R&D ERL SRF Electron Gun
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February 17-18, 2010 R&D ERL Andrew Burrill R&D ERL SRF Electron Gun Andrew Burrill February 17-18, 2010 SRF Electron Gun
description
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? - PowerPoint PPT Presentation
Transcript of R&D ERL SRF Electron Gun
February 17-18, 2010
R&D ERL
Andrew Burrill
R&D ERLSRF Electron Gun
Andrew Burrill
February 17-18, 2010
SRF Electron Gun
February 17-18, 2010
R&D ERL
Andrew Burrill
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
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February 17-18, 2010
R&D ERL
Andrew Burrill
SRF Electron Gun - Physics
Parameter Units ValueFrequency MHz 703.75Iris radius cm 5
Equator Diameter cm 37.9Cavity length cm 25
Beam kinetic energy MeV 2Peak electric field MV/m 35.7
Peak magnetic field A/m 58740 (73mT)Stored energy Joule 8.37
Ratio of Bmax/Emax mT/(MV/m) 2.1075Ratio of Emax/Eacc 1.3998
QRs (geometry factor) 111R/Q 62
Qe (external Q) 37000Power input MW 1
Maximum current mA 500Emittance at 1.4 nC m rms normalized 1.4
Cathode recess mm 1Cathode spot size mm diameter 5Emission phase Degrees 25
Longitudinal loss factor
V/pC 0.7
Transverse loss factor V/pC/m 32
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February 17-18, 2010
R&D ERL
Andrew Burrill
SRF Electron Gun Fabrication & Testing
• one polycrystalline & one large grain gun fabricated
• Polycrystaline at Jlab for processing and testing
• Initial VTA testing complete
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February 17-18, 2010
R&D ERL
Andrew Burrill
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.
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February 17-18, 2010
R&D ERL
Andrew Burrill
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
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February 17-18, 2010
R&D ERL
Andrew Burrill
Preliminary Cavity Test Data
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10.00 15.00 20.00 25.00 30.00 35.000
2
4
6
8
10
12
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1.00E+08
1.00E+09
1.00E+10
1.00E+11
704 MHz BNL Gun without Cathode stalk
power lossEpeak
Epeak (MV/m)
Pow
er L
oss
(W)
QoTesting notes:
r/Q = 61 Ohm, assumes beta=.587L = 8.5 cm (active length of cavity)Qext2 = 5.4e10, bench cal was 9.45e10Qext1 = 1.9e9, bench cal was 1.9e9Epeak/Eacc = 3.76
February 17-18, 2010
R&D ERL
Andrew Burrill
SRF Electron Gun Cryomodule
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February 17-18, 2010
R&D ERL
Andrew Burrill
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
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