How to measure ion energy in a plasma?

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Discussion Overview

The discussion centers around the methods for measuring ion energy in a plasma, specifically addressing the confusion between measuring ion and electron temperatures. Participants explore various techniques and clarify misconceptions about the use of Langmuir probes in this context.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the accuracy of using Langmuir probes for measuring ion temperatures, suggesting that they primarily measure electron behavior due to the mobility differences between electrons and ions.
  • Another participant asserts that Langmuir probes have a long history of use in measuring plasma characteristics, including electron temperature, and suggests looking for alternative methods if Langmuir probes are not suitable for a specific situation.
  • A participant expresses frustration over the focus on Langmuir probes, emphasizing a desire for information specifically about measuring ions and indicating that they are already familiar with the probe's capabilities.
  • One participant acknowledges a misunderstanding regarding the focus on ions versus electrons and admits their experience is more related to ion beam optics, which may not be applicable to the current discussion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the effectiveness of Langmuir probes for measuring ion temperatures, with some arguing for their use while others express skepticism about their applicability to ions specifically.

Contextual Notes

There are unresolved questions regarding the limitations of Langmuir probes in measuring ion temperatures and the potential need for alternative methods depending on specific experimental conditions.

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I was looking at things today and read (on wiki) that the use of Thompson Scattering reveals electron temperature in a plasma, not ion temperature. I thought that's how ion temp was measured (or maybe it is and the wiki text was incomplete)?

Could someone please clarify how ion temperatures in a plasma are measured?
 
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The standard way to do this is using a Langmuir probe.
 
bobob said:
The standard way to do this is using a Langmuir probe.
Really?

Surely the principle of a Langmuir probe is that the electrons are more mobile than ions by orders of magnitude, and the probe measures the fundamental behaviour of those?

I am aware that there are some long winded theories about measuring ion temperatures with Langmuir probes, but I think they are very limited in the scope and theory of what can be done.

I don't think your reply is correct.
 
Well, Langmuir probes have been used for a long time to measure plasma characteristics, including electron temperature. You can go do a search and find that out for yourself easily enough. If you want to do something different or if a Langmuir probe does not easily lend itself to your particular situation, then you need to find a method that applies to your particular situation, since what other methods are available sort of depend on what you are doing. You might want to start looking through Review of Scientific Intruments to see what is most applicable to your particular situation.
 
This forum is like milking a stone.

I know about Langmuir probes, thanks, and don't need to read any more about them.

I just want some FACTS about measuring IONS!

How are ion energies measured in a plasma? (My first post was clearly saying I am not interested in measuring electrons.)
 
Sorry, my mistake. For some reason, I thought the electrons were what you were trying measure. Sorry for misreading. My familiarity with doing tht sort of thing with ions would be more confined to ion beam optics, which is probably not useful in this context.
 

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