Simulation of a method for forming a laser-cooled positron plasma - art. no. 023405

We have simulated the trapping and cooling of moderated positrons in a Penn ing trap in which the positrons lose energy through collisions with a simul taneously stored laser-cooled Be-9(+) plasma. Once the positrons are trappe d, they cool through sympathetic cooling with the Be-9(+) plasma After the positrons cool, their motion parallel to the magnetic field reaches a state of thermal equilibrium with the Be-9(+) ions and they rotate about the tra p axis at the same frequency as the Be-9(+) ions. Therefore, a centrifugal separation will occur, forcing the positrons to coalesce into a cold column along the trap axis. A simulation which, in part, utilizes Monte Carlo tec hniques, indicates a capture efficiency of as high as 0.3% for 300 K modera ted positrons passing through a Be-9(+) plasma with a density of 10(10) ato ms cm(-3) and a column length of 1 cm. This capture efficiency leads to the positron capture rate of similar to 1000 positrons per second, assuming a 100 mCi positron source and 10(-3) for the efficiency far moderating positr ons from the source. The resulting dense reservoirs of cold positrons may b e useful for antihydrogen production and for reaching a plasma state in whi ch the mode dynamics must be treated quantum mechanically.