1. Bialkali Cathode Process Program
Process samples to optimize QE and bandpass K2CsSb cathodes
Small sample test runs, 1.22”
Substrate material tests
Fused silica and B33
No ITO/Al2O3 ALD underlayers
5th run(s) in small tank used to process Bialkali cathodes (1.22”).
Can now deposit 4 simultaneous samples/1 cathode shoot, cover area ~4” wide. 1

2. Run #5 test Bialkali Cathodes.
New geometry,
Cathode too thin
Longer bakeout
& thicker
Lower temp / higher
Alkali vapor pressure
1st deposition
2nd deposition
3rd deposition
Getting the optimal conditions and geometry sorted out
Results suggest some cathode area non-uniformities

3. Cathode/Substrate Plans
Can do more tweaking to optimize depositions need to rotate samples to see if non-uniformity is in the deposition geometry or is just the sample type
Now have new samples with ITO/Al2O3 ALD underlayers
Will use new substrates for next run(s) after we deposit inconel evaporated borders
New larger cathode/seal tank is close to being ready, will switch tanks and commission as soon as tooling is done
The sensitivity of the activated photocathode is considerably higher, with a quantum efficiency of as high as 37% at about 450 Å and a sensitivity cut off energy of about 6.2 eV. The observed decrease of sensitivity at 988 and 520 Å (and probably not observed at ~670 Å) is likely to correspond to 2xEgap+Eaff,, 4xEgap+Eaff,, and 3xEgap+Eaff,, respectively. A much better spectral continuity of the illumination source is required in order to study the UV absorption fine structure.