HIGH-CURRENT SRF CAVITY DESIGN€¦ · 11July2005 Dave Meidlinger (MSU, NSCL) 2005 SRF Workshop...
Transcript of HIGH-CURRENT SRF CAVITY DESIGN€¦ · 11July2005 Dave Meidlinger (MSU, NSCL) 2005 SRF Workshop...
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
HIGH-CURRENT SRF CAVITYDESIGN
Dave MeidlingerTerry Grimm
Walter Hartung
![Page 2: HIGH-CURRENT SRF CAVITY DESIGN€¦ · 11July2005 Dave Meidlinger (MSU, NSCL) 2005 SRF Workshop Issues Driving Cavity Design ¾Transverse multipass/multibunch beam breakup ¾HOM power](https://reader035.fdocuments.in/reader035/viewer/2022071217/604b96323e640306874e2669/html5/thumbnails/2.jpg)
11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
OUTLINE
• Introduction• Primary Concerns that Direct Cavity Design• 6-Cell Elliptical Cavity• 2-Cell Injection Cavity• TM012 Cavity• Summary
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
Objective
• High current ERL (100’s mA) (10 MeV-100’s MeV)
• Simplified HOM damping
• Simplified cavity and cryomodule
• Lower cost
Electron source
Electron cooling / FEL
Beam dump
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
Issues Driving Cavity Design
Transverse multipass/multibunch beam breakup
HOM power dissipation
AVGlossHOM IqkP =
( )QRth Qf
I 1∝
m
mm Q
Rfk ⎟⎟⎠
⎞⎜⎜⎝
⎛=
2π
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
Bunch Frequency
• Setting fbunch = fRFCan simplify HOM damping for a large enough diameter beam pipe.
i.e. all dangerous HOMs above cutoff (low Qs)
Lowers bunch charge for same average current
bunch
AVGlossAVGlossHOM f
IkIqkP2
==
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
frequency
fRF
frequency
CUTOFFfRF
frequency
CUTOFFfRF
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
frequency
fRF
frequency
CUTOFFfRF
frequency
CUTOFFfRF
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
frequency
fRF
frequency
CUTOFFfRF
frequency
CUTOFFfRF
( )QRth Qf
I 1∝
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
HOM Qs
• Trapped modes and HOM couplers – 2100 MHz (JLAB FEL)– Q~ 106, Ith ~ 10 mA
• Above cutoff– Damp in beampipe with ferrite, coupler or wall
losses– Q~ 103 , Ith ~ 10 A
( )QRth Qf
I 1∝
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
Elliptical Cavity Designs
• 100's mA beam current• 1.5 GHz• TM01 cutoff ~1.95fRF and TE11 cutoff ~1.5fRF
• 6o wall angle• Epk / Bpk equals TeSLA value• 2 cells β > 0.50• 6 cells β = 1.0
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
Transit Time Factors
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
v / c
TT
6-Cell
2-Cell
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
Cavity Figures of Merit
2-Cell 6-Cell
Ep / EA - 2.16 2.19Bp / EA mT / (MV/m) 4.59 4.68R / Q Ω 165 535
Geometric β - 0.81 1.0
275
3.9
6Number of Cells - 2
Cell-to-cell Coupling % 2.8
Geometrical Factor Ω 228
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
2-Cell Surface Fields
0 5 10 15 20 25
distance along surface (cm)
|B|
|E|
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
6-Cell Surface Fields
0 10 20 30 40 50 60
distance along surface (cm)
|B||E|
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
-50 -40 -30 -20 -10 0 10 20 30 40 50
axial distance (cm)
Electric Field Profile
2.7% fieldunflatness
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
6-Cell BNL Ampere Class TeSLA CEBAF
Ep / EA - 2.19 2.0 2.00 2.56Bp / EA mT / (MV/m) 4.68 5.8 4.26 4.56R / Q Ω 535 404 1036 482.5
5
Ω
%
-
273.8
3.29
Number of Cells 6 5 9
Cell-to-cell Coupling 3.9 3 1.9
Geometrical Factor 275 225 270
6-Cell Elliptical
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
TM012 Cavity
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
TM012 Cavity
• AdvantagesSimple shape
Easier fabricationBetter film depositionLow loss factor
Single cellEasier tuning
• DisadvantagesHigh peak magnetic fieldsDamping parasitic modes below the accelerating modeLow shunt impedance
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
TM012 Cavity
TM012Ep / EA - 3.06Bp / EA mT / (MV/m) 8.40
Voltage Gain MV 2Ep MV / m 4.8Bp mT / (MV/m) 13.19
R / Q Ω 55
k|| V / pC 0.37
Frequency MHz 353
beam pipe radius cm 17
Geometrical Factor Ω 476
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
TM012 SOLEILEp / EA - 3.06 2Bp / EA mT / (MV/m) 8.40 4.5
Voltage Gain MV 2 2Ep MV / m 4.8 9.42Bp mT / (MV/m) 13.19 21.2
R / Q Ω 55 90
k|| V / pC 0.37 0.75
Frequency MHz 353 353
beam pipe radius cm 17 13
Geometrical Factor Ω 476
TM012 Cavity
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
TM012 SOLEILEp / EA - 3.06 2Bp / EA mT / (MV/m) 8.40 4.5
Voltage Gain MV 2 2Ep MV / m 4.8 9.42Bp mT / (MV/m) 13.19 21.2
R / Q Ω 55 90
k|| V / pC 0.37 0.75
Frequency MHz 353 353
beam pipe radius cm 17 13
Geometrical Factor Ω 476
TM012 Cavity
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
Summary
• Objective: 100's mA of beam current with a simplified design
• Concept: Fill every RF bucket so that all dangerous HOMs are above cutoff.
• 2-Cell injection cavity and 6-Cell cavity designed for this purpose.
• Fabrication of 2-cell prototype to be completed by end of 2005.
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11July2005 Dave Meidlinger (MSU, NSCL)2005 SRF Workshop
HIGH-CURRENT SRF CAVITYDESIGN
Dave MeidlingerTerry Grimm
Walter Hartung