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Electron Beam Generation Based On Negative Electron Affinity Photocathodes

A negative electron affinity (NEA) GaAs photocathode has been used to generate continuous and pulsed electron beams for electron microscopy and time resolved electron beam metrology. Short electron pulses are emitted from the photocathode when excited by a mode locked laser. Laser pulsing the cathode eliminates the need for complex electron beam blanking optics when performing time domain metrology. The GaAs photocathode exhibits a brightness comparable to LaB6 and is stable enough to display real time TV images in both the continuous and pulsed modes of operation. In the time resolved mode, the temporal resolution of the cathode is currently limited by the laser pulse duration, which is approximately 1 ns.