🔭 astrophysics

Scintillation muon telescope module with fiber-optic light collection

Researchers developed and tested a compact, cost-effective, and highly stable scintillation muon telescope module using fiber-optic light collection and silicon photomultipliers, demonstrating long-term stability of better than 0.1% per year without requiring temperature control.

Original authors: Belov S. M., Yanke V. G

Published 2026-02-10

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CC BY 4.0

Original authors: Belov S. M., Yanke V. G

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

The Cosmic Rain Gauge: Catching Invisible Particles from Space

Imagine you are standing outside during a massive rainstorm. You can’t see the individual raindrops easily, but you can place a bucket on the ground to measure how much water falls. If the bucket fills up quickly, you know it’s a downpour; if it barely gets wet, it’s just a drizzle.

Scientists are doing something very similar, but instead of rain, they are trying to catch "Cosmic Rain"—invisible, high-speed particles called muons that are constantly streaming toward Earth from deep space.

This paper describes the invention of a high-tech "bucket" designed to catch these particles and help us predict "space weather."

1. The Invention: A High-Tech "Light Trap"

The researchers built a specialized module (a single unit of a larger telescope) to detect these muons.

The Analogy: Think of the detector like a high-speed camera trap in a forest.

The Scintillators (The Flash): When a muon flies through the detector, it hits a special plastic material that flashes with a tiny, microscopic burst of light. It’s like a tiny lightning bolt triggered by a passing particle.
The Fiber Optics (The Funnel): Because that flash of light is incredibly faint, they use glowing "straws" (fiber optics) to suck that light away from the impact site and carry it to a sensor.
The SiPM (The Super-Sensitive Eye): At the end of the straw is a Silicon Photomultiplier. Imagine an eye so sensitive it could see a single firefly in a dark stadium. This "eye" turns that tiny flash of light into an electrical signal.

2. The Problem: The "Noisy" Atmosphere

Catching the particles is only half the battle. The Earth’s atmosphere is like a thick, moving blanket that changes constantly.

The Analogy: Imagine trying to count how many people are walking through a doorway, but the floor is constantly tilting, and the air pressure is changing, making people stumble or run faster.

Pressure: When the air pressure is high, there is more "stuff" in the way, which can block the muons.
Temperature: When the atmosphere gets warm, it expands, changing the "thickness" of the blanket the muons have to fly through.

The researchers developed a clever computer system that acts like a smart filter. It looks at the weather (pressure and temperature) in real-time and "cleans" the data, subtracting the weather noise so they can see the true signal from space.

3. Why Does This Matter? (Space Weather Forecasting)

Why go to all this trouble to count invisible particles? Because these particles are the "scouts" of the solar system.

The Analogy: Think of cosmic rays as scout ships sent out by the Sun.
The Sun is a temperamental star that occasionally throws massive "solar storms" our way. These storms can mess up our satellites, GPS, and power grids. Because these cosmic particles travel differently than the actual solar wind, they arrive at Earth at different times.

By watching the "muon rain" change, scientists can get an early warning. If the muon count suddenly drops (a phenomenon called a Forbush Decrease), it’s like seeing the scouts retreat—it tells us a massive solar storm is on its way.

4. The Verdict: A Reliable, Low-Cost Tool

The researchers proved that their new "bucket" is:

Super Stable: It doesn't need a fancy, temperature-controlled room to work; it stays accurate even as the seasons change.
Efficient: It’s small, uses very little power, and is cheap enough that they can build dozens of them to create a massive, worldwide "net" to catch cosmic rays.

In short: They have built a reliable, smart, and affordable way to listen to the heartbeat of the Sun, helping us prepare for the unpredictable weather of deep space.

Technical Summary: Scintillation Muon Telescope Module with Fiber-Optic Light Collection

1. Problem Statement

The study of cosmic ray variations is essential for space weather forecasting and understanding heliospheric disturbances. While traditional ground-based networks (neutron monitors and muon telescopes) exist, there is a need for modern, cost-effective, and highly stable detector modules that can be scaled into multidirectional telescopes. Specifically, the researchers aimed to overcome the limitations of older technologies—such as vacuum photomultiplier tubes or bulky Winston cones—by developing a compact, low-power, and stable module capable of continuous, long-term monitoring of the muon component of cosmic rays.

2. Methodology

The researchers developed a scintillation telescope module using a "telescopic configuration" consisting of two layers of plastic polystyrene scintillators (0.5 × 0.5 × 0.05 m³) separated by a 5 cm lead absorber to filter out the soft component of cosmic rays.

Light Collection: Instead of traditional light guides, the module utilizes fiber-optic light collection. Two 2.6 m long optical fibers are embedded in the scintillator, shifting the wavelength (425 nm to 476 nm) to optimize detection.
Photodetectors: The system employs Silicon Photomultipliers (SiPMs) (SensL MicroFC-30035-SMT). These provide high sensitivity, small dimensions, and high gain ( $\geq 3 \times 10^6$ ), making them a modern alternative to vacuum tubes.
Electronics & Data Acquisition (DAQ):
- An integrated amplifier-discriminator and pulse shaper circuit processes the SiPM signals.
- An STM32f103c8t6 microcontroller handles coincidence logic, pulse counting, and environmental monitoring (pressure, temperature, and bias voltage).
- Data is transmitted via TCP/IP (Ethernet) to a server using a three-tier software architecture (Python/PostgreSQL backend and JavaScript frontend).
Data Correction: To isolate primary cosmic ray variations from local environmental noise, the authors implemented a real-time correction method using a multivariate regression model to account for barometric pressure and mass-averaged atmospheric temperature.

3. Key Contributions

Novel Real-Time Processing: The implementation of a real-time mode for all stages of data collection, including the use of an atmospheric model in "reanalysis mode" to correct for temperature effects instantaneously.
Modular Design: The development of an "elementary telescope" module that is compact, low-power, and easily scalable into a large-scale multidirectional muon telescope (e.g., a $4 \times 4$ array).
High-Precision Calibration: Establishing the relationship between SiPM bias voltage and counting efficiency, ensuring that voltage stability requirements ( $\leq 0.1$ V) are met to maintain data integrity.

4. Results

Stability: The module demonstrated exceptional long-term stability, with parameter variations better than 0.1% per year, even without the use of a thermostatic chamber.
Efficiency: The detector counting efficiency was measured at $(98.7 \pm 0.2)\%$ .
Meteorological Coefficients: The study successfully determined the barometric ( $\beta$ $β$ ) and temperature ( $\alpha$ $α$ ) coefficients for the vertical muon component:
- $\beta = (0.17 \pm 0.02) \%/\text{hPa}$
- $\alpha = (0.29 \pm 0.03) \%/^\circ\text{C}$
Validation: Continuous monitoring since February 2022 showed that the telescope's count rate variations correlate consistently with the Moscow neutron monitor, successfully capturing significant cosmic ray events such as Forbush decreases (e.g., the large decrease in May 2025).
Energy Threshold: The coincidence network effectively limits the particle energy threshold to 163 MeV.

5. Significance

This work provides a blueprint for a new generation of cosmic ray detectors. By combining SiPM technology with fiber-optic collection, the researchers have created a tool that is significantly more compact and easier to operate than previous iterations. The high stability and the ability to perform real-time meteorological corrections make this module an essential building block for constructing large-scale, multidirectional muon telescopes. Such networks are vital for the continuous, high-resolution monitoring of the heliosphere and for improving the accuracy of space weather predictions.