Posted: Thu Apr 23, 2009 6:07 pm
at 500MW? milliseconds.. then how long to pump down again?icarus wrote:Solution: After however many days, hours operation it takes to contaminate reaction
a discussion forum for Polywell fusion
https://www.talk-polywell.org/bb/
at 500MW? milliseconds.. then how long to pump down again?icarus wrote:Solution: After however many days, hours operation it takes to contaminate reaction
Those that stay as ions, sure, that might be true. D'you think ALL ash ions will not neutralise? It is a population thing, and with 1E21 alphas pouring out of the reaction volume per second, so if milli-fractional amounts of that population neutralise and find their way back into the reaction volume, they will kill it cold.D Tibbets wrote:Since the fusion ions (weather from DD or PB11 fusion) remain charged in the reaction vacuum vessel they could not reenter the core due to the large positive potential on the magrid
Not sure what you mean. There are no problems to this, so long as you can deal with a thermalised end result. A tokamak starts off trying to *get* a thermalised result.D Tibbets wrote: How are Tokamaks suposed to handle this problem?
Sorry for my osmiumnity, but why? The energy to ionize is small, the ash circulates and nudges things this way and that, and eventually does get upscattered out of the well (hopefully at a low rate). Why is it bad to have the "ash" there?chrismb wrote: The mechanism cannot afford to ionise helium ash that wanders back into the well, but it will do this exactly if the pumps miss ANY of the ash.
I know my fair share of big words - but what is 'osmiumnity'?KitemanSA wrote:Sorry for my osmiumnity
Yes, but where does the ionisation take place? If you are hoping to maintain non-maxwellian distributions, you cannot chance having ions being created anywhere other than at the top of the potential well. Otherwise, you'll get thermalisation, and we're then talking a plain-old game of magnetic confinement.KitemanSA wrote:The energy to ionize is small
The densest known element is either osmium, or between my ears.chrismb wrote:I know my fair share of big words - but what is 'osmiumnity'?KitemanSA wrote:Sorry for my osmiumnity
Actually, near the top of the well but inside the MaGrid is exactly where I expect it to happen. That is where the neutrals (not expecially zippy so they "drift" around there) meet the large flux of electrons being reflected by the MaGrid (maximum zippy) and go bang! No?chrismb wrote:Yes, but where does the ionisation take place? If you are hoping to maintain non-maxwellian distributions, you cannot chance having ions being created anywhere other than at the top of the potential well. Otherwise, you'll get thermalisation, and we're then talking a plain-old game of magnetic confinement.KitemanSA wrote:The energy to ionize is small
Ah! I see. But no need for such self-critique, the question is fair - and there will be some tolerance permitted for a neutral population, but what it is, is the question.KitemanSA wrote: The densest known element is either osmium, or between my ears.
I'm certainly in no position to say yes or no, but the collisions are meant to happen mostly in the centre of the reaction voulme, and the free electrons constrained further to the interior (I thought). Why would ionisation happen more where the ion density is less, and further away from the region of slightly-over-net electrons?KitemanSA wrote:Actually, near the top of the well but inside the MaGrid is exactly where I expect it to happen. ... No?chrismb wrote: where does the ionisation take place?
Would the magnetic field also repel the helium ions? The alpha particles, immediately after they are formed (according to rnebel), make about 1000 trips around the magrid coil before exiting. That's with energies of a few MeV. Wouldn't the low energy (1< eV) helium ions get trapped by the magrid field and begin to pile up, circling the magrid infinitely? Or would the several 15-500K volt charge on the magrid be sufficient to toss away all the low energy ions?D Tibbets wrote:Since the fusion ions (weather from DD or PB11 fusion) remain charged in the reaction vacuum vessel they could not reenter the core due to the large positive potential on the magrid (and the magnetic fields).
It sounds like you've misunderstood the proposed geometry of the wiffleball. The idea of ions being accelerated towards a small central magnetically-confined electron-rich region, which they are initially outside, is wrong. That's what it sounds like you are describing.chrismb wrote:I'm certainly in no position to say yes or no, but the collisions are meant to happen mostly in the centre of the reaction voulme, and the free electrons constrained further to the interior (I thought). Why would ionisation happen more where the ion density is less, and further away from the region of slightly-over-net electrons?