SiPM Microcell Delay Compensation via Localized One-Shot Adjustment
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Solution Overview
Problem
Radiation detection devices employing silicon photomultipliers (SiPMs) face challenges in achieving good timing resolution due to variations in pulse propagation delays across microcells, which are exacerbated by differences in microcell position and trace lengths, leading to degraded performance and reduced active detector area.
Innovation Solution
The solution involves adjusting the trigger level, internal delay, and pulse width of one-shot circuitry, as well as modifying the quench resistance and RC time constant of individual microcells to equalize the timing of output pulses, thereby compensating for signal delays and optimizing transit time across the microcell array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If trace length is extended to equalize propagation delay across microcells, then timing resolution is improved, but parasitics increase and signal pulse shape degrades
Solution Approach 1:
The patent introduces delay compensation circuits at specific microcell locations where propagation delay exceeds a threshold. Rather than uniformly extending all traces, delay elements are selectively placed only in regions needing compensation, maintaining local signal integrity while achieving global timing synchronization across the SiPM array.
Solution Approach 2:
Delay compensation circuits act as intermediary elements inserted into the signal path of specific microcells. These circuits introduce controlled delay to match the propagation time of distant microcells, serving as a mediator that equalizes timing without requiring physical trace extension and its associated parasitics.
2Measurement precision
If additional circuits are incorporated to create delays, then timing equalization is achieved, but pixel space is consumed and active area is reduced
Solution Approach 1:
Delay compensation circuits are selectively placed only in microcells where propagation delay exceeds a predetermined threshold. Microcells already within the acceptable timing window do not receive additional circuits, thereby minimizing the total area consumed by delay compensation while achieving sufficient timing equalization.
3Measurement precision
If trace length is extended to compensate for delay, then timing performance is improved, but driving capability is exceeded and signal pulse shape degrades
Solution Approach 1:
Delay compensation circuits serve as intermediary elements that introduce controlled delay without requiring physical trace extension. This approach avoids exceeding the driving capability of microcells while achieving the necessary timing equalization, preserving signal pulse shape integrity.
4Measurement precision
If delay compensation is applied to all microcells, then timing resolution is maximized, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent implements delay compensation selectively based on the spatial position of microcells. By calculating which microcells exceed the timing threshold and applying compensation only to those specific locations, the fabrication process becomes more manageable while still achieving the required timing resolution performance.
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 ensures that the signal pulses from microcells arrive simultaneously at the processing electronics, effectively leveling transit time delays and enhancing timing resolution without reducing the active area or increasing complexity, thus improving the overall performance of the radiation detection device.
Implementation Method 1
When a bias voltage applied to the silicon photomultiplier (SiPM) is above breakdown, a detected photon generates an avalanche, the APD capacitance discharges to a breakdown voltage and the recharging current creates a signal
Implementation Method 2
a detected photon generates an avalanche
Data Source
AI summary
A system and method for compensating signal delay across a solid state photomultiplier. The method including determining respective arrival times of signals from a plurality of microcells of the photomultiplier, calculating a signal transit time delay difference between the respective arrival times for individual signals, correlating the individual transit time delay differences to an amount of respective signal propagation compensation for respective microcells of the photomultiplier, and introducing the respective signal propagation compensation into circuitry of the respective microcells. The method also includes at least one of adjusting a response shape of a photodiode within each of the plurality of microcells, adjusting operating parameters of a one-shot pulse circuit within the microcells, and modifying circuit design values of each microcells during fabrication of the photomultiplier. A non-transitory computer readable medium and a system for implementing the method on a row, column, and/or individual microcell level are disclosed.