Photoinjector Efficiency Enhancement using Surface Acoustic Waves

Current and future synchrotron radiation light sources and free electron laser facilities are in need of improvements in Electron Gun Technology, especially regarding the cost and efficiency of photoinjectors. Novel electron gun features are needed to enhance the intensity and reduce the emittances of electron bunches produced at a high repetition rate using laser excitation. The generation of Surface Acoustical Waves (SAW) on piezoelectric substrates is known to produce strong piezoelectric fields that propagate on the surface of the material. These fields significantly reduce the recombination probability of electrons and holes, increasing their radiative lifetime by orders of magnitude, which can result in enhanced quantum efficiency of photoemission. This project is developing the use of Surface Acoustic Waves on photocathodes to improve their efficiency, so that lower-power lasers can generate more intense electron beams having smaller emittances. Theory and simulations will be developed for the effect of SAW on photocathode efficiency for high-current conditions. We will perform modeling of a photoemission process in the presence of a moving super lattice generated by a surface sound wave propagating in piezoelectric substrates and evaluate changes in quantum efficiency caused by SAW Commercial Applications and Other Benefits: We propose to enhance the performance of electron guns with a new feature, surface acoustical waves. High-current, low-emittance electron guns are needed for development of high-brightness coherent light sources and for basic research with electron beams. Photoemission enhancement techniques will be developed that may also be used for production of more efficient photovoltaic materials.