Flash Radiography Diode Frustum Cathode Tapered Anode
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Solution Overview
Problem
Existing flash radiography diodes have low efficiency in propagating electron beams and require complex, expensive equipment, with previous designs being magnetically limited and unable to produce high brightness and small spot sizes effectively.
Innovation Solution
A flash radiography diode with a frustum-shaped cathode and a tapered anode, housed in a chamber, where the cathode emits an electrical pulse to the anode, forming a plasma that efficiently pinches electrons to a small spot size, increasing ion flux and X-ray production, and is designed for use with high-impedance pulsed-power drivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional diode designs (Bennett diode, planar diodes, cylindrical anodes) are used, then the device structure is relatively simple, but the electron beam propagation efficiency is low and brightness is limited
Solution Approach 1:
The cathode is segmented into multiple frustum-shaped elements arranged in a specific configuration, with each frustum contributing to electron emission and beam formation. This segmentation allows for optimized electron beam propagation while maintaining manageable structural complexity through modular design
Solution Approach 2:
The invention transitions from conventional two-electrode planar or cylindrical geometries to a three-dimensional frustum-based configuration with specific angular orientations. This dimensional change enables improved electron beam confinement and propagation efficiency by utilizing spatial geometry in multiple dimensions simultaneously
2Speed
If cylindrical anodes with small constant radius are used, then the device structure is simple, but the pinch formation is slow and current density is low
Solution Approach 1:
The anode is designed with an asymmetric conical shape rather than a symmetric cylindrical form. This asymmetry creates a gradient in the electric and magnetic fields that accelerates pinch formation while simultaneously concentrating current density at the tapered region, resolving the trade-off between speed and current density
Solution Approach 2:
The anode geometry parameters (radius, length, taper angle) are optimized to specific ranges that enable both fast pinch formation and high current density. The taper angle and length-to-diameter ratio are carefully selected to balance the competing requirements of rapid plasma formation and sustained high current flow
3Quantity of substance
If cylindrical anodes with large constant radius are used, then higher current is achieved, but pinch propagation is slow and current density is low
Solution Approach 1:
The conical anode geometry transforms the uniform current distribution of cylindrical anodes into a concentrated current path along the taper. This asymmetric shape maintains high total current while accelerating pinch propagation by creating a gradient that guides plasma formation from the base toward the tip
Solution Approach 2:
The smooth curved surface of the conical anode replaces the flat cylindrical surface, creating continuous field gradients that facilitate rapid pinch propagation. The curvature of the conical surface guides the electron beam and plasma formation along a controlled path, maintaining high current while increasing propagation speed
4Device complexity
If high-impedance pulsed-power drivers are used, then the diode can operate with simpler power supply equipment, but achieving high brightness and small spot sizes is difficult
Solution Approach 1:
The frustum cathode and conical anode geometries are optimized for high-impedance operation, with specific dimensions and angles that enable efficient electron beam formation and focusing. These geometric parameters allow the system to achieve small spot sizes and high brightness using the simpler high-impedance power supply configuration
Solution Approach 2:
The frustum cathode elements are arranged and dimensioned to work effectively with high-impedance drivers, creating a distributed emission structure that maintains beam quality despite the simpler power supply. This segmentation allows each element to contribute optimally to the overall beam focus and brightness
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
The diode achieves high brightness and small spot size X-ray production, improving resolution and reproducibility, and is robust enough for multiple shots, with controlled impedance and radial plasma expansion, suitable for high-impedance generators.
Implementation Method 1
the cathode is configured to emit an electrical pulse to the tapered anode
Implementation Method 2
forming a plasma that efficiently pinches electrons to a small spot size
Implementation Method 3
efficiently pinches electrons to a small spot size, increasing ion flux and X-ray production
Data Source
AI summary
A flash radiography diode includes a cathode and an anode. The cathode includes a frustum member with a bore extending through the frustum member. The anode is a tapered anode made of an electrically conductive material and oriented toward the cathode. The anode and the cathode are housed in a chamber with a gap between the anode and the cathode. The cathode is configured to emit electrons to the tapered anode, which electrons strike the anode and create an anode plasma. The anode plasma creates X rays which propagate from the anode.