1. Double Quarter Wave Crab Cavity
Qiong Wu
On behalf of the DQWCC team
12/13/2012
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2. Outline Current Design Cavity parameters
Higher Order Mode (HOM) damping
Fabrication Status
Stiffening and Helium Vessel
Future plan
Summary
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3. The Double Quarter Wave Cavity
Crabbing (fundamental) mode freq.
1st HOM
Cavity length
Cavity width
Beam pipe diameter
Deflecting voltage
Unit
MHz mm MV
DQW crab cavity
400
579
390
148 84 3
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4. Cavity Dimensions 390 337 296 291 362 unit: mm 12/13/12
Fabrication of prototype cavity is underway.
Cavity is made out of only sheet material
291
unit: mm
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5. Electric field (left) and magnetic field (right) of fundamental mode.
Cavity Field
Electric field (left) and magnetic field (right) of fundamental mode.
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6. Cavity Parameters Unit DQWCC Fundamental Mode Frequency MHz 400
Nearest Mode Frequency
579
Vertical Deflection Voltage MV 3
Rt/Q (Fund. Mode)
Ohm
Epeak
MV/m
44**
Bpeak mT
60**
Energy Content J 12
** Might have some decrease in electric field on the cavity and increase of magnetic field at the port opening (ACE3P)
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7. HOMs HOM Damping Electric field deflection mode horizontal mode
longitudinal mode
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8. HOM Couplers
Scheme: I II
III
Loop size: 20 mm × 15 mm
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9. HOM Damping HOM frequency [GHz] Mode Config. R/Q [Ω] Qext-I Qext-II
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
6.02e-4
2074
4120
4630
0.917
30.9
1345
2660
1.88e8
0.949
28.1
3183
3360
2220
1.080
1.54
1071
1350
1920
1.102
1.84e-3
902
1490
2350
1.114
1.06
2663
5040
2630
1.202
5.07e-2
5021
11000
8980
1.247
8.0e-2/6.0e-2
1373
1970
2920
1.291
10.0
778
1060
1450
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10. Cavity with HOM high-pass filter
66 mm
Z. 2nd Joint HiLumi LHC-LARP Annual Meeting
Modified from BNL HOM filter for 56 MHz SRF Quarter Wave Cavity
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11. Fabrication of the Prototype
Courtesy of Niowave Inc.
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12. Design of prototype stiffening
Stiffening material: Ti
Nb to Ti transition by serrated surface plus SS bolts
SS bolts and pins at frame connections
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13. 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)
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14. Plan for 2012-2013 The design of the cavity is complete.
Fabrication of the cavity with stiffening frame is in progress.
We expect the fabrication to be complete in January 2013.
Chemistry and HPR will be done right after the fabrication of the cavity.
Vertical testing, first without HOM couplers then with HOM couplers will be carried out through early 2013.
The testing will be focused on
Deflection voltage
HOMs
Peak fields
Possible multipacting
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15. Prototype fabrication and testing
Fabrication and testing of the cavity and its various RF couplers (FPC, pick-up, HOM) will include:
Cavity fabrication
HOM coupler (two units)
Fundamental Power Coupler and pickup
Chemistry and HPR
Vertical testing (2 rounds)
LLRF
DQWCC project BNL: Qiong Wu, Binping Xiao (Postdoc), John Skaritka, Vito De Monte, Sergey Belomestnykh, Ilan Ben-Zvi, Silvia Verdu Andres (Postdoc starting in Jan. 2013)
Collaborations: Rama Calaga (CERN), Luis Alberty (CERN), Zenghai Li (SLAC), Niowave Inc.
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16. Summary
The DQWCC can provide high deflection voltage in a very compact dimension.
The peak surface field of the cavity is in a safe level at the target deflecting voltage.
It is optimized for LHC installation so that no conflict to the adjacent beamlines.
The fabrication of the cavity will finish January 2013, and pre-testing treatments will start right after.
Large separation between fundamental deflection mode and 1st HOM simplifies the design in HOM damping scheme and high-pass filter design.
Close collaboration with other LARP participants profits greatly to the cavity design and fabrication.
We are looking forward to testing the prototype Nb cavity in the year of 2013.
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17. Reference
Q. Wu, presentation, Double Quarter Wave Crab Cavity, 2nd Joint HiLumi LHC-LARP Annual Meeting, Frascati, Italy, Nov 14-16, 2012
Q. Wu, et. al., HOM Damping and Multipacting Analysis of the Quarter-wave Crab Cavity, Proceedings of IPAC12, New Orleans, LA, May 20-25, 2012
R. Calaga, et. al., A Quarter Wave Design for Crab Crossing in the LHC, Proceedings of IPAC12, New Orleans, LA, May 20-25, 2012
Q. Wu, presentation, LARP CM18/HiLumi LHC Meeting, Fermi Lab, May 7-9, 2012
Q. Wu, S. Belomestnykh, I. Ben-Zvi, Novel deflecting cavity design for eRHIC, Proceedings of SRF11, Chicago, IL, July 25-29, 2011
R. Calaga, presentation, LHC-CC11, CERN, Nov 14-15, 2011
I. Ben-Zvi, presentation, LHC-CC10, CERN, Dec 15-17, 2010
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