16-18 May 2011 LARP CM16 ODU/JLAB PARALLEL-BAR CAVITY DEVELOPMENT Jean Delayen Subashini de Silva Center for Accelerator Science Old Dominion University and Thomas Jefferson National Accelerator Facility Page 1
Parallel Bar Cavity Activities at ODU/JLab • Deflecting Cavity – Jefferson Lab 12 GeV Upgrade (499 MHz) (DOE-NP, ODU-Niowave P1 STTR completed) – Project-X (365.6 MHz ) (ODU-Niowave P1 STTR completed, P2 submitted) • Crab Cavity – LHC Luminosity Upgrade (400 MHz) (LARP, ODU-Niowave P2 STTR) – Electron-ion Collider (750 MHz) (ODU-Niowave P1 STTR completed, P2 submitted) Page 2
Parallel-bar Cavity Properties • Compact design • Supports low frequencies • Fundamental deflecting/crabbing mode has the lowest frequency • No LOMs, no need for notch filter in HOM coupler • Nearest HOM widely separated ( ~ 150 MHz) • Low surface fields and high shunt impedance • Good balance between peak surface electric and magnetic field • Criteria: E p <35 MV/m, B p <80 mT Page 3
Parallel Bar Cavity Concept Two Fundamental TEM Modes – 0 mode :- Accelerating mode – π mode :- Deflecting or crabbing mode TEM Resonant Lines Page 4
Parallel-bar Cavity Concept E field on mid plane B field on top plane (Along the beam line) Deflection is due to the interaction with the Electric Field Page 5
Dimensional Constraints 499 MHz Deflecting Cavity for JLab Upgrade 400 MHz Crabbing Cavity for LHC 4 th Pass Local Scheme at IP5 Beam Line 450 mm 42 R = 20 mm 300 150 mm 5 th Pass mm B 1 B 2 mm Beam Line 194 680 mm mm Hall A V T Global scheme : Hall B Separation between beam pipes – 420 mm Hall C No dimensional constraints in Project-X and ELIC deflecting/crabbing designs Page 6
Evolution of 499 MHz Designs Page 7
Properties of 499 MHz Designs (A) (B) (C) (D) KEK Parameter Units Fig. 1 Fig. 3 Fig. 3 Fig. 3 Cavity [2] Frequency of π mode 499.2 499.0 499.0 499.0 508.9 MHz λ /2 of π mode 300.4 300.4 300.4 300.4 294.8 mm Frequency of 0 mode 517.8 622.8 794.0 911.5 - MHz Frequency of near neighbour mode 517.8 622.8 736.0 753.1 410.0 MHz Frequency of lower order mode - - - - 410.0 MHz Cavity length 394.4 345.0 345.0 345.0 299.8 mm Cavity diameter / width 290.0 319.9 281.2 285.2 866.0 mm Cavity height 304.8 - - - 483.0 mm Bars width at waist 67.0 65.0 65.0 65.0 - mm Bars length 284.0 275.0 275.0 275.0 - mm Bars height / curved height 304.8 300.0 272.7 275.9 - Aperture diameter 40.0 40.0 40.0 40.0 130.0 mm Deflecting voltage ( V T * ) 0.3 0.3 0.3 0.3 0.3 MV Peak electric field ( E P * ) 1.85 2.03 2.4 2.63 4.24 MV/m Peak magnetic field ( B P * ) 6.69 6.33 5.6 5.72 12.23 mT * / E P * 3.62 3.11 2.31 2.18 2.88 mT/(MV/m) B P Energy content ( U * ) 0.031 0.033 0.034 0.039 - J Geometrical factor 67.96 63.98 83.2 85.5 220 Ω [ R / Q ] T 933.98 875.7 839.5 735.6 46.7 Ω 5.6×10 4 7.0×10 4 6.3×10 4 1.03×10 4 Ω 2 6.3×10 4 R T R S * = 1 MV/m At E T Page 8
