Large Area Solid State Photomultiplier Calibration via Digital Signal Processing
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Solution Overview
Problem
Conventional methods struggle to effectively measure and calibrate single photoelectron pulses in large-area Silicon Photomultipliers (SiPMs) due to increased dark counts and the requirement for high gain amplifiers, which are not compatible with readout electronics for large SSPM-based detectors.
Innovation Solution
Characterizing and calibrating large-area SiPMs using high-intensity light pulses that trigger multiple microcells, allowing for the determination of electrical parameters like breakdown voltage and capacitance without the need for high gain amplifiers, and enabling operation in both linear and Geiger modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SPE calibration methods using high gain amplifiers are used, then measurement precision of breakdown voltage is improved, but device complexity increases and compatibility with readout electronics is reduced
Solution Approach 1:
The patent extracts the high gain amplifier from the calibration system and replaces it with a digital signal processing approach. The output signal from the SSPM is directly fed into an oscilloscope or data acquisition system that performs digital averaging and analysis, eliminating the need for analog high gain amplification hardware.
Solution Approach 2:
The patent replaces the mechanical/analog high gain amplifier system with a digital processing system. Instead of using analog amplification to enhance the SPE signal, the system uses digital signal processing techniques including averaging multiple traces and statistical analysis to achieve precise breakdown voltage measurement.
2Power
If high intensity light pulses are used to trigger multiple microcells, then output signal strength is improved, but the ability to isolate single photoelectron pulses is reduced
Solution Approach 1:
The patent employs periodic light pulsing at a repetition rate that allows the SSPM to fully recover between pulses. By controlling the pulse frequency and using signal averaging techniques, the system accumulates multiple traces to extract precise breakdown voltage information while maintaining the ability to distinguish SPE events through statistical analysis of the periodic signal.
Solution Approach 2:
The patent uses light pulse intensities that trigger multiple microcells (excessive action) rather than attempting to trigger only single microcells. This approach generates stronger output signals that can be processed without high gain amplifiers, and the breakdown voltage is determined through statistical analysis of the aggregate response rather than individual SPE isolation.
3Area of stationary object
If large area SSPMs are used, then detection coverage is improved, but dark count rate increases making SPE measurement difficult
Solution Approach 1:
The patent introduces an intermediary processing stage between the SSPM output and the measurement system. A data acquisition system with adjustable time window and averaging capabilities serves as an intermediary that filters out dark count noise by accumulating multiple periodic traces and analyzing the statistical distribution of pulse amplitudes, thereby enabling precise breakdown voltage measurement in large area SSPMs despite high dark count rates.
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 simplifies the calibration of large-area SiPMs by generating output signals proportional to the gain and microcell quantity, facilitating the measurement of electrical parameters and allowing for the investigation of avalanche processes, even in detectors with high dark count rates.
Implementation Method 1
Each pixel detects the photoelectrons with a gain of about 10^6. The output signal is proportional to a gain of the SSPM and a quantity of microcells in the SSPM.
Implementation Method 2
The gain of an SSPM operating in Geiger mode is proportional to the overvoltage (Vov), e.g., the difference between the applied bias voltage (Vbias) and breakdown voltage (Vbr). The Geiger mode process typically results in a well defined single photo electron (SPE) pulses
Data Source
AI summary
Exemplary embodiments are directed to characterizing a solid state photomultiplier (SSPM). The SSPM can be exposed to a light pulse that triggers a plurality of microcells of the SSPM and an output signal of the SSPM generated in response to the light pulse can be processed. The output signal of the SSPM can be proportional to a gain of the SSPM and a quantity of microcells in the SSPM and a value of an electrical parameter of the SSPM can be determined based on a relationship between the output signal of the SSPM and an over voltage applied to the SSPM.