Solid-State Photomultiplier Timing Resolution via Parallel Impedance
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Solution Overview
Problem
Current solid-state photomultipliers (SSPMs) have inferior timing resolution compared to conventional photomultiplier tubes (PMTs), which limits their effectiveness in applications requiring precise timing measurements, such as time-of-flight PET imaging due to their slow single-photon response.
Innovation Solution
Incorporating a low impedance device in parallel with the quenching resistor to reduce overall quenching impedance at high frequencies, enabling a faster single-photon response and improved timing resolution in SSPMs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard quenching resistor is used in the SSPM circuit, then the circuit is simple and stable, but the timing resolution is poor due to slow single-photon response
Solution Approach 1:
The patent applies composite materials principle by combining a quenching resistor and a capacitor to form a composite quenching circuit. This composite structure replaces the simple resistor alone, creating a circuit that maintains stability while achieving faster timing response through the capacitive element's ability to store and release charge rapidly.
Solution Approach 2:
The patent changes the electrical parameters of the quenching circuit by introducing a capacitor with specific capacitance value (0.1 pF to 10 pF) in parallel with the quenching resistor. This parameter modification transforms the circuit's frequency response characteristics, enabling faster timing resolution while maintaining the resistor's stabilizing function.
2Speed
If the quenching resistor value is reduced to improve timing response, then the single-photon response becomes faster, but the dark count rate increases
Solution Approach 1:
The capacitor acts as an intermediary element in the quenching circuit. It mediates between the conflicting requirements of fast response and low dark count rate by providing a low-impedance path for high-frequency signal components while allowing the resistor to maintain the bias voltage and suppress dark counts through its higher impedance at DC.
Solution Approach 2:
The patent introduces dynamic behavior to the quenching circuit through the capacitor, which responds differently to various frequency components of the signal. The circuit dynamically adapts its impedance characteristics based on the input signal frequency, providing low impedance for fast photon detection while maintaining high impedance for DC bias stability.
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 solution results in a SSPM with enhanced timing resolution, facilitating more precise timing measurements and improved performance in applications like time-of-flight PET imaging systems.
Implementation Method 1
Each of the plurality of microcells includes a photodiode coupled to a common electrode through a quenching resistor and configured to convert the impinging photons into electrical signals
Data Source
AI summary
A solid-state photomultiplier is provided for use in imaging detectors. The solid-state photomultiplier includes a plurality of microcells configured to detect impinging photons. Each of the plurality of microcells further includes a photodiode coupled to a common electrode through a quenching resistor and configured to convert the impinging photons into electrical signals, and an impedance device coupled in parallel with the quenching resistor so as to reduce overall quenching impedance at high frequency. Further, techniques are provided for implementing low impedance device with controllable value to the SSPM for optimized timing resolution.