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

This project outlines the development of a system to activate multiple GaAs crystals for spin-polarized electrons production in the Gatling Gun. The Single Cathode Activation Chamber includes design details, motivation, and the current status of the project. From preparation to vacuum management, each step is carefully planned to achieve successful activation of 20 GaAs crystals simultaneously. The setup includes a comprehensive Cathode Preparation Tree, Service Flange, and Vacuum Management system to facilitate the process. Collaborations with experts in Transfer Engineering, Instrumentation Division, and C-AD have been crucial for the project's progress. The project aims to revolutionize electron production for advanced applications.

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

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  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)

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