Whispering Gallery Mode Coupler for Direct HE11 Waveguide Coupling
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Solution Overview
Problem
Modern high-power gyrotrons face inefficiencies in transporting high-order TE modes due to internal diffraction losses, electron beam interactions, and mirror alignment issues, requiring costly adjustable mirrors and large diamond apertures for RF power coupling.
Innovation Solution
A whispering gallery mode converter with a dimpled surface waveguide and step-cut launcher couples RF energy into a corrugated waveguide using a single or dual mode converting reflectors, achieving a near-Gaussian phase distribution and minimum beam waist for efficient HE11 mode propagation, reducing the need for external mirrors and large diamond apertures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a quasi-optical launcher with internal mode converter and step-cut is used, then RF power can be separated from electron beam, but internal diffraction losses occur and mirror alignment issues arise
Solution Approach 1:
The invention extracts the mode conversion function from the traditional internal mode converter and relocates it to the corrugated waveguide structure itself. The waveguide's periodic corrugations perform the mode conversion function that previously required separate internal mirrors and converters, eliminating the associated diffraction losses and alignment issues while maintaining RF-electron beam separation.
Solution Approach 2:
The invention merges the mode conversion function with the waveguide structure by incorporating periodic corrugations directly into the waveguide walls. This integration combines the transmission and mode conversion functions into a single structure, eliminating the need for separate internal mode converters and reducing the number of components that cause losses.
2Productivity
If adjustable mirrors are used for RF transmission, then RF power can be efficiently transported, but device complexity increases and alignment maintenance becomes difficult
Solution Approach 1:
The corrugated waveguide structure performs mode conversion and RF transport self-service through its built-in periodic geometry. The waveguide automatically converts modes and guides RF power without requiring external adjustable mirrors, making the system self-sufficient and eliminating complex alignment requirements while maintaining high efficiency.
Solution Approach 2:
The invention replaces the mechanical adjustable mirror system with a fixed corrugated waveguide structure. The periodic geometric features of the waveguide provide the necessary mode conversion and beam shaping that previously required mechanically adjustable mirrors, eliminating moving parts and alignment complexity while maintaining RF transport efficiency.
3Loss of energy
If large diamond apertures are used for RF coupling, then RF loss is minimized, but manufacturing cost increases significantly
Solution Approach 1:
The invention changes the geometric parameters of the waveguide by introducing periodic corrugations with specific dimensions and spacing. These parameter changes enable the waveguide to perform mode conversion and maintain RF power with much smaller apertures, reducing the amount of expensive diamond material needed while keeping RF losses minimal through the optimized corrugation geometry.
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 solution significantly reduces internal losses, eliminates the need for adjustable mirrors, and decreases the diameter of diamond apertures, achieving high coupling efficiency and cost savings while maintaining RF power quality.
Implementation Method 1
a cylindrical waveguide for propagation of RF energy, the cylindrical waveguide having a plurality of deformations on an inner surface, each said deformation causing a focusing and guiding of incident RF energy to a subsequent deformation
Implementation Method 2
the cylindrical waveguide having a plurality of deformations on an inner surface, each said deformation causing a focusing and guiding of incident RF energy
Implementation Method 3
coupling RF energy to a first mode converting reflector which generates RF with an elliptical radiation pattern and coupling the RF into a second mode converting reflector generating free space RF radiation pattern
Implementation Method 4
the minimum beam waist also having a near-Gaussian phase distribution at the entrance to the corrugated waveguide
Data Source
Figure 1A~1C
Figure 2A~2D-1
Figure 2E~2I
AI summary
A cylindrical whispering gallery mode (WGM) waveguide for a gyrotron has a series of surface dimples of increasing amplitude at beat wavelengths of an (m,n) primary mode with other co-propagating high order modes. The WGM waveguide thereby generates a series of high order modes which are directed to a launch edge, which is in close proximity to one or more mode converting reflectors which minimize the beam waist and produce a phase front for a near-gaussian mode RF at the input of a corrugated waveguide, thereby providing direct coupling of HE11 mode directly into the corrugated waveguide. The mode converting reflectors which receive RF energy from the WGM waveguide launch edge and form the minimum beam diameter near-gaussian beam at the inlet of the corrugated waveguide may be formed from a single mirror or multiple mirrors.