Waveguide Iris Structure for Quadrupole Plasma Generation
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Solution Overview
Problem
Microwave plasma sources for emission spectroscopy face challenges in producing toroidal plasmas, which are more difficult to generate compared to RF ICP sources, resulting in poorer detection limits and more demanding sample introduction requirements, and often rely on expensive argon gas.
Innovation Solution
The use of a waveguide with a novel iris structure that causes a 180-degree phase shift in the electric field, creating a quadrupole electric field arrangement to sustain a quasi-toroidal plasma using nitrogen as the plasma gas, which is more widely available and cost-effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If microwave power is used to generate plasma, then operating cost is reduced by using nitrogen instead of argon, but plasma confinement and stability deteriorate
Solution Approach 1:
The patent introduces an asymmetric iris structure in the waveguide that creates a quadrupole electric field configuration. This asymmetric field distribution enables effective plasma confinement and stabilization using nitrogen gas, resolving the contradiction between using cheaper nitrogen and maintaining plasma stability.
2Device complexity
If conventional waveguide is used for microwave plasma generation, then device simplicity is maintained, but plasma confinement capability deteriorates due to lack of circular symmetry
Solution Approach 1:
The patent deliberately introduces an asymmetric iris structure into the waveguide that generates a quadrupole electric field. This controlled asymmetry creates the necessary field configuration for plasma confinement, overcoming the limitation of conventional symmetric waveguides while maintaining relative structural simplicity.
Solution Approach 2:
The patent modifies the electric field distribution parameters by introducing the iris structure, transforming the field configuration from a simple dipole to a quadrupole arrangement. This parameter change enables effective plasma confinement without requiring complete redesign of the waveguide system.
3Measurement precision
If RF ICP source is used, then toroidal plasma is easily generated with good detection limits, but device complexity increases and argon gas is required
Solution Approach 1:
The patent replaces the RF inductive coupling mechanism with a microwave electric field-based confinement mechanism using an iris structure. This substitution achieves similar toroidal plasma confinement and detection performance while using a different physical approach that can operate with nitrogen gas.
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 enables the generation of a stable, quasi-toroidal plasma with improved analytical performance, comparable to RF ICP sources, while utilizing inexpensive nitrogen, thus addressing the limitations of microwave plasma sources in emission spectroscopy.
Implementation Method 1
an iris structure providing an iris in the electromagnetic waveguide, the iris structure defining an iris hole, a first iris slot along a first side of the iris hole, a second iris slot at a second side of the iris hole which is opposite the first side... causes the electric field in the waveguide to experience a phase shift or change in direction across the iris structure from a first side of the iris structure to a second side of the iris structure opposite the first side
Implementation Method 2
The waveguide is configured to support a desired mode of propagation having a frequency suitable for generating and sustaining a plasma
Implementation Method 3
Waveguide-based apparatus for exciting and sustaining a plasma... an electromagnetic waveguide; and an iris structure providing an iris in the electromagnetic waveguide... having a frequency suitable for generating and sustaining a plasma
Implementation Method 4
an iris hole, and wherein a plasma torch is disposed within the iris hole... an electromagnetic wave may propagate from a first end of the electromagnetic waveguide, and pass through the first iris slot, the iris hole, and the second iris slot
Data Source
AI summary
An apparatus includes: an electromagnetic waveguide and an iris structure providing an iris in the electromagnetic waveguide. The iris structure defines an iris hole. The apparatus further includes an electric field rotation arrangement configured to establish a 2N-pole electric field around a circumference of the iris hole, wherein N is an integer which is at least two. The electric field rotation arrangement may include at least four iris slots, each in communication with the iris hole, wherein a first one of the iris slots is further in disposed at a first side of the iris hole and a second one of the iris slots is disposed at a second side of the iris hole which is opposite the first side.