Plasma Impedance Tomography for Non-Invasive Density Imaging
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Solution Overview
Problem
Current methods for measuring plasma parameters like electron plasma density and magnetic field are invasive, destructive, or limited to relative measurements, and lack the capability for spatially resolved, non-invasive, and absolute measurements, especially in dynamic plasmas.
Innovation Solution
A plasma impedance tomography method using a sensor array of antennas to measure complex self-impedance and mutual impedance over a wide range of frequencies, allowing for remote imaging of plasma parameters by inverting line-averaged spatial information to determine plasma dielectric profiles, enabling absolute density and magnetic field measurements and imaging of dynamic structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Langmuir probes are used to measure plasma density, then simple construction and widespread use are achieved, but invasive single point measurements disrupt the plasma or destroy the probe
Solution Approach 1:
The patent uses electromagnetic waves as an intermediary to measure plasma parameters. Instead of directly inserting a physical probe into the plasma, the system transmits electromagnetic signals through the plasma and analyzes the modified signals to infer density, temperature, and composition. This indirect measurement approach eliminates probe disruption while maintaining measurement capability
Solution Approach 2:
The patent replaces the mechanical Langmuir probe system with an electromagnetic field-based measurement system. By substituting physical contact with electromagnetic wave interaction, the system achieves non-invasive plasma diagnostics that avoid probe destruction and plasma disturbance
2Reliability
If laser induced fluorescence is used to measure particle velocity distributions, then non-invasive measurement is achieved, but only relative not absolute measurement of density is obtained
Solution Approach 1:
The patent measures multiple electromagnetic parameters (amplitude, phase, polarization, frequency) at different frequencies and angles to derive absolute plasma density values. By changing measurement parameters and analyzing their variations, the system transitions from relative to absolute density measurement while maintaining non-invasive operation
3Measurement precision
If plasma tomography is used to reconstruct spatial plasma density profiles, then spatial resolution is achieved, but high-density and high-temperature environments are required to produce required plasma radiation
Solution Approach 1:
The patent creates a universal measurement system that works across diverse plasma conditions (low-temperature laboratory plasmas, high-temperature fusion plasmas, atmospheric pressure plasmas) by using electromagnetic wave interaction rather than relying on specific plasma radiation characteristics. The system performs multiple diagnostic functions including density profiling, temperature measurement, and composition analysis across different plasma regimes
4Reliability
If electrical impedance tomography is used to reconstruct internal conductivity, then non-invasive imaging is achieved, but no reconstruction algorithm has been applied to plasmas
Solution Approach 1:
The patent adapts electrical impedance tomography for plasma by incorporating plasma-specific parameters including electromagnetic dispersion relations, plasma frequency dependence, and magnetic field effects. The reconstruction algorithms are modified to account for plasma's unique electromagnetic properties, enabling successful application to various plasma types
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides non-invasive, absolute measurements of plasma density and magnetic fields with high spatial resolution, suitable for both laboratory and fusion plasmas, and allows for real-time imaging of dynamic structures without disrupting the plasma.
Implementation Method 1
measuring the complex self-impedance and mutual impedance between successive pairs of antennas in a plasma impedance sensor array over a wide range of frequencies
Implementation Method 2
which can be inverted to make images of the plasma dielectric
Implementation Method 3
Plasma tomography uses measurements of plasma radiation along lines of sight to reconstruct spatial plasma density profiles
Data Source
AI summary
A method for non-invasively imaging plasma parameters has been invented. Crossed dipole pairs are used to differentiate changes in the measured complex self- and mutual impedances due to plasma density and magnetic field. Measurements of the complex self-impedance and mutual impedance between pairs of antennas over a wide range of frequencies provide spatial information to create an image of the plasma density and magnetic field. The spectral information is acquired simultaneously using a Gaussian monopulse as the driver signal.