Task 1.3.3 – “Cryomodule”

Paolo PieriniINFN Sezione di Milano - LASA

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Outline

• Schedule borrowed from Alex Karlsruhe presentation• Aim of the task & work split• Comment on existing cryomodule designs, trying to sort

out the rationales behind them– TTF – SNS

• First educated guesses towards work

FI6W-CT-2004-516520: Integrated Project on European Transmutation (EUROTRANS)

GOAL:

Design, construction and test of a full prototypicalcryomodule of the high energy section of the proton linac.

CO-ORDINATING CONTRACTOR:

INFN (I) – Paolo Pierini

MILESTONES:

M1.3.9: Preliminary cryomodule specifications (+9)

M1.3.10: Cryomodule design finalized (+15)

M1.3.11: Cryomodule is ready for test (+30)

M1.3.12: Experimental results of performances (+39)

M1.3.13: Final report: synthesis and design proposals (+42)

DELIVERABLES:

D1.3.7: Preliminary report: specifications for the cryomodule (INFN, +9)

D1.3.8: Report on cryomodule design and schedule (CNRS, +15)

D1.3.9: Final report: test results, synthesis and design proposals (INFN, +42)

TASK 1.3.3

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Aim of the task (contractual 18 months)

• My understanding• Specifications (D1.15 = D1.3.7)

– Make architectural choices to deal with ADS needs– Review possible design with respect to the state of the art (SNS, TTF)

» Get what we can, but “no free meal”– Sketches (not drawings!)– “Back of the envelope” calculations and estimations to support the choices

• Design and Schedule (D1.16 = D1.3.8)– Milestone to see if it makes sense to go ahead (production) with the given

funding and schedule, if we want to make a significative activity– Proceed to confirm (or suggest alternatives) for choices above– Somewhat detailed drawings of the vessel, shields and lines– Checks with mechanical/thermal analysis the main choices– Interfaces and logistics (RF, Cryo, …)

Q: 9?

Q: 15?

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Split of the work for D1.3.7 (Specs)

• Architecture of the system– Specifications: INFN with CNRS

• Dynamic load range– Straightforward from design

• Alignment tolerances– We did not start beam dynamics tolerances estimations in PDS-XADS,

should be possibly a task for 1.3.5. Less straightforward right now, assume SNS?

– Layout of the cold mass: INFN– Interface to cryogenics: CNRS– Interface to RF: CEA or CNRS?

– Couplers?• Still weak point by now in terms of resources

• +9 form April means January 2006– Better start soon

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Commentary on cryomodule designs

• TESLA […borrowing transparencies from Carlo]

• SNS [… commenting published/unpublished material]

• APT• TRASCO

What are the rationales for each design?We cannot adopt any scheme if incompatible with ADS!

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TESLA Cryomodule Design Rationales

• High Performance Cryomodule was central for the TESLA Mission– More then one order of magnitude was to be gained in term of capital and

operational cost

– Low static losses

• High filling factor: to maximize real estate gradient– Long sub-units with many cavities (and quad): cryomodules (12-17 m)

– Sub-units connected in longer strings (2-3 km)

– Cooling and return pipes integrated into a unique cryomodule

• Low cost per meter: to be compatible with a long TeV Collider– Cryomodule used also for feeding and return pipes

– Minimize the number of cold to warm connections for static losses

– Minimize the use of special components and materials

– Modular design using the simplest possible solution

• Easy to be aligned and stable: to fullfil beam requirements

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Performing Cryomodules

Required plug power for static losses < 5 kW/(12 m module)

Reliable Alignment Strategy

Sliding Fixtures @ 2 K

“Finger Welded” Shields

Three cryomodule generations to:improve simplicity and performances minimize costs

2 thermal shields(4 K and 50-70 K)

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Cryomodules installed in TTF II

RF gun

400 MeV 120 MeV800 MeV

ACC 1ACC 2ACC 3ACC 4ACC 5

4 MeV

ACC 4 & ACC 5 ACC 2 & ACC 3

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1 Prototype and 3 generations

Cry 1 Cry 2Cry 3

Module 1 Module 2 & 3 Module 4 & 5

Mainly: Simplification of assembling & alignment strategy

HeGRP is dominant in the cross-section

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From Prototype to Cry 3

Extensive FEA modeling (ANSYS™) of the entire cryomodule

– Transient thermal analysis during cooldown/warmup cycles,

– Coupled structural/thermal simulations

– Full nonlinear material properties Detailed sub-modeling of new components and Laboratory tests

– Finger-welding tests at ZANON– Cryogenic tests of the sliding

supports at INFN-LASA

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•Four C-Shaped stainless steel elements clamps a titanium pad welded to the helium tank.

