The underlying mechanisms involved in the heat loading on the accelerator grids and plasma chamber components of multimegawatt ion sources are experimentally identified. Utilizing numerical techniques, a new accelerator geometry is designed to minimize the heat loading on various source components and maximize the beam brightness. Measurements on an ion source employing this accelerator geometry, during extraction of quasi‐steady‐state beam pulses of 3.2‐MW power, show significantly reduced heat loadings on all its components.