HOM Properties of 499 MHz Designs 1.0E+03 1.0E+03 Ex, Hy Ez Ey, Hx Ex, Hy Ez Ey, Hx 1.0E+02 1.0E+02 1.0E+01 1.0E+01 R/Q ( Ω ) R/Q ( Ω ) 1.0E+00 1.0E+00 1.0E-01 1.0E-01 1.0E-02 1.0E-02 1.0E-03 0 500 1000 1500 2000 0 500 1000 1500 2000 Frequency (MHz) Frequency (MHz) 1.0E+03 1.0E+03 Ex, Hy Ez Ey, Hx Ex, Hy Ez Ey, Hx 1.0E+02 1.0E+02 1.0E+01 R/Q ( Ω ) R/Q ( Ω ) 1.0E+01 1.0E+00 1.0E+00 1.0E-01 1.0E-02 1.0E-01 0 500 1000 1500 2000 0 500 1000 1500 2000 Frequency (MHz) Frequency (MHz) Page 9
Off Axis Nonlinearities Along x [Rectangular] Along x [Cylindrical] Along y [Rectangular] Along y [Cylindrical] 1.05 1.00 Normalized V T along x Normalized V T along y 1.04 0.99 1.03 0.98 1.02 0.97 R 1.01 0.96 1.00 0.95 -20 -10 0 10 20 Offset from the beam axis (mm) Page 10
499 MHz Mechanical Study – Stress Analysis Base model • 3mm thickness Niobium • room temperature • 2.2 atm absolute pressure The model shows above 10000 psi in the cylindrical body Page 11
499 MHz Mechanical Study – Stress Analysis • The cavity has formed head instead of flat heads • Three reinforcing ribs are added • The stress in main body decreased below 7000 psi • The local high stress was developed at the body and rib joint • These local area will be yielded but it does not greatly affect the cavity shape. (confirm this statement please) Page 12
499 MHz Mechanical Study Stress and Deformation Analysis • Stress under 1 atm (14.7 psi) absolute pressure • After the cool down the cavity will be under less than 1 atm pressure • Again there is the same area showing above 7000 psi but it’s limited local where it does not affect much on RF characteristics • Deformation due to the external pressure 1 atm • This deformed model will be (should be) RF studied Page 13
Fabrication Process – 499 MHz Prototype Page 14
Multipacting Analysis • Analyzed using Track3P in ACE-3P code suite from SLAC Electric field Magnetic field 2,000 0.10 1st Order 1,800 0.09 2nd Order • Resonant particles were Particle position on y (m) 0.08 1,600 0.07 3rd Order analyzed over 50 rf Impact Energy (eV) 1,400 0.06 4th Order cycles for the 499 MHz 0.05 1,200 5th Order cylindrical parallel-bar 0.04 0.03 1,000 cavity 0.02 800 • At higher rf cycles very 0.01 0.00 600 few resonant trajectories 0.06 0.10 0.14 0.18 exist 400 Particle position on x (m) 200 Single Particle • The design with bars Trajectory merged on to the walls 0 1.0E+05 1.0E+06 eliminates this E Z ( z , x 0 =5 mm) (MV/m) multipacting condition Page 15
Multipacting Analysis Secondary particles had very low impact energies Magnetic Electric field field 2,000 1st Order 1,800 2nd Order 1,600 3rd Order Impact Energy (eV) 1,400 4th Order 1,200 5th Order � Higher orders of 1,000 multipacting exist at 800 lower gradients 600 400 � At very high gradients 200 there were 0 considerably large 1.0E+04 1.0E+05 1.0E+06 amount of resonant E Z ( z , x 0 =5 mm) (MV/m) particles of 1st order Page 16
