Monday Meeting 24 – 11 - 08 Narong Chanlek

Mechanical Drawing of the J-Lab / Daresbury Laboratory ERLP DC Gun Review The photo injector system for ALICE Require an electron beam of 100 mA with a normalised emittance of < 2 pi mm mrad DC photo gun based on JLAB design Use the GaAs photocathode The GaAs photocathode need to be activated to the NEA state cathode Laser - e Solenoid Mechanical Drawing of the J-Lab / Daresbury Laboratory ERLP DC Gun

Review SF6 XHV Cathode ball Ceramic Cathode e Stem Anode Plate - Laser Vessel removed - e Laser XHV Stem Anode Plate

Review The GaAs surface needs to be cleaned before activated to NEA state Cleaning procedures - Heat cleaning - Atomic hydrogen cleaning Activated by applying caesium and oxidant (either O2 or NF3) onto its clean crystal surface Quantum efficiency and cathode lifetime used to determine the cathode performance Study a range of photocathode material in detail, investigating and developing the various fundamental processes, such as preparation process to maximise their performance The initial focus will be on GaAs, but alternative materials such as Cs2Te and InGaP will be also studied

Surface analysis chamber What I have done Manipulator Surface analysis chamber Load-lock chamber Transfer arm Preparation chamber

X-ray Photoelectron Spectroscopy (XPS) Technique Used to investigate the chemical composition of a material surface. Irradiates a material surface with soft x-rays, Mg K or Al K in a UHV. Cause the electrons to be emitted by the photoelectric effect. The chemical composition of a material is identified by analysing the kinetic energy and the number of emitted electrons.

Low Energy Electron Diffraction (LEED) Technique Used to determine the surface structures of a material Incidents a beam of low energy electrons into the sample surface The electron beam will be diffracted following the Bragg condition. Determine the surface structure from the intensity and diffraction pattern of the back-scattered electrons

XPS data

What I have been doing Upgrading the experimental set up in order to successfully operate the Hydrogen source cracker in the cleaning procedure Fixing the LEED optic Writing the paper my PESP2008 paper which will be published as part of the SPIN2008 Proceedings, by the American Institute of Physics (AIP) Generating more results and reproducing the results in order to publish something next year (if it’s possible)