Multibeam direct writing and projection strategies have been proposed for high throughput electron beam lithography; however, the large beam current required may cause severe beam blur due to the stochastic Coulomb interaction effects between the electrons. From viewpoint of both concept proof and practical system design, evaluation of:the fundamental system limits and the optimum performance in a large range of multiple system parameter variable space is critical for such-high throughput tools. Based on the response surface design approach, well-fitted empirical models of image beam size as a function of various system parameters have been extracted from Monte Carlo simulations of electron interactions for different proposed multi-beam systems. The blurred imaging beam size is examined in a wide range of system parameters: beam currents from 1 to 100 mu A, acceleration voltages;from 25 to 100 kV, column lengths from 1 to 100 cm, field sizes from 0.5 to 2 mm, and demagnification from 4 to 16. Two general tendencies for such systems were observed: the nonuniformity of image defocusing due to the inhomogeneous interbeamlet space charge effect at large field sizes, and the high sensitivity of maximum beam current to column length at a fixed image beam size. Finally, the throughput versus acceleration voltage is evaluated under different assumptions of resolution, resist thickness, and column length. It is concluded that to achieve the throughput required by manufacturing beyond 0.1 mu m resolution, very aggressive design of a short column along with thin resist will be required.