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private:writeups:plasmaimpedanceprobes [2020/07/01 19:13]
admin 		private:writeups:plasmaimpedanceprobes [2020/07/02 14:17] (current)
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 === What it does === === What it does ===
  
-1.  Plasma frequency [Blackwell2005] +Measures 
-Network analyzer performs frequency sweeps.  Look for peak near where you expect $\omega_{pe}$ to be.  +  - Plasma frequency [Blackwell2005] 
 +  - Electron density (by measuring plasma frequency) [Blackwell2005] 
 +  - Plasma potential 
 +  - Collision frequency
  
-2. Electron density [Blackwell2005] +=== Methods ===
-Excite a two-stream instability [Blackwell2005].  Introduce a beam of electrons into a cold, unmagnetized plasma to excite a two-stream instability.  If the beam is weak enough, the instability peaks at roughly the electron plasma frequency.  Since this is effectively another measurement of the plasma frequency, I'm not sure why this is better than the 1st method.  Perhaps exciting the instability has a higher signal/noise ratio?+
  
-=== Advantages/disadvantages ===+PIPs can be operated in a number of methods 
 + 
 +  - Actively driven RF sweeps [Blackwell2005].  Relate the peaks and zero intercepts of Re(Z) and Im(Z) to circuit models and dispersion relationships to get the plasma frequency. 
 +  - Plasma oscillation (excite a two stream instability) [Blackwell2005].  Drive weak beam of electrons into the plasma to excite a two stream instability.  Under correct conditions, its frequency is close to the plasma frequency.  An FFT of passive PIP measurements reveals the frequency.   
 + 
 + 
 +=== Advantages ===
  
   * [Blackwell2005] An improvement over Langmuir probes because contamination of the probe has a larger impact on its measurements than on the PIP.   * [Blackwell2005] An improvement over Langmuir probes because contamination of the probe has a larger impact on its measurements than on the PIP.
 +  * Better resolution and accuracy than traditional Langmuir probes [citation]
 +
 +=== Disadvantages ===
 +
 +  * More complicated.  Requires careful setup/calibration and the use of an expensive network analyzer.
 +  * (Check this) Cannot be used in real-time because the network analyzer data can only be post-processed.  
  
 === Sources of error === === Sources of error ===
private/writeups/plasmaimpedanceprobes.1593630835.txt.gz · Last modified: 2020/07/01 19:13 by admin

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