3D printing plastic scintillator detectors for particle physics

According to ETH Zurich, researchers from the Department of Physics have demonstrated that 3D printing offers a practical way to build large-scale plastic scintillator (PS) detectors for particle physics experiments.

In 2024, the T2K Collaboration began collecting new neutrino data using upgraded detectors, including SuperFGD, a 2-ton detector composed of two million PS cubes. These cubes emit light when charged particles pass through them. Since neutrinos carry no charge, they can only be studied when they interact with other particles like electrons, protons, muons, or pions. Each cube is embedded with three optical fibers, guiding light to 56,000 photodetectors, which reconstruct 3D particle tracks for further study.

Building detectors cube by cube is labor-intensive. Professors Davide Sgalaberna and André Rubbia, alongside an international team, explored whether 3D printing could streamline the process. Their findings, published in Communications Engineering, introduce a fully additively manufactured PS detector for elementary particles.

PS detectors track charged particles with high precision. The material contains fluorescent emitters (fluors) that absorb energy from passing particles and emit near-ultraviolet light. A second fluor shifts this light’s wavelength, allowing optical fibers to capture and transport it efficiently.

For accurate tracking, 3D scintillating detectors must consist of optically isolated units, similar to pixels in a digital screen. Sgalaberna, who led SuperFGD’s development, and his 3DET Collaboration team faced key challenges: choosing suitable materials and finding an AM process that maintains transparency and structural integrity.

To reduce costs and production time, Tim Weber, a mechanical engineer at ETH Zurich, and colleagues developed Fused Injection Modeling (FIM), a hybrid of Fused Deposition Modeling (FDM) and injection molding.

Their process builds 5×5 layers of empty, white-coated plastic scintillator cube molds using FDM. Metal rods create fiber pathways before scintillation material is injected. A heated punch flattens the top, preparing the next layer. Using this method, they fabricated a SuperCube (125 voxels in a 5×5×5 grid). Each voxel takes 6 minutes to print, with automation expected to further reduce this time.

“This is the first time a 3D printed scintillator detector is able to detect charged particles… and reconstruct both their tracks and energy loss,” said Sgalaberna.

Scaling from 2 million to 10 million voxels would significantly enhance experiments like T2K, proving that 3D printing could revolutionize high-energy physics research.