ExB Wien Filter End Cap Magnetic Shims for Field Distribution Control
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Solution Overview
Problem
Existing ExB mass filters face challenges in maintaining the proper ratio of electric and magnetic fields near the end caps and within the entrance and exit apertures, leading to inefficiencies in ion beam separation and focusing.
Innovation Solution
The solution involves mechanically adjusting the magnetic field distribution using magnetic shims and plug shims within the end caps and flux dams to achieve better matching of electric and magnetic fields, allowing for closer spacings between end caps and pole pieces without the need for electromagnetic coils or power supplies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional end cap structures are used with standard magnetic materials, then the device structure is simple, but the magnetic field distribution cannot be properly terminated without negative overshoots or extra B-field peaks within the apertures
Solution Approach 1:
The end cap is divided into regions with different magnetic permeabilities: a first region with higher magnetic permeability and a second region with lower magnetic permeability. This local differentiation allows the magnetic field to be properly terminated in different zones, preventing negative overshoots and extra B-field peaks within the apertures while maintaining overall field matching.
Solution Approach 2:
The end cap employs composite magnetic material structures with varying permeabilities. By combining materials with different magnetic properties in specific configurations, the end cap achieves superior magnetic field termination characteristics that cannot be obtained with uniform magnetic materials alone.
2Manufacturing precision
If electromagnetic coils and power supplies are added for B-field adjustment, then the magnetic field distribution can be precisely controlled, but the device complexity and cost increase significantly
Solution Approach 1:
The end cap structure with differentiated magnetic permeability regions passively adjusts and terminates the magnetic field distribution through its inherent material properties and geometric configuration. This self-adjusting mechanism eliminates the need for external electromagnetic coils and power supplies, achieving field matching precision without increasing system complexity.
Solution Approach 2:
The patent replaces active electromagnetic control systems (coils and power supplies) with a passive magnetic circuit design using composite magnetic materials. The magnetic field distribution is controlled through the strategic placement of materials with different permeabilities rather than through active electromagnetic actuation.
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 approach enhances the matching of electric and magnetic fields throughout the ExB filter, reducing optical aberrations and beam misalignments, leading to improved ion beam separation and focusing performance.
Implementation Method 1
The relative strengths of the electric and magnetic fields are set so that the desired ion species will pass through the mass filter undeflected
Implementation Method 2
since magnetic materials have permeabilities which are proportionately much lower than electrical conductivities (compared with air or vacuum)
Implementation Method 3
uses crossed electric and magnetic fields (ExB) to deflect unwanted ion species off-axis
Implementation Method 4
Smoothly terminating the electric field without either E-field reversals or extra E-field peaks within the apertures is relatively easy with any reasonable electrical conductivity for the end cap metal
Data Source
AI summary
An ExB Wien mass filter providing a method and structure for mechanically adjusting the magnetic field distributions at the mass filter entrance and exit end caps. The reluctance of the flux return path may be modified by configuring pluralities of magnetic shims within slots at the outer diameters of the entrance and exit end caps, and also by configuring pluralities of magnetic plug shims within circular flux dams surrounding the entrance and exit apertures. Advantages of purely mechanical adjustment for the magnetic fields of the present invention, compared with prior art electromagnet adjustment methods include greater reliability, simplicity, lower cost, and lack of power dissipation. The invention may employ either permanent magnets or electromagnets for generation of the mass-separation magnetic field.