High Polarization and High Peak Current Compositionally Graded AlGaAs/GaAs Superlattice Photocathodes for RF Gun Applications

New experiments and technologies in the science of physics employ electrons with a certain and known polarization. Sources of these electrons typically have imperfect polarization less than 80 percent and low quantum efficiencies less than 1 percent. Increasing either or both of these device properties greatly enhances the physics research being undertaken in facilities such as high energy colliders. To increase the amount of extractable, polarized electron current from photocathodes, a new device design has been developed utilizing aluminum gallium arsenide alloy with graded aluminum composition. In the Phase I, several devices with the new design were created and tested. A 25 percent increase in quantum efficiency was measured in the experimental photocathode, validating the theoretical approach. For the Phase II, the design of the structure will be further refined, along with the semiconductor growth technology utilized to create the device. The program will follow a systematic approach of photocathode design, growth, and testing, with collected data fed back into the design for subsequent rounds. Commercial Applications and other Benefits as described by the awardee: This project will produce a highly efficient polarized electron source for use in experimental research at SLAC and other electron collider facilities. These devices have applications in other areas which include magnetic imaging research, surface analysis, Quantum computing and cryptography