•Rolling needles for longitudinal friction

•Cavities longitudinal position independent from the HeGRP contraction.

•x and y defined by reference screws

•Longitudinal position defined through an Invar Rod

A model has been developed to measure real friction force and test extreme conditions

Friction force: < 1 N

Sliding Supports and Invar Rod

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TESLA Cryomodule Concept Peculiarities

Positive• Very low static losses• Very good filling factor: Best real estate gradient• Low cost per meter in term both of fabrication and assembly

Project Dependent• Long cavity strings, few warm to cold transitions• Large gas return pipe inside the cryomodule • Cavities and Quads position settable at ± 300 µm (rms)• Reliability and redundancy for longer MTTR (mean time to repair)• Lateral access and cold window natural for the coupler

Negative• Longer MTTR in case of non scheduled repair• Moderate (± 1 mm) coupler flexibility required

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SNS Cryomodule

• Possibly more similar to ADS requirements

Peculiarities!!

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Design Rationales• Fast module exchange and independent

cryogenics (bayonet connections)1 day2K production in CM

• Warm quad doubletModerate filling factor

• Designed for shipment 800 km from TJNAF to ORNL

• No need to achieve small static lossessingle thermal shield

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Design for shipment (TJNAF to ORNL)

g/2

5 g

4 g

Spaceframe concept

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.3.3Around the cold mass

Tank

50 K thermal shield

Magnetic shields

Vacuum chamberEnd Plate

• Helium to cool the SRF linac is provided by the central helium liquefier• He then piped to the 4.5K cold box and sent through cryogenic transfer lines to

the cryomodules• Joule Thomson valves on the cryomodules produce 2.1 K (0.041 bar) LHe for

cavity cooling, and 4.5 K He for fundamental power coupler cooling• Boil-off goes to four cold-compressors recompressing the stream to 1.05 bar

and 30 K for counter-flow cooling in the 4.5K cold box

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SNS He Flow

HEATER ATWINDOW

BAR20

BAR20

50K SHIELD

LHe

SEPARATORPHASE

CONDUCTOROUTERCOUPLERPOWER

GUARD VACUUM & RELIEFCOOLDOWN & POWER COUPLER RETURN

SUPPLY HP HELIUMHELIUM RETURN T.L.

HELIUM SUPPLY T.L.

4 BARSURGE

TANK

END FLANGEHEAT STATION COUPLER HEAT

STATIONS (2)COUPLER HEATSTATIONS (2)

END FLANGEHEAT STATION

SUBCOOLER2K

20BAR

He Supply 4.5 KHe Return

2 K

50 K Shield

Coupler and flange thermalization with 4.5 K flow

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SNS Cryomodule Assembly

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Alignment strategy

• Cavity string is supported by the spaceframe

• Each target sighted along a line between set monuments (2 ends and sides)

• The nitronic rods are adjusted until all the targets are within 0.5 mm of the line set by the monuments

• Cavity string in the vacuum vessel: the alignment is verified and transferred (fiducialized) to the shell of the vacuum vessel.

• Indexing off of the beamline flanges at either end of each cavity

• Nitronic support rods used to move the cavity into alignment

• Targets on rods on two sides of each flange.

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Modules during tests

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And in ORNL (during PAC05)

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The APT Coupler Dominated Case

• Huge power specs• 100 mA cw!• Everything built

around coupler…

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The TRASCO Conceptual DesignI-DEAS Student Edition : Design

• Short module, interchangeable, sliding supports, G10 frame• Alignment transferred to rails in vessel

• Slide-in from side

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First guesses for EUROTRANS

• Assuming two cavities, β=0.47– Coupler? Important component for boundaries on cryo design

• Preserve independence of modules (à la SNS)– Easy connection/disconnection– 2 K production at module– Reliable interfaces (most troubles in SNS are leaks in iso vacuum)

• CNRS has much more cryogenics expertise than INFN

• CW machine, no need to design for low static losses– Single thermal shielding at 40-50 K is enough

• Choose an alignment strategy– Fast and reliable

• Borrow, as much as possible, technologies from proven designs– E.g. welding techniques for shields and sliding supports from TESLA