--- Michel > > Either way will work. > Are you sure? A ref to a fusor where the outer > electrode is the more negative one would be welcome,
The Hilsch "improvement" to the original idea uses the negative inner grid. Farnworth tried everything else, including an electron gun(s) outside the chamber, with or without a dedicated grid, to accelerate the negative charge. Like Gow at Berkeley, PF at first used a cylinder for containment, instead of a sphere. There was also a 'mini accelerator'. As I understand the situation, at this range of potential (< 100 keV) there is a rather substantial advantage in accelerating negative deuterium molecular ions (D2-) instead of positive deuterons. Order of magnitude advantage in current. He is one such reactor: http://49chevy.blogs.com/fusor/images/396pxus3386883__fusor.png Back to the 'virtual' electrode. As you know, when you fire an array of electron beams into a plasma, as PF did on occasion, the electrons do not go very far, so in effect- THIS can be your virtual electrode, sans grid (from the perspective of the inner volume. The plasma tends to bifurcate in charge, like a natural capacitor, depending on the polarity of the outer containment. If your plasma is colder, and the predominant species is (D2-)then you may want the structure to be negatively charged (NOT grounded) and an inner grid positive- to accelerate the ions. If you think that arrangement sounds counter-intuitive, then you are not familiar with the incredible nuclear reactor design of Kapitza, from the 60's. Kapitza is the famous Russian who also invented the tokomak. He was able to achieve a virtual charge separation, and fusion, in a charged *D2 GAS* near one atm pressure! - no real plasma required ! Yes, this muddies the definition of "plasma". I wish I could find the url quickly for that one, but it will have to wait unless you have time to look. It may not be online as it preceded the breakup of the USSR. I have often thought (in a bit of historical revisionism) that if PF and Kapitza had gotten together with decent funding in the 60's (impossible at the time) they could have pushed a hybrid idea for warm D fusion to breakeven. The breakeven would probably be complex, and have to come from what happened to the neutrons -- after they left the Fusor, (multiplication via subcritical U fission) but who cares (nowadays)? Jones
