Technical Aspects of the Cryostat for a Front End Proton Driver Linac

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Technical Aspects of the Cryostat for a Front End
Proton Driver Linac

• FNAL
• 26AUG04
• Joel D. Fuerst
• Physics Division

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The Rare Isotope Accelerator (RIA)
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Cavities for the RIA Baseline Design

• 9 different cavity types
• 6 dt structures _at_ 4.2 K
• 3 e-cells _at_ 2.1 K
• Cavities 1,2,3,8,9 borrowed from other
  accelerators
• Cavities 4-7 under development

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Baseline Linac cryomodules

• 1st contains 2 b.024, 5 b.03, 1 b.06 QTY 1
• 2nd contains 9 b.06 QTY 3
• 3rd contains 8 b.15 QTY 6
• 4th contains 8 b.26 QTY 10
• 5th contains 7 b.39 QTY 8
• 6th contains 4 b.49 QTY 14
• 7th contains 4 b.61 QTY 21
• 8th contains 4 b.81 QTY 8
• RIB linac cryostats QTY 9
• Existing ATLAS cryostats QTY 10
• Cryostats for bunchers magnets QTY 61

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Cavities for the RIA ANL Update Design
115 MHz ?0.15 Corrected QWR
57.5 MHz QWR-based structures .02lt ? lt0.14
172.5 MHz ?0.14 HWR
345 MHz ?0.62 Triple-spoke
345 MHz ?0.5 Triple-spoke
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ATLAS Split Ring Cryomodule (1978)

• end loading
• common vacuum space
• forced flow LHe cooling

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Positive Ion Injector (PII) Cryomodule (1990)

• space efficient design
• top loading
• common vacuums
• stagnant bath LHe cooling

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PII Cryomodule Online
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PII Cryomodule During Maintenance

• Space efficient
• Top loading
• Versatile
• Straightforward alignment capability

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Design Evolution

• Cylindrical
• Common vacuum
• Top loading

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Design Evolution (contd)

• Cylindrical
• Separate vacuums
• End loading

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Top-loading, Separated Vacuum Box Design
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Cryomodule End Detail

• Top loading detail
• Module-to-module
• spacing

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Module-to-Module Spacing
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RIA Cryomodule Cavity String
Separate beam and insulating vacuum systems
Clean-room assembly to this point
Cavities are sealed up in a clean environment
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RIA Cryomodule Intermediate Assembly
Remove cavity assembly from clean room
Suspend clean assembly from top plate
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RIA Cryomodule Final Assembly
Lower assembly into vacuum vessel
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Top-Loading Box Cryomodule with TSRs
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Magnetic Shield Assembly
To minimize cost, the magnetic shield is
assembled from 26 pieces of pre-annealed, flat
sheet. A simple, battened-seam design proved
cost-effective to install and provides excellent
shielding of the earths field, with the remnant
field less than 20 mG over most of the interior
volume.
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Thermal Shield Assembly
The thermal shield is made from sections of 1/16
ETP copper. The sections hang from LN2 manifolds
and stand off from the box with G10 buttons.
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Cavity Assy Suspended from Cryomodule Lid
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Support Rod Geometry
The support system is designed with the goal that
there be no net shift in cavity elevation upon
cooldown. At the same time the structure should
be adequately stiff to prevent swaying of the
cold mass. The support members are angled from
the rails in towards the center of the module in
such a way that the longitudinal shrinkage of the
rails offsets the vertical shrinkage of the
members and of the stainless steel cavity helium
vessels.
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Fabrication Completed in June 2004

• Constructed at Meyer Tool Mfg
• Box
• Lid
• Thermal shield
• MLI blanket
• Magnetic shield
• Cryo vac manifolds
• Support frame

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Prototype Fabrication (contd)

• O-ring sealed lid
• Modular shield designs
• He, N2, vac manifolds
• Cold Al cavity support frame

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Prototype Fabrication (contd)

• Modular shield designs
• Mag shield assembled in sheets
• Batten strips provide contact

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Prototype Fabrication (contd)
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Assembly test schedule

• JUN04 delivery of box cryomodule major components
• AUG04 complete installation of thermal shield/MLI
• SEP04 clean assembly of QWR HWR on support
  frame
• OCT04 complete dressed cavity/lid assembly, fit
  to box
• OCT04 cool down for engineering run
• Static heat leak
• Alignment
• Microphonics
• High-field operation
• Long-term testing

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Subsystems Input Coupler Slow Tuner

• Prototype coupler operational on double spoke
  cavity
• revised coupler and pneumatic slow tuner to be
  tested on half-wave cavity

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MB VTA Cavity Performance Data
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4.2 K Residual Resistivity 320-350 MHz
Half-wave class structures
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Frequency Stability Double Spoke
Probability Density
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Frequency Stability ANL Half-wave
Probability Density
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Two-spoke Cavity Transfer Function
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Cavity Refrigeration Loads

• RIA operates CW, not pulsed
• Dynamic gtgt static heat load
• Aim for lowest Rres (high Q)
• Design plant for turn-down

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Baseline Driver Linac Design Dynamic Loads
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ANL Update Linac Design Dynamic Loads
(Assumes Rres 69 nW)

• Include 2742 W static 50 K shield
  liquefaction 40 margin
• Carnot power 2622 kW
• Installed power with hCarnot of 30 factor 1.3
  11.4 MW
• Dissipation is 115-120W/m for TSRs
  microphonics issues

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Comparison of Power Density

• Magnets
• Tevatron (warm iron) 3.0 W/m
• RHIC (cold iron) 1.8 W/m
• SRF
• SNS (pulsed) 15 W/m
• CEBAF 28 W/m
• RIA (cw) 55 W/m,
• elements could exceed 100 W/m for triple spoke
  option

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Summary

• Prototype box cryomodule to be tested Winter
  04/05
• 250K cavities, couplers, tuners,
  instrumentation
• Separate beam and insulating vacuum
• SS, top loading, O-ring seal
• Suitable for all DT structures