Multi-Lobed Microwave Resonator for Plasma Core Coupling
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Solution Overview
Problem
ECR ion sources face issues with inefficient microwave power deposition in the plasma core, leading to a 'void' along the central axis and poor wave-plasma coupling due to cylindrical symmetry and geometric mismatch in conventional resonators.
Innovation Solution
A microwave resonator with a multi-lobed chamber geometry that mimics the B-minimum magnetic field structure, featuring a three-dimensional shape and diffractive slots in the waveguides for distributed microwave injection, enhancing electromagnetic field coupling and plasma confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cylindrical chamber with rectangular aperture coupling is used, then the device structure is simple, but the microwave power deposition is not concentrated in the plasma core and a plasma void is created along the central axis
Solution Approach 1:
The patent replaces the conventional cylindrical chamber with a multi-lobed chamber geometry that breaks the cylindrical symmetry. This asymmetric design allows the microwave fields to be concentrated along the central axis, eliminating the plasma void while improving power deposition accuracy in the plasma core.
Solution Approach 2:
The patent transitions from a two-dimensional cylindrical cross-section to a three-dimensional multi-lobed structure. The multi-lobed geometry introduces additional spatial dimensions for field distribution, enabling better control over microwave power deposition patterns and achieving concentration along the central axis.
2Device complexity
If a rectangular waveguide aperture is used for microwave coupling, then the coupling structure is simple, but there is an intrinsic mismatch of geometry and impedance leading to poor wave-plasma coupling
Solution Approach 1:
The patent modifies the geometric parameters of the waveguide coupling structure by replacing the rectangular aperture with diffractive slots of specific dimensions and arrangements. These parameter changes optimize the impedance matching between the waveguide and plasma, significantly improving wave-plasma coupling efficiency.
Solution Approach 2:
The diffractive slots act as an intermediary structure between the rectangular waveguide and the plasma chamber. This intermediate element transforms the microwave fields in a controlled manner, enabling efficient energy transfer while maintaining compatibility with the simple waveguide structure.
3Ease of operation
If conventional cylindrical symmetry is maintained, then the chamber design is straightforward, but the microwave power deposition is not concentrated in the plasma core
Solution Approach 1:
The patent introduces asymmetric multi-lobed geometry to break the cylindrical symmetry, which enables the microwave fields to constructively interfere along the central axis. This asymmetric design dramatically improves power absorption efficiency in the plasma core while maintaining reasonable design complexity.
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
Improves the brilliance of the ion beam and plasma confinement by optimizing wave-plasma coupling and microwave power absorption within the plasma core.
Implementation Method 1
diffractive apertures for the injection of microwaves into the chamber (101)
Implementation Method 2
electrons are accelerated or decelerated in a resonant manner when the following electron cyclotron resonance condition is satisfied
Implementation Method 3
electrons moving in a magnetic field revolve around the magnetic field lines due to the Lorentz force
Implementation Method 4
The electrons of the plasma are confined in a superposition of an axial component of the magnetic field and of a radial component of the magnetic field
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Microwave resonator (100), comprising a chamber (101) made of metal material configured to contain a plasma, the chamber comprising a first and a second end face (101a, 101b) and extending along a central axis (z) between the first and second end face, and a microwave launching device (110) configured for injecting microwaves into the chamber. At the first end face (101a) the chamber has a cross section of multi-lobed shape that tapers toward the second end face (101b). At the second end face (101b) the chamber has a cross section having the same shape as the cross section of the first end face (101a) and rotated 180° about the central axis (z), the cross section of the second end face (101b) tapering toward the first end face (101a). At an intermediate plane, the shape of the cross section of the first end face (101a) merges with the shape of the cross section of the second end face (101b).