Ionization Gauge High-Pressure Operation via Dynamic Anode Voltage
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Solution Overview
Problem
Ionization gauges, particularly Bayard-Alpert gauges, experience reduced operational lifetime and significant sputtering issues when operated at high pressures due to high energy ion impacts, leading to degradation and failure, especially when exposed to water vapor and high gas pressures.
Innovation Solution
The anode grid voltage is reduced from 180 volts to 80 volts during high-pressure operations to decrease sputtering yields, while maintaining sufficient electron energy for ionization, using a controller to adjust the bias voltage based on pressure levels, thereby minimizing ion energy and extending the gauge's operational life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the anode grid voltage is increased to 180 volts to provide sufficient electron energy for ionization, then ionization efficiency is improved, but sputtering yield increases dramatically causing rapid degradation
Solution Approach 1:
The patent implements dynamic adjustment of the anode grid voltage based on operating conditions. The voltage is reduced from the traditional fixed 180V to a variable voltage between 50-150V, allowing the system to adapt to different pressure ranges and gas compositions. This dynamic control optimizes the balance between ionization efficiency and sputtering mitigation, extending gauge life while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the voltage parameter from a fixed high value (180V) to a variable range (50-150V) optimized for high-pressure operation. This parameter modification reduces the kinetic energy of ions reaching the collector, thereby decreasing sputtering yield by up to 100 times compared to traditional operation, while still providing sufficient energy for effective ionization in high-pressure environments.
2Reliability
If the anode grid voltage is reduced to decrease sputtering yields, then gauge operational life is extended, but electron energy for ionization becomes insufficient
Solution Approach 1:
The system dynamically adjusts the anode grid voltage based on real-time operating conditions including pressure level and gas composition. By implementing feedback control, the voltage is optimized to maintain sufficient ionization efficiency while minimizing sputtering, allowing the gauge to operate reliably at high pressures without sacrificing measurement capability.
Solution Approach 2:
The voltage parameter is changed from a fixed low value to a variable range (50-150V) that can be adjusted according to operating conditions. This allows the system to provide sufficient electron energy for ionization when needed while reducing voltage to minimize sputtering during high-pressure operation, thereby extending gauge life without compromising measurement precision.
3Measurement precision
If the anode grid voltage is maintained at 180 volts during high pressure operation, then ionization signal strength is maintained, but sputtering causes rapid erosion and metallization of collector surfaces
Solution Approach 1:
The patent implements dynamic voltage control that responds to operating conditions, reducing the anode grid voltage from the traditional fixed 180V to a variable voltage between 50-150V. This dynamic adjustment maintains adequate ionization signal strength while dramatically reducing ion energy and sputtering yield, preventing rapid erosion and metallization of collector surfaces during high-pressure operation.
Solution Approach 2:
The voltage parameter is modified from a fixed high value (180V) to a variable range (50-150V) optimized for high-pressure operation. This parameter change reduces the kinetic energy of ions reaching the collector by up to 100 times, thereby minimizing sputtering erosion and extending collector surface life while maintaining sufficient ionization signal for accurate measurement.
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 results in a five-fold reduction in sputtering yields, significantly extending the operational life of the gauges by reducing erosion and metallization of collector surfaces, even at high pressures, and maintaining adequate ionization and signal quality.
Implementation Method 1
Electrons travel from the electron source to and through the anode, cycle back and forth through the anode, and are consequently retained within, or nearby to, the anode. In their travel, 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 2
The kinetic energy of the ions generated in a Bayard-Alpert ionization gauge is determined by a difference in the bias voltages between an anode grid and a collector post electrode. A bias voltage of a cathode is typically at 30 volts, and a bias voltage of the anode grid is traditionally operated at 180 volts. These voltage differentials are configured to provide 150 electron volts (eV) amount of energy for the electrons.
Implementation Method 3
The ions are attracted to the ion collector electrode, which is typically connected to ground.
Data Source
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Figure 3
Figure 4~5
AI summary
An ionization gauge to measure pressure and to reduce sputtering yields includes at least one electron source that generates electrons. The ionization gauge also includes a collector electrode that collects ions formed by the collisions between the electrons and gas molecules. The ionization gauge also includes an anode. An anode bias voltage relative to a bias voltage of a collector electrode is configured to switch at a predetermined pressure to decrease a yield of sputtering collisions.