Double Quarter Wave Crab Cavity Qiong Wu 5302013
Double Quarter Wave Crab Cavity Qiong Wu 5/30/2013 1 5/30/13
Outline �Proof of Principal (POP) design �POP cavity testing preparation �FPC port design options �Fewer HOM coupler port layout and filter update �Peak fields and field nonlinearity with coupler ports �Helium vessel, tuner, and magnetic shielding �Future plan �Summary 2 5/30/13
DQWCC POP version 390 337 296 362 295 unit: mm Crabbing (fundamental) mode freq. 1 st HOM Cavity length Cavity width Beam pipe diameter Deflecting voltage Unit MHz mm mm mm MV DQW crab cavity 400 579 390 148 84 3. 3 3 5/30/13
POP cavity testing preparation � April 22 – Cavity received from Niowave after HPR � April 23 – Cavity inspection in class 10, 000 cleanroom � May 8 – Mounting of motion linkage to the cavity frame � May 14 – Getting the top plate ready with new parts for 4 crab cavity � May 22 – FPC installation and vacuum hookup to top plate � May 23 – Cavity passed leak check and kept under vacuum � May 24 – Cable and LLRF calibration � May 28 – Thermal sensor and FPC motor installation and inspection � May 29 – Cavity into dewar with cable and vacuum lines connected � May 31 – Start cool down 5/30/13 � June 3 – Cold test starts
5 Mounting linkage parts Cavity in clean room FPC motion linkage Cavity under top plate Block house and control area Cavity and testing dewar 5/30/13
POP version in LHC Cavity length along beam pipe (with 4 mm wall thickness included): 390 mm Cavity width perpendicular to beam pipe (with 4 mm wall thickness included): 295 mm Gap between cavity outer surface and nearby beam pipe outer surface: 1. 24 mm # of ports total: 6 # of HOM couplers: 4 Inner diameter of all coupler ports: 28 mm 6 4/9/13
Slimmer cavity for LHC (400 MHz) Gap [mm]: Cavity width @ waist [mm]: 1. 2 147. 5 Cavity length [mm]: Ep/Bp @ 3. 3 MV [(MV/m)/m. T] 390 44/62 143. 4 405 42/63 140. 4 449 38/69 5. 3 8. 3 7 4/9/13
FPC implement (large port) 8 a Peak B field @ FPC port: 67 m. T for 3. 3 MV deflection voltage 5/30/13
FPC implement (small port) 9 a Peak B field @ FPC port: 71 m. T for 3. 3 MV deflection voltage 5/30/13
Electric field HOMs deflection mode horizontal mode longitudinal mode 10 HOM Damping 5/30/13
Fewer HOM Couplers Scheme: II I Loop size: 20 mm × 15 mm 11 5/30/13
IV Scheme: II V 12 5/30/13
13 HOM frequency [GHz] Mode Config. R/Q [Ω] Qext-III 0. 579 Longitudinal 108 864 1360 1770 0. 671 Horizontal 70. 5 1526 3080 3260 0. 700 Hybrid (y, z) 0. 24/0. 25 929 1310 2210 0. 752 Deflection 34. 9 1418 2020 3350 0. 800 Horizontal 6. 02 e-4 2074 4120 4630 0. 917 Horizontal 30. 9 1345 2660 1. 88 e 8 0. 949 Longitudinal 28. 1 3183 3360 2220 1. 080 Deflection 1. 54 1071 1350 1920 1. 102 Horizontal 1. 84 e-3 902 1490 2350 1. 114 Deflection 1. 06 2663 5040 2630 1. 202 Horizontal 5. 07 e-2 5021 11000 8980 1. 247 Hybrid (y, z) 8. 0 e-2/6. 0 e-2 1373 1970 2920 1. 291 Deflection 10. 0 778 1060 1450 1. 353 Horizontal 2. 46 e-4 951 2060 6730 1. 408 Deflection 9. 84 e-3 3480 10100 2760 5/30/13
14 HOM frequency [GHz] Mode Config. R/Q [Ω] Qext-II Qext-IV Qext-V 0. 579 Longitudinal 108 1360 1021 0. 671 Horizontal 70. 5 3080 1521 1569 0. 700 Hybrid (y, z) 0. 24/0. 25 1310 1191 1193 0. 752 Deflection 34. 9 2020 1826 1843 0. 800 Horizontal 6. 02 e-4 4120 2080 2054 0. 917 Horizontal 30. 9 2660 1330 1359 0. 949 Longitudinal 28. 1 3360 6712 6703 1. 080 Deflection 1. 54 1350 1577 1389 1. 102 Horizontal 1. 84 e-3 1490 959 819 1. 114 Deflection 1. 06 5040 2994 2646 1. 202 Horizontal 5. 07 e-2 11000 5460 5525 1. 247 Hybrid (y, z) 8. 0 e-2/6. 0 e-2 1970 1969 1978 1. 291 Deflection 10. 0 1060 1198 1209 1. 353 Horizontal 2. 46 e-4 2060 1040 3800 1. 408 Deflection 9. 84 e-3 10100 1040 12200 5/30/13
