Dual-Surface Electron Beam Source for Switchable Spot Size
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Solution Overview
Problem
Existing electron beam sources for additive manufacturing face a tradeoff between high power and low intensity for large electron beam currents, and high intensity for low electron beam currents, making it challenging to achieve the required power variations for efficient manufacturing.
Innovation Solution
An electron beam source with a cathode design featuring a base and a protrusion, where the cathode is capable of emitting electrons from both the top surface and the base surface, allowing for switching between different spot sizes by adjusting the grid voltage, thereby achieving high power and low intensity for large currents, and high intensity for small currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the emission area of the cathode is increased to achieve high power, then the maximum power of the electron beam is improved, but the beam intensity deteriorates in the low current regime
Solution Approach 1:
The cathode is segmented into two distinct emission surfaces: a top surface and a base surface. By controlling the grid voltage, electrons can be emitted from either the top surface alone (for high intensity/low current) or both surfaces simultaneously (for low intensity/high power), effectively segmenting the emission function to resolve the contradiction between power and intensity.
Solution Approach 2:
The invention introduces dynamic control of the electron emission by varying the grid voltage. This allows the effective emission area to change dynamically: at lower grid voltages only the top surface emits (high intensity), while at higher grid voltages both top and base surfaces emit (high power). This dynamic adjustment resolves the fixed trade-off between power and intensity.
2Power
If the cathode size is increased to provide high power, then the power output is improved, but the beam intensity decreases for low electron beam currents
Solution Approach 1:
The cathode structure is segmented with a protrusion containing the top surface and a base surface separated by sidewalls. This segmentation allows independent control of emission areas: the top surface provides high intensity for precision work, while adding the base surface increases total emission area for high power applications, resolving the contradiction between power output and manufacturing precision.
Solution Approach 2:
Different regions of the cathode are assigned different functional qualities: the top surface is optimized for high intensity emission (small effective area) suitable for precision manufacturing, while the base surface provides additional emission area for high power output. The grid voltage controls which region is active, allowing local quality optimization for different operational requirements.
3Adaptability or versatility
If different spot sizes are required for different manufacturing operations, then the versatility is improved, but the device complexity increases due to multiple optics settings
Solution Approach 1:
The cathode structure itself provides the spot size variation function through its dual-surface geometry. By changing the emission area (top surface only or top plus base surfaces), the system self-adjusts the beam spot size without requiring external optics changes. This eliminates the complexity of multiple optics settings while maintaining versatility.
Solution Approach 2:
The single cathode structure performs multiple functions: it can operate in high intensity mode (top surface only) for precision work and high power mode (both surfaces) for bulk processing. This multi-functionality is achieved through grid voltage control rather than multiple specialized components, reducing device complexity while improving versatility.
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 enables quick switching between different electron beam spot sizes during manufacturing without changing the beam shaping optics settings, allowing for efficient power variations and improved material processing in additive manufacturing.
Implementation Method 1
a cathode, an anode and a grid for regulating an electron beam current... the cathode is having a base and a protrusion with sidewalls and a top surface... emission from the top surface of the cathode only and to a second spot size corresponding to emission from the top surface and the base surface
Data Source
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AI summary
Provided is an electron beam source (200) for generating an electron beam comprising a cathode (240), an anode and a grid for regulating an electron beam current. The cathode has a base (242) and a protrusion (244) with sidewalls (247) and a top surface (248). The base surface and the top surface are essentially flat. The base surface and the top surface are arranged at a predetermined distance D from each other. The base is larger than the protrusion. The electron beam source further comprising a control unit adapted for changing an applied voltage to the grid for switching a spot size of the electron beam on a target surface between at least a first a first spot size corresponding to emission from the top surface of the cathode only and to a second spot size corresponding to emission from the top surface and the base surface of the cathode.