O. Siegmund, J. McPhate UCB, SSL 1 SSL 8in Photocathode 3 rd Try 8” PC/Seal Test Chamber –<10 -9 Torr base vacuum, RGA operational, fully baked Same 5mm thick, 8.7” polished B33 window as try #2, never let up to air. –NiCr border electroded Baked at 375°C for 24 hours “ALL” visuals & photoresponse from #2 GONE Deposited Na 2 KSb photocathode RGA record for entire process Cathode everywhere but extreme corners –

O. Siegmund, J. McPhate UCB, SSL 2 8” -Na 2 KSb bialkali 3 rd Process Somewhat too blue, but was a short process, only 2 KSb cycles. Can add cycles next shot. Same window as #2 – still have surface contamination so next day QE was degraded. Uniformity much better than before. Generally ±15%.QE curve was measured at the upper right where it is ~0.9 (relative)

O. Siegmund, J. McPhate UCB, SSL 3 8” Na 2 KSb Process #2 - Comparison Uniformity measurements worse in middle and corners. Cathode 2A was very blue, and decayed during deposition process – indicative of possible window contamination #2A

O. Siegmund, J. McPhate UCB, SSL 4 8in Photocathode Plan Prepare new windows. Optimize cleaning processes and use oxygen plasma clean as last step (have run sample tests last week to verify). Deposit electrode with “X” conductor across the diagonals (tooling ready). Use larger 40mm alkali sources. Can shoot 3 or 4 cathodes in one pumpdown using Alkali/Sb materials, and employing high temperature vacuum bakes between.