From bare cavities to dressed cavities to cryomodules : Introduction to specifications
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Transcript of From bare cavities to dressed cavities to cryomodules : Introduction to specifications
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The HiLumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
From bare cavities to dressed cavities to cryomodules: Introduction to specifications
Ofelia Capatinaon behalf of the CERN specification team
LHC-CC13, 6th Crab Cavity WorkshopOC, 9/December/2013 1
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Functional specification
OC, 9/December/2013 LHC-CC13, 6th Crab Cavity Workshop 2
https://espace.cern.ch/HiLumi/WP4/Lists/Team%20Discussion/AllItems.aspx
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General
OC, 9/December/2013 LHC-CC13, 6th Crab Cavity Workshop 3
LHC Point 1 (vertical crabbing)4 cavities / IP side/ beamto be installed during LS3 LHC Point 5 (horizontal
crabbing)4 cavities / IP side/ beamto be installed during LS3
SPS BA4 (vertical or horizontal crabbing)One or two cryomodules with 2 identical cavities to be tested before LS2
SM18 areaCold tests and clean room facilities – cold test of cryomodules prior tunnel installation
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• LHC environmentGeneral
OC, 9/December/2013 LHC-CC13, 6th Crab Cavity Workshop 4Paolo Fessia
4 cavities / IP side / beam between D2 and Q4=>Total 32 cavities in LHC
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• LHC environment
General
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• SPS environment
General
OC, 9/December/2013 LHC-CC13, 6th Crab Cavity Workshop 6Alick Macpherson talk tomorrow
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• SPS environment
General
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Cryomodule
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LHC configuration SPS configuration
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• Parameters
Cavity
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Parameter Units LHC SPS
Beam Energy GeV 450- 7,000 120 270 450
Kick voltage/cavity MV 3.4 3.4
Nb of cavities 2
Frequency MHz 400.79 400.73 400.78 400.79
DF0 kHz 0 -58.2 -12.2 -2.4
Bandwith kHz ~ 1 ~ 1 ~ 1 ~ 1
Detuning kHz ±5.5 ±21.7
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Bare cavities
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• Three valid Nb prototypes exist – very compact concepts to allow for their integration in LHC
4-rod (UK)
RF Dipole (ODU)
Double ¼-wave (BNL)
Covered by talks this morning
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• Cavity maximum dimensions (SPS and LHC)• Maximum radius external dimension (including wall
thickness) at room temperature < 145 mm, both planes (vertical and horizontal)
• Adjacent beam pipe at 194mm horizontally from the cavity beam pipe
Bare cavities
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Dressed cavities
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• Helium tank and tuner designs are part of cavity design since their behaviour determine cavity operation behaviour
4-rod (UK)
RF Dipole (ODU)
Double ¼-wave (BNL)
Covered by next talks this after-noon
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• Tuning (SPS tests)• Frequencies at SPS tests to be adjusted (“slow”) with
tuner during operation: • Required total range ~ 80 kHz• Required resolution ~ 200 Hz (bandwidth ~ 1kHz)
• Tuning (LHC operation)• Required total range ~ 11 kHz• Required resolution ~ 200 Hz
Dressed cavities
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• Stability / pressure fluctuation (SPS and LHC)• Operating helium pressure ~ 20 mbar• Pressure stability: 1 mbar• Design cavities for sensitivity to pressure
fluctuation accordingly • Cavity bandwidth ~ 1kHz => sensitivity to
pressure fluctuation should be significantly lower (cavity specific)
Dressed cavities
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• Remarks / tuning• If ~ mm/kHz (cavity specific) => cavity stability
and shape adjustment in the order of 100 nm !• Tuning system has also to compensate for shift
in frequency due to manufacturing, processing, cooldown etc… (cavity specific)
• Cavity mechanical design compromise between • Rigidity to ensure stability (Lorentz
detuning, pressure fluctuation, …)• Flexibility to ensure tunability
Dressed cavities
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• Helium tank (SPS and LHC)• Operating temperature 2 K (saturated superfluid
helium)• Maximum pressure • Safety valve set pressure 1.8 bar• Rupture disc 2.2 bar
