High-luminance radioluminescent lamp

In a preferred embodiment, a radioluminescent lamp having a glass face plate with a plurality of parallel planer light guides, each preferably having a transparent glass, sapphire or quartz base member, disposed perpendicularly with respect to the glass face plate and coated on both sides with a thin film of radioluminescent phosphor material. The plates are mounted in a sealed envelope filled with tritium gas, the radioactive decay of the tritium causing the phosphor to luminesce. The phosphor material and all but one of the edges of each light guide are overcoated with a reflective material, such as aluminum, to guide the generated light to a single edge of the light guide, which edge is adjacent the glass face plate. The phosphor is preferably a calcium sulfide-based material forming a continuous, binder-free layer on the transparent base member. The resulting structure has a high phosphor-surface-area to tritium-gas-volume ratio and directional light guiding, yielding a substantially higher output light density than conventional radioluminescent lamps.