Enhanced Quantum Efficiency of Photocathodes with Polarized Emission

The negative-electron-affinity (NEA) photocathodes which produce polarized electrons are a vital component of electron accelerators such as that at the Stanford Linear Accelerator Center (SLAC), which is used in the current generation of photocathodes. Quantum efficiencies thus far are on the order of 1%, meaning only 1% of the photons hitting the photocathode result in the emission of an electron. Increasing the quantum efficiency is vital to increasing the usable electron current. The end result of the combined Phase I Phase II effort will be a new generation of robust photocathodes capable of yielding intense, highly polarized electron beams for use in advanced electron colliders. We have previously achieved & gt 85% polarization using a strained-superlattice formed from alternating layers of GaAs and GaAsP approximately ten monolayers thick. For this program we will increase the quantum efficiency and extractable polarization current by adding an optical reflector to the design. Commercial Applications and Other Benefits: Spin polarized low energy electron microscopes (SPLEEM) and future colliders will benefit from a polarized electron beam with increased intensity.