Tackling Systematic Uncertainties in SiPM Arrays
In 2021, our paper on systematic uncertainties of SiPM arrays for JEDI was published in the Journal of Instrumentation. This work, conducted at Forschungszentrum Jülich, addressed a fundamental challenge in modern detector physics: understanding and quantifying systematic uncertainties in Silicon Photomultiplier (SiPM) arrays.
What Are SiPMs?
Silicon Photomultipliers represent a revolution in light detection. Unlike traditional photomultiplier tubes, SiPMs are solid-state devices that offer compact form factors, high quantum efficiency, excellent time resolution, and immunity to magnetic fields.
The JEDI Experiment
JEDI (Jülich Electric Dipole moment Investigations) searches for the electric dipole moment of charged particles, specifically protons and deuterons. Finding a non-zero EDM would be revolutionary, pointing to new physics beyond the Standard Model.
Systematic Uncertainties: The Hidden Challenge
In precision experiments, systematic uncertainties can dominate the error budget. Our work focused on identifying, characterizing, and mitigating systematic effects in SiPM detector arrays.
Temperature Effects
SiPM gain varies significantly with temperature, typically around 2-3% per degree Celsius. We developed temperature compensation algorithms that reduce these variations to less than 1% over operational ranges.
Optical Crosstalk
When a SiPM pixel fires, it can trigger neighboring pixels through optical crosstalk. This affects both gain measurements and position resolution.
Dark Counts
SiPMs generate noise from thermal generation, after-pulsing, and correlated noise cascades. Understanding these contributions was essential for detector performance optimization.
Experimental Methodology
Our systematic study used environmental chambers for precise temperature control, calibrated light sources, and fast digitizers for waveform analysis. Testing over 100 SiPM modules required extensive automation and data management.
Key Findings
We identified manufacturing variations as the dominant source of non-uniformity and determined optimal operating conditions balancing detection efficiency, noise rate, and temperature sensitivity.
Impact on Detector Development
This work influenced specifications for future SiPM-based detectors in particle physics, nuclear physics, and medical imaging applications.
Lessons for Experimentalists
Key takeaways for working with systematic uncertainties:
- Embrace attention to detail
- Question every measurement assumption
- Document thoroughly
- Master statistical methods
- Collaborate across expertise areas
Precision measurement is a craft developed through years of careful practice.
Published in Journal of Instrumentation, Vol. 16, December 2021 DOI: 10.1088/1748-0221/16/12/P12021