Variable Radius Electron Beam Ion Source for High Current Density
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Solution Overview
Problem
Existing methods for producing highly charged ions, such as electron-beam ion sources, face limitations in achieving high current density due to Brillouin flow constraints and lens aberrations, resulting in suboptimal ion production.
Innovation Solution
An electron beam with a variable radius is used within a drift tube of constant radius to create local ion traps, leveraging magnetic optical focuses to achieve higher current densities, and the geometry is adjusted for ion extraction through a conical anode and negative potential distribution, enabling higher ion current densities beyond Brillouin limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electron beam current density is increased to improve ion production, then the ion charge and beam current improve, but the current density is limited by the Brillouin flow constraint
Solution Approach 1:
The patent applies dynamics by transforming the electron beam from a constant radius to a variable radius that changes along the propagation direction. This dynamic geometry allows the beam to be compressed to a small spot size at specific locations, creating localized regions of extremely high current density that exceed the Brillouin limit, thereby resolving the contradiction between improving ion production and the current density limitation.
Solution Approach 2:
The patent implements local quality by creating localized regions of high current density through variable beam geometry rather than uniformly increasing current density throughout the entire beam. The beam radius is varied so that it is large in most regions (avoiding Brillouin limit issues) but compressed to a small spot at specific locations where ionization is needed, achieving high ion production without requiring uniformly high current density.
2Quantity of substance
If electrostatic lenses are used to focus the electron beam to increase current density, then the beam focus improves, but lens aberrations and high voltage requirements reduce the achievable current density
Solution Approach 1:
The patent replaces the mechanical electrostatic lens system with a magnetic field-based focusing mechanism. Instead of using electrostatic lenses that suffer from aberrations and high voltage requirements, the invention uses a magnetic field to guide and focus the electron beam, achieving high current density without the drawbacks of lens-based systems.
Solution Approach 2:
The patent changes the fundamental parameter of beam geometry from constant radius to variable radius along the propagation direction. This parameter change enables the beam to naturally focus to high current density regions without requiring external lenses, eliminating lens aberrations and high voltage requirements while achieving the desired beam focus quality.
3Productivity
If the electron beam radius is reduced to increase current density, then the ionization efficiency improves, but the beam becomes more susceptible to thermal velocity effects and aberrations
Solution Approach 1:
The patent applies dynamics by making the beam radius a variable parameter that changes along the propagation direction rather than being constant. The beam is designed to have a large radius for most of its length (maintaining stability and reducing susceptibility to thermal effects) and is dynamically compressed to a small radius only at specific locations where high ionization efficiency is needed, thus resolving the contradiction between ionization efficiency and beam stability.
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 allows for the production of highly charged ions with significantly higher current densities than traditional methods, enhancing ion trap performance and extraction efficiency.
Implementation Method 1
The electron beam of variable radius, which propagates in the drift tube of constant radius
Implementation Method 2
The highly charged ions are prepared in local ion traps with extremely high current density
Implementation Method 3
The axially symmetric magnetic field is used for focusing the electrons emitted from cathode of the electron gun into the electron beam
Implementation Method 4
there is the method for the production of highly charged ions in crossover of the electron beam, which is focused by the system of electrostatic lenses
Data Source
AI summary
The invention relates to a novel ion source, which uses method for the production of highly charged ions in the local ion traps created by an axially symmetric electron beam in the thick magnetic lens. The highly charged ions are produced in the separate local ion traps, which are created as a sequence of the focuses (F1, F2, and F3) of the electron beam (EB) rippled in the magnetic field (B(z)). Since the most acute focus is called the main one, the ion source is classified as main magnetic focus ion source (MaMFIS/T), which can also operate in the trapping regime. The electron current density in the local ion traps can be much greater than that in the case of Brillouin flow. For the ion trap with length of about 1 mm, the average electron current density of up to the order of 100 kA/cm2 can be achieved. Thus it allows one to produce ions in any charge state for all elements of the Periodic Table. In order to extract the ions, geometry of the electron beam is changed to a relatively smooth electron beam by setting the potential of the focusing electrode (W) of the electron gun negative with respect to the potential of the cathode (C).