Theoretical treatment of the current neutralization of high-intensity light ion beams in argon

We have modeled the current neutralization of intense light ion beams propagating through low pressure argon gas in the drift region of the applied-B radial ion diode. Our description of the current neutralization process results in a set of equations, each having the form of a system with an intrinsic magnetic decay time constant and driven by the time derivative of the beam current. The time constant is proportional to the gas electrical conductivity, for which we employ a time-dependent model. Comparing our calculations to experiments, we find that our computations duplicate the qualitative behavior of the system in portions of the drift region free of applied magnetic fields; however, in regions with strong applied fields, we underpredict the degree of current neutralization found experimentally. The addition of carbon ions to the beam model improves the neutralization.