SiPM Temperature Compensation via Reference Microcell Dark Current
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Solution Overview
Problem
Conventional silicon photomultiplier (SiPM) detectors face performance degradation due to temperature variations, which affect timing and energy resolution, and are limited by indirect temperature measurement and optical crosstalk in conventional cooling systems.
Innovation Solution
Integration of reference microcells on the same die as SiPM pixels, operated in Geiger mode, with charge-sensitive amplifiers to measure dark current and provide real-time temperature compensation, using a hybrid cooling/heating control system to adjust temperature within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cooling systems are used to reduce dark noise and stabilize temperature, then dark noise contribution is reduced, but temperature measurement accuracy is limited due to indirect measurement via thermocouple sensing package temperature
Solution Approach 1:
The SiPM device itself serves as the temperature sensor by utilizing its intrinsic dark current characteristics. The dark current, which flows through the SiPM microcells, is directly measured to determine the actual operating temperature of the sensor, eliminating the need for separate thermocouple measurements. This self-measurement approach provides accurate temperature data directly from the sensing element.
Solution Approach 2:
The mechanical/thermal measurement system (thermocouple sensing package temperature) is replaced with an electrical measurement system that directly measures the dark current of the SiPM microcells. This substitution allows for more accurate temperature determination since the dark current is directly related to the actual operating temperature of the semiconductor device.
2Device complexity
If temperature compensation is not implemented in real-time, then device complexity is reduced, but timing and energy resolution are degraded due to temperature variations
Solution Approach 1:
A feedback mechanism is implemented where the dark current measurement continuously provides temperature information, which is then used to adjust the bias voltage applied to the SiPM microcells. This closed-loop system automatically compensates for temperature variations, maintaining stable breakdown voltage and gain without requiring complex external temperature control equipment.
Solution Approach 2:
The bias voltage parameter is dynamically adjusted based on measured temperature conditions. By changing the bias voltage in response to temperature variations, the system compensates for temperature-induced changes in breakdown voltage and gain, thereby maintaining consistent timing and energy resolution across different operating temperatures.
3Device complexity
If multiple pixels are multiplexed together to reduce complexity, then device structure is simplified, but accuracy is limited by optical crosstalk and inability to account for non-uniformity of each device
Solution Approach 1:
The SiPM device is segmented into multiple independent microcells, each with its own dark current measurement capability. This segmentation allows individual temperature monitoring and compensation for each microcell or pixel, preventing optical crosstalk from affecting measurement accuracy while maintaining the compact structure of the multiplexed array.
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
Improves timing and energy resolution by accurately monitoring and compensating for temperature variations, reducing noise and ensuring stable detector performance across varying conditions.
Implementation Method 1
measuring a dark current of the reference microcell to determine an actual temperature of the SiPM device
Implementation Method 2
controlling a hybrid cooling/heating system to adjust the temperature of the SiPM device to be within a predetermined temperature range
Implementation Method 3
compensating for effects of the temperature variation on a breakdown voltage and a gain of the SiPM device
Data Source
AI summary
A SiPM tile includes SiPM arrays on a detector die, each of the SiPM arrays including a first plurality of microcells and a second plurality of reference microcells dispersed on the die, each reference microcell including an optically-opaque mask, a readout circuit each including a respective charge sensitive amplifier (CSA) connected to one of the reference microcells, each CSA configured to accumulate the dark current of the reference microcell during a selected time window, a hybrid temperature control circuit configured to receive an output signal from each CSA, and to determine the real-time temperature of the die based on the received output signal, to provide the real-time temperature to a temperature compensation and correction control unit that adjusts a cooling/heating system flow provided to the die, the adjustment based on the real-time temperature. A method for compensating the operating temperature variation of the SiPM tile is also disclosed.