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General specifications
LHC Crab cavities
O. Capatina, L. Alberty, K. Brodzinski, R.Calaga,
E. Jensen, V. Parma CERN
LHC Crab Cavity Engineering MeetingOC, 13/December/2012 1
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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 cavity
assembly
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Functional specification
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Parameters
Cavity
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Parameter Units Value
Frequency MHz See next page
Cavity b 1Design gradient MV 3.3 (pushed=5.0)
R/Q W >300
Q0 >1 x 1010
Qext 1 x 106
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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
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Dimensions
Cavity
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R. Calaga, Superconducting Technologies Workshop, Dec. 2012
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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
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Position of 2nd beam pipe: RF-Dipole
Vittorio Parma, Loren Wright
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Position of 2nd beam pipe: QWR
Vittorio Parma, Loren Wright
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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
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SPS tests
Frequencies at SPS tests to be adjusted with tunerduring 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
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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 definedin 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
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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 andcryo-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 cavitiesnot 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), vacuumvessel to be treated for the same risk
category as the most critical one
Helium tank
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CERNs 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
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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
H li k
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The application of the European Directive for pressure equipment 97/23/EC:
o Harmonised European Standards for the design, fabrication and inspection of pressureequipment, which ensure conformity with the Directive 97/23/EC:
EN 13445 Unfired Pressure Vessels
Part 1: General
Part 2: Materials
Part 3: Design
Part 4: Fabrication
Part 5: Inspection and testing
Other parts: 6, 7, 8 & 9
EN 13458 - Cryogenic vessels - Static vacuum insulated vessels
Part 1: Fundamental requirements
Part 2: Design, Fabrication, Inspection and Testing
Part 3: Operational requirements
Helium tank
H li t k
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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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H li t k
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Pressure equipment example of safety file
Helium tank
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H li t k
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Helium tank
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Pressure equipmentexample of some manufacturingrequirements 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 HarmonisedEuropean 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
H li t k
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Pressure equipment example of somemanufacturing 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) / Brazingprocedure 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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M ti hi ldi
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Static magnetic field shielding required
The field to be below 1 T at the outer
surface of the cavity
Numerical simulations to determine the
material thickness and specification, aswell as geometry
Recommended to evaluate the effect
inside and outside the helium vessel(compatible with cavity compactness
requirements)
Magnetic shielding
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