Numerical simulations of self-pinched transport of intense ion beams in low-pressure gases

The self-pinched transport of intense ion beams in low-pressure background gases is studied using numerical simulations and theoretical analysis. The simulations are carried out in a parameter regime that is similar to proton beam experiments being fielded on the Gamble II pulsed power generator [J. D. Shipman, Jr., IEEE Trans. Nucl. Sci. NS-18, 243 (1971)] at the Naval Re search Laboratory. Simulation parameter variations provide information on s caling with background gas species, gas pressure, beam current, beam energy , injection angles, and boundaries. The simulation results compare well wit h simple analytic scaling arguments for the gas pressure at which the effec tive net current should peak and with estimates for the required confinemen t current. The analysis indicates that the self-pinched transport of intens e proton beams produced on Gamble II (1.5 MeV, 100 kA, 3 cm radius) is expe cted to occur at gas pressures between 30 and 80 mTorr of He or between 3 a nd 10 mTorr of Ar. The significance of these results to ion-driven inertial confinement fusion is discussed. (C) 1999 American Institute of Physics. [ S1070-664X(99)03610-1].