A mobile high spatial-resolution Muography instrument based on large-area Micromegas detectors

TL;DR

The paper presents μSTC-R400, a mobile muography instrument based on four resistive Micromegas detectors (each $400~\mathrm{mm}\times 400~\mathrm{mm}$) with a channel-encoded multiplexing readout to achieve high spatial resolution. The readout chain combines front-end STAGE ASICs, back-end DAQ, and self-trigger capability to enable operation in field conditions, demonstrated in an underground subway tunnel and at Dashu Mountain. The system achieves a spatial resolution around $\sim$ $0.188~\mathrm{mm}$ and an angular resolution of about $0.6~\mathrm{mrad}$, while maintaining robustness in harsh environments. These results show that Micromegas-based muography with multiplexed readout can provide precise, portable imaging of internal structures with reduced electronics complexity.

Abstract

Muon radiography is an imaging technique based on muon absorption in matter that allows measurement of internal details in hidden objects or structures. This technique relies on measuring cosmic-ray muons tracks accurately, which reflects the incoming muon flux from both the target object and the open sky. In this paper, we report on the construction of a high spatial resolution muography instrument based on Micromegas detectors. Using four layers of 400 mm ${\times}$ 400 mm Micromegas detectors, channel multiplexing circuits, and the versatile readout system, a moveable muography instrument named $μ$STC-R400 was designed and constructed. Results show that the channel multiplexing circuits can resolve hit positions correctly, and the spatial resolution of the detector is approximately 190 $μ$m. Experiments were conducted at an under-construction subway tunnel and outdoors near a mountain, demonstrating the $μ$STC-R400's ability to maintain high spatial resolution outside the laboratory and its robustness in harsh environments.

Figures (17)

• Figure 1: Principle of muon radiography. A tracking system, typically an array of position-sensitive detectors, measures the incident muon flux. As muons traverse an object, their flux is attenuated due to absorption and scattering.
• Figure 2: Simplified cross-sectional structure of the Micromegas detector. Note that the thicknesses of the drift region and the amplification gap are not drawn to scale.
• Figure 3: Structure of the readout strips on the anode PCB, where the second and third layers form the orthogonal readout strips. The germanium layer is coated after PCB manufacture.
• Figure 4: Photograph of the Micromegas detector ($\mathrm{400~mm\times 400~mm}$) used in this research.
• Figure 5: Photograph of the multiplexing circuit that connects 512 detector strips to 64 readout electronics channels.