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

2

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 Review10/3/2012

3

Design criteria

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

Support Beamline is supported by HGRP onto three posts mounted on vacuum vesselWeights: Beamline ~1 Ton, Coldmass ~3 Ton, Module ~7 Ton

Alignment • Allowable transverse offset (x,y): 2mm for cavities, 1.6 mm for quads• Allowable pitch: 1.5 mrad (1.2 mm over the length of cavity)• Precision machined support interfaces with alignment pins/keys provides

precision alignment at room temperature and allows for differential thermal contractions at cold

Thermal shielding • Minimize heat leak at 2 K, 5 K, and 40-80 K• Insulation vacuum to eliminate convective heat transfer by gases• 40K thermal shield with multi-layer insulation to reduce radiation heat

inleak• Support system with low thermal conductivity material G10

Magnetic shielding Magnetic field at cavity location should be <3 mGTwo layers of magnetic shields, one wraps cavity and the other on 40K shield

Cryogenic environment Cavities are immersed in 2 K liquid helium bathCryogenic piping is inside module, providing 2K, 5K and 40-80 K cooling

Vibration Push resonant frequency higher with proper support/stiffness to cooling pipes to minimize vibration effect on cavity tuning and RF power requirements

Cost Minimize linac length and transverse diameterYun HE, MLC External Review10/3/2012

10/3/2012 Yun HE, MLC External Review 4

Cross-sectional view of module

HGRP

Vacuum vessel38” dia. OD

Input coupler

HGRP support post + alignment

40K shield + Mu-metal shield

Rails

2K-2 Phase

Cryogenic valves

4”

9.5”

Cavity in 2K Helium bath

Yun HE, MLC External Review 5

1. Beamline and its support

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

10/3/2012

6

Beamline sub-assembly

Taper HOM load Taper HOM loadSC magnets/BPMs

Manual gate valve

Beamline interconnection

Pneumatic gate valve

9.8 m

Beam

Yun HE, MLC External Review

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

10/3/2012

Alignment pins provides horizontal alignment

7

Supports for cavity

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


Material: Ti Grade 2 •LHe vessel •supports

10/3/2012


Supports for other beamline components

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

10/3/2012

9

QuadsDipoleBPMs

Port for pre-cool

SC magnets/BPMs package

Port to 2K/2 phase lineHigh temperature superconducting current leads


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

Sliding postFixed Point

Sliding post

10

Beamline strongback - Helium gas return pipe

High precision machined mounting surfaces with central pin holesProvide precision alignments of beamline components



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?

10/3/2012

Adjust post position Bellows

12

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

Post

Suspension bracket


Vacuum vessel top flange

HGRP

10/3/2012

Port for coupler Port for instrumentation and access to tuner

Hanger for lifting & transportation

Ports for GV& SC magnets

Port for postPorts for cryogenic valves

Rails for cold mass insertion

ɸ37-1/4” ID, 3/8 Thickness

Material: 38” OD x 3/8” wall carbon steel cylinderSS 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

13

Vacuum vessel


Port for pressure relief

14

Vacuum vessel – reinforcements and references

Stiffening rings to top port

Reference arm for survey target

Cross-section of top port

Reinforcement around the opening


SS flange with O-ring seal

Brackets for waveguide supports


Vacuum vessel – production steps

10/3/2012

• 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


2. Thermal design

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

10/3/2012

2nd stage -- 5K intercept (Al)

5K braids clamped to 5K manifold

3rd stage -- 40K intercept (Al)

2K HGRP

300K

G-10 tube

17

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

Conduction

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

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

40K shield


18

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

Support post – production steps

G10 tube Al disk Tooling

• Cool down Al disk along with tooling to LN2

• Put on G10 tube• Press top plate• Let assembly #1 warm up to room temperature

Al ring

• Warm up Al ring along with tooling to 200 oC• Put on assembly #1• Let assembly #2 cool down to room temperature

Step #1 Step #2 Step #3 Step #4

Step #5 Step #6 Step #7 Step #8

Step #1 Step #2

10/3/2012 Yun HE, MLC External Review

Then repeat Step #2 & #3

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

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

Intermediate cover connects two adjacent sections

Lower sheet , 1/8” thick

Extruded pipe to supply 40K helium gas cooling

19

40K thermal shield – general information


Fixed Point Sliding postSliding post

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

10/3/2012

welded

Array of 1”x2” fingers with 0.08” gap

bolted

welded

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

40K thermal shield – finger welding

40-80 K cooling pipes

20Yun HE, MLC External Review10/3/2012

21

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

Temperature Tensile strength Yield strength

Al 1100-H14 77 K 205 MPa 140 MPa

300 K 125 MPa 115 MPa

Al 6063-T52 4 K 385 MPa 250 MPa

300 K 220 MPa 195 MPa

Data from AMS handbook

Data from Cryogenic materials data handbook


22

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



3. Cryogenic environment

• Layout of cooling pipes• 2K cooling loop

10/3/2012

24

Cryogenic manifolds

HGRP1.8K gas

6K returnGas @3 bar

80K returnGas @18 bar

2K-2 Phase1/3 full level

4.5K supplyFluid @3 bar

40K deliveryGas @20 bar

40K supply•Gas @20 bar

2K supplysubcooled liquid @1.2 bar

2K


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

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

25

2K cooling loop


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

HGRPΦ280mm

9.5mm wall

Cavity immersed in 2K helium bath

Large diameter provides low impedance for large mass flow

10/3/2012

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

26

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

10/3/2012

27

Material and size of sub-assemblies

Material Size

Beamline 6 sets of cavity/coupler/HOM/tuner1 set of magnets/BPMs

9.8 m

Vacuum vessel Carbon steel 9.15 m x Ф 0.96 m

Helium gas return pipe2K-2phase pipe

Ti, grade 2 9.65 m x Ф 0.28 m9.65 m x Ф 0.10 m

Support post G10 (FRP)w/ Al & SS rings/disks

40 K thermal radiation shield Al 1100-H14Al 6063-T52

9.65 m Upper: 6.35 mm thickLower: 3.175 mm thick

Cryogenic piping SS 316L Five Φ50mm pipes + local distribution pipes

Interconnection module Carbon steel

Cryo-feed entry module Carbon steel 2.2 mYun HE, MLC External Review10/3/2012

Mechanical Design of Main Linac Cryomodule (MLC)

Documents

Transcript of Mechanical Design of Main Linac Cryomodule (MLC)