Vacuum Capacitor Assembly for Mass Spectrometer RF Measurement
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Solution Overview
Problem
Mass spectrometers face stability issues in measuring RF amplitude due to environmental fluctuations such as temperature changes and humidity, which affect capacitor performance and introduce parasitic capacitance and inductance from wiring, leading to inaccurate voltage measurements.
Innovation Solution
A capacitor assembly with superposed plates mounted within a vacuum enclosure and a rectifier connected to the second plate within the enclosure, minimizing parasitic effects and reducing environmental influences by maintaining a vacuum and using insulating spacers to reduce dielectric heating and RF heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If capacitors are used to measure RF amplitude in ambient conditions, then the measurement system is simple and easy to implement, but environmental fluctuations (temperature, humidity) cause capacitor plate expansion and permittivity changes leading to measurement instability
Solution Approach 1:
The patent places the capacitor plates inside a vacuum enclosure, creating an inert environment free from humidity and temperature-induced atmospheric changes. This eliminates the permittivity variations and surface effects caused by ambient air, thereby stabilizing the capacitance measurement while maintaining system simplicity.
2Ease of operation
If wiring is added to connect the capacitor to external circuitry, then the capacitor can function as a sensor, but parasitic capacitance and inductance from the wiring introduce measurement errors and drift
Solution Approach 1:
The patent extracts the rectifying function from the external wiring and places it directly inside the vacuum enclosure on the capacitor assembly. This eliminates the need for long external wiring connections, thereby removing the parasitic capacitance and inductance that would otherwise degrade measurement precision.
Solution Approach 2:
The patent merges the rectifier with the capacitor assembly by mounting it directly to the vacuum enclosure wall adjacent to the capacitor plates. This integration combines the sensing and signal processing functions into a single compact unit, eliminating separate wiring connections and their associated parasitic effects.
3Device complexity
If the capacitor operates in ambient conditions, then no special enclosure is needed, but RF dielectric heating and ambient temperature changes cause thermal expansion and measurement drift
Solution Approach 1:
The vacuum enclosure creates a stable inert environment that isolates the capacitor plates from RF dielectric heating and ambient temperature fluctuations. This prevents thermal expansion and permittivity changes, maintaining stable capacitor composition and spacing throughout operation.
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 configuration significantly reduces the impact of environmental changes and parasitic effects, providing stable and accurate RF voltage measurements by minimizing the presence of air and water vapor and reducing RF heating, thereby enhancing the performance of mass spectrometers.
Implementation Method 1
mounted within a vacuum enclosure of a mass spectrometer
Implementation Method 2
the circuitry associated with the second capacitor plate includes a rectifier contained within the vacuum enclosure
Data Source
AI summary
A capacitor assembly (1) for measuring the level of radio frequency voltage in a mass spectrometer. The assembly (1) includes an RF sensing capacitor (2) with first and second capacitor plates (3, 4), a rectifying circuit (5) and a vacuum housing feedthrough (6), all of which are mounted within a vacuum enclosure of the mass spectrometer. The first capacitor plate (3) is adapted for connection to a voltage source and mounted within the enclosure by first insulating spacers (31). The second capacitor plate (4) is nested within the first insulating spacers (31) and mounted within the enclosure by second insulating spacers (41). The rectifying circuit (5) is electrically connected to the second capacitor plate (4) and to the vacuum housing feedthrough (6).