This study investigates the radiation-induced attenuation (RIA) of an Anti-Resonant Hollow-Core Fiber (AR-HCF) exposed to neutron and gamma radiation in a nuclear reactor environment. The AR-HCF—with a revolver-style structure—was characterized for RIA and compared to a solid, pure-silica-core fiber. Experimental results demonstrate that the AR-HCF exhibits substantially higher radiation tolerance compared to pure-silica, solid-core fibers, by about a factor of six in terms of dB/m. Numerical modeling in COMSOL Multiphysics (Version 6.3) was performed to simulate potential contributors of RIA, including silica compaction due to neutron fluence and changes in light confinement. These simulations ruled out these effects as primary causes of the measured attenuation. We also show that our results are consistent with the radiolytic generation of nitric acid within the hollow core, an interpretation that aligns with findings from a prior study. The results included in this manuscript provide insight into the behavior of AR-HCFs in the radiation field of a nuclear reactor, a topic with very limited prior literature, and underscore their potential for use in high-radiation environments such as fission and fusion reactors, particle accelerators, and space applications. The findings also point to promising future directions, including spectral characterization and dosimetry applications that leverage the unique properties of these fibers.

The development of high-field, large-bore magnets based on High-Temperature Superconductors (HTS) is a strategic challenge with impact across high-energy physics, fusion energy, and other scientific and societal applications. In particular, the target decay and capture solenoid for the Muon Collider and the central solenoid of next-generation fusion devices both demand solenoids capable of producing a 20 T peak field in a bore larger than 1 m, at 20 K, with stored energy exceeding 300 MJ (single coil). Such performance is well beyond present state-of-the-art, requiring a dedicated programme to validate conductor technologies, magnet architectures, and protection strategies. This paper presents the results of a feasibility study originated from discussions between CERN and Eni on a common solenoid concept serving as technology validation for both high-energy physics experiments and magnetic-confinement fusion devices such as tokamaks. The main result of the study, which brought together universities and research centers, is a “20@20” model coil concept. We report here the rationale for the selection of the target performance of the “20@20” model coil, and the highlights of the study, which was instrumental to identify high priority developments required towards its realization.