CRYOMODULES ENGINEERING DESIGN

P. 1

CRYOMODULES ENGINEERING DESIGN

Patricia DuchesneIPNO – Accelerator Division

Institut de Physique Nucléaire d’Orsay

MAX School

MAX School

SPL cryomodule

MAX cryomodule

ESS cryomodule

SPIRAL2 cryomodule

P. 2

CONTENTS

MAX School2013/10/02

INTRODUCTION

BASIC FUNCTIONS

MAIN COMPONENTS

CRYOGENIC SCHEME OF A CRYOMODULE

THERMAL ASPECTS

MECHANICAL ASPECTS

DIFFERENT CONCEPTS OF SUPPORTING

ASSEMBLY PROCESS

CONCLUSION

P. 3

CONTENTS


INTRODUCTION

BASIC FUNCTIONS

MAIN COMPONENTS

THERMAL ASPECTS

MECHANICAL ASPECTS


ASSEMBLY PROCESS


P. 4

DESIGN OF A CRYOMODULEIN

TRO

DUCT

ION

A cryomodule is an unit cell of an accelerator that contains some Superconducting Radio Frequency (SRF) cavities and all the components required to their operation at cryogenic temperatures.


SPL Layout (2010): segmented architecture Warm quadrupole

Cryomodule(3 cavities =0.65 ) Cryomodule

(8 cavities =1 )

SPL Cryomodule (8 cavities =1)

P. 5

A cryomodule is:

DESIGN OF A CRYOMODULEIN

TRO

DUCT

ION

The accelerator design (accelerating and guide components, sequence)

The overall cryogenic system (independent subsystems or connected each other)

The expected performance of the accelerator (reliability, availability ...)

The costManufacturing cost: high filling factor (long cryomodule, short interconnections)Operating cost: static heat losses (long cryomodules cryogenically connected)


Type of cavities, number of cavities, focusing elements:The accelerator design determines in part

the composition of the cryomodule

Independent cryogenic subsystems or connected to each other:

The overall cryogenic system impacts on the segmentation of the accelerator and

therefore on the cryomodule

A part of an overall cryogenic systemA part of an accelerating section

The design of a cryomodule depends on several parameters:

P. 6

CRYOMODULES/CRYOSTATS, SEVERAL EXAMPLES

SNS, TENNESSEE-USA

DESY- HAMBURG-GERMANY

J-PARC-TOKAI-JAPAN

LHC – CERN-SWITZERLAND

GANIL-SPIRAL2 FRANCE ESS-LUND-SWEDEN

INTR

ODU

CTIO

N

CEBAF, J-LAB-VIRGINIA-USA

Beginning in 2019


P. 7

CONTENTS


INTRODUCTION

BASIC FUNCTIONS

MAIN COMPONENTS

THERMAL ASPECTS

MECHANICAL ASPECTS


ASSEMBLY PROCESS


P. 8

A cryogenic environment for the cold mass Cryogenic distribution (piping, phase separator, valves): He coolant (liquid or gas) at required temperatureso The vessels of the cavities/magnets are filled with liquid helium at 4K or

lower temperature.o The active thermal shield can be cooled with helium gas o The magnetic shieldo The power coupler

BASIC FUNCTIONSBA

SIC

FUN

CTIO

NS Thermal insulation (shield, vacuum and superinsulation) against all sources of heat

transfer from room temperature to cryogenic temperatureo Heat conductiono Heat transfer by convectiono Thermal radiation

Supporting and positioning componentso Structural support of the cold masso Precise alignment of the cavities regarding the beam and reproducibility

with thermal cycles Interface between the cold mass and the room temperature

o Connection points for integrated systems: current, RF, instrumentation and cryogenics

Magnetic protection against the magnetic field from the earth and other sourcesMAX School2013/10/02

P. 9

CONTENTS


INTRODUCTION

BASIC FUNCTIONS

MAIN COMPONENTS

THERMAL ASPECTS

MECHANICAL ASPECTS


ASSEMBLY PROCESS


P. 10

ESS Spoke Cryomodule

Vacuum vessel

Thermal shield

Cryogenic piping

Magnetic shield

String of cavities

1,80m

MAIN COMPONENTS

Vacuum vessel Thermal Insulation Interface

Supporting components

MAI

N C

OM

PON

ENTS

Supporting components Supporting and positioning

Thermal shields Thermal Insulation

Cryogenic piping Cryogenic environment

Magnetic shield Magnetic protection

Cold mass (cavities, magnets)


P. 11

Assembly string: ultra cleanliness required for the internal walls of the cavity and those of the coupler The string is prepared in clean room with mounting of the power couplers, warm cold transitions and vacuum valves at the extremities

