FAQ - Gas flow rates in a fusor

[Richard Hull]

Of course, my 200mev was hyperbole. The reaction actually peaks about 1-2mev and then the oppenheimer phillps reaction occurs and fusion drops to near zero.

The upshot is that no amateur here will ever attain a voltage where fusion rolls off, but instead is only enhanced. One sees a part of the cross sectional curve near 200kev where an increase in voltage repays the effort in ever smaller increments. Still, it climbs out to 1mev or more. The best part of the curve starts to roll rapidly after 150kev. So, no amateur will likely ever hit this range either due to neutron fluence and x-ray issues cutting his life short with continuous operation at this level.

Within the above context, The amateur will only see more neutrons with increasing voltage applied to the fusor at any given current and pressure.

Richard Hull

[Frank Sanns]

Did you say 200 TeV?

My post was more on effiency than total output. Just adding to your expert posts. No argument here.

Frank Sanns

[Richard Hull]

Frank, We need to watch our respective resorting to tongue in check word salads and hyperboles. (it was Gev) I fear some folks might have trouble following the more esoteric, extended scientific humor.

Back to more serious issues swimming around efficiency..........

Efficiency! Let's face it, we pretty much bull-head our way to neutrons in d-d fusion. Its cross section is pretty lousey and focusing the deuterons with guns would make the power consumption even higher. (most likely)

Certainly, at the amateur level, most fusion is going to be a power hog efficiency wise. Orders of magnitude efficiency gains are needed. What is amazing is that you can do real fusion hooked to your home wall outlet for about ~5 cents per reactor running hour! For the Amateur devices, the operating costs are low to non-existant (related to $3.00/gallon gasoline powering the average $32,000 SUV to go to the store to purchase a loaf of bread), but the fusor efficiencies are and will be, for a virtual infinitude of time, an abomination.

I mused over how many "breakthrough", 35% boosts in total input efficency of the fusor would be needed to achieve "no excess power, breakeven" operation. At about 8 such advances per decade we would need a string of 48 or more stunning 35% increases to hit no power gain break even or a Q of 1.

Fusion will need a massive singular stride based on some unknown and as yet un-imagined force or power to come home to papa. (total gravity intensity control, etc)

A bunch o' Euros and Dollars thrown at the ITER is a vain effort. Still, the possibility of an amateur bumping a fusor efficiency by 35% is more likely than the "supposedly" near break even fusion systems being sent that far forward. Of course they don't count all the beans in their operational reports to the public, either.

Richard Hull

[DaveC]

Richard -

I think what you're showing, very clearly is that fusion progress is NOT going to happen by accident, not is it likely to happen by simply bludgeoning with more current and voltage.

The way of progress, is to formulate some sort of theory - based on either prior experimentation or other known data - and the construct an experiment to test that theory. This takes a lot of time, based on my limited experience. Getting the data into one's head is one hurdle, then there is getting an "idea" to test, and then there's building the apparatus to test the idea.... and then.... there's doing it again and again until one gets it right. And often.. then and only then...discarding the "idea" as incorrect.

We should be very much wary of inadvertently getting into the monkeys and typewriters syndrome... expection chaos to breed order. Never happens.

I'm not sure what to suggest as a next step....quite possibly pursuing the higher pressure regime... and finding what it takes to operate there.... but my question is: at the higher Neuts/sec figures was the efficiency higher or lower? I tend to agree with Frank, that quite likely, higher efficiency comes from other causes, and could well occur at lower voltages and currents.

"Efficiency" data... would be a good benchmark for the present fusor designs. Effic. = (neuts/sec) / (kV x amps) For now just ignore all pump power and etc. Just use the Fusor input power. This would also allow all the speculations about inner shell designs, sizes and even polarities... to be settled.

Also... the Fusor scale factor could be checked... eventually... with a 2X diameter fusor... with eveything inside to the same 2X scale. This data should.... point out something...

The more I think of it... the more convinced I become that simply max Neut/sec is not enough of the story, unless..... it is true that the kV and amps are proportionally increased.

There's a couple things to do on the long Winter evenings ahead.

Dave Cooper

[Richard Hull]

Efficiency is little measured in the amateur efforts, as we tend to struggle to a point of static operation and hang there at any pressure or other parameter point. The real issue is that we have the cross sectional curve to deal with. A very small move up in voltage may double the number of neutrons near 30kv as the curve is steep and remains steep up to over 100kv. This is a factor that must not be confused with simple efficiency. One just gets a lot more fusion for only a little voltage increase in the amateur power supply end of the pool. Jon Rosenstiel is a prime example. I know of no one who has reached his voltages or his neutron output (fusions/sec). There is an obvious limit, of course based on the curves where you are getting little or nothing extra in return. We are no where near this level, of course.

I am pretty sure that this curve-voltage-accelerator path is not where the big boys are. They like bulk heating, just like the sun does, unfortunately they are looking at the maxwellian tail of the curve. (so is nature for that matter) There is a lot of energy under that curve where nothing happens.

