A team of researchers at the European Organization for Nuclear Research, known as CERN, is testing innovative hollow-core optical fibers designed to withstand extreme radiation in particle accelerator environments. These slender fibers, no thicker than a human hair, could significantly enhance the monitoring of particle beams at the Super Proton Synchrotron (SPS), CERN’s second-largest accelerator.
The new technology employs a microstructured design that allows light to be guided through the fiber using resonance and antiresonance effects. By filling these hollow fibers with a scintillating gas—a gas that emits flashes of light when struck by particles—scientists have developed a powerful radiation sensor. This advancement not only helps in adjusting the beam profile and position but also has the potential to enable real-time measurements of the delivered beam dose.
Traditional monitoring devices, such as multi-wire proportional chambers and scintillator detectors, often struggle in high-radiation environments. The ability of these hollow-core optical fibers to operate reliably under such conditions makes them a promising solution for future CERN experiments and medical applications, including FLASH radiotherapy, a technique that delivers radiation at ultra-high dose rates for cancer treatment.
Measuring particle beams accurately is vital for both experimental physicists and beam physicists. CERN’s operations depend on extensive data collected from thousands of beam sensors distributed throughout the accelerators. However, the reliability of these sensors can diminish at high energies or intensities. This challenge is also relevant for researchers developing accelerators for medical use, as extreme conditions demand innovative monitoring tools.
The collaboration between CERN’s beam diagnostics team and researchers in medical technology aims to create tools that can endure extreme radiation levels. Initial tests conducted at CERN’s various facilities, including the CLEAR facility, in 2024 and 2025 involved exposing a fiber filled with an argon-nitrogen mixture to an electron beam. A silicon photomultiplier, capable of detecting single photons, was connected to the fiber, which transmitted signals each time the beam passed through.
Results presented at the recent International Beam Instrumentation Conference were promising. According to Inaki Ortega Ruiz, who leads the beam instrumentation consolidation for the SPS North Experimental Area, “The fiber’s measurements of the beam profile closely matched those from a traditional YAG screen, a crystal that glows when struck by particles. Even after receiving a radiation dose high enough to damage many instruments, the fiber showed no sign of performance loss.”
While these initial findings are encouraging, further research is planned to enhance the connection between the fiber and the detector. Future tests will also explore sealed fibers pre-filled with gas and investigate the fibers’ long-term radiation hardness.
This groundbreaking work at CERN not only holds potential for improving accelerator operations but may also pave the way for advancements in medical treatments, demonstrating the interconnected nature of scientific research and its applications in diverse fields.
