SPRES study on surface of barium tungsten cathodes coated with os film

In order to study the characteristics of barium tungsten cathodes coated with Os film during activation, a photoelectron spectroscopy using synchrotron radiation (SPRES) at Beijing Synchrotron Radiation Laboratory is utilized. SPRES is a far more sensitive tool to determine surface composition than either XPS or AES. The cathode, manufactured by ourselves, has a stated impregnant composition of 6BaO/CaO/2Al₂O₃, a tungsten matrix porosity of 25-26%, and a sputter-deposited coating of Os approximately 0.35μm thick. The cathode is activated by heating according to A→B→C steps: A-step 950°C × 60 min, B-step 1050°C × 60 min, and C-step 1150°C × 60 min. The vacuum is kept below 1×10^-8 Pa during measurements. The photon energies for SPRES collection are 700 eV and 900 eV, and scan step is 0.16 eV. All photoemission spectra are adjusted by adjusting the Pt4f of the Pt slice welded to the cathode holder surface as 71.20 eV.