Joseph Chikva wrote:D Tibbets wrote:Of course not all ions are confined and conditioned in this manner. Some just have too much energy, and may escape if they hit a cusp and fly to the vessel wall, stealing energy from the magrid in doing so.
I do not see any other possibility for ions to have too much energy besides instability.
I am repeating once again: instability's wave accelerates some ions at the expense of energies of others.
Also you see the advantage for Polywell in its spherical geometry. I know one very effective way to fight with instabilities - creation of a strong longitudinal magnetic field that dramatically expands the stability area. In spherical geometry it is impossible.
You are stuck on instabilities, which may or may not be important depending on various conditions and definitions. If you are picturing a columnated beam of charged particles, any perturbation could be considered an instability. Certainly there can be standing wave and traveling wave effects. These can be harmful or useful depending. This wave interaction I believe is the basis for POPS enhancing effects..
Local Coulomb collisions (instabilities if you wish to call them that), I believe, are generally the mechanism for most thermalization. Fusion plasmas are generally considered to be weakly coupled, which means that there are local effects, but they do not dominate over globel effects like space charge (potential well).
I wonder if you are confusing thermalized plasma with an monoenergetic plasma. In a thermalized plasma, there is a high energy tail that is significantly hotter than the reference- average temperature. In a more monoenergetic plasma this highe energy tail has not yet formed through difficult to avoid thermalization. The potential well determines the average temperature of either type of plasma, but initially at least there is no significant high or low energy tail. It is the Coulomb collisions that leads to the energy spread. The ions have close to the full potential well energy, so it does not require much upscattering before escape the potential well. Bussard mentioned this and predicted the potential well energy required to contain upscattered ions for reasonable amounts of time. I'm not sure I followed is arguement, but his arguement seemed to be that ~ 20% excess energy was required, rather than the much higher level that Carlson predicted- based I believe on his assumption that the average temperature of the plasma was derived from a Maxwell Boltzman distribution, not a claimed monoenergetic plasma, where the average temperature is much closer to the mean temperature with a significantly smaller thermal spread. Keep in mind that in a Tokamak the maximum average temperatur obtainable may be in the range of 10-15 KeV, while most of the fusion would be occuring at the less prevelent ions near the end of the high energy tail, so you have to be certain you retain these higher energy ions. In a machine with monoenergetic plasmas the average temperature ideally matchs the fusion target temperature- perhaps 80 to 200 KeV depending on the fuel. You are actually happy to see the upscattering ions escape, so they do not compound the thermalization cascade, etc., provided you can figure out how to avoid too much input energy loss. Annealing is a key for this as it impeads the thermalization and thus the numbers of ions above some level that you want to get rid of.
As far as a cylindrical geometry being better than a spherical, I don't think so. There is a symmetrical center to a sphere, but not in a cylinder. If there is any convergence in a cylinder it is primarily linear or two dimensional, while it is three dimensional in a sphere. In a cylinder your density would increase as the square of any focus, a sphere density would increase as the third power of any focus. And, before you argue that you are doing things at the ends of the cylinder to direct ions towards the middle between the ends, you are only trying to convert the cyclindrical geometry into a pseudo spherical geometry.
Dan Tibbets
To error is human... and I'm very human.
