1. Bialkali Cathode Process Program
Small window cathode development, 1.22” samples
Process samples to optimize QE and bandpass
Na2KSb, K2CsSb cathodes
Use several substrate materials, SiO2, verify B33
Test MgO/ITO/conductor underlayer for cathodes
Large size window cathode study, 8” windows.
Study source alkali design for large cathodes
Develop techniques to make larger area uniform QE
Optimize cathode QE levels
Test metal/ITO conductor underlayer for cathodes
Test metalization and sealing techniques
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.

2. 1.22” Substrate Sample test Bialkali Cathodes.
Small sample test runs, 1.22”
Substrate material tests
Fused silica and B33
ITO and MgO ALD layers
Preparing 2nd run in small tank used to process Bialkali cathodes (1.22”).
Can now deposit 4 simultaneous samples/1 cathode shoot. 2

3. ALD ITO/MgO Layer Properties for Windows
1.22” samples
Quartz
Quartz + ITO 4.5nm
Quartz +ITO + MgO 5nm
1.22” samples deconvloved
ITO 4.5nm
ITO + MgO 5nm
Red
Blue
Black
Black
Blue
Samples coated by Joe Libera, measured by Lisa Pawlowicz
Our resistance measurements give about
104 to 105
Ohms/sq,
So very much comparable
to CERN.
Braem, NIMA 2003

4. Cathode Process Equipment Status
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.
Large 16” flange tank, takes full size windows (8.7”) to test
Quantum efficiency
QE Uniformity
Seal tests Status - design done, being welded up
Evaporation tooling for 8.7”
Windows and 8” MCPs.
Status, done except for one part

5. 8” Tube and Cathode Process Tank System
3” window test article on metal frame with Indium seal
Indium wells and ceramic frames for detector window seal tests are on order,
Will need to be brazed before seal tests.
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.
UHV 18” process Chamber:-
Status:- chamber in fab - due Sept, other hardware mostly in house.

6. Cathode/Substrate Factoids
Wet cleaning of ITO / MgO ALD coat is OK
Oxygen plasma cleaning of ITO / MgO is NOT OK
Proper pre cleaning of window substrates essential and includes precautions for handling
ITO 4.5nm has UV transmission and conductivity as predicted
MgO 5nm UV transmission is good
No problems with inconel evaporated borders good adhesion/conduction
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.