Measuring Ion Temperature in Plasma: Why Use Tungsten/Molybdenum Probes?

In summary, the use of tungsten or molybdenum probes in plasma measurements is due to their refractory properties. These materials have high melting temperatures and sputtering thresholds, making them ideal for high temperature applications. While a single Langmuir probe can be used for measuring electron temperature, it may not be as accurate for measuring ion temperature.
  • #1
mkbh_10
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I am nt able to understand why we are not able to measure ion temperature in plasma using single probe method ?

Why tungsten or molybednum probes are used ?
The book says due to their refractory properties but i am nt getting it .



TO mod , i didnt find a plasma related section so posted this here so please move it if there is one .
 
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  • #2
Unfortunately we don't have a plasma physics forum, so other than HEP, one could probably post in Gen Phys or Classical Physics.

What type of plasma?

Here are some papers that might be of interest.

http://www.ktu.lt/lt/mokslas/zurnalai/medz/medz0-91/16%20Testing...(pp.346-350).pdf

http://epsppd.epfl.ch/Hersonissos/pdf/P2_142.pdf

http://www.terrapub.co.jp/journals/EPS/pdf/5112/51121309.pdf

http://depts.washington.edu/rppl/presentations/APS2009/2009-APS-poster-24.pdf

In the last reference (poster), look at Table 2. A Comparison of Material Sputtering Threshold, and note the ranking of W, Ta, and Mo compared to other materials. The refractory metals have high melting temperature and high sputtering threshold, so they are ideal for certain high temperature applications.

I believe a single Langmuir probe can be used for temperature measurement - at least electron temperature - but perhaps ion temperature is of interest.

http://www-ferp.ucsd.edu/boedo/Diagnostics/Te_Fluctuations/Rudakov_htpd_00.pdf
 
Last edited by a moderator:

1. What is ion temperature in plasma?

Ion temperature in plasma refers to the average kinetic energy of charged particles (ions) in a plasma. It is a crucial parameter in studying plasma characteristics and behavior.

2. Why is it important to measure ion temperature in plasma?

Measuring ion temperature allows scientists to understand the energy distribution and dynamics of charged particles in a plasma. This information is essential for studying plasma processes and optimizing plasma-based technologies, such as fusion reactors and plasma thrusters.

3. Why use tungsten/molybdenum probes for measuring ion temperature in plasma?

Tungsten and molybdenum are both high-temperature materials that can withstand the harsh conditions of plasma environments. They also have a low sputtering rate, which means they do not contribute significantly to the plasma's ionization, making them ideal for accurate temperature measurements.

4. How do tungsten/molybdenum probes measure ion temperature in plasma?

Tungsten/molybdenum probes work on the principle of thermionic emission, where the ions' temperature is determined by the amount of current produced when the probe is heated. The higher the ion temperature, the higher the current produced by the probe.

5. What are the limitations of using tungsten/molybdenum probes for measuring ion temperature in plasma?

One limitation is that the probes can only measure the temperature of ions with a specific charge-to-mass ratio. This means that they may not accurately measure the temperature of all ions in the plasma. Additionally, the probes' placement in the plasma can also affect the accuracy of the temperature measurement.

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