Subcritical-Voltage Magnetron Control for Broad RF Power Range
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Solution Overview
Problem
Magnetron power sources for RF applications lack efficient control over a broad range of output power and phase, making them inadequate for variable load requirements, particularly in superconducting RF cavities where precise power and phase control are necessary to mitigate microphonics-induced frequency variations.
Innovation Solution
A 2-stage magnetron system operating with a subcritical cathode voltage and a strong injection phase-locking signal allows for broad power control through phase modulation and high-voltage cathode power supply feedback, enabling efficient power control over a 10 dB range without diverting power to a dummy load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a magnetron operates as a conventional oscillator with constant cathode voltage, then it provides stable output power, but it lacks efficient control over a broad range of output power and phase
Solution Approach 1:
The patent operates the magnetron in a dynamic subcritical regime where the cathode voltage is maintained below the threshold for self-oscillation. This allows the magnetron to transition from a self-oscillating state to an injection-locked state, enabling continuous variable control of output power and phase through the injection signal rather than requiring complex voltage modulation.
Solution Approach 2:
The patent introduces an injection-locked signal as an intermediary to control the magnetron's output. This external signal acts as a mediator that locks the magnetron's oscillation frequency and phase, allowing precise control of output power and phase without directly modulating the cathode voltage or using dummy loads.
2Adaptability or versatility
If output power is controlled by diverting power to a water-cooled dummy load, then power range control is achieved, but system efficiency decreases
Solution Approach 1:
The patent extracts the power control function from the traditional dummy load approach and relocates it to the injection-locked signal mechanism. By controlling the magnetron in subcritical operation, the system achieves variable power output directly from the magnetron itself rather than diverting fixed power to a dummy load, eliminating the energy waste associated with dummy load dissipation.
3Reliability
If cathode voltage is increased to enable free running oscillations, then the magnetron can operate autonomously, but power control becomes less efficient
Solution Approach 1:
The patent applies partial action by operating the magnetron with cathode voltage below the threshold required for full self-oscillation. This subcritical operation mode provides just enough voltage to allow the magnetron to respond to injection signals, enabling efficient power control while maintaining sufficient autonomous operation capability when needed.
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 achieves high-efficiency power control with low phase noise and precise frequency stability, suitable for superconducting RF accelerators and other applications, by directly controlling output power and phase without the inefficiency of dummy load redistribution.
Implementation Method 1
Magnetron power sources for RF applications lack efficient control over a broad range of output power and phase
Implementation Method 2
an injection phase-locking signal RF signal is fed into the magnetron through the magnetron output antenna
Implementation Method 3
an injection phase-locking signal RF signal is fed into the magnetron through the magnetron output antenna. This is the usual operating mode for phase-locked magnetron RF power sources
Implementation Method 4
Operating a magnetron with the cathode voltage lower than that needed for free running oscillations, (below the Kapitza critical voltage or equivalently below the Hartree voltage), a sufficiently strong injection phase-locking signal enables the output power to be generated and to be controlled over a broad power range by small changes in the cathode voltage
Data Source
AI summary
A system and method of operating a magnetron power source can achieve a broad range of output power control by operating a magnetron with its cathode voltage lower than that needed for free running oscillations (e.g., below the Kapitsa critical voltage or equivalently below the Hartree voltage) A sufficiently strong injection-locking signal enables the output power to be coherently generated and to be controlled over a broad power range by small changes in the cathode voltage. In one embodiment, the present system and method is used for a practical, single, frequency-locked 2-magnetron system design.