SRF Cryomodule Development for ERL Applications · PDF fileallow cavity string insertion. ...
Transcript of SRF Cryomodule Development for ERL Applications · PDF fileallow cavity string insertion. ...
SRF Cryomodule Development for ERL Applications
Peter McIntosh (STFC)
HOM Diagnostics and Suppression in SC Cavities.
Cockcroft Institute, 25 – 27 Jun 2012
Outline
• Collaboration Team • Cryomodule Evolution:
– Cavity – Tuner – Coupler – HOM Absorber – Assembly
• Cold Testing • ALICE Integration • Summary & Outlook
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• International collaboration initiated in early 2006: – ASTeC (STFC) – Cornell University – DESY – FZD-Rossendorf – LBNL – Stanford University – TRIUMF (2009)
• Fabricate new cryomodule and validate with beam.
• Dimensioned to fit on ALICE: – Same CM footprint – Same cryo/RF interconnects – ‘Plug Compatible’
Collaboration Team
Target Cryomodule Specification
Parameter ALICE Target
Frequency (GHz) 1.3 1.3
Number of Cavities 2 2
Number of Cells/Cavity 9 7
Cavity Length (m) 1.038 0.807
Cryomodule Length (m) 3.6 3.6
R/Q (Ω) 1036 762
Eacc (MV/m) 12 - 15 >20
CM Energy Gain (MeV) 27 >32
Qo <5 x 109 >1010
Qext 4 x 106 4 x 106 - 108
Max Cavity FWD Pwr (kW) 10 SW 20 SW
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Cryomodule Design Evolution
3 Layers of Magnetic Shield
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New CM
Cavity Development
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• 2 x 7-cell superstructure cavities provided by DESY (7Z2 and 7Z4).
• Original ALICE 3D cryomodule drawings provided by FZD Rossendorf.
• Outer CM vessel provided by Stanford.
• End groups re-designed by LBNL, STFC and Cornell: – large b-p HOM absorbers, – larger variable FPC.
• Cavity modifications performed and validated by Cornell.
• Component testing and CM integration performed at Daresbury – 1st UK achievement!
Cavity Geometry Parameterisation
Cell Small beam pipe
Pre-end Tesla Cell Large Beam Pipe
r1 39 35 35 53
rx1 18.1 12 12 11.1
ry1 25 19 19 8
xlen2 67 57.65 57.7 61.5
r2 104.94 104.94 103.3 104.94
rx2 33 42 42 40
Ry2 33 42 42 40 5
DESY Superstructure
TESLA 9-cell 7-cell
Number of Cells 9 7
R/Q (Ω) 1036 762
Epk/Eacc 2 2.23
Hpk/Eacc (mT/(MV/m)) 4.21 4.69
Cell-cell Coupling (%) 1.9 1.9
Cavity Performance
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Superstructure Modifications
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Testing and He Vessel Integration
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• Cavities had to be heavily etched (400 to 500 µm) before reaching acceptable performance.
• Both cavities were baked at 115°C for 48 hours.
• FE limit during last tests due to difficulty with cleaning He-jacketed cavities. Fixed for final cleaning before shipped to Daresbury.
• Expect performance improvement with final assembly.
Cavity Qualification
1.0E+09
1.0E+10
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0
Qo
Eacc (MV/m)
Before He vessel weldingAfter He vessel welding
ALICE OperationalTarget
Design Target
1.0E+09
1.0E+10
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0
Qo
Eacc (MV/m)
Before He vessel welding
After He vessel weldingDesign Target
ALICE OperationalTarget
Cavity #1
Cavity #2
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Tuner Development
• Employed a modified Saclay-II tuner assembly: – Wider aperture. – Low voltage piezo cartridges.
Saclay-II
Modified Saclay-II
• Dual cams precision aligned and pinned.
• Stiffness tests completed.
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• Utilised Cornell ERL injector coupler as original design.
• Cold section of the Cornell injector coupler too long to load into the cryomodule.
• Removed 80 K intercept ring and two bellows convolutions.
• Reduced the 2 K to 5 K transition tube.
• Shortened the coupler cold section by 15 mm and modified 80K skeleton to allow cavity string insertion.
Coupler Development
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Coupler Testing
Vac 1
Vac 3
Vac 2
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<10
K V
aria
tion
• Cornell ERL injector CM HOM absorber utilised for high current operation (up to 100mA).
• Investigation on Cornell ICM identified that Ceralloy bulk resistivity increases considerably at T<80K, resulting in significant charge build-up.
• Fracture problems also identified with the TT2 ferrite material.
• Modification to remove all ferrite and ceramic tiles on the beam-side only.
