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Mechanical Design of Main Linac Cryomodule (MLC). Yun He, Dan Sabol, Joe Conway On behalf of Matthias Liepe, Eric Smith, James Sears, Tim O’Connell, Ralf Eichhorn. Outline. Design criteria Beamline and its support Beamline components Helium gas return pipe

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Mechanical design of main linac cryomodule mlc

Mechanical Design of Main Linac Cryomodule (MLC)

Yun He, Dan Sabol, Joe Conway

On behalf of

Matthias Liepe, Eric Smith, James Sears, Tim O’Connell, Ralf Eichhorn


Outline

  • Design criteria

  • Beamline and its support

  • Beamline components

  • Helium gas return pipe

  • Support posts and alignment components

  • Vacuum vessel

  • Thermal and magnetic design

    • Post

    • 40K thermal shield

    • Magnetic shields

    • Multi-layer insulation

  • Cryogenic environment

    • Layout of cooling pipes

    • 2K cooling loop

  • Materials, sizes and weights of sub-assemblies

  • Yun HE, MLC External Review


    Design criteria

    Cryomodule provides support, alignment, cryogenic environment, thermal shielding and magnetic shielding for the cavities

    Yun HE, MLC External Review


    Cross-sectional view of module

    HGRP support post + alignment

    Rails

    40K shield

    + Mu-metal shield

    Cryogenic valves

    HGRP

    4”

    2K-2 Phase

    9.5”

    Input coupler

    Vacuum vessel

    38” dia. OD

    Cavity in 2K Helium bath

    Yun HE, MLC External Review


    • Beamline and its support

      • Beamline string components

      • Helium gas return pipe

      • Support posts and alignment components

      • Vacuum vessel

    Yun HE, MLC External Review


    Beamline sub-assembly

    • 9.8 m long

    • six packages of 7-cell cavity/Coupler/tuner

    • a SC magnets/BPMs package downstream

    • five regular HOM absorbers/two taper HOM absorbers

    • A gate valve at each end to keep beamline a UHV unit

      • One manual, to be opened once two modules are connected

      • One pneumatic

    Cavity package with coupler, tuner and HOM absorber

    Beam

    9.8 m

    Beamline interconnection

    SC magnets/BPMs

    Taper HOM load

    Taper HOM load

    Manual gate valve

    Pneumatic gate valve

    Yun HE, MLC External Review


    Supports for cavity

    • Material: Ti Grade 2

    • LHe vessel

    • supports

    Flexible support allows 1mm differential thermal displacement of helium vessel relative to HGRP during cool-down/warm-up

    Alignment pins provides horizontal alignment

    Yun HE, MLC External Review


    Supports for other beamline components

    Alignment keys allow for differential thermal displacement of beamline components relative to HGRP

    Yun HE, MLC External Review


    SC magnets/BPMs package

    High temperature superconducting current leads

    Port to 2K/2 phase line

    Port for pre-cool

    BPMs

    Dipole

    Quads

    Yun HE, MLC External Review


    Beamline strongback - Helium gas return pipe

    • Beamline (~ 1 Ton) is suspended under HGRP via three support posts

      • Center post fixed, side posts allow differential contractions during cool-down

    • Material : Grade 2 Ti, ID Φ280mm, wall thickness 9.5mm

    • Similar thermal expansion rate with niobium

    • Does not need transition for being welded to Nb

    Fixed Point

    Sliding post

    Sliding post

    High precision machined mounting surfaces with central pin holes

    Provide precision alignments of beamline components

    Yun HE, MLC External Review


    Helium gas return pipe -- production steps

    • Final precision machining of top and bottom surfaces and pin holes with one set-up

    • Heat treatment to relieve internal stress?

    Yun HE, MLC External Review


    Support post -- alignment components

    • Three posts connected to HGRP to support cold mass ( ~3 Ton)

    • Posts are fastened to suspension brackets

    • Adjustable brackets allow alignment of cold mass position to vacuum vessel references

    Adjust post position

    Bellows

    Suspension bracket

    Vacuum vessel top flange

    Post

    HGRP

    Yun HE, MLC External Review


    Vacuum vessel

    Port for post

    Ports for cryogenic valves

    Port for pressure relief

    Hanger for lifting & transportation

    Port for coupler

    Ports for GV

    & SC magnets

    Port for instrumentation and access to tuner

    • Material:

      • 38” OD x 3/8” wall carbon steel cylinder

      • SS 316L for all flanges

    • Lining with Co-Netric mu-metal shielding

      • Or a mu-metal shield on 40K shield? To be decided

    • Painted:

      • interior with polyurethane and exterior with marine paints

    • A top port for spring-loaded gas relief disk (ID 4”)

      • to prevent insulation vacuum from over pressurization in case of accidental spills of LHe

    Rails for cold mass insertion

    ɸ37-1/4” ID, 3/8 Thickness

    Yun HE, MLC External Review


    Vacuum vessel – reinforcements and references

    Cross-section of top port

    Reinforcement around the opening

    Reference arm for survey target

    Stiffening rings to top port

    Brackets for waveguide supports

    SS flange with O-ring seal

    Yun HE, MLC External Review


    Vacuum vessel – production steps

    • Weld supports/end flanges

    • Align end flanges holes within 0.1°

    • 0.002” flatness/coplanar/parallelism for bottom plates to vessel cylinder reference and each other

    Drill the holes

    • Weld side flanges and brackets for waveguide supports

    • Weld top flanges and survey arms

    • Weld rail supports and align them within 0.02”

    • Final machining on all flanges’ sealing surfaces, holes on bottom supports and waveguide brackets

