General specifications LHC Crab cavities

General specificationsLHC Crab cavities

O. Capatina, L. Alberty, K. Brodzinski, R. Calaga,

E. Jensen, V. Parma – CERN

LHC Crab Cavity Engineering MeetingOC, 13/December/2012 1

• Cavity

• Tuning

• Helium tank

• Magnetic shielding

Overview

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RF Power Coupler

Cavity

Helium Tank

Tuner

HOM Coupler

Bi-phase helium tube

Magnetic shielding

Beam pipe

TTC Meeting 3OC, VP, 7/November/2012

SPL beta = 1 cavityassembly

Functional specification

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• Parameters

Cavity

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Parameter Units Value

Frequency MHz See next page

Cavity b 1

Design gradient MV 3.3 (pushed=5.0)

R/Q W >300

Q0 >1 x 1010

Qext 1 x 106

• Parameters

Cavity

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Parameter Units LHC SPS

Beam Energy GeV 7,000 55 120 270

Frequency MHz 400.79 400.b 400.c 400.c

• Dimensions

Cavity

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R. Calaga, Superconducting Technologies Workshop, Dec. 2012

• Dimensions• RF design for internal shape at cold• Design for manufacturing by scaling:• Warm (room temperature)/cold shrinkage• Shape modification due to EP, BCP, ..• Deformation due to operation conditions

(internal vacuum + external pressure)• …

• Integration specification takes into account external dimension (including wall thickness) of the cavity as manufactured, at room temperature

Cavity

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Position of 2nd beam pipe: 4-ROD

Vittorio Parma, Loren Wright

Position of 2nd beam pipe: RF-Dipole

Vittorio Parma, Loren Wright

Position of 2nd beam pipe: QWR

Vittorio Parma, Loren Wright

• Dimensions

• Maximum radius external dimension (including wall thickness) at room temperature < 145 mm

• Cavities dimensions to be revisited (reduced)

Cavity

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• RF Multipoles

Cavity

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R. Calaga, Superconducting Technologies Workshop, Dec. 2012

• SPS tests• Frequencies at SPS tests to be adjusted with tuner

during operation (slow tuning needed only) – set only once (between 400.c and 400.d ~ 10kHz)

• Detuning (when cavity not in use)• Range of detuning required: + or - 1.5 kHz ± 200 Hz • Time requirements: fast tuning (fast to be defined in

more detail)

Tuning

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Parameter Units LHC SPS

Frequency MHz 400.79 400.b 400.c 400.d

Bandwidth Hz 400 400 400 400

• LHC – operating frequency

• Detuning (when cavity not in use)• Range of detuning required: + or - 1.5 kHz ± 200 Hz • Time requirements: fast tuning (fast to be defined in

more detail)

Tuning

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Parameter Units LHC SPS

Frequency MHz 400.a 400.b 400.c 400.d

Bandwidth Hz 400 400 400 400

• Frequency• Bandwidth of 400 Hz ()• mm/kHz (cavity specific) => cavity stability and

shape adjustment in the order of 10 nm !

• Mech. design compromise between • Rigidity to ensure stability (Lorentz

detuning, …)• Flexibility to ensure tunability

• Remark: tuner to work in one direction (or compensate for play)

Tuning

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• Process for tuning taking into account• Deformation during manufacturing O(MHz)• Processing (hundreds kHz)• Cold/warm (hundreds kHz)• Operating conditions (< kHz)

Tuning

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• Temperature• Operating temperature 2 K

(saturated superfluid helium)• Heat losses to be evaluated in detail –

dimensioning of helium tank, cryo-module and cryo-plant accordingly• Static • Dynamic• ~ 3 W / cavity• But exact and realistic value (especially for SPS

tests) – important to estimate and measure

Helium tank

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• Helium tank to be dimensioned correctly to extract maximum heat load • Heat flux in He II depend on bath temp. and

channel dimension

Helium tank

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• Helium tank to be dimensioned correctly to extract maximum heat load • If helium cross section expected to

extract (order of magnitude) 1 W/cm2 => detailed calculations needed

Helium tank

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• Interfaces • Ideally same helium tank and interfaces for all cavities –

not realistic?

