▎ 摘　　要

NOVELTY - The method involves moving one electron beam at a constant speed above a hyperbolic metamaterial at d is equal to 100nm~500nm, and the hyperbolic metamaterial is made of silicon and graphene consisting of alternating layers. The thickness of silicon is 50-200 nm, and the thickness of graphene is 1 nm. The electron source comprises s 20 to 60 pairs of silicon and graphene alternating layers. The radiation spectrum is between 2 terahertz (THz) and 20 THz. The velocity of the electron beam is smaller than the phase velocity of the electromagnetic wave in the hyperbolic metamaterial. USE - Method for designing free electron source used in biomedicine, imaging and communication based on thresholdless Cherenkov radiation. ADVANTAGE - The special structure design makes the electromagnetic wave to have a large wave vector along the material transmission direction, and the free electron velocity is reduced by several orders of magnitude in the formation of Cherenkov radiation. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic perspective view of the dispersion relationship of electromagnetic waves in an hyperbolic meta-materials (HMM) and a surrounding electron beam. (Drawing includes non-English language text)