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

1

• 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

2

Cryomodule Design Evolution

3 Layers of Magnetic Shield

3

New CM

Cavity Development

4

• 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

6

Superstructure Modifications

7

Testing and He Vessel Integration

8

• 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

9

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.

10

• 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

11

Coupler Testing

Vac 1

Vac 3

Vac 2

12

<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

11

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

14

Absorber Cold Tests

16

• Cavities aligned on assembly fixture.

• Helium Tank leak checked • Cold couplers conditioned. • HOMs cleaned and

assembled.

Cavity String Assembly

17

• 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

18

Cold Coupler Integration II

19

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

20

HOM Absorber Integration II

Central HOM Assembly Half HOM Assembly

21

Completed Cavity String Assembly

22

80K Skeleton Assembly

• 80K shield: – Thermal shields and links installed.

– 2 Mu-metal layers assembled with MLI.

23

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

24

• 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

25

• 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

26

CM Component Cooling

27

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)

29

ALICE Cryomodule Integration TCF 50 2K BOX 1500 L Dewar NEW LINAC BOOSTER

COOL-IT

28

Concept Design Build

COOL-IT Evolution

31

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.

32

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

33

THANK YOU!