Summing-induced signal distortion mechanisms and suppression methods in SiPM array gamma spectroscopy detectors

Pulse height analysis (PHA) is commonly used in scintillation γ-ray spectroscopy because it is simple and fast. However, in systems utilizing summed outputs from multi-channel silicon photomultiplier (SiPM) arrays, PHA becomes increasingly susceptible to waveform distortions inherent to the summing architecture. Such distortions alter the signal shape and significantly degrade the energy resolution. In this study, we systematically investigate the characteristics and origins of such abnormal signals using a 16-channel SiPM array coupled to a NaI(Tl) scintillator. By analyzing the pulse area-to-height ratio distributions, we show that summing-induced distortions tend to exhibit broadened pulse shapes and deviate significantly from the single-event signal profile. To mitigate this issue, a threshold-based waveform discrimination method is introduced. This method identifies and rejects abnormal pulses based on receiver operating characteristic (ROC) curve optimization, offering practical improvement in spectral performance when PHA must be retained for speed or simplicity. However, waveform correction alone cannot restore distorted signals. To address this limitation, we further explore pulse area analysis (PAA) as an alternative approach that is inherently less sensitive to distortion effects. Our experiments show that PAA improves energy resolution by 24.25% over conventional PHA, reaching 9.40% at 662 keV. These findings highlight the limitations of amplitude-based methods under summed readout architectures and suggest that PAA, when applicable, offers a more robust solution for compact gamma spectroscopy using SiPM arrays. This work provides both theoretical insights and practical strategies for mitigating signal anomalies in modern scintillation detectors. • Summing-induced waveform distortions degrade energy resolution in SiPM arrays. • Single-event spatial distortion is a rate-independent mechanism. • ROC-based thresholding effectively identifies and rejects abnormal signals. • Pulse Area Analysis (PAA) improves energy resolution by 24.25% over standard PHA. • Practical distortion suppression strategy is proposed for summed SiPM detectors.