Cathode Holder Alignment for Precise Filament-Cathode Gap
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Solution Overview
Problem
Conventional alignment methods for filament and cathode in ion implantation systems lead to premature failure due to misalignment, resulting in reduced lifetime and productivity of the ion source.
Innovation Solution
A cathode apparatus with a cathode holder and filament device that includes locating and positioning features for precise alignment, eliminating the need for external alignment fixtures, ensuring consistent gap distances and concentricity between the filament and cathode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional alignment methods are used for filament and cathode, then the alignment process is simple, but alignment precision deteriorates leading to premature failure
Solution Approach 1:
The cathode holder is pre-configured with locating features (grooves, protrusions) and positioning features (steps, shoulders) that automatically establish the correct gap distance and concentricity between filament and cathode during assembly, before the ion source begins operation. This preliminary alignment structure eliminates the need for complex external alignment fixtures and ensures consistent positioning from the start.
Solution Approach 2:
The cathode holder acts as an intermediary component between the filament and cathode, providing mechanical support and precise positioning. The holder's locating and positioning features mediate the alignment relationship, ensuring the filament maintains the correct gap distance and concentricity relative to the cathode without direct contact or complex adjustment mechanisms.
2Manufacturing precision
If external alignment fixtures are used, then alignment precision improves, but device complexity increases
Solution Approach 1:
The alignment function is merged into the cathode holder structure itself. The locating features (grooves, protrusions) and positioning features (steps, shoulders) are integrated into the holder's design, combining support, positioning, and alignment functions into a single component. This eliminates the need for separate external alignment fixtures and reduces overall system complexity.
Solution Approach 2:
The cathode holder structure serves itself by providing built-in locating and positioning features that automatically establish correct alignment during assembly. The grooves, protrusions, steps, and shoulders work together to self-align the filament and cathode without requiring external tools or complex adjustment procedures, making the system self-aligning and easier to assemble.
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
Enhances the productivity, stability, and lifetime of the ion source by reducing alignment errors and preventing premature failure of the filament and cathode.
Implementation Method 1
A filament 12 is resistively heated to a temperature at which thermionic emission of electrons occurs
Implementation Method 2
The cathode 14 is biased negatively with respect to an arc chamber 16 in which it resides as a so-called 'arc voltage', and the emitted electrons are accelerated toward a center 18 of the arc chamber
Implementation Method 3
A magnetic field (not shown) that is parallel to a center axis 24 defined by the cathode 14 and repeller 22 generally confines the emitted and repelled electrons to define a so-called 'plasma column', thus improving ionization and plasma density even further
Implementation Method 4
A feed gas (not shown) is flowed into the arc chamber 16, and the emitted electrons subsequently ionize the feed gas, thus forming a plasma (not shown) from which ions can be extracted via an extraction slit 20 in the arc chamber
Data Source
AI summary
A cathode apparatus for an ion source has a cathode with a positioning feature and a blind hole. A cathode holder has an aperture defined by a thru-hole and a locating feature defined along an aperture axis. The thru-hole receives the cathode along the aperture axis in first and second alignment positions based on a rotational orientation of the positioning feature with respect to the locating feature. The first alignment position locates the cathode at a first axial position along the aperture axis. The second alignment position locates the cathode at a second axial position along the axial axis. A filament device has a filament clamp, a filament rod defining a filament axis, and a filament coupled to the filament rod. The filament clamp is in selective engagement with the filament rod to selectively position the filament along the filament axis within the blind hole.