An electron beam apparatus that includes a vacuum chamber, a large-area cathode disposed in the vacuum chamber, and a first power supply connected to the cathode. The first power supply is configured to apply a negative voltage to the cathode sufficient to cause the cathode to emit electrons toward a substrate disposed in the vacuum chamber. The electron beam apparatus further includes an anode positioned between the large-area cathode and the substrate. The anode is made from aluminum. The electron beam apparatus further includes a second power supply connected to the anode, wherein the second power supply is configured to apply a voltage to the anode that is positive relative to the voltage applied to the cathode.