Polarized GaAs photo cathode development and the preparation of Gatling Gun cathodes at BNL

1. Polarized GaAs photo cathode development and the preparation of Gatling Gun cathodes at BNL TheSingle Cathode ActivationChamber

2. Outline • Motivation • Single Preparation Tree • The Cathode Holder • The Service Flange • Vacuum Management • Current Status • Summary

3. Motivation • Gatling Gun is going to use GaAs crystals to produce spin polarized electrons • GaAs crystals need to be “activated” before electron production • Procedure of activating one GaAs crystal at a time is well understood and state of the art • Gatling Gun will use 20 crystals simultaneously • Activating 20 GaAs crystals is challenging

4. Multiple Cathode Preparation System Tree 2/4 Tree 1/4 Grand Central To gun chamber Manipulator Train

5. Single Preparation System • Going from 2 beams to 20 beams is easy compared to going from 1 beam to 2 • Proof of Principle can and will be done by using 2 cathodes only • Develop a single (manually operated) preparation system to feed the Gatling Gun • Use a transport vessel to transport activated cathodes between Tree and Gun

6. Single Cathode System

7. Single Cathode System Supporting tripod

8. Single Cathode System Activation chamber (“Tree”)

9. Single Cathode System Horizontal manipulator (vacuum suitcase)

10. Single Cathode System Connector

11. Single Cathode System Vertical manipulator

12. Single Cathode System

13. Single Cathode Preparation Tree

14. Single Cathode Preparation Tree Service flange (1st floor) Leak valve for O2 Cooling water (in) Cooling water (out) Thermo couple Heater (in) Heater (out)

15. Single Cathode Preparation Tree 2nd floor HABS Thermo couple Cooling water (in) Cooling water (out) Leak valve for H2 Power connector HABS (eventually) Port for 650 nm / 780 nm laser Anode Viewport

16. Single Cathode Preparation Tree 3rd floor NEG pump Pressure gauge Ion pump

17. Single Cathode Preparation Tree 4th floor Residual gas analyzer Cs dispenser (in) Cs dispenser (out)

18. Single Cathode Preparation Tree Inside view Manipulator to move mask Feed through for Cs source (in) Feed through for Cs source (out) Support rods for mask Cs source Mask

19. The Cathode Holder 10 x 10 mm2GaAs crystal Cap with 8mm opening for holding sample in place Conical shape for self alignment, sealing & enhanced heat transfer Thermal Break Spring for conformance & soft stop

20. The Cathode Holder

21. The Service Flange Heater feed through Mask Oxygen tube Heater wire Heater wire Cathode holder

22. The Service Flange Heater (out) Leak valve for O2 Heater (in) Cooling water (in) Cooling water (out) Thermo couple

23. The Service Flange Thermo couple Heater (in) Heater (out) Cathode Leak valve for O2 Heater filament O2 nozzle

24. Pumps and Vacuum Main chamber • Pumps • 15 l/s Ion pump (Gamma Vacuum) • 80 l/s Ion pump (Gamma Vacuum) • 2x 400 l/s CapaciTorr NEG pumps (SAES Getters) • Gauges • RGA (Stanford Research Systems) • Extremely High Vacuum Gauge AxTRAN (Ulvac) • Hot-Cathode Ionization Gauge 3BG-03 (VacLabInc)

25. Pumps and Vacuum Cross • Pumps • 2 l/s Dry Scroll pump (Agilent/Varian) • 50 l/s Turbo pump (Agilent/Varian) • 15 l/s Ion pump (Gamma Vacuum) • Gauges • Convectron Gauge (Granville-Phillips) • Bayard-Alpert ionization gauge (Granville-Phillips)

26. Pumps and Vacuum Vacuum suitcase • Pumps • 15 l/s Ion pump (Gamma Vacuum) • Gauges • Convectron Gauge (Granville-Phillips) • Bayard-Alpert ionization gauge (Granville-Phillips)

27. Current Status

28. Summary • Use single cathode preparation tree (“Tree”) to supply Gatling Gun with two cathodes at a time • In the beginning use unpolarized Bulk-GaAs samples • Tree is already assembled and under vacuum in Building 966 • First activation will take place very soon

29. Acknowledgments • J. Pietz (Transfer Engineering) • J. Walsh, W. Smith (Instrumentation Division) • T. Seda, D. Pate (C-AD)