Abstract: A dielectric loaded superconducting linear accelerator (linac) is disclosed which includes an accelerating structure formed of a cylindrical sapphire crystal having a centrally disposed passage for reception of a particle beam to be accelerated. A superconductive material layer, such as niobium, surrounds the exterior surface of the sapphire crystal. When the linac is operated at a superconductive temperature of less than 2.degree.K, the loss tangents of the sapphire and niobium are very low so that the linac operates very efficiently. The uniform shape of the sapphire crystal insures that wakefields generated by the charged particles as they pass through the linac will be minimized. The linac has a very high Q which enables it to store energy over a long period of time and reduces peak power requirements.