chamber. Time will tell. In the interum I will try to finish up some of the grid size experiments and a few other modifications while I am scrounging again.
Who was it that said fusion was fun?????

Frank S.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
3l
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Re: Pulsing in deuterium

Post by 3l »

Hi Frank:

You have figured out my next step.

I just hit a brick wall in pulse fusion.
There is a problem in the fusor chamber at the proper pressure to do pulse fusion you run out of fuel. Before you really get started in 10 pulses or less. But the worst problem is reflectance
at 1.3 GW, the plasma itself is a problem. The 1.3 GW magic wattage is the point at which the column of plasma starts behaiving the charaterics as a straight wire inductor. I tried going up in voltage to cure this but the plasma kicked back the electrical pulse above this wattage. This limits neutron production to 10^8 neutrons/10 pulses. The pressure issue possibly could be solved and I've tuned the LRC ratio before
manualy but the time factor would be a killer litterally milliseconds
to correct for added fuel. Not pretty. Vacuum systems that pump down in milliseconds don't exist. The method works to a point then won't scale up. It barely ecks out above Jon's mega run numerically but the flux numbers are sad. I've decided to go to gunned fusor systems.

Guns are as tough as pulsing but you can use slower vacuum systems to pull it off. The fuel issue vanishes as the ion gun is differentially pumped relative to the lower pressure of the reaction chamber. That allows for high numbers of ions to be created at the right pressure with the right amount of deuterium gas. The acceleration and collision of those ions in the lower pressure side of the gunned system
ensures greater mean free path for more efficiency.

This method has a proven track record as a high neutron producer.

But all the pulse power methods will have a home in gunned systems.

Why?

To get into the usable power range will mean raising the Pontiac Fusors by 10,000 fold.

To do that will require the generation of large flows of ions, on standard power that will mean caps,chargers,high power switchs ect.

The End ??? LOL :^)

Happy Fusoring!
Larry Leins
Fusor Tech
Frank Sanns
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Re: Pulsing in deuterium

Post by Frank Sanns »

Hi Larry,

Yes, many problems we do have with fusion both pulsed and continuous.

I am curious though, if the proverbial fusion match could be lit with one pulse, would it sustain if fuel were contiued to be fed? I know the energy radiates away with Temperature^4 but if the initial rate is high enough, it should be self sustaining. What if a blast of deuterium is injected into the inner grid just as the pulse fires? The dynamics of the pulse will still be the same but right when it is at its peak intensity, pop in the deuterium. Will that deuterium be consumed or will it just dillute things down? Will it act like adding a blast of pure oxygen to a torch when you want to burn through a piece of steel or will it be like putting water on a fire?

Frank S.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
3l
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Re: Pulsing in deuterium

Post by 3l »

Hi Frank:

No one has done it yet!
The trouble is to have the match stay lit while additional fuel is applied. The preconditions are very hard with fuel in the way to start the match. So prefilling is out.

Happy Fusoring!
Larry Leins
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DaveC
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Re: Pulsing in deuterium

Post by DaveC »

Frank and Larry -

In the steady state "fusor", the match is already lit, so to speak. It is just a very small match. And... the fusor keeps on working.. at the pico watt level, with the tiny match lit. Granted that doesn't mean the fusor would stay lit if a watt level output were being generated. But Inertial Electrostatic Confinement means the pressure created by the momentum change, that results when electrostatically propelled ions collide and reverse direction. It is this pressure (which is no different from the pressure on a vessel's walls when gas molecules rebound from it) .. which confines the ions as they fuse.

But, as I have discussed elsewhere, the principal problem with pulse operation is the limited supply of ions. At any voltage we discuss here, the ions are moving rather slowly, and there are not enough in the entire fusor, to make very large currents possible. Although I = dQ/dt, you must have enough Q in motion to create the large values of I presumed for the capacitor discharges. That fact is, the Caps will not be able discharge all that current into the plasma, since there are not enough carriers Ions) for the current. Another way to regard is that the lack of charge carriers creates an effective impedance mismatch, resulting in a very large reflected power wave. High SWR, and low delivered power.

Something further to consider in the fast pulse regime is that this method is used with barrier discharge lamps to improve light output, because the fast pulse does NOT couple to the gas ions and produce plasma... Instead, it pumps up the energy levels of the gas molecules. If the impulse is fast enough, few gas molecules are ionized!!

Now we are considering existing ions, presumably generated by an external ion gun, and then extracted into the fusor chamber for acceleration by the HV pulse. Other than the prospect of higher standoff capability of feedthroughs, in pulsed operation, there seems to be little else to recommend the pulsing approach over CW.

For appropriate mean free paths..(aka - same pressure regimes) there are the same number of molecules of D2 in the chambers. At the same voltages, CW and pulse will tend to move the same number/ sec, but with fast pulses, fewer ions will actually be formed, from the neutral molecules. Hence they will actually have at, best, the same instantaneous currents, BUT... the CW mode will have an average current. many times larger.

The advantage pulsing COULD provide, (if we knew how to do sub pico second risetime pulsing), is a general synchronism in the movement of the ion clouds towards the center. But bear in mind that even pico second timing is about 7 orders of magnitude too sloppy for actual ion "time phasing". These are formidable challenges... I don't have any good ideas at the moment. But I think the analysis is more or less correct.

