Functioning of high-Tc bulk superconductor lenses (supertrons) for intense electron beams

Self-magnetic fields of intense electron beams of nanosecond order (∼340 keV, ∼1 kA, ∼10 ns) diffused through the walls of high-Tc Bi-based sintered superconductor tubes (Supertrons) with a velocity of ∼10⁴ m/s. The reaction to this slow viscous diffusion confines the electron beams to the bores of the tubes. The velocity will be one of criteria for applying sintered superconductors to high-frequency devices. The magnetic fields that were confined to the bores increased with lowering operation temperatures, being about 200 G at 90 K for a 3-mm-thick wall tube.