Ion Trajectory Control in Ion Pump Cathodes
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Solution Overview
Problem
In ion pumps, the inefficient sputtering of material from cathode plates due to uncontrolled impact angles of positively charged ions leads to suboptimal particle trapping and vacuum maintenance, as ions often pass through the plates without immediate sputtering and lack controlled trajectories.
Innovation Solution
The introduction of surface structures and posts extending from the vacuum chamber wall towards the cathode plates, aligned with the openings of cylindrical anodes, creates an electric field that controls the trajectory of ions, ensuring they strike the cathode plates at optimal angles for efficient sputtering, thereby maximizing material deposition and vacuum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ions are accelerated toward the cathode plate without trajectory control, then the ion flux to the cathode is high, but the sputtering efficiency is low due to uncontrolled impact angles
Solution Approach 1:
The cathode assembly is segmented into multiple components: the cathode plate, backing surface, and multiple surface structures (posts or protrusions) extending from the backing surface. These segmented elements work together to control ion trajectories while maintaining high ion flux, resolving the contradiction between sputtering efficiency and structural complexity.
Solution Approach 2:
The surface structures (posts or protrusions) act as intermediary elements between the uncontrolled ion flux and the cathode plate. These intermediaries guide and focus the ions onto the cathode at optimal angles for sputtering, thereby improving efficiency without requiring complete redesign of the ion source or acceleration field.
2Strength
If the cathode plate is made thicker to improve structural strength, then the mechanical strength increases, but the sputtering efficiency decreases because ions may pass through without proper interaction
Solution Approach 1:
The cathode system is divided into the cathode plate (for structural strength) and separate surface structures on the backing surface (for ion guidance). This segmentation allows the plate to be thick and strong while the surface structures optimize ion interaction, resolving the contradiction between strength and sputtering efficiency.
Solution Approach 2:
Instead of relying solely on cathode plate thickness (one dimension) to control ion interaction, the invention introduces surface structures that extend into the ion path from the backing surface. This adds a new dimensional approach to ion-cathode interaction, allowing optimal sputtering angles to be achieved independent of plate thickness.
3Productivity
If surface structures are added to control ion trajectories, then the sputtering efficiency improves, but the manufacturing complexity increases
Solution Approach 1:
The surface structures are merged with the cathode assembly, where the backing surface and surface structures form an integrated unit. This merging simplifies manufacturing by reducing the number of separate components that need to be assembled, while still providing the trajectory control functionality needed for high sputtering efficiency.
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 solution enhances the sputtering efficiency by directing ions to strike the cathode plates within a desired range of angles, increasing the amount of material sputtered and improving the overall performance of the ion pump in maintaining ultra-high vacuum conditions.
Implementation Method 1
An electrical potential is applied between the anode and the cathode... The resulting positively charged ion is accelerated by the electrical potential between the anode and the cathode toward one of the cathode plates
Implementation Method 2
magnets on opposite sides of the cathode plates generate a magnetic field that is aligned with the axes of the anode cylinders... trapping electrons within the cylindrical anodes through a combination of the electrical potential and the magnetic field
Implementation Method 3
The introduction of surface structures and posts extending from the vacuum chamber wall towards the cathode plates, aligned with the openings of cylindrical anodes, creates an electric field that controls the trajectory of ions
Implementation Method 4
The positively charged ion is eventually trapped by the cathode and is thereby removed from the evacuated space. Typically, the positively charged ion is trapped through a sputtering event in which the positively charged ion causes material from the cathode to be sputtered into the vacuum chamber of the pump
Data Source
AI summary
An ion pump includes an anode, a backing surface having at least one surface structure extending toward the anode and a cathode positioned between the anode and the backing surface and having an opening such that the at least one surface structure is aligned with and extends from the backing surface towards the opening.