Hybrid concept to fusion

[Francisl]

Contamination of the plasma has been a problem in DPF devices as shown by LPPFusion’s latest report. I propose a hybrid solution to reduce the contamination. It may have some weaknesses but could spark an interesting discussion.
Mass spectrometry and calutron machines can separate heavy contaminant ions from the lighter fuel ions. They may process the fuel too slowly to be practical for a dpf. If you look at a seperator schematic it has three basic parts: an ion source, a magnet and a collector. I suggest using a plasma railgun as the ion source using the fusion fuel, a magnet and the collector is the back end of a dpf device. Some type of plasma wave shaping system would have to create a smooth wave front as the plasma enters the dpf. The plasma wave would contact the high voltage high current electrodes and form the plasma sheath as normal. The rest of the operation proceeds as usual in the dpf.
I see two advantages if this system works. First, the fuel should be cleaner entering the dpf and the plasma wave front should be moving too fast for the heavy ions from the electrodes to catch up. Second, the plasma wave is already moving at a high speed so the capacitor bank doesn’t have to use so much energy accelerating the plasma which leaves more energy for the pinch phase.

[Focus Fusion Society]

It is certainly an interesting idea to try to inject clean plasma for the pinch and rather than trying to clean the chamber. There could also other ways of doing it such as similar to NIF using a capsule.
However, there would be some substantial risks and challenges to overcome:
Rail system would be a huge investment in time and money LPP probably can’t afford
Preionization would no longer be possible without pre-existing plasma
There is no guarantee this approach would help reduce plasma contaminants as the vaporization of electrode surface might still introduce a large amount

[Francisl]

I admit the system is unorthodox and may not work. Can we divide it into components that collaborators could research and advise on?
Railgun systems have been built with big power supplies to handle heavy payloads. The amount of fuel for a dpf would be a light load and could use a much smaller railgun machine. There is a big difference between the mass of fuel and metal contaminants. That could reduce the size of the separation magnets. If preionization of the dpf chamber is still needed it would be handled in a different way. The vaporization of the dpf electrodes is a major unknown because the plasma sheath may not outrun the heavy electrode ions. The operators of plasma railguns could comment on how much metal is present in their plasmas.

[Francisl]

At first I was thinking that a modified dpf could act as the ion source to accelerate the plasma to go through the magnet. Then I decided that maybe a railgun would be cheaper and easier to make. The power supply would not be as expensive as for a dpf because the rise time is not as critical. Tabletop systems could be made in university labs to test the concepts. The small dpf machines at university physics labs that are used to train fusion scientists would be ideal for testing.

[Author]

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