Cavity: elliptical, spoke, quarter-wave, and half-wave resonators

COLD MASS (CAVITIES, MAGNETS)

String of dressed superconducting RF cavities (equipped with their helium vessel and their ancillaries) and possibly presence of superconducting magnets of focalization

SC Cavity: Pure niobium, Helium vessel: titanium, stainless steel

ESS String of spoke cavities

MAI

N C

OM

PON

ENTS

Vacuum valve

Cold Tuning system

Power coupler

Helium vesselInter cavity bellows

Warm cold transition


P. 12

Around the cavity (shield at low temperature)To be efficient, the shield has to be cooled before the critical temperature of the cavity (superconductivity) Around all the components of the vacuum vessel (shield at room temperature)

MAGNETIC SHIELD

Providing a protection against the earth magnetic field and fields from other sources (ex: magnet stray fields)AMUMETAL (nickel-iron alloys) at room temperature, CRYOPERM at low temperatures

magnetic shield (Cryoperm) around each cavity:

ESS Spoke Cryomodule SPL Short Test Cryomodule

Magnetic shield with a cooling system between two walls

(Cryoperm):

MAI

N C

OM

PON

ENTS


P. 13

Cryogenic piping depends on the cryogenic distribution system of the accelerator(see § Cryogenic scheme of a cryomodule): - Cryomodule cryogenically connected to form a cryo-string (minimizing the number of cryogenic feeds) Cooling and return pipes integrated into the cryomodule- Cryomodule cryogenically independent Each cryomodule is connected to the Cryogenic Transfer Line (CTL) via a valve box.

CRYOGENIC PIPING

Pipes providing cryogenic fluids at different temperaturesStainless steel, aluminium or copper

Cryogenic piping provides cryogenic fluids to: - Thermal shield- Magnetic shield- Power coupler- Warm to cold transition- Cavity

Biphasic tubeThermal

shield tube

Warm to cold transition pipe

Coupler tube

MAI

N C

OM

PON

ENTS

Magnetic shield tube

Cryogenic valves


P. 14

THERMAL SHIELDS

Active thermal shield at intermediate temperature (50-80K) Passive thermal shield (Multi Layer Insulation)

Thermal shield

To minimize the radiation heat transfer

Metallic shield: aluminium or copper actively cooled at 50K-80KIts design is strongly conditioned by the problematic of thermal contractions and of assembly

MAI

N C

OM

PON

ENTS

MLI (Multi Layer Insulation): composed of some reflective layers (aluminium) alternated of some insulating spacers (mylar) placed on:the surface of the thermal shield (~ 30 layers) the surface of the components at lower temperatures (~ 10 layers)

MLI


P. 15

SUPPORTING COMPONENTS

Supports maintaining all the components in the vacuum vesselResin, composite, Titanium alloy, ...

Stiff and stable over the lifetime: Support the weight of the components and maintain the good alignment of the cold mass

Warm to cold transitions: limit conduction heat transfer

MAI

N C

OM

PON

ENTS

Tie rods


P. 16

It must provide:− Floor fixing supports− Ports for coupler, cryogenic piping, instrumentation ...− Attachment points of the cold mass− Supports for alignment− ...

VACUUM VESSEL

Metallic vessel containing the insulating vacuum to minimize convection heat transfer

A tight structure: guarantee 10-7 bar inside the vacuum level

A rigid structure: No risk of buckling

Carbon steel, stainless steel, aluminium (pressure requirements, magnetic shield potential, the cost ...)

Vacuum vessel

Cover endsSupports

Optical alignment

Instrumentation port

coupler portAttachment point

of the cavity

Safety valve

MAI

N C

OM

PON

ENTS


P. 17

ESS Elliptical Cryomodule:

~ 6,5m

1,2m

ESS Spoke Cryomodule:

1,3m

2,8m

SPL Short test Cryomodule:

~ 7m

0,8m

VACUUM VESSEL

SPIRAL2 Cryomodule B:

2,8m

1,16m

Examples of vacuum vessel studied at IPNO:

MAI

N C

OM

PON

ENTS

MAX Spoke Cryomodule:

1,2m

1,9m


P. 18

CONTENTS


INTRODUCTION

BASIC FUNCTIONS

MAIN COMPONENTS


THERMAL ASPECTS

MECHANICAL ASPECTS


ASSEMBLY PROCESS

P. 19

CRYO

GEN

IC S

CHEM

E O

F A

CRYO

MO

DULE

COOLING MODES


SRF cavities are generally cooledwith an isothermal saturated bath (equilibrium vapour and liquid phases):- T = 4.2K and P = 1 bar- T < 2.1K and P < 30 mbarStable pressures, limitation of pressure fluctuations that have an impact on the cavity frequency A bath at T< 4.2K is generated by isenthalpic expansion, through Joule-Thomson valves (pumping)

