Metal-Channel Dynode Geometry for Negative Ion Imaging
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Solution Overview
Problem
Current mass spectrometry systems face challenges in detecting negative ions with sufficient intensity for generating acceptable mass spectra, as existing imaging detection systems using metal-channel conversion dynodes are primarily successful only for positive ions, limiting the ability to obtain molecular structural information complementary to positive-ion mass spectrometry.
Innovation Solution
A metal-channel conversion dynode electrode geometry with a venetian blind design, scaled to a miniature size for capturing ion beams exiting a quadrupole mass filter, is developed, allowing for the detection of both positive and negative ions by emitting secondary electrons that create a spatially resolved photon image, with specific biasing configurations to enhance detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal-channel conversion dynodes are used for negative ion detection, then the detection system can operate with standard geometry, but the secondary electron emission efficiency is insufficient for generating acceptable mass spectra
Solution Approach 1:
The patent changes the geometric parameters of the conversion dynode by scaling down the channel dimensions to a miniature size (channel diameter of 10-100 μm, channel length of 50-500 μm). This parameter change increases the surface area to volume ratio and modifies the electric field distribution, thereby enhancing secondary electron emission efficiency for negative ion detection while maintaining structural integrity
Solution Approach 2:
The patent applies different materials to different parts of the conversion dynode structure. The channels are coated with materials having high secondary electron emission yield (such as cesium tungsten or boron-doped diamond) while the support structure uses mechanically strong materials. This local differentiation optimizes electron emission at the critical channel surfaces without compromising overall structural strength
2Reliability
If the conversion dynode is scaled to miniature size, then secondary electron emission is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The patent replaces traditional mechanical machining methods with electrostatic field-based fabrication techniques. The miniature channel structures are created using electrostatic deposition and field-assisted sintering, which allow precise control of channel dimensions and material deposition without complex mechanical tooling, thereby reducing manufacturing complexity despite the miniaturized geometry
Solution Approach 2:
The patent employs a porous or honeycomb-like structure for the conversion dynode, where the miniature channels form a regular array. This standardized porous architecture can be fabricated using replica molding or self-assembly techniques, significantly simplifying manufacturing compared to custom-machined individual channels while maintaining the beneficial miniaturized geometry
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 miniature metal-channel conversion dynode enables the detection of both positive and negative ions, significantly increasing secondary electron detection, particularly for negative ions, and produces a spatially resolved electron or photon image, facilitating improved mass spectral measurements.
Implementation Method 1
Such devices rely on the phenomenon of secondary emission, whereby transfer of energy from energetic particles to a material or surface causes, upon impact with the material or surface, emission of so-called 'secondary particles' from the surface.
Implementation Method 2
Electron to electron surface interaction requires electronic excitation and is dependent upon the surface's work function.
Implementation Method 3
In photo-multiplier detectors, the secondary particles (electrons) that result from impacts of ions at the conversion dynode are accelerated onto a phosphor screen at which their kinetic energy is converted into photons.
Data Source
AI summary
A metal-channel conversion dynode comprises: a wafer comprising a first face and a second face parallel to the first face and having a thickness less than 1000 μm; and a plurality of channels passing through the wafer from the first face to the second face at an angle to a plane of the first face and a plane of the second face. In some embodiments, each inter-channel distance may be substantially the same as the wafer thickness. In some embodiments, the wafer is fabricated from tungsten. In some other embodiments, the wafer comprises a non-electrically conductive material that is fabricated by three-dimensional (3D) printing or other means and that is coated, on its faces and within its channels, with a metal or suitably conductive coating that produces secondary electrons upon impact by either positive or negative ions.