Rotary X-Ray Target Assembly for 750 keV Vacuum Stability
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Solution Overview
Problem
Current x-ray sources struggle to achieve high enough x-ray photon energies, particularly above 300 keV, necessary for effective imaging of large or dense objects, due to limitations in vacuum dielectric strength and electrical breakdown, which restricts the achievable voltage and electron beam energy.
Innovation Solution
A multi-stage voltage multiplier with nested shield electrodes is used to maintain a higher potential difference between the high-voltage electrode and the grounded enclosure, allowing for electron energies of up to 750 keV, and a rotating target assembly with a novel vacuum seal and kinetic energy absorption system to manage thermal stress and maintain high vacuum conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If higher voltage is applied to increase electron beam energy for high-energy x-ray production, then x-ray photon energy is improved, but vacuum dielectric strength is exceeded causing electrical breakdown
Solution Approach 1:
The voltage multiplier circuit is divided into multiple stages (first voltage doubling stage, second voltage doubling stage, etc.), where each stage operates at a lower voltage level. The shield electrodes are also segmented into multiple nested stages, creating intermediate vacuum regions that prevent dielectric breakdown by distributing the voltage stress across multiple lower-voltage interfaces rather than one high-voltage interface.
Solution Approach 2:
The patent employs nested shield electrodes where inner shield electrodes are positioned within outer shield electrodes, creating a multi-layered vacuum enclosure structure. This nesting allows intermediate vacuum chambers to be formed between nested shields, enabling the system to maintain higher overall voltage while keeping local electric field strengths below breakdown thresholds through the intermediate vacuum regions.
2Use of energy by moving object
If higher electron beam energy is used to penetrate dense objects, then imaging capability is improved, but target overheating increases
Solution Approach 1:
The target is designed to rotate at controlled speeds, dynamically distributing the electron beam impact across different portions of the target surface. This rotational motion prevents localized overheating by continuously bringing fresh target material into the beam path while allowing previously irradiated areas to cool down, effectively managing thermal stress during high-energy operation.
Solution Approach 2:
The target is segmented into multiple discrete target portions or segments arranged around the rotation axis. This segmentation allows each segment to experience reduced cumulative heating, and enables selective replacement or cooling of individual segments if needed, improving overall thermal management during high-power electron beam operation.
3Duration of action of stationary object
If rotary target assembly is used to manage thermal stress, then target durability is improved, but vacuum seal complexity increases
Solution Approach 1:
The vacuum seal structure employs nested magnetic seals where inner magnetic seal assemblies are positioned within outer magnetic seal assemblies. This nested configuration provides multiple sealing interfaces in series, enhancing the overall vacuum seal reliability for the rotating target assembly while maintaining a compact structure. The nested design allows the system to achieve robust vacuum sealing despite the complexity of rotating components.
Solution Approach 2:
The patent replaces traditional mechanical contact seals with magnetic field-based seals. The magnetic seals create sealing forces through magnetic attraction and field interactions without requiring direct mechanical contact between rotating and stationary components. This substitution eliminates wear and friction issues associated with mechanical seals while providing reliable vacuum sealing for the rotary target assembly.
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 enables the production of x-ray beams with peak energies up to 750 keV, improving imaging capabilities for dense objects while preventing target overheating and maintaining a stable vacuum environment.
Implementation Method 1
a multi-stage voltage multiplier with nested shield electrodes is used to maintain a higher potential difference between the high-voltage electrode and the grounded enclosure, allowing for electron energies of up to 750 keV
Implementation Method 2
electrons from the electron beam generator irradiate a portion of the annular target region while the target rotates, enabling the production of x-ray beams with peak energies up to 750 keV
Data Source
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AI summary
Disclosed herein are a high-voltage generator for an x-ray source, an x-ray gun, an electron beam apparatus, a rotary vacuum seal, a target assembly for an x-ray source, a rotary x-ray emission target, and an x-ray source. These various aspects may separately and/or together enable the construction of an x-ray source which can operate at energies of up to 500 kV and beyond, which is suitable for use in commercial and research x-ray applications such as computerised tomography. In particular, the high-voltage generator includes a shield electrode electrically connected intermediate of a first voltage multiplier and a second voltage multiplier. The electron beam apparatus includes control photodetectors and photo emitters having a transparent conductive shield arranged therebetween. The rotary vacuum seal includes a pumpable chamber at a position intermediate between high-pressure and low-pressure ends of a bore for a rotating shaft. The rotary target assembly is configured such that when a torque between a bearing housing and a vacuum housing exceeds a predetermined torque, the bearing housing rotates relative to the vacuum housing. The rotary x-ray emission target has a plurality of target plates supported on a hub, the plates being arranged on the hub to provide an annular target region about an axis rotation of the hub. The x-ray gun is provided with a shield electrode maintained at a potential difference relative to the x-ray target different to the electron beam emission cathode.