Others, may wish to comment and make corrections.

Dave Cooper
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Adam Szendrey
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Re: Pulsing in deuterium

Post by Adam Szendrey »

The "problem" is that ions will not stay confined if no power is applied (no voltage on the grids). Just as the sun needs gravity to keep up the required pressure in the core.
If a fusor would produce say 5 kW of fusion power, and the input would be 3 kW, through the usual "boiling" process one could get out about 4 kW at best (since the shell of the fusor is heated by all the input power, the sum of heat energy (radiation included) would be around 7-8 kW (this would heat the water)).
But that way you could power the HV supply, in a closed loop. Ofcourse we are lightyears away from this :).
Fission is easy because it just "happens". Take out the control rods and off we go. But fusion has to be forced. That's why fusion power will hardly be a viable power source in the near future..or ever.
My personal oppinion is that fusion will only be a possible power source on the large scale. Say multi-TW power plants....but even with a TW of continous input power (hardly imaginable) that picowatt of fusion power would become a mere Watt. Unless fusion has an exponential nature as Larry hopes.

Adam
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Richard Hull
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Re: Pulsing in deuterium

Post by Richard Hull »

Dave has done a good job of talking about the problems with pulsed fusion and Adam has done a good job of restating a long held belief I have had for a long time.

Fusion, itself, is the problem.

Fusion is easy in the sense that on a specifically examined fused particle pair, you get back tremendously more energy than you put into the system. It appears to be the ultimate winner in energy for the future.

On a bulk particle basis, of those herded into the process, it is about a billion times per unit mass less efficient than burning wood which is just an electronic process!

Somehow that carrot hangs out there and countless thousands think that it is just a matter of a tweek or two and the process will go from 1 fusion in a trillion tries to near perfection of one on one. It is the expenditure of energy for the trillion attempts that so horribly swamps out the tremendous energy gain of that one fusion that stands in the way.

It is stunning to see this work trudge on and money spent on the same old devices with soupped up motors like the new Princeton Stellarator project.

I have long felt that "grid ready" fusion energy at this stage of the game is a dead horse which we are mindlessly beating.

Lets take some of those old swords (plutonium containing nukes) and beat them into plowshares by pushing fission back into a viable and growing power industry. There is energy out there just sitting on the shelves in secret DOD locations. They are remenants of the cold war that blessedly never heated up.

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
Frank Sanns
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Re: Pulsing in deuterium

Post by Frank Sanns »

Yes, very good input by all.

Let me ask the question another way. If two deuteriums fused, how close would adjacent deuteriums have to be for them to fuse also. More precisely, how close would the atoms be to have a high probability of fusing i.e 1 in 1,000. Yes, I think that is the million dollar question.

Frank S.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Richard Hull
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Re: Pulsing in deuterium

Post by Richard Hull »

Franks question is the million dollar question.

To fuse 1per thousand deuterons they would have to be literally touching AND AT FUSION ENERGY! This last part is the key. This is why the goof balls in tokomaks and stellarators attempt to confine and heat bulk plasmas. It is only through the high density AT FUSION ENERGY that large amounts of fusion are possible with any efficiency. Alas, they have found ZERO ways to succeed at the task, (or even come close), but have spent a gang o' our bucks trying.

They are relying on bulk heating to do the job, but at fusion temps, matter just can't be retained in any dense form known to man except for microseconds as in the H bomb. Unfortunately and unlike fission there is no way known to man to slow the process to an electrical power friendly rate.

Accelerators and colliders work well and in small sizes where the material is not bulk heated but accelerated to fusion energies for target or mutual particle collision. To do this, the mean free path must be sufficient to allow for electrostatic acceleration of the particles over a "non-arcing" distance. This means a vacuum, and a vacuum means close to zero density. The fusion "current" is reduced to nothing and the density at target is also low so there is a large fraction of wasted energy in such systems with failed fusions. However, these latter systems do fusion easily, cheaply and in small sized devices.

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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Adam Szendrey
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Re: Pulsing in deuterium

Post by Adam Szendrey »

I think these runaway events of the fusor are the light at the end of the tunnel. They show that there is a lot more to fusion than what we already know. If we would know why and how they happen, we may be able to build a much more efficient reactor. Though even a thousand fold increase is not enough..not even a million fold. But who knows...we may be able to increase the efficiency to practical levels one day.

Adam
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Richard Hull
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Re: Pulsing in deuterium

Post by Richard Hull »

Runaway events, if real fusion events, could indeed point in a new direction, but first we need just one real event where instrumentation is at hand with neutron activation systems setup prior and read well afterwards.

Saying one had a runaway event without real numbers is like saying "a whole flock of 'em flew over that time....Didn't you see 'em?"

One stunning event in the Farnsworth's team ledger and two possibles here with no data points is still just a tantalizing carrot hung out there. The pro's have had a whole bunch of carrots hung out over the years! As such, no one is doing hand springs over carrots anymore.

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
morgothia
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Re: Pulsing in deuterium

Post by morgothia »



well they have created solid hydrogen what if you fast bombarded a bit of this (tho keeping it solid long enough would be the hard part many many torr at supercooled lvls)

that would give density needed to properlly "pulse" the fusor tho there would be many other things to work out first. Its just an idea hope it helps in someway.


patrick donahue
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