Ion Sensor With Conical Collector Reduces Secondary Electron Noise
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Solution Overview
Problem
Conventional ion sensors face challenges in achieving a good signal-to-noise ratio, particularly when testing ion thrusters with low propulsive powers, and struggle with high spatial resolution and measuring accuracy due to secondary electron interference.
Innovation Solution
An ion sensor design that combines the ion repeller and collector functions in a single electrode with a diaphragm opening and a blind hole featuring a conical funnel-shaped depression at the bottom, which reduces secondary electron escape and enhances precision by increasing their neutralization on the collector surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional grid electrode or single orifice design is used, then the sensor can operate with simpler construction, but the signal-to-noise ratio deteriorates due to secondary electron interference
Solution Approach 1:
The patent combines the ion repeller and collector functions into a single electrode component. The electrode has a through-opening for ion passage and an blind hole with a conical depression that serves as the collection surface, merging two previously separate functions into one integrated component.
Solution Approach 2:
The conical depression in the blind hole converts the harmful effect of secondary electrons into a beneficial one. The depression geometry causes secondary electrons to be directed toward the collector surface where they are neutralized, transforming the noise problem into a feature that enhances measurement accuracy.
2Quantity of substance
If the diaphragm opening diameter is increased to improve signal strength, then the sensor signal increases, but the spatial resolution deteriorates
Solution Approach 1:
The patent transitions from a two-dimensional flat collector surface to a three-dimensional conical depression. This dimensional change increases the effective collection area within a compact footprint, allowing sufficient signal collection while maintaining a small diaphragm opening diameter for high spatial resolution.
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 achieves a strong sensor signal with a good signal-to-noise ratio and high spatial resolution, allowing for accurate current measurement with reduced secondary electron interference, suitable for testing ion thrusters with milli- or micro-newton propulsive powers.
Implementation Method 1
The electron repelling electrode is placed at a negative electric potential during operation of the ion sensor, whereby there is formed an electrostatic field which decelerates and finally repels the electrons contained in an inflowing plasma
Implementation Method 2
The ion repelling electrode is, for its part, placed at a positive electric potential, this positive electric potential generally being variable in terms of its strength. Depending on the strength of the positive electrostatic field, ions up to a specific energy are repelled by the field
Implementation Method 3
these ions come into contact with a metallic collector face, where they cause a current flow in the metal material forming the collector face
Data Source
AI summary
An ion sensor comprises an electron repelling electrode to be placed at a negative electric potential, and an ion repelling electrode to be placed at a variable positive electric potential. The electron repelling electrode is formed by a diaphragm element having a diaphragm opening for the passage of an ion beam. The ion repelling electrode forms a blind hole which faces the diaphragm opening with its open hole end and the hole surface of which forms a collector face for detecting impinging ions. With such an ion sensor it is possible, for example, to test the energy spectrum of the ions contained in an exhaust plasma plume of an ion thruster.