Accelerator magnets are often cooled with subcooled liquid: Surfaces completely covered with liquid, stabilization of superconductors

Helium phase diagram

Saturated Helium I

Saturated Helium II

Superfluid Helium

PressurizedHelium II

PressurizedHelium I

P. 20

CRYO

GEN

IC S

CHEM

E O

F A

CRYO

MO

DULE

P&ID (Piping and Instrumentation Diagram)


Example of P&ID of ESS spoke cryomodule:

• Safety elements (burst disk, pressure safety valves),• Control valves• Vacuum circuit• Process diagnostics, Sensors

String of cavities at 2K

Saturated helium II bath at 2K in the

phase separator pipe

3 bar, 4.5K31 mbar

Cool down lines Filling linesHelium gas return lines

19.5 bar, 40K

helium gas line

Cryogenic Transfer Line (CTL) Helium supply and return pipes

Cold boxCryogenic distribution (valves) and Heat exchanger

Cryomodule

P. 21

CONTENTS


INTRODUCTION

BASIC FUNCTIONS

MAIN COMPONENTS

THERMAL ASPECTS

MECHANICAL ASPECTS


ASSEMBLY PROCESS


P. 22

PHYSICAL MECHANISMS OF HEAT LOSS

Conduction heat transfer:- Penetrations from room temperature (power coupler, instrumentation…)- Mechanical supports

Conduction heat transferRadiation heat transfer

RF cavities2K-4K

293K

Insulation vacuum

40K - 80K

Identify all heat losses: Impact on the choices of materials and geometric shapes Total static heat load (in relation to the cryogenic fluid consumption).

Dynamic heat load (operation of the cavity and power coupler):• Pulsed operation: Pstatic >> Pdynam get a good thermal insulation • Continuous wave operation (CW): Pdynam>>Pstatic focus on the problems of heating

THER

MAL

ASP

ECTS

Supp

orts

Coup

ler

Thermal

shield

Vacuum

vessel

Radiation heat transfer:- The most important (varies in T4)

Convection heat transfer:- Negligible with a good insulating vacuum into the vessel (< 10-3mbar)


P. 23

HEAT CONDUCTION

Geometry: A, L

Material with low conductivity l(T)

Thermal intercepts at intermediate temperatures:

2

1

T

T

λ(T).dTLAQ

A : section (m²)L : length (m)l(T) : thermal conductivity (W/mK-1)

300 K4 K

L1

Q1

L2

80 KQ2

300 K4 K

L

Q

x0

T

AISI 304L Calculated from: constantQ

AISI 304L

Transfer by heat conduction All mechanical supports

Heat load (W) by conduction is given by the Fourier law:

THER

MAL

ASP

ECTS

To limit Q while guaranteeing mechanical strength:


P. 24

Without any thermal intercept: by rodWλ(T).dTLAQ 23.0

4

300

300K

4K

80Kx

0

L

4

80

80

300

480 λ(T).dTxAQλ(T).dT

xLAQ

cTTwcT

WQ

with Ẇ: Required work for refrigerator to dissipate Q at Tc (Tw=300K)

Lxa

Lx

aLxW

QQWWW

21

480480

1

4296

80220

Optimum: x/L = 0.65

WQWQ 04.0459.080

Without any thermal intercept

With a thermal intercept at 80K

0.65

Ẇ=17.2W against Ẇ=4.8W

HEAT CONDUCTION

Example: Support rods between the helium vessel and the vacuum vesselMaterial: AISI 304LDiameter D: 8mmLength L: 665mm

The optimal position x can be defined by minimizing the power required to dissipate the heat taking into account Carnot efficiency

Ideal Carnot cycle: THER

MAL

ASP

ECTS

With a thermal intercept at T=80K:

==>

==>


P. 25

Example: Support rods of SPIRAL2 CRYOMODULE B

HEAT CONDUCTION

Lateral rods between the cavity and the vacuum

vessel, thermalized at 80K

Copper tresses between the rods and the thermal shield

THER

MAL

ASP

ECTS


P. 26

Example: Support posts of cryomodules type TTF (XFEL, ILC)

HEAT CONDUCTION

2

1

T

T

λ(T).dTLAQ

Heat loads:

WQ

WQ

WQ

04.08.1

84.05.4

6.970

Estimation of the refrigerator load:Carnot efficiency

WWWWW 3.938.15.470

Without thermal intercepts:

WQ 79.2 WW 2.462

THER

MAL

ASP

ECTS

Aluminium disk connected to the thermal shield at 70K

Aluminium disk connected to the thermal shield at 4,5K

Tube G-11 thickness 2.2mm, ext=300mm70K

4,5K

300K

1,8K

L1=27mm

L3=10mm

L2=37mm


P. 27

Where is the thermal radiation power from surface 1 to surface 2.