HOM Absorber
Beamlet distortion through Cornell injector cryomodule
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Before Cryomodule
HOM Absorber Qualification
DISMANTLE AND INSPECTION
READY FOR FINAL ASSEMBLY
TT2 TILE REMOVAL
COLD TESTING OF CERAMIC TILES
ASSEMBLY AND ORBITAL WELDING
THERMAL CYCLING TO 80K AND LEAK CHECK
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Absorber Cold Tests
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• Cavities aligned on assembly fixture.
• Helium Tank leak checked • Cold couplers conditioned. • HOMs cleaned and
assembled.
Cavity String Assembly
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• Cold coupler section aligned and ‘jacked’ into position.
• Simulation tests performed with equivalent size/weight to verify assembly process.
• The scissor mechanism is operated inside a sealed bag to prevent migration of particulates.
Cold Coupler Integration I
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Cold Coupler Integration II
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HOM Absorber Integration I
• Central HOM absorber surrounded by rigid support cage.
• Restricts longitudinal movement of both input couplers.
• Absorber thermally isolated by thin titanium support rods.
• End HOM absorbers uses spring support.
• Translation stage included to provide longitudinal flexibility during cool-down.
HOM support spring
HOM translation stage
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HOM Absorber Integration II
Central HOM Assembly Half HOM Assembly
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Completed Cavity String Assembly
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80K Skeleton Assembly
• 80K shield: – Thermal shields and links installed.
– 2 Mu-metal layers assembled with MLI.
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Cavity String Installation
• Warm coupler section fitted after the installation of the cavity into the isolation vessel.
• The isolation vessel and cavity string assembly are then rotated to allow warm couplers to be installed horizontally.
• The rotation frame designed so that it can split and installed around the existing cryomodule support frame.
• After the rotation a slide assembly and other tooling is implemented to install the warm coupler sections.
Warm Coupler Assembly I
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• Rotation of the cryomodule. • Guide rail assemblies
attached. • Central and outer coax
assemblies installed. • Alignment is critical to
ensure correct orientation of waveguide flanges.
Warm Coupler Assembly II
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• Assembly completed.
• Cryogenic performance tests between 300 and 80 K passed successfully.
• Instrumentation validated.
• Tests are being extended to liquid helium temperatures.
• One of the cavity RF tuners fails during cooldown: – Investigations ongoing as to
the fundamental cause.
CM Cold Testing
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CM Component Cooling
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Cryomodule Cooling Circuits Additional port To feed new gas lines into the Cryomodule
HOMs and Couplers in parallel. Radiation shield in series. 30
COOL-IT Heat Exchanger • Input He gas at 300 K, maximum 10 bar, 10 g/S LHe at 4 K • Output He gas at 5 – 6 K, 5 W, ~ 5 bar He Gas at 80 – 90 K, 175 W, ~ 5 bar • Only one control valve for the operation with HOMs as primary cooling load • Operation fully independent of ALICE Cryo-system (except for LHe and LN2 supply)
• Three main components – Heat Exchanger Box, A compound transfer Line (TLx), and a LHe transfer line (TLy)
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ALICE Cryomodule Integration TCF 50 2K BOX 1500 L Dewar NEW LINAC BOOSTER
COOL-IT
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Concept Design Build
COOL-IT Evolution
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Summary & Outlook • Collaborative CM contributions all now fully
integrated. • HOM absorber modifications implemented based
upon Cornell ICM results. • Cavity performance exceeds ALICE requirements:
– Anticipate improved capability. • ALICE integration requires separate heat exchanger for coupler and HOM intercepts, plus GHe 80K distribution:
– Hardware tested and installed on ALICE awaiting CM.
• CM scheduled to be installed on ALICE later this year.
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Cornell University • Sergey Belomestnykh (now BNL) • Eric Chojnacki (now ???) • Zack Conway (now ANL) • Georg Hoffstaetter • Matthias Liepe • Hasan Padamsee • Peter Quigley • James Sears • Valery Shemelin • Vadim Veshcherevich DESY • Dieter Proch • Jacek Sekutowicz HZDR-Rossendorf • Andree Buechner • Frank Gabriel (now retired) • Peter Michel LBNL • John Byrd • John Corlett • Derun Li • Steve Lidia
Stanford University • Takuji Kimura • Todd Smith (now NPS) STFC • Bob Bate (now Liverpool Univ) • Carl Beard (now PSI) • Mike Cordwell • Peter Corlett • Phil Davies • Eric Frangleton • Philippe Goudket • Tom Jones • Peter McIntosh • Keith Middleman • Ali Sheraz • John Strachan • Shrikant Pattalwar • Alan Wheelhouse TRIUMF • Bob Laxdal • Shane Koscielniak
Team Acknowledgements
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THANK YOU!