Relativistic Magnetron Virtual Cathode Design
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Solution Overview
Problem
The lifetime of high power relativistic magnetrons is limited by intense electron bombardment of the cathode, leading to destruction and decreased efficiency due to cathode plasma expansion and gas expulsion, which also limits pulse repetition rate.
Innovation Solution
A magnetron design utilizing a virtual cathode formed by a dimensional discontinuity in the vacuum channel, where the electron beam current exceeds the space-charge-limiting current, eliminating the need for a physical cathode and reducing plasma expansion and ion back bombardment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a physical cathode is used in a relativistic magnetron, then microwave generation is enabled, but the cathode lifetime is limited due to intense electron bombardment and plasma expansion
Solution Approach 1:
The patent creates a virtual cathode that replicates the functional properties of a physical cathode without the harmful physical structure. The virtual cathode is formed by injecting an electron beam into the interaction space where it creates a space-charge region that mimics cathode behavior, enabling microwave generation without the destructive electron bombardment and plasma expansion associated with physical cathodes.
Solution Approach 2:
The patent extracts the harmful physical cathode structure from the magnetron system while retaining the essential electron source function. By removing the physical cathode and replacing it with an externally injected electron beam, the system eliminates cathode deterioration, plasma expansion, and ion back bombardment while maintaining microwave generation capability.
2Productivity
If a physical cathode is used in a relativistic magnetron, then electron emission is achieved, but efficiency decreases due to cathode plasma expansion
Solution Approach 1:
The virtual cathode replicates the electron emission function without the energy-wasting plasma expansion. The electron beam is injected directly into the interaction space, creating a space-charge region that performs the same function as a physical cathode but without the harmful plasma effects that cause energy loss.
Solution Approach 2:
The patent converts the harmful effect of space charge, which normally limits current in physical cathode systems, into a beneficial virtual cathode structure. By carefully controlling the electron beam injection, the space charge creates a stable virtual cathode that improves efficiency while eliminating the harmful plasma expansion associated with physical cathodes.
3Productivity
If a physical cathode is used in a relativistic magnetron, then microwave generation is enabled, but pulse repetition rate is limited due to gas expulsion
Solution Approach 1:
The patent removes the physical cathode that is the source of gas expulsion, thereby eliminating the limitation on pulse repetition rate. The externally injected electron beam provides electron emission without the cathode material that would otherwise be depleted and expel gas, enabling higher repetition rates.
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 design enhances the magnetron's efficiency and pulse duration, allowing for long pulse, high power, and high repetition rate microwave generation without the drawbacks of traditional cathodes.
Implementation Method 1
a dimensional discontinuity in a vacuum channel of the magnetron that creates a region where a current of an electron beam exceeds a space-charge-limiting current of the magnetron so as to form a virtual cathode
Implementation Method 2
When the azimuthal phase velocity of one of eigenmodes of the resonant system is close to the azimuthal drift velocity of the electrons, energy of the electrons is transferred to this electromagnetic wave
Implementation Method 3
a steady axial magnetic field fills the vacuum annular region between the cathode and anode
Data Source
AI summary
The present invention provides a relativistic magnetron including an anode with an entrant channel, the channel having an input end, an output end and a dimensional discontinuity between the ends. The channel is connected to the magnetron and has an anode defining an interaction space located between the dimensional discontinuity and output end. Also provided is a cathode, located upstream, a spaced distance away from the interaction space towards the input end, the cathode is adapted to send an electron beam into the interaction space where the electron beam forms a virtual cathode in the interaction space.