Microwave Plasma Reactor Waveguide Tapering for Reflection Control
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Solution Overview
Problem
Existing microwave plasma reactors face challenges in maximizing energy absorption while minimizing microwave radiation reflection, leading to reduced efficiency in plasma generation and stability, particularly when dealing with greenhouse gas abatement in semiconductor manufacturing effluent streams.
Innovation Solution
The design incorporates a waveguide with a convergent tapered portion and an electrically conducting member protruding into the resonant cavity at maximum electromagnetic intensity, along with a movable tuner and cooling mechanisms, to enhance energy absorption and plasma sustainability without reflecting microwave radiation back into the generator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If tuning screws are added to the waveguide to minimize microwave radiation reflection, then microwave reflection is reduced, but energy absorption into the plasma is reduced
Solution Approach 1:
The invention removes the tuning screws from the waveguide structure entirely, extracting the problematic element that caused the contradiction. Instead of using tuning screws to minimize reflection, the patent uses a convergent tapered waveguide portion that achieves both reflection minimization and maintains energy absorption capability
Solution Approach 2:
The invention changes the geometric parameters of the waveguide by introducing a convergent tapered portion with specific length (approximately one half wavelength) and angle. This parameter change allows the waveguide to minimize reflection through its tapered geometry while preserving energy absorption into the plasma
2Reliability
If a fixed electrically conducting member is used in the resonant cavity, then plasma generation is improved, but maintenance and optimization are difficult
Solution Approach 1:
The electrically conducting member is divided into two segments: a fixed base portion attached to the resonant cavity and a replaceable tip portion that can be independently removed and replaced. This segmentation allows the tip to be optimized or replaced for maintenance while keeping the stable base portion in place
Solution Approach 2:
The invention introduces adjustability to the electrically conducting member by making the tip replaceable and potentially movable. This dynamic feature allows optimization of the member's position or configuration while maintaining the overall structural stability provided by the fixed base
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 configuration allows for efficient plasma generation and sustainability with lower power input (2-6 kW), effectively addressing the challenge of greenhouse gas abatement by intensifying the electric field and optimizing energy absorption, thereby enhancing the reactor's efficiency and operational stability.
Implementation Method 1
a waveguide for conveying microwave radiation to the resonant cavity
Implementation Method 2
means arranged to form an electromagnetic standing wave within the resonant cavity from the microwave radiation
Implementation Method 3
the electrically conducting member comprises a replaceable tip protruding into the resonant cavity located at a maximum intensity of the electromagnetic field formed within the resonant cavity
Implementation Method 4
The presence of the tapered portion of the waveguide serves to tune the waveguide to inhibit the reflection of microwave radiation within the waveguide without reducing the energy absorption into the plasma
Implementation Method 5
the PFCs are subjected to impact with energetic electrons causing dissociation into reactive species
Data Source
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AI summary
A microwave plasma reactor (10) comprises a reactor chamber, a microwave resonant cavity (14) located within the reactor chamber, a waveguide (16) for conveying microwave radiation to the resonant cavity, the waveguide having a convergent tapered portion, means for forming an electromagnetic standing wave within the resonant cavity from the microwave radiation for initiating and sustaining a plasma within the resonant cavity, the resonant cavity having a gas inlet and a gas outlet, and conduit means extending from the gas outlet for containing a plasma conveyed from the resonant cavity with a gas flowing from the gas inlet to the gas outlet.