• N. Chanlek, R.M. Jones
  UMAN, Manchester
• J.D. Herbert, L.B. Jones, K.J. Middleman, B.L. Militsyn
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

Gallium Arsenide (GaAs) photocathodes have in recent year been widely used and have become the focus for use in modern accelerators and light sources such as the Accelerators and Lasers in Combined Experiments (ALICE) and the International Linear Collider (ILC). Once activated to a Negative Electron Affinity (NEA) state and illuminated by a laser, these materials can be used as a high-brightness source of both polarised and un-polarised electrons. This work presents an effective preparation procedure including heat cleaning, atomic hydrogen cleaning and the activation process for NEA GaAs photocathode. The stability of quantum efficiency (QE) and lifetime of NEA GaAs photocathode have been studied in the load-lock and photocathode preparation system for the ALICE photo- electron gun which has a base pressure in the order of 10^-11 mbar. These studies are also supported with experimental evidence from surface science techniques such as Photoelectron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED) to demonstrate the processes at the atomic level.