HEAT RADIATION

Heat load (W) by radiation is given by the Stefan-Boltzmann law:

).(.. 42

4111212 TTSFQ

: Stefan Boltzmann constant (=5.67x10-8 W/m²K-4)S1 : Surface area (m²)F12 : View factor (depends on geometry and emissivity)

12Q

111

1

22

1

1

12

SS

F

To limit :

Material with low emissivity (shiny surfaces...)

Active thermal shield at intermediate temperature

Passive thermal shield MLI (MultiLayer superInsulation)

12Q

12Q

Transfer by heat radiation All surfaces of the components

THER

MAL

ASP

ECTS

Infinite coaxial cylinders:(simplified model of a thermal shield with the vacuum vessel)


P. 28

MLI layers around active aluminium thermal shield: 30 MLI layers from 293K: 1.5W/m²

WQ masscold 53

WQ

WQ

masscold

shieldthermal

2.0

68

WQ

WQ

masscold

shieldthermal

2.0

3.3

HEAT RADIATION

Example: Heat load by radiation with or without thermal shieldsVacuum vessel in stainless steel: Cold mass (string of cavities):Diameter = 0.8 m Diameter = 0.5 m = 0.2 = 0.1T° = 293K T° = 2K

THER

MAL

ASP

ECTS

Without any shield:

Active aluminum thermal shield: Diameter = 0.7 m = 0.1T° = 75K


P. 29

HEAT RADIATION

Example: Thermal shields of the Cryomodule B – SPIRAL2

MLI placed on the magnetic shields of each cavity, piping and bellows

Active thermal shield in copper

MLI placed on the thermal shield

THER

MAL

ASP

ECTS


P. 30

EVALUATION OF THE STATIC HEAT LOAD

From the heat load budget cryogenic fluids consumption(dimensioning of the cryogenic plant)

293K50K

4K

Static heat load at 50K:

• Thermal shield

• Warm to cold transition


• Warm to cold transition

• Power coupler

• Supporting system


• Helium port


• Supporting system

Rod

Vacuum vessel

Thermal shield

Helium vessel

Cavity

Warm to cold transition

THER

MAL

ASP

ECTS


Example: Heat load budget of a cryomodule

P. 31

EXAMPLES OF THE STATIC HEAT LOAD

Cryomodule B – SPIRAL2

THER

MAL

ASP

ECTS

Components Static loads at 80K [W]

Static loads at 4K [W]

Thermal shield 46.7 0.42

Supporting system (rods) 3.93 2.55

Warm to cold transitions 1.67 1.54

Two power couplers 10 1.5

Two cold tuning system 1.07 0.16

Instrumentation 0.3 2.30

Total 64 8.5

ComponentsStatic

loads at 50K [W]


Thermal shield 10 0.4

Supporting system (rods) 4 0.2

Warm to cold transitions 6 0.4

Safety equipement 4.1 0.25

Two power couplers - 2.

Control valves 3 1.5

Instrumentation 8 0.2

Total 35 5.

ESS Spoke Cryomodule (in progress)

Static loads at 40/80K [W]

Static loads at 4K [W] Static heat

loads at 2K

Total 70 13 3.5

Cryomodule Type TTF

MAX Spoke Cryomodule (in progress)Components




Thermal shield <30 - 0.2

Space frame 16 1 <0.1

Warm to cold transitions 4.34 - 0.2

Safety equipement <2. - 0.1

Two power couplers <35 <7 <2.1

Instrumentation <5 0.5

Total <92 <8 <3.2


P. 32

CONTENTS


INTRODUCTION

BASIC FUNCTIONS

MAIN COMPONENTS

THERMAL ASPECTS

MECHANICAL ASPECTS


ASSEMBLY PROCESS


P. 33

MECHANICAL STRENGTH

External pressure

Patm Patm

Patm Patm

Gravity: 1g

2K or 4K

50K 293K

MEC

HAN

ICAL

ASP

ECTS

Temperature field• Thermal contractions• Thermal stresses

Gravity• Weight of the components

Impact on the alignment and the stability of the components

Vacuum vessel

Thermal shield

Cavities

Vacuum


P. 34

Temperature field in an assembly Thermal contractions and stresses

After the cool down, the temperature field in a cryomodule:

Theses contractions can create some high thermal stresses. Solving problem of stresses will depend on the type of connection between the components according to their function:

String of cavities at 2/4K: niobium, titanium, stainless steel...Thermal shields at 50/80K: copper, aluminiumCryogenic lines from 2K to 300K: stainless steel, aluminium...Supports from 2K to 300K

String of cavities

Thermal shield

2-4K50-80K300K

- Supporting,- Transferring cryo fluid- Vacuum circuit

TEMPERATURE FIELDM

ECHA

NIC

AL A

SPEC

TS

Some thermal contractions appear on all components: With different temperatures With different materials


P. 35

How to estimate the thermal contractions and stresses?

