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Polarized GaAs photo cathode development and the preparation of Gatling Gun cathodes at BNL. The Single Cathode Activation Chamber. Outline. Motivation Single Preparation Tree The Cathode Holder The Service Flange Vacuum Management Current Status Summary. Motivation. - PowerPoint PPT Presentation
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Polarized GaAs photo cathode development and the
preparation of Gatling Gun cathodes at BNL
TheSingle Cathode Activation
Chamber
Outline
Motivation Single Preparation Tree
• The Cathode Holder• The Service Flange• Vacuum Management
Current Status Summary
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
Multiple Cathode Preparation System
Tree 1/4
Tree 2/4
Manipulator
Train
Grand Central
To gun chamber
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
Single Cathode System
Single Cathode SystemSupporting tripod
Single Cathode SystemActivation chamber (“Tree”)
Single Cathode SystemHorizontal manipulator (vacuum suitcase)
Single Cathode SystemConnector
Single Cathode SystemVertical manipulator
Single Cathode System
Single Cathode Preparation Tree
Single Cathode Preparation Tree
Leak valve for O2
Cooling water (in)Cooling water (out)Thermo coupleHeater (in)Heater (out)
Service flange (1st floor)
Single Cathode Preparation Tree2nd floor
HABS (eventually)Port for 650 nm / 780 nm laserAnodeViewport
Thermo coupleCooling water (in)Cooling water (out)Leak valve for H2
Power connector
HABS
Single Cathode Preparation Tree3rd floor
NEG pumpPressure gaugeIon pump
Single Cathode Preparation Tree4th floor
Cs dispenser (in)Cs dispenser (out)
Residual gas analyzer
Single Cathode Preparation TreeInside view
Feed through for Cs source (in)Feed through for Cs source (out)
Support rods for mask
Mask
Manipulator to move mask
Cs source
The Cathode Holder
10 x 10 mm2 GaAs crystal
Conical shape for self alignment, sealing & enhanced heat transfer
Spring for conformance & soft stop
Cap with 8mm opening for holding sample in place
Thermal Break
The Cathode Holder
The Service Flange
Heaterfeed throughOxygen
tubeMask
Cathode holder
Heater wire
Heaterwire
The Service Flange
Heater (out)
Leak valve for O2
Cooling water (in)
Cooling water (out)Thermo couple
Heater (in)
The Service Flange
Heater (out)
Leak valve for O2
Thermo couple Heater (in)
Heater filamentO2 nozzle
Cathode
Pumps and Vacuum
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 (VacLab Inc)
Main chamber
Pumps and Vacuum
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)
Cross
Pumps and Vacuum
Pumps• 15 l/s Ion pump (Gamma Vacuum)
Gauges• Convectron Gauge (Granville-Phillips)• Bayard-Alpert ionization gauge (Granville-Phillips)
Vacuum suitcase
Current Status
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
Acknowledgments
J. Pietz (Transfer Engineering) J. Walsh, W. Smith (Instrumentation Division) T. Seda, D. Pate (C-AD)