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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

slide2

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

slide3

Design criteria

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

Yun HE, MLC External Review

slide4

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

slide5

Beamline and its support

      • Beamline string components
      • Helium gas return pipe
      • Support posts and alignment components
      • Vacuum vessel

Yun HE, MLC External Review

slide6

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

slide7

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

slide8

Supports for other beamline components

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

Yun HE, MLC External Review

slide9

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

slide10

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

slide11

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

slide12

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

slide13

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

slide14

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

slide15

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

slide16

2. Thermal design

        • Support post
        • 40K thermal shield
        • Magnetic shields
        • Multi-layer insulation

Yun HE, MLC External Review

slide17

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

slide18

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

slide19

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

slide20

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

slide21

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

slide22

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

slide23

Cryogenic environment

      • Layout of cooling pipes
      • 2K cooling loop

Yun HE, MLC External Review

slide24

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

slide25

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

slide26

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

slide27

Material and size of sub-assemblies

Yun HE, MLC External Review

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