X-ray Detection Gain Calibration Using Pulser Injection
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Solution Overview
Problem
Existing X-ray analyzers face challenges with signal drift and non-linearity in energy scale calibration, leading to inaccurate and inconsistent measurements due to temperature sensitivity and the use of charge-sensitive pre-amplifiers, which are not adequately addressed by current calibration methods that require frequent manual interruptions and lack efficient compensation for non-linear effects.
Innovation Solution
A novel calibration method using a pulser to inject calibration pulse signals into the electronic amplification and digitization system, employing a single common reference voltage to stabilize the energy scale and account for non-linearity, allowing for frequent automatic calibration with minimal disruption to operations and continuous measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual calibration is performed frequently to correct energy scale drift, then measurement accuracy is improved, but device operation is interrupted and productivity decreases
Solution Approach 1:
The calibration pulse signal is injected continuously or periodically into the amplification and digitization system before actual X-ray measurements to pre-correct for gain drift. This preliminary calibration action occurs in the background without interrupting the main measurement function, allowing both high accuracy and continuous productivity
Solution Approach 2:
A calibration pulse signal serves as an intermediary reference that mediates between the unstable electronic system and the measurement requirements. This pulse signal passes through the same amplification and digitization path as X-ray signals, providing a reference for real-time gain correction without requiring manual intervention or interrupting normal operation
2Measurement precision
If manual calibration is performed to correct energy scale drift, then measurement accuracy is improved, but operational convenience deteriorates
Solution Approach 1:
The system performs self-calibration by automatically injecting and processing calibration pulse signals through the electronic chain. The microprocessor monitors the digitized pulse amplitudes and automatically adjusts calibration parameters without requiring user intervention, making the system both accurate and easy to operate
Solution Approach 2:
The system continuously monitors the amplitude of calibration pulse signals after they pass through the amplification and digitization system. This feedback information is used by the microprocessor to detect gain drift and automatically adjust calibration parameters, maintaining accuracy without manual intervention
3Power
If charge-sensitive pre-amplifiers are used to amplify detector signals, then signal amplification is improved, but non-linearity and temperature sensitivity increase
Solution Approach 1:
Calibration pulse signals serve as an intermediary reference that passes through the charge-sensitive pre-amplifier and subsequent electronics. By monitoring how these known pulses are amplified and digitized, the system can detect and correct for non-linearity and temperature-induced gain changes in the pre-amplifier, maintaining reliability while using high-gain amplification
Solution Approach 2:
The system dynamically adjusts calibration parameters based on monitored changes in the amplification chain characteristics. By continuously tracking the response to calibration pulses and updating calibration factors, the system compensates for temperature sensitivity and non-linearity of the charge-sensitive pre-amplifier, maintaining energy scale stability across varying conditions
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
Disclosed are circuits (1a) for automatic calibration of the gain of electronic amplification and digitization systems for use with X-ray detectors. The calibration is based on injecting predetermined pulses into the electronic system and deriving a calibration ratio based the digital value of their amplitude with the digital value of the same pulses, unamplified and digitized with a high accuracy reference ADC. All ADCs, as well as the DACs used to control the pulser amplitude are referenced to a single common reference voltage (14). Calibration for non-linearity of the gain is disclosed with an alternative embodiment for the same circuits.