Temporary design for required inductance value, will change to avoid high field and thermal issue. HOM high-pass filter 6. 6 cm 7. 6 cm Filter design goal: Ø High attenuation at 400 MHz Ø High transmission @ all HOM frequencies Ø Efficient and sufficient cooling Ø Compact design, no interference with other components Ø Practical fabrication Ø As universal as possible to all versions Ø Meet with the schedule 15 5/30/13
Peak fields and field nonlinearity with coupler ports Large FPC port Small FPC port Deflection voltage (MV) 3. 3 Peak E @ 3. 3 MV (MV/m) 37. 6 37. 4 Peak B @ 3. 3 MV (m. T) 81 88 Electric center offset (mm) 1. 67 0. 03 Multipole b 3 (m. T·m)/m 2 © Z. Li with 1096 ACE 3 P 1074 Solution of high B field near port region for 56 MHz SRF Quarter Wave Cavity. Decreased peak B field @ port by ~30% 16 5/30/13
© B. Xiao @ CC workshop 2012 Helium Vessel Design • Preliminary design of the helium vessel • The vessel will play a role in stiffening/tuning the cavity • Clearance for other beam lines in the vicinity. • Compact design which saves LHe • Stress relief connections to the coupling ports(not shown here) 17 12/13/12
Tuner - Design © B. Xiao @ CC workshop 2012 • Thermal leak from one drive shaft and piezoelectric wires. • Threaded rod (or differential screw) provides coarse tune. • Piezoelectric in series with threaded rod provides fine tune. • Step motor (RT) is attached to the cryomodule with a Conflat flange. The single rod linkage into the cryostat limits thermal load. 18 • Effectively use the space: give more space to couplers make the magnetic shielding 12/13/12 easier
Magnetic Shielding © B. Xiao @ CC workshop 2012 • Requirement: Less than 1 μT on cavity surface • Magnetic field 48 μT: Vertical 44 μT, Horizontal 20 μT (//pipe) • Material: 2 mm Cryoperm 10 with μr=150000 • Shield cavity, vessel, and loose fit to beam pipe 19 12/13/12
© B. Xiao @ CC workshop 2012 Magnetic Shielding (2) 20 12/13/12
Plan for SPS testing • We will finalize the cavity parameters according to the official requirements. • Optimization of HOM coupler and filter. • Meet with RF requirements: transmission coefficient, peak field, multipacting (MP), power output • Meet with mechanical requirements: heat production, pressure/vacuum level, mechanical tolerance, thermal contraction, brazing/welding possibility, assembly sequence • Design of the DQWCC tuner and helium vessel for SPS beam test will start right away • Mechanical engineers involved • Refer to other designs • Collaboration • Fermilab – coupler ports, tuner mechanism, helium lines, etc. • SLAC – 3 D simulation with parallel computing for cavity field distribution, MP, peak surface field, etc. 21 5/30/13
Summary � POP cavity testing coming up soon (next week). � FPC port has been designed for the required dimensions. � We decreased the number of HOM couplers to three, and the location of the couplers is chosen. � The peak field on the HOM ports can be decreased significantly by optimizing the shape of the port. All port openings should be made into same dimensions to balance the field. � HOM coupler filter design is underway with novel ideas. � We are using all the resource available to us at BNL to improve our design of the entire crab cavity assembly. 22 5/30/13
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