They are hoping that, with ignition, that tail lifts into a major regime, ultimately, supplying the running energy that used to cost so much. With bulk heating you really have to have the right vessel and herein lay their rub. Magnetics are needed to keep the erossive plasma running around the center of the racetrack.

There is no end of hope on obtaining successful, power ready fusion in most all quarters where it is seen to be done, from the filmy, elusive, cold fusion arena, to the IC and IEC areas, to the annointed and fully supported bulk heating efforts. The problem with fusion is it is so damned easy to do in the lab. The carrot hangs out there and has driven men forward for years.

I find it stunningly ironic that nature doesn't do fission in a normal, readily observable fashion. As a matter of fact, she hides it well and natural fission in, say, U238 or Th232 buzzes along at such a slow rate it was never detected until someone poked it with a sharp stick (neutrons). From the date of this first single poke, man had a bomb destroying cities in 7 years and energy from it flowing out of outlets in 25 years.

On the other side of the coin, nature is downright rubbing our noses in fusion as she powers a universe with it. Sadly, with billions of the money and 50 plus years we are still picking at it like the proverbial scab. Not one fusion watt has powered anything from an outlet. The H bomb is a purely fission powered device. It seems like fusion has no middle regime. We can make a bomb based on it, provided we fission power it, but can't get it to produce just short of a bomb with full control.

I have come to the sad conclusion that confinement is the issue and we can't confine by any of the common methods in our current physics kit as we have no gravity control in it. IC and IEC use the term "inertial" and inertia is electrical in nature at the core.

We can only get things moving kinematically by accelerating them and to do this we need to convert locked down potential energy and all of this is electrical in nature, save for fission which will light off an H bomb.

It is gravity control or nuclear density control or some unappreciated internal nuclear process ala cold fusion that will probably win the fusion battle.

The current efforts are rather shabby by any standard. We lack experience at "assmbly". We are hunter gatherers used to burning and reduction of higher systems for their hidden potential energies.

The idea of taking two things of no real potential energy and spending a massive amount of energy to join them and in the process get back extra energy is foriegn to us, especially when they just refuse to join in a quantity that pays us back the energy spent. Yes, it is tempting, especially, as the universe is obviously powered by this method.

I fear all the magnetic bottles and special ceramic lined torus racetracks and all the firing of matter particles at targets or collisional schemes are sad temptresses forever letting us do fusion well short of the mark.

We need new tools regarding matter confinement. Gravity control and pinpoint amplification of it would be nice.

In the mean time, efficiency in the 10% -35% range at 6-8 orders of magnitude below breakeven is a good way to while away the time. Certainly, it could make some pretty impressive amateur devices when judged by current standards.

Richard Hull

P.S. one thing is for sure..................Anyone going to this FAQ on gas flow rates and following it out to the end will sure get a wild ride!

[Tom Dressel]

Richard, my impression from your original post on this thread was, that you got more "neutrons per volt" at 25 microns and high flow rates than at 8 to 10 microns and low flow rates. My question is: at the high flow rates (pressures), is the voltage threshold to start fusion lower, or the same as, at the lower flow rates ( pressures)? If increasing the flow rate of D2 decreases the fusion threshold voltage, what in your opinionis the MINIMUM voltage required for fusion, at say 25 microns.

Tom Dressel

[Richard Hull]

I have NO measured data on pressure vs. voltage beyond the fact that at the higher pressures I got more neutrons than at the lower pressures. Notice I did not mention FLOW RATE! I am not sure the flow rate was any higher than before and have no way to quantify that.

Pressure is pressure. And, by theory, and the Lawson criteria, more fuel in the reactor means more fusion at any given voltage.

We seem to have determined that a FLOW of gas assists in fusion for some, as yet, unquantified reason. All fusioneers report this latter condition.

It is important that one realize that you can have many different flow rates at any given, fixed pressure. I am not sure this means beans.

I am sure that I got less fusion for a specific voltage at lower maintained pressures. Again, all of this is in tune with theory and the Lawson criterion.

Only those with a calibrated mass flow controller in their gas line, plus, a calibrated capacitive manometer can answer the varying flow rate issue at fixed pressures. Flow rate and pressure are determined by both the setting of the gas line flow valve and the vacuum throttle valve in a flowing gas fusor.

These two items, coupled with voltage are the three big adjustments in the fusor, assuming you are shooting for a target or constant current.

Many are the subtlties in neutron producing, functioning, fusors and one can't preset anything in amateur construction. It ultimately comes down to an operator learning his or her device and the delicacy of its controls. Once learned, you can go to anyone else's fusor and pick up their unit's idosynchrosies. Both Brian Mc Dermot operated my fusor well at the recent HEAS gathering, once they adapted to the subtlies of fusor IV. Both Frank Sanns and Carl Willis took a turn at it back in 2004.

Fusors are NOT smooth sailing until you locate a patch of quiet water (find the sweet spot in all the variables in the area you want to operate)

Richard Hull

Richard Hull