Catching a neutrino is famously hard. These "ghost particles" slip through ordinary matter almost without a trace, so physicists build vast, dense detectors and slice them into ever-finer pieces to catch the faint flashes a particle leaves behind. A prototype from Switzerland now suggests there may be a far simpler way — by treating the detector like a camera.
Researchers from ETH Zurich and EPFL have tested the first demonstrator of a system, dubbed PLATON, that images the three-dimensional track of a particle inside a single solid block of scintillator, the light-emitting material used to spot charged particles. The work and its supporting simulations were published in Nature Communications.
From millions of fibres to one block
Today's approach can be staggeringly complex. In Japan's T2K neutrino experiment, one detector packs roughly two tonnes of sensitive material into about two million cubes threaded with 60,000 optical fibres; other experiments rely on millions of hair-thin scintillating fibres. As detectors grow, that segmentation becomes a bottleneck of cost and engineering.
PLATON removes the fibres entirely. Instead, it watches the glowing block with a light-field camera — a micro-lens array paired with a fast single-photon sensor called SwissSPAD2. The sensor registers not only where light appears but precisely when, sampling 97,000 times a second. From that flood of timed flashes, the team can reconstruct a particle's path through material that has not been physically divided at all.
In laboratory tests and simulations centred on neutrino detection, the prototype reconstructed particle positions to within about 200 micrometres. The researchers expect further work on the optics to push resolution below a millimetre even in detectors larger than a cubic metre.
The payoff reaches beyond neutrinos. The same technique could streamline the calorimeters used at particle colliders and some searches for dark matter — cutting the complexity, and potentially the cost, of the instruments physicists depend on to probe the universe's most elusive ingredients. The prototype is a first step, but it points to detectors that are at once bigger, simpler and sharper.