Gyrotron Coupler Using Mode Converting Reflectors
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Solution Overview
Problem
High-power gyrotrons face inefficiencies in RF power transmission due to high-order TE modes, requiring complex internal mirrors and large diamond apertures for RF-electron beam separation, which leads to internal diffraction losses, electron beam depression, and alignment issues.
Innovation Solution
A launch coupler system that converts helically propagating Whispering Gallery modes into HE11 mode within a corrugated waveguide using a step-cut launcher and integrated mode converting reflectors, reducing the need for adjustable mirrors and large diamond apertures by generating a quasi-Gaussian intensity profile for efficient coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-order TE modes are used in gyrotrons, then power generation capability is improved, but RF power transmission efficiency deteriorates
Solution Approach 1:
The invention changes the mode parameters by converting high-order TE modes (TEmn with m,n>>1) into WG modes through a mode converter. This parameter transformation enables efficient RF power transmission while maintaining the high power generation capability of the gyrotron cavity.
Solution Approach 2:
The invention introduces an intermediary WG mode as a bridge between the high-order TE modes generated in the cavity and the HE11 mode suitable for transmission. The WG mode acts as an intermediate state that facilitates efficient energy transfer and mode conversion.
2Reliability
If quasi-optical launcher with internal mirrors is used, then RF-electron beam separation is improved, but device complexity increases
Solution Approach 1:
The invention extracts and eliminates the complex adjustable internal mirrors from the gyrotron system. Instead, it uses a simplified waveguide-based mode converter that achieves RF-electron beam separation through waveguide mode transformation rather than optical mirrors.
Solution Approach 2:
The invention replaces the mechanical mirror-based quasi-optical system with a waveguide-based electromagnetic field system. The mode converter uses waveguide geometry and WG modes to achieve separation without mechanical adjustable mirrors.
3Temperature
If large diamond aperture is used for RF output, then thermal management is improved, but cost increases
Solution Approach 1:
The invention changes the output mode parameters to HE11, which has different field distribution characteristics that allow for smaller aperture sizes. This reduces the amount of expensive diamond material needed while maintaining adequate thermal management capabilities.
Solution Approach 2:
The invention replaces expensive large-diameter diamond components with smaller, more cost-effective diamond elements. The HE11 mode coupling enables this substitution while maintaining system performance.
4Manufacturing precision
If adjustable mirrors are used in quasi-optical launcher, then RF beam quality is improved, but alignment difficulty increases
Solution Approach 1:
The invention removes the adjustable mirrors entirely from the system, eliminating alignment difficulties. RF beam quality is maintained through precise waveguide geometry and mode converter design rather than mechanical adjustment.
Solution Approach 2:
The mode converter is designed to automatically establish the correct WG modes and field patterns without requiring external alignment adjustments. The system is self-configuring through its fixed geometric structure.
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 external mirror alignment, and achieves high coupling efficiency (>95%) into corrugated waveguides, resulting in cost savings and improved thermal management.
Implementation Method 1
a cylindrical waveguide supporting Whispering Gallery (WG mode or WGM) having a step cut launcher with a launch edge
Implementation Method 2
the first reflector generating RF with an elliptical radiation pattern and coupling the RF into a second mode converting reflector
Implementation Method 3
a second mode converting reflector generating free space wave for coupling into a corrugated waveguide where it propagates in an HE11 mode
Implementation Method 4
coupling into a corrugated waveguide where it propagates in an HE11 mode
Data Source
AI summary
A cylindrical waveguide with a mode converter transforms a whispering gallery mode from a gyrotron cylindrical waveguide with a helical cut launch edge to a quasi-Gaussian beam suitable for conveyance through a corrugated waveguide. This quasi-Gaussian beam is radiated away from the waveguide using a spiral cut launch edge, which is in close proximity to a first mode converting reflector. The first mode converting reflector is coupled to a second mode converting reflector which provides an output free-space HE11 mode wave suitable for direct coupling into a corrugated waveguide. The radiated beam produced at the output of the second mode converting reflector is substantially circular.