SIMS Ion Detector Using Scintillator Readout Across Detection Gaps
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Solution Overview
Problem
Secondary ion mass spectrometers face a detection gap between 1×10^6 and 1×10^8 ions/second due to limitations in digital and analog modes, leading to inaccurate correlation and artificial 'jumps' when switching between modes, and inability to accurately measure ion arrival rates below 1×10^8 ions/second.
Innovation Solution
An improved ion detector system with a scintillator and solid-state photomultiplier configuration that enables simultaneous operation of counting and analog modes, using electron emission plates, lightguides, and reflective surfaces to enhance signal separation and noise ratio, allowing for accurate detection across a broader dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital pulse counting mode is used for detection, then individual ion events can be identified and counted with inherent quantification, but the mode is restricted to relatively low rates of ion arrival and cannot accurately measure ion arrival rates above approximately 1×10^6 ions/second due to pulse stack-up
Solution Approach 1:
The patent combines digital pulse counting mode and analog mode into a single detection system, allowing the detector to operate in both modes simultaneously or switch between them seamlessly. This merging eliminates the detection gap by integrating the strengths of both modes: the precision of pulse counting for low ion rates and the high-rate capability of analog mode for ion rates above 1×10^6 ions/second.
Solution Approach 2:
The detector is designed to dynamically switch between digital and analog operating modes based on the ion arrival rate. The system can adapt its detection method in real-time, transitioning from pulse counting at lower rates to analog detection at higher rates, thereby expanding the overall detection range and maintaining measurement accuracy across varying ion flux conditions.
2Productivity
If analog mode is used for detection above 1×10^8 ions/second, then high current secondary ion signals can be measured, but the current is insufficient to provide accurate readings for estimating arriving ions at rates below 1×10^8 ions/second
Solution Approach 1:
The patent merges analog mode detection with digital pulse counting capability, enabling the system to use analog detection for high ion rates while maintaining the option to use pulse counting for lower rates. This combination ensures that at any ion arrival rate, the system can select the mode that provides accurate measurements, thereby resolving the precision limitation of analog mode at lower rates.
Solution Approach 2:
The detector can change its operational parameters dynamically, switching between digital and analog detection modes based on the ion arrival rate. This parameter change allows the system to optimize measurement accuracy for each detection regime, using pulse counting when ion rates are low enough to resolve individual events and analog mode when ion rates are high.
3Power
If electron multiplier is used in analog mode, then high current signals can be detected, but accurate measurement of ion arrival rates is not possible due to statistical variations in secondary electron emission and long term variations from surface condition changes and aging
Solution Approach 1:
The patent combines electron multiplier analog mode with Faraday cup detection or digital pulse counting, creating a hybrid system that compensates for the statistical variations inherent in electron multiplier operation. By merging multiple detection approaches, the system can cross-validate measurements and maintain accuracy despite the limitations of any single mode.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor detection signals and adjust operating parameters to compensate for statistical variations and aging effects. By continuously monitoring performance and making real-time adjustments, the system maintains measurement accuracy even when using electron multiplier in analog mode for high current signals.
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
The system provides improved detection performance with faster event separation and accurate measurement of ion arrival rates, bridging the detection gap and ensuring precise analysis across varying ion fluxes.
Implementation Method 1
an electron emission plate coupled to a first electrical potential and configured to emit electrons upon incidence on ions
Implementation Method 2
the scintillator configured to emit photons from the backside upon incidence of electrons on the front side
Implementation Method 3
a lightguide coupled to the backside of the scintillator and confining flow of photons emitted from the backside of the scintillator
Implementation Method 4
a solid-state photomultiplier coupled to the light guide and having an output configured to output electrical signal corresponding to incidence of photons from the lightguide
Data Source
AI summary
An ion detector for secondary ion mass spectrometer, the detector having an electron emission plate coupled to a first electrical potential and configured to emit electrons upon incidence on ions; a scintillator coupled to a second electrical potential, different from the first electrical potential, the scintillator having a front side facing the electron emission plate and a backside, the scintillator configured to emit photons from the backside upon incidence of electrons on the front side; a lightguide coupled to the backside of the scintillator and confining flow of photons emitted from the backside of the scintillator; and a solid-state photomultiplier coupled to the light guide and having an output configured to output electrical signal corresponding to incidence of photons from the lightguide. A SIMS system includes a plurality of such detectors movable arranged over the focal plane of a mass analyzer.