february 17-18, 2010 r&d erl david pate r&d erl photocathode deposition and transport system...
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February 17-18, 2010
R&D ERL
David Pate
R&D ERL Photocathode Deposition
and Transport System
David Pate
February 17-18, 2010
Photocathode Deposition and Transport System
February 17-18, 2010
R&D ERL
David Pate
Photocathode Deposition and Transport System
2
February 17-18, 2010
R&D ERL
David Pate
Outline
• Design criteria and principles
• Subsystems description
• Photos
• Status and overall schedule
February 17-18, 2010
R&D ERL
David Pate
Design Criteria and Principles
• Deposit CsK2Sb photocathodes on the end of a removable cathode stalk for use in our 704 MHz SRF injector. – Additional capabilities for manufacturing and testing cesium
dispenser photocathodes being developed by University of Maryland.
• Install, remove, rejuvenate, & replace cathode without exposing source or cathode to atmosphere.
• Deposit Cs, K, & Sb on cathode tip surface at pressures in the 10-10 to 10-9 Torr range.
• Heat cathode as high as 850ºC for cleaning and maintain 130ºC to 150 ºC during deposition.
• Remove & replace deposition sources without breaking deposition chamber vacuum.
• Be able to negotiate BNL ERL facility labyrinth.• Provide capability for in-situ QE measurement.
February 17-18, 2010
R&D ERL
David Pate
Subsystems Description
Deposition System• Deposition sources for Cs, K,
and Sb• All-metal construction
including gate valves-all bakeable to 250oC
• 250 l/s ion pump with (2) NEGs, predictable base pressure 10-10 torr range after bakeout
• Radiant heater for cathode tip cleaning
February 17-18, 2010
R&D ERL
David Pate
Subsystems Description Cont’d
Deposition System Cont’d• SAES alkali metal
dispensers for Cs & K; heated baffled box for Sb
• Rough pumping by oil-free TMP
• Deposition process controlled by quartz crystal monitor
• Laser port and collector for QE measurement
February 17-18, 2010
R&D ERL
David Pate
Subsystems Description Cont’d
Transport System
• Two vacuum crosses separated by long stroke bellows
• 200 l/s Ion pump on front cross; 40 l/s pump on rear cross (additional NEGs)
• All metal construction, all components bakeable to 250oC
• (2) Dedicated transport carts for cathode assembly
February 17-18, 2010
R&D ERL
David Pate
Photo of Deposition and Transport System
February 17-18, 2010
R&D ERL
David Pate
Status and Overall Schedule
Deposition System• Deposition system delivery from AES• All systems tested and modified where
necessary• Redesign K and Sb source arms completed• Base pressure of 3.2 x 10-10 torr established• Awaiting source installation and 2500C bake
February 17-18, 2010
R&D ERL
David Pate
Status and Overall Schedule-Continued
Transport Cart-1&2• Delivery of both transport cart from AES• Unable to obtain base vacuum pressure• Both transport carts dissembled by BNL and AES• Parts cleaned at AES, vacuum baked at BNL• Ion pumps returned to GAMMA for rebuild• Redesign of cathode flexible cooling lines and TCs• Redesign of cathode stalk guide tube• Order placed for addition of NEG pumps
February 17-18, 2010
R&D ERL
David Pate
Commissioning Plan
• The production of a cathode requires a transport cart tested and operational.
• We look forward to producing a cathode and testing the deposition system when a transport cart becomes available, which we anticipate will be first quarter 2010.
February 17-18, 2010
R&D ERL
David Pate
Operation Instructions
• Will be developed using an initial recipe for cathode production developed from the second generation deposition system
• The AES deposition system uses similar technology to the second generation deposition system