Efficient cooling and pre-acceleration of positron beams via a surface-plasmon wakefield

Phase-space cooling of positron beams in plasma remains a central challenge for realizing compact, high-brightness positron sources. Here we propose and numerically demonstrate a surface-plasmon–driven wakefield scheme that simultaneously provides longitudinal and transverse phase-space cooling as well as pre-acceleration of a positron beam in a dense plasma micro-tube. Coupled Geant4 and particle-in-cell (PIC) simulations show that a single-stage configuration can integrate positron generation, phase-space cooling, and pre-acceleration within a self-induced surface-plasmon wakefield that sustains an average accelerating gradient of 0.5 TV/m. In this scheme, the positron beam is accelerated to 5.68 GeV within 33.4 ps, while its relative energy spread is compressed to 10.3%, its transverse emittance and divergence are strongly reduced, and the longitudinal capture efficiency exceeds 95%. This surface-plasmon wakefield cooling stage provides a compact pathway toward next-generation high-brightness positron injectors based on plasma micro-structures.