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SRF Electron Gun. R&D ERL SRF Electron Gun. Andrew Burrill. February 17-18, 2010. SRF Electron Gun . What are we building? ½ cell SRF injector with an independently cooled demountable cathode stalk designed for use with CsK 2 Sb photocathodes What makes this unique?
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SRF Electron Gun R&D ERLSRF Electron Gun Andrew Burrill February 17-18, 2010
SRF Electron Gun What are we building? ½ cell SRF injector with an independently cooled demountable cathode stalk designed for use with CsK2Sb photocathodes What makes this unique? • Ability to couple 1 MW of RF power to the gun via 2 coaxial couplers • Novel pringle tip FPC to improve coupling and reduce beam effect on beam • Plans to deliver up to 500 mA average current from the gun • Cathode delivery system can be outfitted with a wide variety of cathode materials from metals to dispensers • Use of a quarter wavelength RF choke joint for the cathode insertion. • High Temperature Superconducting Solenoid
SRF Electron Gun Fabrication & Testing • one polycrystalline & one large grain gun fabricated • Polycrystaline at Jlab for processing and testing • Initial VTA testing complete
Cavity Processing • Cavity was tuned to pre-determined frequency prior to shipment to Jlab • Cavity was given a bulk, 140 um BCP treatment • 10 hours at 600C Furnace treatment • 25 um BCP, HPR, Assembly • Ultrasonic thickness measurements are being taken along the way. • To date show an actual etch rate ~60% of the sample etch rate.
Cavity Testing Summary • Preliminary VTA test completed last week on the cavity without the VTA cathode inserted. • Goal was to measure the performance of the cavity independent of the choke joint. • Data shows signs of multipacting/ radiation in the cavity requiring further investigation • Multipacting analysis did not look at the cavity without the cathode stalk as this is not a useful operational mode of the cavity • Low Field Q value was 1e10 in line with superfish simulations • Goal for the next test is the install the VTA cathode and provide a DC bias to help suppress multipacting in the choke region. • This should help identify the location of the multipacting
Summary • Cavity is progressing well in the processing and testing phase • FPC conditioning should take place by end of April • Hermetic String Assembly complete by end of August • Installation into cryomodule by December • Testing in early 2011