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Jefferson Lab CLAS12 Superconducting Solenoid magnet Requirements and Design Evolution
Renuka Rajput Ghoshal John Hogan Ruben J. Fair Probir K. Ghoshal Cesar Luongo Latifa Elouadrhiri Jefferson Lab
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Outline Introduction Physics requirements Magnet Design Constraints Conductor Decision Cooling choice Design meets specifications Design iterations Path forward
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Introduction: Jefferson Laboratory
Continuous Electron Beam Accelerator Facility (CEBAF): a superconducting electron machine based on two linacs in racetrack configuration presently being upgraded to 12 GeV CHL-2 Construction of the new Hall D Upgrade of the instrumentation of the existing Halls Upgrade of the arc magnets Compattare con quella dopo High electron polarization Beam Power: 1MW Beam Current: 90 µA Max Enery Hall A-C: 10.9 GeV Max Energy Hall D: 12 GeV
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Introduction: CLAS12 Technical Scope
Optimized for exclusive and semi-inclusive reactions Large coverage in J and f angles Small angle capabilities Capable to operate at luminosity of 1035 cm-2sec-1 Particle ID up to high momentum for e-/π-, π/K/p, γ/πo separation Good momentum & angle resolution for use of missing mass techniques Operate Polarized Target
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CLAS12 MM CND
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CLAS12 – Physics Requirements
Solenoid DC Torus CTOF SVT EC Solenoid HTCC PCAL FTOF Torus LTCC TORUS provides magnetic field for particle tracking: Generate high integral ∫Bdl, needed for good momentum resolution for high momentum forward-going charged particles. Solenoid provides: magnetic field for tracking of central particles Moeller electron shield uniform field (ΔB/B < in 2.5 x 4 cm cylinder) for polarized target operation
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Central Detector – Space and Field Requirement
CND CTOF MM SVT
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Note: Part of Magnet Specification document Bid document 764 pages
Magnet Design Requirements Note: Part of Magnet Specification document Bid document 764 pages
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Solenoid magnet with cryo-can and electronics racks
Solenoid magnet and Cryogenics Solenoid magnet with cryo-can and electronics racks
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Hall B Detector magnets
CLAS12 Detector Magnets in the Hall Hall B Detector magnets Torus Magnet Solenoid magnet
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Solenoid Magnet in operational position
Solenoid Magnet in the Hall in operational position Solenoid Magnet in operational position
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Magnet Concept and design from various perspectives
Magnets from various perspectives Magnet User/Physicist: Maximum field strength, Very high field homogeneity over a larger volume minimum space, fastest ramping, no quenching, … Magnet Manufacturer/Industry: Maximum margin (low field), No space Constraint Low Homogeneity requirement Minimum cost/ Maximum profit Maximize probability of success on 1st ramp (90% of nominal is “Good Enough”) Biggest problem: Missing links between the above 2 perspectives
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Magnet Concept and design from various perspectives
Magnets from various perspectives Magnet Engineer-3rd perspective: Somewhere between the 2 perspectives above! The most rational agent in the equation that can bring together both sides, Making the Physicist as happy as possible , while building a magnet with reasonable budgets for money and risk.
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Solenoid Dimensional Space
Magnet Design Constraints Solenoid Dimensional Space
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CND and CTOF & HTCC around Solenoid magnet
Magnet Design Constraints CND and CTOF & HTCC around Solenoid magnet
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CTOF Detector around Solenoid magnet
Magnet Design Constraints CTOF Detector around Solenoid magnet
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Conductor Decision The conductor is SSC cable (Outer dipole design) soldered in a copper channel.
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Conductor Decision The cable is made of 36 strands fabricated into a Rutherford style form with 1.01o keystone.
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Conductor Decision
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Cooling Choices Vendor chose to conduction cool the magnet using a minimum volume of Liquid Helium. Pros and cons of conduction cooling: Pros Mainly for Physical Science magnets in case of space and Helium constraints Low requirement of liquid Helium Need less space Cons Conduction cooling is less forgiving for higher than anticipated heat loads. Conduction cooling is less forgiving for any types of voids. Longer cooling time due to limited cooling capacity (initial cool down and cooling after quench) Might pose a limitation on fast ramping due to eddy current heating in the conductor
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Main Parameters of current design are:
Design Meets Specifications Main Parameters of current design are:
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Design Iterations: Cryogenic Cooling Design Original Design Optimized Design Pressure Atm Sub-atm LHe temp 4.2K 3.6K Temp Margin 1.12K 1.71K SC Correction coils Original Design Optimized Design Location OD of main magnet coils (far from target area) Inside the bore – (close to target area) Size Large (Ø ~1.5m) Small (Ø ~50mm) Comment Needs very strong coils to compensate for field uniformity Needs less field & easier to assemble Final design will be based on field map of the rest of the magnet Detector shielding induces unbalanced axial forces on solenoid Axial support added to design
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Summary Specifications Clear and concise
Understand the implications of not meeting one or more specifications Importance of various design parameters Do not over constrain the magnet design Discussions with Magnet Engineers Discussions with Vendors at various stages Design the magnet in concert with detectors Detailed information about the environment that the magnet is required to operate in (Materials: support structure, equipment, target, etc.) Do not limit the magnet design by predetermining the type of conductor. In most cases, commercially available conductor might be suitable.
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Back-up Slide Back-up Slide
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Abstract As part of the Jefferson Lab 12GeV accelerator upgrade project, one of the experimental halls (Hall B) requires two superconducting magnets. One is a magnet system consisting of six superconducting trapezoidal racetrack-type coils assembled in a toroidal configuration and the second is an actively shielded solenoidal magnet system consisting of 5 coils. In this presentation the physics requirements for the 5 T solenoid magnet, design constraints, conductor decision, and cooling choice will be discussed. The various design iterations to meet the specification will also be discussed in this presentation.
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Magnet Design Constraints
Magnet Specification
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