Ionization Gauge Electron Source Shielding
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Solution Overview
Problem
Ionization gauges fail prematurely when operated at high pressures due to sputtering, which causes deposition of sputtered atoms on the electron source and feed-through insulators, leading to electric leakage and gauge failure.
Innovation Solution
The ionization gauge design positions the electron source and collector structures in a parallel arrangement, with shades between them to inhibit direct sputtered atom paths and minimize exposure to sputtered atoms, allowing for controlled deposition and extended operation at high pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electron source and collector are arranged in a parallel arrangement with large surface area facing each other, then the gauge can measure pressure effectively, but sputtered atoms from the collector can directly reach the electron source causing premature failure
Solution Approach 1:
The patent repositions the electron source from a parallel arrangement to an end position along the collector axis, changing the spatial dimension of the configuration. This dimensional change eliminates the direct line-of-sight path for sputtered atoms while preserving pressure measurement functionality through the ionization volume.
Solution Approach 2:
The patent introduces shades as intermediary structures positioned between the collector and electron source. These shades block the direct path of sputtered atoms, acting as protective mediators that prevent contamination while allowing the gauge to maintain its measurement capabilities.
2Adaptability or versatility
If the gauge operates at high pressure above 10^-4 Torr, then the gauge can measure higher pressure ranges, but sputtering increases causing deposition on the electron source and premature failure
Solution Approach 1:
The patent accepts that sputtering will occur at high pressures but redirects the harmful sputtered atoms away from the electron source using shades and geometric configuration. This converts the harmful effect into a controlled process where deposition occurs on designated surfaces rather than critical components, enabling reliable high-pressure operation.
3Reliability
If shades are added to block sputtered atoms from reaching the electron source, then the electron source is protected from contamination, but the device complexity increases
Solution Approach 1:
The patent designs the shades to serve multiple functions: blocking sputtered atoms, defining the ionization volume boundaries, and potentially serving as additional collection surfaces. This multi-functionality reduces the need for separate protective components, minimizing the increase in device complexity.
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 design significantly reduces the impact of self-sputtering on filament emission efficiency, preventing premature failure and enabling reliable operation at pressures above 10^-4 Torr by shielding the electron source from sputtered atoms, thus extending the operational lifetime of the gauge.
Implementation Method 1
a hot cathode electron source positioned at an end of an ionization volume
Implementation Method 2
the electrons collide with molecules and atoms of gas that constitute the atmosphere whose pressure is desired to be measured. This contact between the electrons and the gas creates ions
Implementation Method 3
The ions are attracted to the ion collector electrode, which is typically connected to ground
Implementation Method 4
Sputtering is a problem when operating the ionization gauge at high pressures, such as above 10 -4
Data Source
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Figure 3A
AI summary
An ionization gauge to measure pressure, while controlling the location of deposits resulting from sputtering when operating at high pressure, includes at least one electron source that emits electrons, and an anode that defines an ionization volume. The ionization gauge also includes a collector electrode that collects ions formed by collisions between the electrons and gas molecules and atoms in the ionization volume, to provide a gas pressure output. The electron source can be positioned at an end of the ionization volume, such that the exposure of the electron source to atom flux sputtered off the collector electrode and envelope surface is minimized. Alternatively, the ionization gauge can include a first shade outside of the ionization volume, the first shade being located between the electron source and the collector electrode, and, optionally, a second shade between the envelope and the electron source, such that atoms sputtered off the envelope are inhibited from depositing on the electron source.