Reply To: Mind, Spirit, Science connection?

[redsnapper]

Henning wrote:

electrodes themselves (for example: highly-conductive, Xray-transparent, ceramic electrodes that can handle 2000 degC; better yet, virtual electrodes that can handle 500MdegC)

Read: quite-conductive (36 nΩ·m, compared to 16.78 nΩ·m of copper at 20 °C), x-ray-transparent, beryllium electrodes that can handle 2400 °C

The electrodes never get into contact with the 500 M°C (actually 2 G°C) pinch.

I think you missed my point. I was hypothesizing an improved electrode. Beryllium melts at 1278degC, and what I’ve been reading about FF is that electrode temperature would be limited to 700degC – perhaps somewhat arbitrarily. Seems like I remember the words “electrode erosion” or something like that – I’m sure that the higher the electrode temperature, the quicker it sublimates into the plasma – however hot the plasma is that surrounds the electrodes. (Resistivity tends to go up with temperature, as well, though I don’t know the specifics of Be. That could be a design factor, too.) Still, a limit is a limit, which if raised, tends to open new opportunities. So I was hypothesizing that some future ceramic (ceramics typically handle much higher temperatures than metals) might be developed that had the resistivity and Xray transparency of Be, but because of the higher temperature allowed, would relax the cooling challenge. This is called science fiction, or literary license – take your pick. 🙂 You do remember Scotty’s amazing exposition of transparent aluminum in the “save the whales” Star Trek movie?

And you’re right. Any physical surface representing the cooling boundaries (walls) never sees even the bulk fluid temperatures (using the word fluid here very fluidly – meaning plasma), because there must be a boundary layer gradient if there is indeed any heat transfer to the wall; further, I understand that the highest temperatures are within the plasmoids, which are microscopic and deep within the inner electrode. That’s why I was guessing that the plasma actually contacting the walls would be much cooler than the plasmoid temperatures. 500M vs. 1G or 2G seemed like an illustrative swag. But the bulk plasma is at such a low density that the heat transfer coefficient to the walls is such that the walls might indeed be as cool as 700degC, or 2400degC, or whatever – a few orders of magnitude lower than the “bulk” plasma temperature. Of course, my basic understanding of this system is feeble. Perhaps the “bulk” plasma temperature is only 700degC. After all, suppose a single shot (capacitor discharge) lasts only a microsecond – that’s plenty of time to take a few micrograms of localized plasmoid from 700degC up to 2GdegC – and if time-to-next-shot is a few milliseconds, there’s plenty of time for the residual plasma (not counting the hot ions that shot out the end of the core into the Rogowski coil) to begin to equilibrate and smooth out the temperature to a much-lower average. I assume also that only the teensiest fraction of the plasma actually fuses, so virtually all the plasma that’s heated during the pre-ignition phase remains at the required temperature until the plasmoid dissipates. I think if I saw quantitative simulation data of plasma temperature profiles in the DPF core I might quit making such terrible assumptions. Animated color CGI of the simulation is great, but it doesn’t show what I need to know to avoid gross error.