• Standardization of interfaces for all cavities assemblies - is a very strong requirement• Choice of helium tank material (stainless steel /

titanium) – strong impact on transitions:• Beam pipe (suggestion to use SS for flanges)• Cryo-module piping

• HOM (and LOM) extraction, Main power coupler, Pick-up

Helium tank

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• Remark:Design (cavity and helium tank) to take into account:• Interfaces for handling and transport• Interfaces for cavity processing• Interfaces for vertical tests at cold• Interfaces for alignment in cryomodule

Helium tank

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• Pressure• Operating helium pressure ~ 20 mbar• Pressure stability: 1 mbar• Design cavities for sensitivity to

pressure fluctuation accordingly (200 Hz/mbar would be too large)

• Cavity bandwidth 400 Hz => sensitivity to pressure fluctuation should be significantly lower.

Helium tank

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• Pressure• Maximum pressure (transients)• Safety valve set pressure 1.8 bar• Rupture disc 2.2 bar

• Pressure equipment• All the cryo-module assembly:

cavitie(s), helium tank(s), vacuum vessel – to be treated for the same risk category as the most critical one

Helium tank

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CERN’s safety policy regarding pressure equipment:

• The general requirements for mechanical equipment during its life-cycle are defined by a specific General Safety Regulation;

• A General Safety Instruction defines the requirements specific to pressure equipment;

Some general requirements:

• A Safety File of the equipment shall be prepared and updated by the Department;• A risk analysis shall be carried out in order to assess critical loading scenarios;• Full traceability shall be ensured from design to commissioning;

The following documentation applies by order of priority:

Internal Specific Safety Instructions

European Union Directives

European Directive 97/23/EC on the ‘Approximation of the laws of the Member States concerning pressure equipment

Harmonised European Standards

EN 13445, EN 13458, (...)

Helium tank

The application of the European Directive for pressure equipment 97/23/EC:

Covers pressure equipment with a maximum allowable pressure greater than 0.5 bar (gauge)

Defines the essential safety requirements which allow to comply with the directive & allow free movement within the EU market

The equipment is classified into risk categories according to their stored energy and the hazard of the fluid

For each risk category, modules allow to assess conformity

The adoption of European Harmonised Standards ensures conformity with the requirements of the Directive

Table for assessment of risk category

Front page: Directive 97/23/EC

Higher Risk Categories require the participation of Notified Bodies

Helium tank

The application of the European Directive for pressure equipment 97/23/EC:

o Harmonised European Standards for the design, fabrication and inspection of pressure equipment, which ensure conformity with the Directive 97/23/EC:

EN 13445 – Unfired Pressure VesselsPart 1: GeneralPart 2: MaterialsPart 3: DesignPart 4: FabricationPart 5: Inspection and testingOther parts: 6, 7, 8 & 9

EN 13458 - Cryogenic vessels - Static vacuum insulated vesselsPart 1: Fundamental requirementsPart 2: Design, Fabrication, Inspection and TestingPart 3: Operational requirements

Helium tank

• Pressure equipment• Remark:

All the cryo-module assembly: cavitie(s), helium tank(s), vacuum vessel – to be treated for the same risk category as the most critical one

• Could be treated at CERN as special equipment: not necessity of the CE marking but same quality requirements

• For 1.8 bar pressure relieve valve => design for 1.8*1.43 = 2.6 bar for cavity ext pressure, helium tank internal pressure

Helium tank

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• Pressure equipment – example of safety file

Helium tank

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Helium tank

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• Pressure equipment – example of some manufacturing requirements for a category I equipment• Materials• All materials have to be supplied with a certification of type

3.1 according to EN 10204:2004 (compliance with the order and indication of test results attested by the manufacturer)

• Materials covered by Harmonised European Standards automatically do comply with the requirements of PED

• Remarks: • Niobium and Titanium not covered by the Harmonised

European Standards • In the frame of special equipment it can be accepted on

the basis of the risk analysis and of proven behavior at operating temperature

• Pressure equipment – example of some manufacturing requirements for a category I equipment• Every weld shall be identified on manufacturing

drawings and linked to an appropriate weld procedure: • Welding procedure specification (WPS) / Brazing

procedure specification (BPS);• Welding procedure qualification record (WPQR)/ Brazing

procedure approval record (BPAR);• Welding operators qualification /Brazer approval;

• Radiographic inspection of 25% of the total circumferential seams and 100% of the total longitudinal seams.

• ...

Helium tank

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• Static magnetic field shielding required• The field to be below 1 µT at the outer

surface of the cavity • Numerical simulations to determine the

material thickness and specification, as well as geometry• Recommended to evaluate the effect

inside and outside the helium vessel (compatible with cavity compactness requirements)

Magnetic shielding

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