DL = a . L . DT

T1

T2

L

DLa : Thermal expansion coefficient (1/K or 1/°C)L : Characteristic length (m)DT : Difference between final and initial temperatures (K or °C)

A rod:

A tube:

DR = a . R . DT

T1

T2DR

R

According to the Hooke Law:

DD

a ELLE

SF

If a tensile force F is applied to extend the length to the initial length:

Thermal contractions:

Thermal stresses:

THERMAL CONTRACTIONS AND STRESSES

Thermal expansions of different materials DL/L:

MEC

HAN

ICAL

ASP

ECTS


P. 36

DD

a ELLE

SF

Boundary conditions: Release some

degrees of freedom

Ex: Rotary joint, slide link

- For supporting,- For transferring cryo fluid- For the vacuum circuit

Limiting the thermal stresses according to the type of connections

Material with high Re (yield stress) or Rm (Ultimate stress)

Curved tube (lyre)

Bellows

THERMAL CONTRACTIONS AND STRESSESM

ECHA

NIC

AL A

SPEC

TS

Material with low expansion coefficient: aEx: Resins, composites, TiA6V

Material with low Young modulus: E

Ex: Resins, composites

Geometry: Flexibility

Ex: compensator bellows, curved tube...


P. 37

Example: Support rod between the helium vessel and the vacuum vessel

Cstλ(T).dTLAλ(T).dT

xAQ

T

T

T

T

2

11

1. Temperature profile in the rod:

Cutting the rod in several sections, each defined by an average temperature:

DD Tiii LLLL 293

2. Contraction of the rod:

3. Contraction of the helium vessel:DR = a . R . DT

4. Thermal stress in the rod:

293LRLEE DD

(Helium vessel and vacuum vessel are supposed infinitely rigid)

For L=400mm: AISI 304L: DL = 0.67 mmG10: DL = 0.47

mmTIA6V: DL = 0.36

mmFor R=150mm: AISI 304L: DR = 0.38 mm

Titanium: DR = 0.19 mm

For Helium vessel AISI 304L:Rod in AISI 304L : = 525 MPaRod in TIA6V: = 200 MPa

Vacuum vessel

Helium vessel

300 K4 K

Lx0

T


ECHA

NIC

AL A

SPEC

TS


P. 38

Example: Support posts of MAX cryomodule


ECHA

NIC

AL A

SPEC

TS

Fixed Point

Table SliderInvar Rods

Cavity Sliders

DX : 3,5 mmDX : 0.4 mmDX : 0.1 mm

DZ DZ

1. Displacements at 2K – Stationary state:

2. Transient temperature gradients during the cooling down:

Non uniform temperature of the table during the cooling down due to the non-balanced flow in the table cooling tubes150K

80K

300KDT max d X d Y d Z V.M.

Transient state 70 K (150-80) 3,4 mm 2,7 mm 1 mm 43 MPa

Stationary state 0 (80-80) 3,4 mm 1,6 mm 1 mm 50 MPa

~ 3K

~ 10K~ 295K ~ 80K


Mobile Point

Complex shape FEM analysis (behaviour during cool down)

P. 39

Each country has an applicable construction standard norm for the pressure vessels:Requirements for the design, the materials, the fabrication, the control tests.Ex: CODAP (France), European norm EN 13445, ASME(United States).

In the CODAP:• Classification of the pressure vessels according to the volume, the maximum allowable pressure and the nature of fluid.• A vacuum vessel does not fall into a risk category but the design and the fabrication follows the rules.

The external pressure generates on the walls of the vacuum vessel: Some deformations Risk of misalignment Some compressive stresses Risk of buckling

Patm

P=0

For simple shapes:•Using of design by formulae (CODAP, European norm) with a safety factor (takes into

account the manufacturing defects: geometry, materials)• Analytical formulae (Roark) without safety factor

For more complex shapes:• Finite Element Model analysis

EXTERNAL PRESSUREM

ECHA

NIC

AL A

SPEC

TS

Determine the critical buckling pressure:

Theses requirements are applicable for the design of: the vacuum vessel, the nozzles, the flanges and the bellows.


