Charge Detector Reset Calibration for Low-Signal Ion Measurement
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Solution Overview
Problem
Existing electrostatic linear ion trap (ELIT) designs face challenges in distinguishing valid charge measurements from noise, especially as charge signal levels approach the noise floor, leading to uncertainty in mass-to-charge ratio and charge measurements in charge detection mass spectrometry (CDMS).
Innovation Solution
The implementation of an improved charge detection mass spectrometer that includes an electrostatic linear ion trap (ELIT) with a calibration apparatus to reset the charge detector to a predefined reference charge level between ion measurement events, and the use of a charge generator to induce high-frequency charges for gain drift compensation in the charge preamplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charge detection is performed at low signal levels, then measurement sensitivity is improved, but measurement precision deteriorates due to noise interference
Solution Approach 1:
The charge detector is reset to a predefined reference charge level between ion measurement events, preparing the detector in advance for accurate low-level charge detection by eliminating residual charge that would contribute to noise
Solution Approach 2:
A feedback mechanism is implemented where the measured charge signal is used to control the charge generator, which applies compensating charge to maintain the detector at a reference level, thereby reducing noise and improving measurement precision
2Measurement precision
If multiple passes through charge detection cylinder are used, then measurement precision improves, but measurement time increases
Solution Approach 1:
The charge detector is continuously reset and maintained at the reference charge level between measurements, eliminating dead time and ensuring that the detector is always ready for the next ion measurement, thus maintaining high measurement speed while achieving improved precision through multiple passes
3Reliability
If charge detector sensitivity is increased, then detection capability at low signal levels is improved, but reliability deteriorates due to false positive detections
Solution Approach 1:
A reference charge level is introduced as an intermediary standard against which all charge measurements are compared. This reference level acts as a threshold that distinguishes valid ion signals from noise, improving detection reliability while maintaining precision through consistent reference-based 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 solution enhances the range of valid, detectable charge measurements by reducing noise interference and maintaining accurate charge detection, even at low signal levels, thereby improving the precision of mass-to-charge ratio and charge measurements in CDMS.
Implementation Method 1
controlling the charge generator to induce high frequency charges on the charge detection cylinder
Implementation Method 2
electrostatic linear ion trap (ELIT) in which ions are made to oscillate back and forth through a charge detection cylinder
Implementation Method 3
charge detection cylinder... provides for multiple measurements for each ion
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A CDMS may include an ELIT having a charge detection cylinder (CD), a charge generator for generating a high frequency charge (HFC), a charge sensitive preamplifier (CP) having an input coupled to the CD and an output configured to produce a charge detection signal (CHD) in response to a charge induced on the CD, and a processor configured to (a) control the charge generator to induce an HFC on the CD, (b) control operation of the ELIT to cause a trapped ion to oscillate back and forth through the CD each time inducing a charge thereon, and (c) process CHD to (i) determine a gain factor as a function of the HFC induced on the CD, and (ii) modify a magnitude of the portion of CHD resulting from the charge induced on the CD by the trapped ion passing therethrough as a function of the gain factor.