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Pulse compression radar reflectometry to measure electron density in plasma with parasitic reflections
Bin Li1, Hong Li, Zhipeng Chen
1CAS Key Laboratory of Basic Plasma Physics and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
The Review of Scientific Instruments
|August 7, 2008
Summary
Pulse compression radar reflectometry effectively measures plasma electron density profiles. This technique uses frequency sweeps and Fourier transforms to eliminate parasitic reflections, improving measurement accuracy compared to traditional methods.
Area of Science:
- Plasma physics
- Wave-particle interactions
- Electromagnetic diagnostics
Background:
- Electron density profiles are crucial for understanding plasma behavior.
- Traditional reflectometry methods can be limited by parasitic reflections.
- Accurate measurement of plasma parameters is essential for fusion energy research.
Purpose of the Study:
- To introduce and validate pulse compression radar reflectometry for electron density profiling.
- To demonstrate the method's ability to mitigate parasitic reflections.
- To evaluate the trade-off between spatial and electron density resolution.
Main Methods:
- Utilizing the relationship between pulse temporal width and frequency bandwidth (Δt ∝ 1/Δf).
- Employing sweep-frequency microwaves and Fourier transforms to convert frequency-domain reflectivity to time-domain response.
- Implementing a time-gating technique to eliminate parasitic reflections.
Main Results:
- The pulse compression radar reflectometry method successfully obtains electron density profiles.
- Parasitic reflections were effectively eliminated from the temporal response using time gating.
- Experimental results showed good agreement with measurements from a double Langmuir probe.
Conclusions:
- Pulse compression radar reflectometry offers an advantageous alternative to traditional reflectometry for plasma diagnostics.
- The time-gating method significantly overcomes limitations posed by parasitic reflections.
- Achieving an optimal balance between spatial and electron density resolution is key for this technique.
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