LaBr3 Scintillation Detector Alpha Decay Rejection
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Solution Overview
Problem
Conventional methods for rejecting α decay events in LaBr3 scintillators are prone to measurement variability due to arbitrary integration windows and threshold settings, leading to inaccurate identification of γ ray events, especially in high energy regions.
Innovation Solution
An LaBr3 scintillation detector that calculates the ratio of peak value to total charge amount and uses an error propagation expression function as a threshold to identify and reject α decay events in real-time, incorporating a low-pass filter to remove high-frequency noise and correct for saturation, thereby objectively distinguishing γ ray events from α ray events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods use arbitrary integration windows and threshold settings to identify α decay events, then the identification process can be performed, but the measurement result varies depending on the setting and identification accuracy deteriorates
Solution Approach 1:
The patent transforms the identification method from using arbitrary integration windows and thresholds to using the ratio of peak value to total charge amount. This parameter change eliminates the need for arbitrary settings and provides objective identification criteria for α decay events based on intrinsic waveform characteristics rather than externally imposed parameters.
Solution Approach 2:
The identification system uses the waveform signal's own characteristics (peak value and total charge amount ratio) to identify α decay events, rather than requiring external arbitrary parameters. The method is self-contained and does not depend on externally set integration windows or thresholds, making the system self-sufficient and objective.
2Measurement precision
If background subtraction of α decay is performed to measure low activity γ rays, then the measurement can be conducted, but it takes time to obtain sufficient statistics due to low counting rate
Solution Approach 1:
The patent extracts and removes α decay events from the measured spectrum in real-time by identifying them through the peak-to-total charge ratio method. By separating and eliminating α decay events as they are detected, the system obtains clean γ ray spectra without requiring time-consuming background subtraction procedures.
Solution Approach 2:
The identification and rejection of α decay events occurs continuously during the measurement process rather than requiring separate background measurement and subtraction steps. This continuous action maintains the useful measurement process uninterrupted, reducing total measurement time while maintaining accuracy.
3Reliability
If detection efficiency for high energy gamma rays is increased, then the measurement capability is improved, but the counting rate remains low requiring longer measurement time
Solution Approach 1:
The patent converts the harmful effect of low counting rates (which would require long measurement times) into a benefit by implementing real-time α decay event rejection. This eliminates the need for long measurements to achieve sufficient statistics, as α decay events are continuously removed during measurement, effectively improving the signal-to-noise ratio and reducing required measurement time.
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 enables accurate detection of γ ray events with reduced accidental rejection rates, particularly in the high energy region of 1.5 to 3 MeV, by utilizing measurable values like peak voltage and total charge amount, thus enhancing the utilization of LaBr3 scintillators' characteristics.
Implementation Method 1
an LaBr3 scintillator is excellent not only in time resolution but also in energy resolution
Implementation Method 2
a photoelectric converter that converts light emitted from the LaBr3 scintillator into an electric signal
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The present invention identifies α decay and other events included in the emission of an LaBr3 scintillator and only collects γ ray events. An LaBr3 scintillation detector is provided with an LaBr3 scintillator 10, a photomultiplier tube 12, an oscilloscope 14, and a computer 18. The computer 18 detects a peak value Vp and a total charge amount Qtotal of a voltage waveform signal and calculates an error propagation expression function for a ratio of the peak value Vp to the total charge amount Qtotal. This error propagation expression function is used as a threshold function for identifying and removing α decay events. The α decay events are identified from the peak value Vp and total charge amount Qtotal, which are measurement values that can be measured in real time.