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Every second, about a hundred invisible particles, muons, pass through your body. They are born high in the sky when cosmic rays collide with air atoms, raining down on Earth. These particles are so penetrating that they can pass through a multi-story building, but they slightly change direction when they encounter dense material, such as lead or uranium. This property is the basis of muon tomography: a method that lets you see inside a closed truck or a volcano without opening it.

A research group has created a miniature detector for such imaging, based on the gas amplification technology known as Thick-GEM. It works like a sponge: in its pores, a passing particle knocks out electrons, which then trigger an avalanche that amplifies the signal. Usually, such plates are made with micron-sized holes, but here they were enlarged by a factor of 5–20: this simplifies production, makes the device more robust and cheaper, while maintaining accuracy. A plate measuring 4 by 5 centimeters, manufactured at a local facility, underwent a series of tests.

First, the detector was “trained”—different voltages were applied to find the mode where it sees particles best without being overwhelmed by noise. Then, they measured how many muons it catches. It turned out that in both single-layer and double-layer configurations, the device registers 99.5% of all passing particles — an almost perfect counter. Using a narrow beam from an iron-55 source, they determined the spatial resolution: 30 micrometers, which is three times thinner than a human hair.

Such a detector could become the heart of a portable scanner for customs or industry. Instead of bulky X-ray machines — a box that sees hidden cavities and different materials by how muons deflect in their bulk. And all this uses the free rain of cosmic particles that falls constantly.