Plasmoid Contamination in a Dense Plasma Focus

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Discussion Overview

The discussion revolves around the potential contamination of plasmoids in Dense Plasma Focus devices due to the ionization of cathode materials alongside the fill gas, such as deuterium. Participants explore the implications of this contamination on plasma confinement and the complexity of calculating impurity concentrations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether cathode material is ionized and trapped in the plasmoid, potentially polluting it.
  • Another participant acknowledges that electrostatic plasma guns generate impurities that can degrade confinement, noting the complexity of calculating impurity concentrations.
  • Experimental approaches to estimate impurity levels include assessing electrode erosion over multiple discharges, but determining the actual concentration in the plasmoid is described as complex.
  • A suggestion is made to search for literature on "Plasma-Material Interactions (PMI)" and "Impurity Transport" to find relevant studies, although it is noted that most existing research focuses on tokamaks and stellarators rather than Dense Plasma Focus devices.

Areas of Agreement / Disagreement

Participants generally agree on the complexity of the issue and the challenges in calculating impurity concentrations, but there is no consensus on the specifics of how cathode material impacts plasmoid contamination.

Contextual Notes

The discussion highlights limitations in current understanding, particularly regarding the specific interactions and calculations needed to assess impurity levels in Dense Plasma Focus devices.

Who May Find This Useful

Researchers and students interested in plasma physics, engineering applications of plasma devices, and the study of plasma-material interactions may find this discussion relevant.

Warpspeed13
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Ok I'm posting this here as well since It falls under both engineering and high energy physics, since I haven't gotten an answer on the high energy physics thread. So I've been researching Dense Plasma Focus devices for a while now and a question just occurred to me. Since the fill gass such as deuterium is being ionized and then compressed and fused in the Plasmoid, wouldn't some of the cathode material also be ionized and the trapped in the Plasmoid polluting it? If this is the case what equations would you use to calculate the number of cathod material atoms trapped in the Plasmoid in moles?

See Dense Plasma Focus (http://en.m.wikipedia.org/wiki/Dense_plasma_focus)
 
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Yes, one of the problems with electrostatic plasma guns is that they tend to generate tons of impurities that degrade confinement. Unfortunately, calculating the impurity concentrations isn't easy. Experimentally, you can look at the erosion of the electrodes over numerous discharges to get an idea of how much material is ejected per shot. But not all of the material is getting confined by the plasmoid. A separate calculation is needed to determine the concentrations of the impurities in the plasmoid. This calculation is pretty complex, and would be worthy multiple scientific publications.
 
Cool thank you very much, your answer is really helpful. I had no idea it would be that complex. Do you know where I could find any articles / doctoral thesis's on this subject?
 
Try searching "Plasma-Material Interactions (PMI)" and "Impurity Transport." If you have access to academic journals then use engineering village (or a similar database). If not than use google or google scholar.

As its name suggest PMI is the discipline that studies the interaction between plasmas and material surfaces. Among other things, it attempts to understand that rate at which that the plasma erodes the material surface.

Impurity transport studies the confinement of impurity ions in the plasma. It is a huge field, but most of the work to-date has been geared towards tokamaks and stellarators. I doubt that you will find anything specific to the dense plasma focus. But it is a starting point.
 
Thank you.
 

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