An electron multiplier includes a plate having a plurality of interconnected particles, e.g., fibers, having electron-emissive surfaces. The particles may include a neutron-sensitive and/or neutron reactive material, such as .sup.6Li, .sup.10B, .sup.155Gd, .sup.157Gd,--and/or hydrogenous compounds, in excess of their natural abundance. The particles may include an X-ray sensitive and/or X-ray reactive material, such as Pb.