    • Precision machining of survey arms

    • Install rails

    Yun HE, MLC External Review


    • 2. Thermal design

      • Support post

      • 40K thermal shield

      • Magnetic shields

      • Multi-layer insulation

    Yun HE, MLC External Review


    Support post – thermal design

    • A major source of heat leak via conduction

    • Same design/size as those in TTF, supports up to 5 Ton weight Material: Fiber reinforced plastic (FRP) G10, low thermal conductivity, from ACPT

    • Four stages of shrink-fit metal discs/rings, with MLI on intercept discs

    4th stage -- 300K (SS 316L)

    300K

    Conduction

    3rd stage -- 40K intercept (Al)

    40K shield

    G-10 tube

    2nd stage -- 5K intercept (Al)

    2K HGRP

    1st stage -- 2K (SS 316L)

    5K braids clamped to 5K manifold

    Yun HE, MLC External Review


    Support post – production steps

    • Plan to use the same company who built the posts for ILC cryomodule

      • Four stages of shrink-fit metal discs/rings, w/ interferences of 0.15-0.3 mm

    Step #1

    Step #2

    Step #3

    Step #4

    G10 tube

    Al disk

    Tooling

    Al ring

    Step #1

    Step #2

    • Cool down Al disk along with tooling to LN2

    • Put on G10 tube

    • Press top plate

    • Let assembly #1 warm up to room temperature

    • Warm up Al ring along with tooling to 200 oC

    • Put on assembly #1

    • Let assembly #2 cool down to room temperature

    Then repeat Step #2 & #3

    Step #5

    Step #7

    Step #6

    Step #8

    Yun HE, MLC External Review


    40K thermal shield – general information

    • Three sections, each mounted on a post, fixed joint on middle post and flexible joints on side posts

    • Three sections are rigidly connected by intermediate covers as a whole

    • Material: Al 1100-H14, high thermal conductivity and light weight

    • + Mu-metal (?, to be decided) + MLI (30 layers)

    • 40-80 K helium gas cooling in extruded pipe which is welded to upper sheet

    • Shield sheets are connected by fasteners

    • Venting holes to prevent excessive pressure build-up in case of accidental spills of LHe

    Fixed Point

    Sliding post

    Sliding post

    Top sheets (1/4” thick) support 40-80 K manifolds and lower portion of the shield

    Lower sheet , 1/8” thick

    Intermediate cover connects two adjacent sections

    Extruded pipe to supply 40K helium gas cooling

    A cone shaped shield will be attached to the coupler penetration opening

    Yun HE, MLC External Review


    40K thermal shield – finger welding

    40-80 K cooling pipes

    Fingers increase the elasticity , reduce thermal stress due to temperature gradient during cool-down

    welded

    Array of 1”x2” fingers with 0.08” gap

    welded

    bolted

    Yun HE, MLC External Review


    40K thermal shield – materials

    • Al 1100-H14 for shield

    • high thermal conductivity and high strength

    • It is used on Injector cryomodule/HTC thermal shields – good workability

    • Al 6063-T52 (or T6), for extruded pipe

    Data from Cryogenic materials data handbook

    Data from AMS handbook

    Yun HE, MLC External Review


    Magnetic shields and multi-layer insulation

    • Two layers of magnetic shielding

    • A sheet of Mu-metal 4K (0.04” thick A4K) shield on the cavity LHe vessel

    • Hydrogen annealed after welding for optimal performance at 2K

    • Mounted in half shells; Perm nuts for joining the overlap seams

    • A sheet of Mu-metal (0.02” thick A4K) shield on 40K shield or lining on vacuum vessel?

    • Multi-layer insulation (MLI) blankets

    • 30 layers on the 40K thermal shield

    • 5 layers on He vessel, HGRP, all cryogen pipes

    • Venting holes to prevent excessive pressure build-up in case of accidental spills of LHe

    Yun HE, MLC External Review


    Yun HE, MLC External Review


    Cryogenic manifolds

    • Six lines of ɸ50 mm pipes @ 2K, 4.5-6K, 40-80K running half-linac length

    • Each cryomodule has local manifolds with the flow adjusted by four valves

    2K supply

    subcooled liquid @1.2 bar

    6K return

    Gas @3 bar

    • 40K supply

    • Gas @20 bar

    80K return

    Gas @18 bar

    HGRP

    1.8K gas

    2K-2 Phase

    1/3 full level

    40K delivery

    Gas @20 bar

    4.5K supply

    Fluid @3 bar

    2K

    Yun HE, MLC External Review


    2K cooling loop

    A JT valve controls liquid helium to 2K-2 phase line

    2K-2 phase pipe feeds helium to helium vessels of cavities and SC magnets

    Vapor returns back to cryogenic feed box via HGRP through single connection in the middle

    Large diameter provides low impedance for large mass flow

    HGRP

    Φ280mm

    9.5mm wall

    • 2K-2 phase

    • 1/3 full, monitored by a level sensor

    • ɸ87 mm, adequate area for superfluid counterflow

    • Chimney w/ large cross-section for gas flow to HGRP

    Cavity immersed in 2K helium bath

    • Material of 2K-2 phase, HGRP pipes and LHe vessel

    • Grade 2 Ti

      • Similar thermal expansion rate with niobium

      • Does not need transition for being welded to Nb

    Yun HE, MLC External Review


    2K-2 phase pipe

    • A bellows section in chimney allows differential thermal contractions of beamline vs. HGRP during cool down

    • A welding lip allows cut-off/re-weld a mal-functional cavity

    A few supports attached to HGRP to increase pipe’s natural frequency

    Kapton thermofoil heater, to keep the refrigeration load constant when RF power is off

    Yun HE, MLC External Review


    Material and size of sub-assemblies

    Yun HE, MLC External Review


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