400 MHz Elliptical Parallel-Bar Cavity 400 MHz E Field H Field Page 17
Cavity Properties – Elliptical Design Rectangular Elliptical Parameter Unit Shaped Shaped Frequency of π mode 400.0 400.0 MHz λ /2 of π mode 374.7 374.7 mm Frequency of 0 mode 411.0 687.0 MHz Nearest mode to π mode 411.0 611.6 MHz Cavity reference length 444.7 445.0 mm Cavity width / diameter 300.0 290.0 mm Cavity height 383.2 408.6 mm Bars length 330.0 330.0 mm Bars width 55.0 60.0 mm • Frequency separation of the first two Aperture diameter 84.0 84.0 mm modes ~ 211 MHz compared to 11 * ) 0.375 0.375 MV Deflecting voltage ( V T MHz in the rectangular design * ) Peak electric field ( E P 2.2 3.4 MV/m • Reduced cavity width to meet the * ) 7.9 7.71 mT Peak magnetic field ( B P LHC crab cavity specifications mT / * / E P * 3.6 2.27 B P (MV/m) Geometrical factor ( G = QR S ) 74.1 109.4 Ω [ R / Q ] T Ω 413.34 255.68 3.1×10 4 2.8×10 4 Ω 2 R T R S * = 1 MV/m At E T Page 18
Higher Order Modes – 400 MHz Fewer low frequency modes compared to the rectangular design with larger separation of modes 1.0E+03 1.0E+03 Ex, Hy Ez Ey, Hx Ex, Hy Ez Ey, Hx 1.0E+02 1.0E+02 1.0E+01 1.0E+01 R/Q ( Ω ) R/Q ( Ω ) 1.0E+00 1.0E+00 1.0E-01 1.0E-01 1.0E-02 1.0E-02 1.0E-03 1.0E-03 1.0E-04 0 500 1000 1500 2000 0 500 1000 1500 2000 Frequency (MHz) Frequency (MHz) Page 19
400 MHz LHC Crab Cavity NIOWAVE Present design www.niowaveinc.com 20 20
400 MHz LHC Crab Cavity NIOWAVE 800 MHz Aluminum model www.niowaveinc.com 21
400 MHz LHC Crab Cavity NIOWAVE 800 MHz Aluminum model www.niowaveinc.com 22
400 MHz LHC Crab Cavity NIOWAVE 800 MHz Aluminum model www.niowaveinc.com 23
Shunt Impedance – 400 MHz ⎡ ⎤ • Longitudinal Impedance: R * Longitudinal Impedance: 20 k Ω = ⎢ ⎥ Z Q , Z ext n ⎣ ⎦ Q * Transverse Impedance: 0.4 M Ω /m ω ⎡ ⎤ • Transverse Impedance: R = Z ⎢ ⎥ Q , T ext n ⎣ ⎦ c Q * E. Shaposhnikova – LHC-CC10 T 1.0E+07 Ex, Hy Ez Ey, Hx 1.0E+06 1.0E+05 Q ext 1.0E+04 1.0E+03 1.0E+02 500 1000 1500 Frequency (MHz) Page 24
HOM Coupler Designs – 400 MHz 1.0E+05 1.0E+07 Transverse Impedance Z T ( Ω /m) Longitudinal Impedance Z Z ( Ω ) 1.0E+06 1.0E+04 1.0E+05 1.0E+03 1.0E+04 1.0E+03 1.0E+02 1.0E+02 Ez 1.0E+01 Ex, Hy Ey, Hx 1.0E+01 1.0E+00 1.0E+00 500 750 1000 1250 1500 500 750 1000 1250 1500 Frequency (MHz) Frequency (MHz) Page 25
Cylindrical Parallel-Bar Cavity Designs for Horizontal and Vertical Crabbing Cylindrical Parallel-Bar Cavity with Cylindrical Parallel-Bar Cavity Trapezoidal Shaped Bars with Curved Bars Page 26
Cylindrical Parallel-Bar Cavity Designs for Horizontal and Vertical Crabbing Cylindrical Parallel-Bar Cavity Cylindrical Parallel-Bar Cavity with with Curved Bars Trapezoidal Shaped Bars E Field H Field E Field H Field Surface E Field Surface H Field Surface E Field Surface H Field Page 27
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