P. 40

L

De

CODAP: Calculation of the maximal allowable pressure

Material: Steel P235GH NF EN 10028-2External diameter De: 800mmLength L: 6500mmThickness: 10mm

KeDe

BPa

/34 K=1 : for normal operation

K=1.35 : for exceptional operation

eeD

eDL , 0002.0A- From a chart, determine the coefficient A = f( )

- From a chart, determine the coefficient B = f(A, material, T°) )(20 MPaB

Pa = 0,33 MPa

Roark Formulae: Calculation of the critical buckling pressure

41

1807,02

2

2

2

Re

RLeEPcrit

Pcrit = 1,04 MPa

Safety factor ~ 3: Pcrit (Roark) = 3,15 x Pa (CODAP)

Example: unstiffened cylindrical vacuum vessel

(Formulae available for short tube)

MEC

HAN

ICAL

ASP

ECTS


EXTERNAL PRESSURE

P. 41

Linear buckling

Pcrit=23 bars (no safety factor)

Buckling

Elastic materialElasto-plastic material

• Elasto-plastic material• Introduction of a geometrical defect

Linear buckling: Pcrit=42 bars

Non linear buckling: Pcrit=8 bars

Example: SPL Short Test CryomoduleMaterial: Steel type P235GHExternal diameter De: 800mmLength L: 7000mmThickness: 10mm (bottom) / 6mm (top)

SPL Cryomodule (last version)

Top cover

Bottom part

Flat flanges + O-ring

Extended study: Non linear buckling

Complex shape FEM analysis

SPL cryomodule (old version)

MEC

HAN

ICAL

ASP

ECTS


EXTERNAL PRESSURE

P. 42

CONTENTS


INTRODUCTION

BASIC FUNCTIONS

MAIN COMPONENTS

THERMAL ASPECTS

MECHANICAL ASPECTS


ASSEMBLY PROCESS


P. 43


All structural supports of the components inside the vacuum vessel (cavities, shields...)

To be a transition from the room temperature to a low temperature

Supporting the components

Position accuracy and preserving the stability of the cold mass

Whatever the type of support, the required functions are:

Limit the conduction heat transfers

Thin and long structureLow conductivity material

Have a sufficient stiffnessLimit thermal contractions and stresses

Thick and massive structure

The mechanical design of the supports depends on 2 technical contradictions

DIFF

EREN

T CO

NCE

PTS

OF

SUPP

ORT

ING


P. 44

Tie rods

Cold mass

Vacuum vesselTie rods

Vacuum vessel

Cold mass

Gas Return

Pipe

Support postsVacuum vessel

Cold mass

Compressive posts

Cold mass

Vacuum vessel

Pad supports

Spaceframe

Tie rods

• Assembly methods• Alignment strategy (warm / cold / inside / outside)• Cold mass weight (LHC)• Length of the string of cavities• Cryogenic distribution system (large GRP)• Team member’s experience•...

The choice depends on:

DIFFERENT CONCEPTS OF SUPPORTINGDI

FFER

ENT

CON

CEPT

S O

F SU

PPO

RTIN

G

GRP with support posts Compressive posts

Space frame Others ...

There is no only one solution...MAX School2013/10/02

P. 45

Join the rods to the vacuum vesselPossibility to align after cooling down

TIE RODS

Example: Cryomodule B - SPIRAL2

Vertical rodsAntagonist rods in horizontal

o To support the weighto Vertical displacement of the cavity to anticipate for alignment

o To adjust lateral alignmento To maintain the lateral alignment of the cavity

DIFF

EREN

T CO

NCE

PTS

OF

SUPP

ORT

ING

Cold mass

Vacuum vessel

Identical DL Using of the antagonist rods• Preservation of the alignment in the plane formed by the

rods: The rods have the same thermal contraction• Limitation of thermal stresses: the rod does not undergo

the thermal contraction of the cold mass • Longer supports: Limit the conduction heat transfers


P. 46

COMPRESSIVE POSTSDI

FFER

ENT

CON

CEPT

S O

F SU

PPO

RTIN

G

Vacuum vessel

Cold mass

Pad supports

Example: MAX Cryomodule for spoke cavities

Using of some pad supports (with table)• The alignment of the string of cavities is realized outside the vacuum vessel• The alignment is then realized by adjusting the vacuum vessel with an external referential (transfer beam axis)

