O. Siegmund, J. McPhate UCB, SSL 1

8in Photocathode 2nd Try

• 8” PC/Seal Test Chamber– <10-9 Torr base vacuum, RGA operational, fully baked

• Chamber configured for 8in depositions• 5mm thick, 8.7” polished B33 window

– NiCr border electroded

• Deposited Na2KSb photocathode

• RGA record for entire process• Cathode everywhere but extreme corners –

However, cathode very blue, shows signs of contamination (window surface??).

O. Siegmund, J. McPhate UCB, SSL 2

8” bialkali 2nd Process

Shooting the cathodeWindow post deposit – 9” PCProper contact! Only small corner uncoated.

O. Siegmund, J. McPhate UCB, SSL 3

8” Process #2 -Na2KSb

Uniformity measurementsworse in middle and corners. Indicative of a conductivity problem. Not unexpected for a thin cathode. Need conductor “X” stripes.

Cathode is very blue, multiply QE by 1.1 to account for process tankwindow transmission. Also decayedduring deposition process – indicative of insufficient alkali pressure and possible window contamination.

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8in#2, 12-20-11

Tube Q...

Wavelength (nm)

QE

O. Siegmund, J. McPhate UCB, SSL 4

8” Cathode Process Plan

• Second cathode is thin – blue and shows signs of window contamination, poor conductivity

• First bake out cathode and shoot a second for extra data• Add a conductor “X” and border and clean a new window• Upgrade alkali channels to 40mm to increase pressure• Investigate window surface condition for tin/contamination• Continue process runs