Neutral Beam Plasma Diagnostics for Low-Density Electric Field Measurement
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Solution Overview
Problem
Current diagnostic methods, such as the heavy ion beam probe (HIBP), are ineffective for measuring the potential and electric field of low-temperature and low-density plasma, as they require high temporal-spatial resolution and are not applicable to plasma with low parameters.
Innovation Solution
A diagnostic method and system that selects candidate particle elements based on operation parameters like background magnetic field, electron temperature, and density, calculates beam trajectories and signal-noise ratios, and generates a neutral beam for collision ionization to measure potential and electric field distribution in plasma, using a solid-state thermionic source and Pierce electrode equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If heavy ion beam probe (HIBP) is used to measure potential and electric field, then measurement precision is improved, but adaptability deteriorates for low-temperature and low-density plasma
Solution Approach 1:
The patent changes the particle mass parameter by using different neutral beam elements (hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon) to optimize the diagnostic performance for different plasma conditions. This allows the system to adapt from high-temperature core plasma to low-temperature edge plasma by selecting appropriate beam elements with different masses and ionization characteristics
Solution Approach 2:
The neutral beam probe diagnostic system is designed to perform multiple measurement functions: measuring plasma potential, radial electric field, and their fluctuations across different plasma regions (core and edge). By using variable neutral beam elements and adjustable incident energies, the single diagnostic system can replace multiple specialized diagnostics, achieving universality across different plasma temperature and density regimes
2Adaptability or versatility
If neutral beam with low incident energy is used, then adaptability to low-parameter plasma is improved, but signal-noise ratio deteriorates
Solution Approach 1:
The patent optimizes the incident energy parameter of the neutral beam based on the selected beam element and target plasma conditions. For low-temperature plasma, lower incident energies (e.g., 1-10 keV) are used to match the plasma potential range, while for high-temperature plasma, higher energies are employed. This dynamic parameter adjustment maintains adequate signal-noise ratios across different plasma regimes
Solution Approach 2:
The diagnostic system uses composite measurement approaches by combining signals from multiple neutral beam elements with different ionization cross-sections and mass-to-charge ratios. This composite measurement strategy enhances the signal-noise ratio through signal averaging and cross-validation, particularly in low-parameter plasma where individual measurements may be noisy
3Measurement precision
If high incident energy neutral beam is used, then signal-noise ratio is improved, but adaptability to low-parameter plasma deteriorates
Solution Approach 1:
The neutral beam incident energy is made dynamically adjustable rather than fixed. The system can switch between high energy (for high-temperature core plasma with good signal-noise requirements) and low energy (for low-temperature edge plasma requiring adaptability). This dynamic adjustment allows the same diagnostic system to adapt to varying plasma conditions while maintaining adequate measurement quality
4Measurement precision
If beam trajectory calculation is performed for multiple candidate elements, then measurement precision is improved through optimal selection, but device complexity increases
Solution Approach 1:
The patent performs preliminary beam trajectory calculations and signal-noise ratio assessments for multiple candidate neutral beam elements before actual plasma diagnosis. This pre-characterization allows selection of the optimal beam element for specific plasma conditions, avoiding the need for complex real-time adjustments during measurements. The preliminary work includes calculating Larmor radii, ionization cross-sections, and expected signal strengths for each candidate element
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
The method provides high temporal-spatial resolution and sufficient signal-noise ratios for measuring potential and electric field fluctuations in plasma with low parameters, suitable for studying turbulent inhibition and confinement improvement in magnetic confinement fusion plasma.
Implementation Method 1
heating solid-state thermionic source corresponding to the neutral beam particle element to generate ions
Implementation Method 2
accelerating the ions by utilizing Pierce electrode equipment to obtain a directed ion beam
Implementation Method 3
subjecting the directed ion beam to exchange with a preset neutral gas charge to generate a neutral beam with a preset incident energy
Implementation Method 4
collision ionization between the single-charged ion beam and electrons in the plasma
Implementation Method 5
effective electron-impact ionization cross-section data
Implementation Method 6
the primary beam deflects and exits the plasma under the action of a background magnetic field
Implementation Method 7
based on energy difference between the primary beam and the neutral beam, obtaining a potential of the first sampling area according to law of conservation of energy
Data Source
AI summary
A diagnostic method and system for measuring potential and electric field of plasma are provided. According to operation parameters of a magnetic confinement fusion device and relevant parameter data of a plurality of candidate particle elements, signal-noise ratios are calculated. to select a neutral beam particle element. Beam trajectories varying in incident velocity, incident angle and sampling area are obtained by iterative calculation, and a preset parameter which enables the beam trajectories to pass through an entrance slit of an analyzer is obtained. A neutral beam that meets the preset parameter is injected into the plasma. An energy of the primary beam generated by collision ionization in a sampling area is measured, and potential of the sampling area is obtained according to law of conservation of energy. Sampling areas are detected to obtain potential spatial distribution of the plasma and a radial electric field, and the diagnostic is finished.