MuGrid-v2: A novel scintillator detector for multidisciplinary applications

TL;DR

This work presents MuGrid-v2, a cost-efficient muon detector based on a monolithic plastic scintillator with an embedded light-guide grid designed for absorption muography. By integrating wavelength-shifting fibers and a TOFPET2-based readout, the system achieves millimeter-scale spatial resolution and robust detection efficiency ($ ext{efficiency} ext{ per-layer} ightarrow ext{~86–91} ext{%}$) while significantly reducing manufacturing complexity. In open-sky field tests and a campus building case study, MuGrid-v2 demonstrates reliable performance and the ability to resolve geometric muon-flux variations induced by architectural features, with a best spatial reconstruction of $4.6 ext{ mm}$ when incorporating time information. The results support widespread, field-ready muography applications, and future work includes expanding to a $2 ext{π}$ coverage grid and automating data-analysis workflows for non-expert deployment.

Abstract

Muography, traditionally recognized as a potent instrument for imaging the internal structure of gigantic objects, has initialized various interdisciplinary applications. As the financial and labor costs of muography detector development hinder their massive applications, we develop a novel muon detector called MuGrid by coupling a monolithic plastic scintillator with the light guide array in order to achieve competitive spatial resolution while substantially reducing production costs. For a prototype detector in 30 cm $\times$ 30 cm, the intrinsic spatial resolution has been optimized toward a millimeter scale. An outdoor field muography experiment was conducted to monitor two buildings for validation purposes. The test successfully resolved the geometric influence of architectural features based on the attenuation of muon flux in a good agreement between experimental results and the simulation prediction.

Figures (10)

• Figure 1: The left panel illustrates the design evolution and concept of the MuGrid-v2 system. Compared to placing optical fibers on the light guide cubes, embedding them in the light guide structure provides a more stable fixation solution while also enhancing fiber collection efficiency for scintillation photons. The implementation of 3D printing technology makes the production of this complex structure relatively easy. The right panel shows the detector in assembly and the finished prototype.
• Figure 2: The color of each channel corresponds to the signal amplitude. The red dot denotes the reconstructed position.
• Figure 3: The overall workflow of the MuGrid detector.
• Figure 4: The variation of dark count rates with an increase of the discriminator threshold. At each step, the number of photoelectrons points to a specific threshold plateau.
• Figure 5: multi-photoelectron spectrum measured with the S13360-1350 biased at 4.5 V overvoltage in both QDC and ToT mode. It is worth noting that a dip appears in both figure. This splitting feature is not caused by different photoelectron peaks but rather results from signal reflection induced by impedance mismatch at the ASIC input interface.