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SSL 8in Photocathode 3 rd Try

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

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SSL 8in Photocathode 3 rd Try

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  1. SSL 8in Photocathode 3rd Try • 8” PC/Seal Test Chamber • <10-9Torr base vacuum, RGA operational, fully baked • Same 5mm thick, 8.7” polished B33 windowas try #2, never let up to air. • NiCr border electroded • Baked at 375°C for 24 hours“ALL” visuals & photoresponse from #2 GONE • Deposited Na2KSb photocathode • RGA record for entire process • Cathode everywhere but extreme corners –

  2. 8” -Na2KSb bialkali 3rd Process 1.09 0.91 0.94 0.88 0.85 0.82 1.15 0.94 1.00 0.88 1.09 0.91 0.79 0.88 1.00 0.97 1.27 Somewhat too blue, but was ashort 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).

  3. 8” Na2KSb Process #2 - Comparison 0.85 0.64 0.58 0.55 1.06 0.96 0.61 0.50 0.98 #2A Cathode 2A was very blue, and decayedduring deposition process – indicative of possible window contamination. Uniformity measurementsworse in middle and corners.

  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.

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