1. Monday Meeting 24 –
Narong Chanlek

2. 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

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

4. 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

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

6. 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.

7. 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

8. XPS data

9. 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)