# Plasmoid Contamination in a Dense Plasma Focus

Tags:
1. Jul 19, 2014

### Warpspeed13

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 occured 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)

2. Jul 19, 2014

### the_wolfman

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.

3. Jul 20, 2014

### Warpspeed13

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?

4. Jul 20, 2014

### the_wolfman

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.

5. Jul 20, 2014

Thank you.