Muon tomography is a non-destructive imaging technique that uses cosmic-ray muons to probe dense materials. A plastic Scintillating Fiber (SciFi) detector with a one-dimensional SiPM array offers a compact and high-resolution solution. However, constructing a large-area SciFi detector demands reducing the number of readout channels while maintaining detector performance. To address this challenge, we present a 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. A multiplexed SciFi detector module comprising 21 SiPM channels read out through 7 electronic channels are constructed. Electronic tests show that this module 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.
Categories: physics.ins-det hep-ex