Polarized GaAs photo cathode development and the preparation of Gatling Gun cathodes at BNL
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Transcript of Polarized GaAs photo cathode development and the preparation of Gatling Gun cathodes at BNL
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Polarized GaAs photo cathode development and the
preparation of Gatling Gun cathodes at BNL
TheSingle Cathode Activation
Chamber
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Outline
Motivation Single Preparation Tree
• The Cathode Holder• The Service Flange• Vacuum Management
Current Status Summary
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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
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Multiple Cathode Preparation System
Tree 1/4
Tree 2/4
Manipulator
Train
Grand Central
To gun chamber
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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
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Single Cathode System
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Single Cathode SystemSupporting tripod
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Single Cathode SystemActivation chamber (“Tree”)
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Single Cathode SystemHorizontal manipulator (vacuum suitcase)
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Single Cathode SystemConnector
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Single Cathode SystemVertical manipulator
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Single Cathode System
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Single Cathode Preparation Tree
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Single Cathode Preparation Tree
Leak valve for O2
Cooling water (in)Cooling water (out)Thermo coupleHeater (in)Heater (out)
Service flange (1st floor)
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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
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Single Cathode Preparation Tree3rd floor
NEG pumpPressure gaugeIon pump
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Single Cathode Preparation Tree4th floor
Cs dispenser (in)Cs dispenser (out)
Residual gas analyzer
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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
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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
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The Cathode Holder
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The Service Flange
Heaterfeed throughOxygen
tubeMask
Cathode holder
Heater wire
Heaterwire
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The Service Flange
Heater (out)
Leak valve for O2
Cooling water (in)
Cooling water (out)Thermo couple
Heater (in)
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The Service Flange
Heater (out)
Leak valve for O2
Thermo couple Heater (in)
Heater filamentO2 nozzle
Cathode
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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
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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
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Pumps and Vacuum
Pumps• 15 l/s Ion pump (Gamma Vacuum)
Gauges• Convectron Gauge (Granville-Phillips)• Bayard-Alpert ionization gauge (Granville-Phillips)
Vacuum suitcase
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Current Status
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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
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Acknowledgments
J. Pietz (Transfer Engineering) J. Walsh, W. Smith (Instrumentation Division) T. Seda, D. Pate (C-AD)