Novel Schemes for the Collimation of Neutral Electron-Positron Beams

Despite the intrinsic difficulty in reproducing neutral pair plasmas in the laboratory, recent experiments carried out using a laser driven set-up have for the first time created a neutral ion free electron-positron plasma, with high-density and divergence on the order of 20 mrad. However, although small this divergence leads to the beam quickly losing density, so that within the first few mm any collective behaviour in the plasma is lost.

For a meaningful study of the dynamics of electron positron beams in the laboratory, it is necessary that these beams be kept highly collimated. Numerical simulations indicate that an electron beam with a converging full-cone angle of 20 mrad incident onto a lead target, initiates an electrodynamic cascade that produces a highly collimated neutral electron-positron beam. Here, through analytical and numerical analysis we show that the electron beam can be converged onto the target by using a system comprising of three miniature magnetic quadrupoles, along with obtaining the parameters for these quadrupoles.