My impression on losses in the Polywell is as follows:ladajo wrote:Yes you are correct, I was mixing ideas in my head regarding particles and fields, and not clear in my intent.WizWom wrote:Um... Gauss' law would say you're absolutely and totally wrong.ladajo wrote:Dan,
I see it more as a bucket with holes as well as evaporation and birds that drink.
Flux in does not equal Flux out. It is loss mechanism dependant.
There are no magnetic monopoles, so net flux through a closed surface must be zero. That means if a field line goes in, it must come out.
1) Cross field transport. This is proportional to machine size and B field strength. Because electrons have significantly smaller gyroradii compared to ions, the size can be significantly smaller for the same cross field (ExB drift) transport dependent electron life times. The ions in the Polywell are supposed to be electrostatically contained within the Wiffleball border and thus they do not experience this transport, unless they are sufficiently upscattered. Also, the ions have low speeds in the Wiffleball border region, so any magnetic domain induced gyroradii are corespondingly small. In the upscattered ion case, they would also have shorter cusp confinement times, so this cusp loss mechanism would possibly still dominate for these select ions. The cross field transport is why Tokamaks have to be so big to achieve adequate ion magnetic containment, even though they do not have the cusp losses that the Polywell has (unless you consider macro instabilities as temporary cusps, and you ignore diverters, which are apparently needed for any working tokamak).
2) Electron losses through cusps. Electrons are at the bottem of their potential well when they enter a cusp, so losses need to be kept as small as possible by pinching the cusp throats nearly closed via the Wiffleball effect. Efficient recirculation relaxes this limit considerably, to the extent that the Wiffleball traping is more important for maintaining useful density/ fusion rates. Ion losses through cusps is apparently trivial as they are contained electrostatically below the cusps due to the potential well established by the excess electrons.
The electron cusp losses are perhaps 100 times as great (or more) as electron cross field transport losses. This estimate is based on the 2008 patent application that mentioned that if recirculation can recycle the cusp lost electrons by up to ~ 100X, then these loses would approach the cross field losses.
3) Radiation losses. Cyclotron losses are apparently modest. Bremsstrulung losses need to be accounted for, especially with high Z fuels (P-B11) and increasing drive energies. Ion mixing ratios apparently can help this some. With P-B11 fusion, operating around the fusion crossection resonance peak could also help some, especially if the ion populations can be kept within a narrow center of mass (?) energy range near this peak.
4) Input losses- ie: inefficiencies in the ion and electron guns, any losses from electrons that do not travel cleanly through a cusp, interference with cusp behavior and/ or recirculation due to the guns being near the cusps, etc.
5) Unshielded magrid surfaces or supports in the locations near the cusps that interferes with efficient recirculation. Based on what Nebel said about the WB7 nub heating. This may be the most significant area where additional gains can be made.
On the opposite side of the coin are things that increase the fusion rate, such as maintaining confluence, monoenergetic populations, and possible POPS effects. Also, the Wiffleball trapping factor that maximizes obtainable densities within the machine.
PS: As mentioned in the 2008 patent application, especially with high Z fuels like boron, as the positive alpha fusion ions leave the system, they leave behind the electrons. At least with gas puffing systems (as opposed to ion guns) this may greatly decrease the needed input electron current necessary to maintain the potential well. I'm not sure how this would effect the electron energy balance( net effective energy of the hot injected electrons and the cool secondary ionization electrons).
Dan Tibbets
