ANS winter 2010 Conference

[chrismb]

The only comparison that I can think of would be with pictures of the glow in Tokamaks. Is the densities similar? Perhaps, at least in WB6. Is the recombination glow intensity similar? What does this glow in Tokamaks represent compared to the ratios above?

I'm glad you have thought that through and recognise if you see a glow plasma you are not seeing a really hot plasma. There is no plasma glow in the reaction zone of a tokamak, at fusible temps. You only see it at the edge where it is interacting with the outer wall. I don't see why you would see any glow plasma in a thermal reaction volume above a few 10's eV. That's why I didn't understand that photo of a 'WB' on EMC2 website.

[TallDave]

and when you get losses to the outer chamber surfaces neutralisations may occur that would 'pollute' the thermal mix such that if you are trying to pump the ion trapping with electrons then they'll have to work pretty hard.

It seems possible, but I suspect we'll find the effect is insignificantly small, given that the edge is the bottom of the well for electrons and we're flooding the WB with hot electrons. The electron drive is going to be working pretty darn hard regardless because this is a driven system and the electrons dominate the losses.

[D Tibbets]

The only comparison that I can think of would be with pictures of the glow in Tokamaks. Is the densities similar? Perhaps, at least in WB6. Is the recombination glow intensity similar? What does this glow in Tokamaks represent compared to the ratios above?

I'm glad you have thought that through and recognize if you see a glow plasma you are not seeing a really hot plasma. There is no plasma glow in the reaction zone of a tokamak, at fusible temps. You only see it at the edge where it is interacting with the outer wall. I don't see why you would see any glow plasma in a thermal reaction volume above a few 10's eV. That's why I didn't understand that photo of a 'WB' on EMC2 website.

Well, yes, a hot plasma will have very little glow, but by your arguments there would always be some from recombinations/ charge exchange. Assuming thermalization, some of the recombined electrons would fall into low enough orbitals (at least briefly) and emit a visible photon in the process. It is unavoidable. That is why I tried to make the point, that what is important is the relative occurrence of this event. The less frequent, the dimmer the light will be, so you need very good night vision to see it (photomultiplier tubes in my example). How dim does this process need to be before it is insignificant? I have no idea.

Dan Tibbets