• 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.

• B.L. Militsyn, B.D. Fell, L.B. Jones, J.W. McKenzie, K.J. Middleman
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• I. Burrows, R.J. Cash
  STFC/DL, Daresbury, Warrington, Cheshire
• H.E. Scheibler, A.S. Terekhov
  ISP, Novosibirsk

ALICE is an Energy Recovery Linac built at STFC Daresbury Laboratory to investigate the process of energy recovery. The project is an accelerator research facility intended to develop the technology and expertise required to build a New Light Source (NLS) in the UK based on a suite of Free-Electron Lasers. Currently the ALICE gun accommodates only a single photocathode at any one time, and the system must be vented to atmospheric pressure for photocathode replacement. To meet the stringent vacuum demands for good photocathode lifetime, the system then requires baking for up to three weeks. A new load-lock cathode preparation system has been designed as an upgrade to the ALICE gun. The load-lock can accommodate up to six photocathodes, and permits rapid transfer of photocathodes between the load-lock activation chamber and the gun, thus maintaining the vacuum. The photocathode preparation facility was successfully commissioned in spring 2009, and has since permitted a quantum yield of 15% to be achieved at a wavelength of 635 nm. Presently, a new gun vessel and photocathode transport system is under manufacture, with a view to this being fully-installed on ALICE in Spring 2012.

• Y.M. Saveliev, R. Bate, R.K. Buckley, S.R. Buckley, J.A. Clarke, P.A. Corlett, D.J. Dunning, A.R. Goulden, S.F. Hill, F. Jackson, S.P. Jamison, J.K. Jones, L.B. Jones, S. Leonard, P.A. McIntosh, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, A.J. Moss, B.D. Muratori, J.F. Orrett, S.M. Pattalwar, P.J. Phillips, D.J. Scott, E.A. Seddon, B.J.A. Shepherd, S.L. Smith, N. Thompson, A.E. Wheelhouse, P.H. Williams
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• P. Harrison, D.J. Holder, G.M. Holder, A.L. Schofield, P. Weightman, R.L. Williams
  The University of Liverpool, Liverpool
• D. Laundy
  STFC/DL, Daresbury, Warrington, Cheshire
• T. Powers
  JLAB, Newport News, Virginia
• G. Priebe, M. Surman
  STFC/DL/SRD, Daresbury, Warrington, Cheshire

Progress made in ALICE (Accelerators and Lasers In Combined Experiments) commissioning and a summary of the latest experimental results are presented in this paper. After an extensive work on beam loading effects in SC RF linac (booster) and linac cavities conditioning, ALICE can now operate in full energy recovery mode at the bunch charge of 40pC, the beam energy of 30MeV and train lengths of up to 100us. This improved operation of the machine resulted in generation of coherently enhanced broadband THz radiation with the energy of several tens of uJ per pulse and in successful demonstration of the Compton Backscattering x-ray source experiment. The next steps in the ALICE scientific programme are commissioning of the IR FEL and start of the research on the first non-scaling FFAG accelerator EMMA. Results from both projects will be also reported.