D Tibbets wrote:As far as your approach, I have not sen it, but from comments it seams to be two collimated beams of ions at two different speeds, with some space charge neutralization. The fast beam overtakes the slower beam and hopefully make fusions. Several thoughts:
This sounds like essentially beam target fusion, just with a different frame of reference. Or, if you prefer beam- beam fusion, except with a negative handicap that has to be overcome. With opposed beams the velocities are additive, in this scheme the velocity of the slower beam is subtrative. This means that the total input energy per possible collision goes up. I suppose this might be tolerable if other concerns compensated.
You are right when talk about more effectiveness of colliding from opposite directions. As we need the proper collision energy in center-of-mass frame. But from the other side of view beams colliding from opposite directions defocus each other as to the repulsive forces of space charge there also adds magnetic repulsive of opposite moving currents.
In my proposal when faster particle catches up slower moving at the same direction we need only partial compensation of space charge for focusing as unidirectional currents attract each other.
If the temperature of beams would be low their attractive effect (pinch effect) is so strong that the quasi-crystal structures can be observed in some conditions.
http://nonneutral.pppl.gov/ and e.g.
http://accelconf.web.cern.ch/accelconf/ ... OP5B06.pdf
Now about proper collision energy
If tritium nucleus moves with energy 10 keV and the deuterium nucleus catches it up with 300 keV collision energy in center-of-mass frame equal to ~132 keV.
Is that more than enough? Or no?
Also, we should spend rather more energy per each fusion event but if we recall the efficiency of various ways to heat plasma in other fusion experiments that would be acceptable.
In any case we spend hundreds of keVs and waiting MeVs.
D Tibbets wrote:But two moving beams at different velocities are still essentially opposing colliding beams, just with a different frame of reference. If you are concerned about two stream instabilities with opposing beams, how is that different from this scheme?
Here you are right too.
But electron-electron two-stream instability occurs very early in very low stream (beam) densities due to lower mass of electrons (1836 times lower than proton). Ion-ion two-stream instability will occur at higher (mega-amperes order). I am not proposing to use so high currents.
D Tibbets wrote:Using some numbers, and ignoring the losses from the two different speeds in the same direction, if the effective collision energy ~ 100 KeV, then with D-T fuel you might have 10 scattering collisions for each fusion collision. Assume that each scattering collision leads to the loss of one (or should that be two ) ions, and that space charge scattering/ defocus is controlled) . Then for each fusion collisionn (~17 MeV yield) you would lose ~ 1 MeV . This ignores other losses like Bremstrulung, etc. Still you might optimistically expect a net positive Q of perhaps 5-10 (?). With D-D, the scattering collision rate over the fusion rate would be at least 10 times higher, and the yield per fusion might be ~ 6 MeV. So for each 6 MeV fusion you would lose ~ 10 MeV or more. No way to come out with a positive Q. So, this might work with this probably extreamly optimistic analysis, but only with D-T fuel. You could push D-D fuel energies to higher levels and perhaps decrease the scattering to fusion ratios, but other losses would add up- such as Bremsstrulung, and the gain per fusion event would decrease.
Practically we will not loss any ion because self-magnetic field will return then them back.
Bremstrulung would be the very significant factor. From one side that will carry out the spent energy. From another side that will add stability as G.I. Budker has proved that in his “Stabilized electron beam” paper.
In general I consider two types of reaction D+T and D+He3 with fusion event output 17.6 and 18.3MeV correspondently.
D+T with faster deuterium nucleii and D+He3 with faster He3.
For D+T I estimate energy to be spent as 300 keV for pair of nucleii and 150-500 keV for electron (as we need only tenth of electron current we need only one 1.5-5 MeV electron per 10 fusion events)
I can not estimate Bremstrulung losses at this stage as that depend on a number of factors should be considered). Technically Bremstrulung losses will be compensated by externally applied electric field.
Also, D-D reaction is less acceptable not only due to its lower yield but also due to equal rate of acceleration of Deuterium nucleii in different beams. As we need to compensate the alignment of velocities inevitably will be observed, usage of the different types of nucleii is preferable (but not obligatory). Faster beam will accelerate the slower beam decelerating itself. And externally applied electric field will compensate that then securing the velocity difference at acceptable level. And it is easy ifin fastermoving beam we will use the particles having higher rate of acceleration: D for D+T and He3 for D+He3
D Tibbets wrote:Another question. If you are interested in fusion power, not only positive energy balance is required, but also reasonable energy density.
Also correct!
But as mentioned above we can have the density of quasi-crystal – and that is higher even in Plasma Focus (10^26 as I know).
We can but need not so high! As that is possible at the expense of higher electron current.
Power density is proportional to square of number density. And so on.
Thanks.
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