Invar rod

adjustable pods

Sliding table

Sliding support

Use sliding supports and invar rod• The thermal contractions of the table is not transmitted to the cavity • Longitudinal position of the cavity is fixed by the invar rod

o To maintain longitudinal alignment of the cavity

o To support the weighto Vertical displacement of the cavity to anticipate for the alignment

o To adjust alignmento To maintain alignment

o To maintain alignment


P. 47

GRP WITH SUPPORT POSTS

Example: TTF Tesla Test Facility cryomoduleSame solution for XFEL and ILC

Vacuum vessel

Cold mass

Gas Return

Pipe

Support posts

GRP

Cavity

70K shield4K shield

Vacuum vessel

Coupler port

Support post

2 phasepipe

Sliding support

Invar rod

Use Helium GRP as structural support• Large diameter pipe (because of pressure drop)

Use composite thermalized support posts• At the centre: support fixed to the vessel• At the extremities: sliding supports for removing the effect of thermal

contractions of the GRP

Use sliding supports and invar rod• The thermal contractions of the GRP are not transmitted to the cavity • Longitudinal position of the cavity is fixed by invar rod

DIFF

EREN

T CO

NCE

PTS

OF

SUPP

ORT

ING


P. 48

Using of the antagonist rodsPreserve the alignment of the cavities

SPACE FRAME

Example: ESS Cryomodule for elliptical cavities (solution type SNS)

DIFF

EREN

T CO

NCE

PTS

OF

SUPP

ORT

ING

Door knob and RF wave guide

Coupler

50K Thermal shield

Spaceframe (300K)

He tank & Cavity

Supporting rods

Vacuum vessel

Positioning jacks

(3 at 120°)

Biphasic He pipe

Cold mass

Vacuum vessel

Pad supports

Spaceframe

Tie rods

Using of a space frame• The alignment of the string of cavities is realized outside the vacuum vessel• The alignment is then realized by adjusting the vacuum vessel with an external referential (transfer beam axis)


P. 49

Using of the double walled tube of the power coupler as support• Provides the alignment of each cavity along beam axis (fixed point)

Using of the inter-cavity supports• Relative sliding between adjacent cavities along the beam axis• Provides a second vertical support (limits vertical self-weight sag)

OTHER: SUPPORTING BY POWER COUPLER DI

FFER

ENT

CON

CEPT

S O

F SU

PPO

RTIN

G

Example: SPL SHORT CRYOMODULE

RF coupler double-walled tube flange fixed to vacuum vessel

Inter-cavity supports


P. 50

CONTENTS


INTRODUCTION

BASIC FUNCTIONS

MAIN COMPONENTS

THERMAL ASPECTS

MECHANICAL ASPECTS


ASSEMBLY PROCESS


P. 51

ASSEMBLY STEPSAS

SEM

BLY

PRO

CESS

Inside the clean room• Assembly of the string of cavities with its power couplers with a preliminary

alignment

For each step, it’s necessary to provide:- Some specific tooling- Some suitable infrastructures

Outside the clean room: Insertion of all components inside the vacuum vessel• Assembly of the other equipments of the string of cavities: Cold tuning system,

magnetic shield, instrumentation,...• Assembly of the thermal shields, cryogenic distribution lines,...• Insertion inside the vacuum vessel• Procedure of alignment


P. 52

Insertion and connections of the cavities in the intermediate part of the vacuum vessel:

Inside the clean room:

Assembly of the cavity with:- the power coupler- the cold tuning system (CTS)

Cavities

CTS

Power couplerClean room handling

apparatus One part of the vacuum vessel

Transport carriage

ASSE

MBL

Y PR

OCE

SSASSEMBLY PROCESS OF CRYOMODULE B – SPIRAL2


P. 53

Outside the clean room:Magnetic shield & MLI Top plate with cryogenic

line, part of thermal shieldthermal shield Cylinder of the vacuum vessel

Finish with the bottom of the vacuum vessel

Withdrawal of the carriageClosing of the top coverRaising of the assembly

Ready to be tested

ASSE

MBL

Y PR

OCE

SSASSEMBLY PROCESS OF CRYOMODULE B – SPIRAL2


P. 54

Finalization of the dressing of the cavities:- Cold tuning system,- Magnetic shield,- Some cryogenic pipes,- thermal shield

Inside the clean room:Assembly of the string of cavities with

the power couplers on the sliding table

ASSE

MBL

Y PR

OCE

SSASSEMBLY PROCESS OF MAX CRYOMODULE

Outside the clean room:

Cryostating:- Displacement of the vacuum vessel for the insertion- Assembly of supporting posts,...- Closing of the vacuum vessel

Pre-alignmentAdjustment of

alignment


P. 55

Finalization of the dressing of the cavities:- Magnetic shield,- Some cryogenic pipes,- Supporting rods- Thermal shield

Inside the clean room:Assembly of the string of cavities with

the power couplers on a specific tooling

ASSE

MBL

Y PR

OCE

SSASSEMBLY PROCESS OF ESS SPOKE CRYOMODULE

Outside the clean room:

Cryostating:- Insertion in the vacuum vessel- Assembly of supporting rods- Cold tuning system, cryo. Pipes,...- Closing of the vacuum vessel

Adjustment of alignment

Pre-alignment


P. 56

ASSE

MBL

Y PR

OCE

SSALIGNMENT

Objective:Align the beam tubes of all cavities along the beam axis.