• Helium tank to be dimensioned correctly to extract maximum heat load (static + dynamic)
• SPS only: Minimize reasonably the liquid helium volume (max. 40 L/cavity if possible)
Dressed cavities
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• Materials (SPS and LHC)• Helium tank material not imposed; however titanium
involves• More complex interfaces • Not covered by the Harmonised European
Standards • Stainless steel flanges (1.4429, AISI 316LN) for beam
pipe interface• Equivalent to EN conventional material grades are
preferred
Dressed cavities
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• SPS :• 2 (identical) cavities in a cryomodule• 3 different cryomodules
Cryomodule
OC, 9/December/2013 LHC-CC13, 6th Crab Cavity Workshop 18Shrikant Pattalwar talk tomorrow
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• SPS :• 2 (identical) cavities in a cryomodule• 3 different cryomodules
Cryomodule
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Shrikant Pattalwar talk tomorrow
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• SPS :• 2 (identical) cavities in a cryomodule• 3 different cryomodules
Cryomodule
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Thomas Nicol talk tomorrow
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• SPS :• 2 (identical) cavities in a cryomodule• 3 different cryomodules
Cryomodule
OC, 9/December/2013 LHC-CC13, 6th Crab Cavity Workshop 21Thomas Nicol talk tomorrow
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• SPS :• 2 (identical) cavities in a cryomodule• 3 different cryomodules
Cryomodule
OC, 9/December/2013 LHC-CC13, 6th Crab Cavity Workshop 22Luis Alberty talk tomorrow
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• SPS :• 2 (identical) cavities in a cryomodule• 3 different cryomodules
Cryomodule
OC, 9/December/2013 LHC-CC13, 6th Crab Cavity Workshop 23Luis Alberty talk tomorrow
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• Design principle, dimensions and interfaces (RF, cryo) to be standardized as much as possible
• Metric system !
Cryomodule
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• SPS:• Two circuits: 2 K and 80 K• Operated at 2 K saturated helium bath -> ~20 mbar• Screening at 80 K provided with LN2• Main interface from the top
Cryogenics
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helium tank
crab cavity
common pumping collector
thermal screen at ~80 Kcryostat interface
CWT
Power coupler intercept
CWT
Krzysztof Brodzinski talk tomorrow
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• LHC - Alignment requirements (position accuracy and position stability) – based on general beam dynamics considerations:• Transverse rotation per cavity should be less than 5 mrad• Transverse misalignment per cavity (in both planes) should
be less than 0.7 mm• Cavity tilt with respect to the longitudinal axis should be
less than 1 mrad• Cavity longitudinal misalignment should be less than 10
mm
Alignment
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• SPS • Alignment required for operation less than LHC
• To limit SPS crymodule complexity (win time and limit risk)• No active alignment needed for SPS tests • Foresee a system for monitoring the cavity
positions instead
Alignment
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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
Magnetic shielding
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• Integration into cryostat at CERN - most likely location SM18
• Cold tests of full cryomodules in SM18 prior tunnel installation
Cryostating
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Vittorio Parma talk tomorrow
Mathieu Therasse talk tomorrow
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• Fundamental Power Couplers• Talk by Eric Montesinos tomorrow
• Impedance budget and HOM power & couplers• Talk by Benoit Salvant tomorrow
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Couplers
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• Bare cavities for SPS designed to be the same as for the LHC• Dressed cavity for SPS tests design as much as possible
compatible with LHC • Conceptual design of SPS cryomodule for the 3 cavities • 2 identical cavities in 3 different cryomodule• Effort to standardize interfaces, basic choices in-
between the 3 cryomodules• The 3 SPS cryomodules could be tested in SM18 (if no
down-selection since then)• 1 or 2 cryomodules to be tested in SPS, after test in SM18• SPS cryomodule design as much as possible compatible
with the LHC OC, 9/December/2013 LHC-CC13, 6th Crab Cavity Workshop 31
Summary