In broad-beam ion sources an inhomogeneous plasma distribution has a strong
effect on both the maximum extractable ion current and the broad-beam prof
ile. An approximate plasma distribution function is determined by fitting c
alculated accelerator-grid currents to corresponding experimental data, thu
s efficiently replacing complicated and expensive plasma probe measurements
. (C) 2000 American Institute of Physics. [S0034-6748(00)52002-4].