Multiplexed SiPM Readout of Plastic Scintillating Fiber Detector for Muon Tomography

TL;DR

This paper introduces a multiplexing scheme for SiPM readout in plastic scintillating fiber detectors, enabling large-area muon tomography with reduced channels while maintaining high efficiency and resolution.

Contribution

A novel diode-based multiplexing method that significantly reduces readout channels for SiPM arrays in scintillator detectors, validated through simulations and experimental tests.

Findings

Multiplexing achieved with up to 49 SiPM channels using only 7 electronic channels.

Detector maintained over 95% detection efficiency and 0.65 mm spatial resolution.

Low crosstalk and preserved linearity over a wide dynamic range.

Abstract

Muon tomography is a non-destructive imaging technique that uses cosmic-ray muons to probe dense materials. Bar scintillator and scintillating fiber detectors equipped with one-dimensional SiPM arrays offer compact, high-resolution solutions, but large-area implementations require effective reduction of readout channels while preserving detector performance. To address this challenge, we present a novel multiplexing scheme based on a diode-based symmetric charge division circuit combined with a position-encoding algorithm, enabling up to $N_{\textrm{SiPM}}^{\textrm{max}}=C^{2}_{N_{\textrm{ele}}}$ SiPM channels to be read out using only ${N_{\textrm{ele}}}$ electronic channels. Circuit simulations confirm the feasibility of the multiplexing design and guide the choice of appropriate diodes to preserve SiPM signal integrity. The approach was validated using a SciFi detector module comprising 21 SiPM channels multiplexed into 7 electronic channels. Electronic tests show that this multiplexing circuit exhibits low crosstalk between electronic channels, and preserves linearity over a dynamic range from $\sim$10 to 122 photoelectrons. Cosmic-ray measurements further show that the multiplexed SciFi detector achieves a detection efficiency above 95\% and a spatial resolution of about 0.65~mm, with only minor degradation compared to the direct (per SiPM channel) readout. These results verify that the proposed method provides a scalable and cost-effective readout solution for large-area muon tomography systems and is applicable to other scintillator-based detectors employing similar one-dimensional SiPM array readout.