AN ELECTRON-POSITRON BEAM-PLASMA EXPERIMENT

Advances in positron trapping techniques have made it possible to perform the first electron-positron plasma experiments in a laboratory. An electron-positron beam-plasma system is studied by transmitting a low-energy electron beam through positron plasmas stored in cylindrical and quadrupole Penning traps. In the cylindrical trap, positron heating consistent with a two-stream instability is observed. In the quadrupole trap, a transit-time instability is excited, leading to a large amplitude oscillation of the positron plasma and ejection of positrons from the well.