1. Align the cavities inside the cryomodule2. Align the cryomodule with respect to the others

The beam tubes are not accessible when the cryomodule is closeTransfer the beam tubes axis: External references (new fiducials)

Taylor Hobson sphere

retroreflector

Laser trackerTotal station (Theodolite)

Measurement equipments:

P. 57

ASSE

MBL

Y PR

OCE

SSALIGNMENT STRATEGY FOR CRYOMODULE B SPIRAL2


Beam axis

2nd offset axis

1st offset axis

2nd offset axis

1st offset axis

Offsets of the beam axis on the helium vessel:

Fiducialization bench (=section of the linac structure):- Alignment of the cavities in the cryomodule- Offset the beam axis on the support of the cryomodule

Offset axis of the cryomodule

2 Offset axes of the cavity

Beam axis

Reference axis for alignment of all components on the accelerator

The tolerated maximum static errors for the global alignment are:- ± 1 mm for the displacement of the cryomodules- ± 0.3° for the rotation (X,Y) of the cryomodules

P. 58

ASSE

MBL

Y PR

OCE

SSALIGNMENT OF SPL CRYOMODULE

BUDGET OF TOLERANCEStep Sub-step Tolerances (3σ) Total envelopes

Cryo-module assembly

Cavity and He vessel assembly ± 0.1 mm Positioning of the cavity w.r.t. external

referential ± 0.5 mm

Supporting system assembly ± 0.2 mm

Vacuum vessel construction ± 0.2 mm

Transport and handling (± 0.5 g any

direction)N.A. ± 0.1 mm

Reproductibility/Stability of the cavity

position w.r.t. external referential

± 0.3 mmTesting/operation

Vacuum pumping

± 0.2 mmCool-down

RF testsWarm-up

Thermal cycles

Example of budget tolerance: SPL Cryomodule


Specific tooling for the alignment of the string of cavities: 4 spheres by cavity to

adjust the alignment

P. 59

CON

CLU

SIO

NCONCLUSION


Mechanical, thermal, vacuum and cryogenics.

The mechanical design of a cryomodule depends on a variety of parameters that need some knowledge in:

At IPNO Laboratory, the mechanical design of the cryomolules is assumed by the design office: - 6 engineers - 7 draughtman designers

Supported by other colleagues from the Accelerator Division (total: 90 persons):- Expert in cryogenics and vacuum- Expert in RF cavity design- Expert in beam dynamics

P. 60

References


• H. Saugnac, IPN Orsay, “Cryostat : construction et mise en oeuvre”, Journées cryogéniques d’Aussois, 2003

• Paolo Pierini, INFN-Milan, “overview of cryomodules for proton accelerators”, ESS Bilbao initiative workshop, 2009

• N. Ohuchi, KEK, “Fundamentals of cryomodule”, SRF 2009 tutorial program, 2009

• T. H. Nicol, Fermilab, “Fundamentals of Cryomodule Design: Theory and Practice, Part II – Mechanical Considerations”, SRF 2011 tutorials

• V. Parma, CERN, “Cryostat design II: Application to cryostat design”, Cryostat Design Seminar at GSI, 2005

• H. Saugnac, IPN Orsay, “Design review of the SPIRAL2 cryomodule B”, 2008

• P. Duthil, S. Rousselot & P. Duchesne, IPN Orsay, “ SPL Cryomodule Conceptual Design Review - Vacuum Vessel and Assembly Tooling”, 2011

• D. Reynet, P. Duthil & S. Bousson, IPN Orsay, “Engineering Design of the ESS Spoke Cryomodule”, SLHIPP meeting, 2013

• G. Olivier & J.P. Thermeau, IPN Orsay, “ESS Cryomodule for elliptical cavities (Medium and high beta)”, SLHIPP meeting, 2013

P. 61MAX School2013/10/02

THANK YOU FOR YOUR ATTENTION

CRYOMODULES ENGINEERING DESIGN

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n cryomodulescryostats

overall cryogenic systema

accelerator design

cryomodule8 cavities

number of cavities

cavities b

active thermal shield