1. 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

2. Outline
Introduction
Physics requirements
Magnet Design Constraints
Conductor Decision
Cooling choice
Design meets specifications
Design iterations
Path forward

3. 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

4. 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

5. CLAS12 MM
CND

6. 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

7. Central Detector – Space and Field Requirement
CND
CTOF MM
SVT

8. Note: Part of Magnet Specification document Bid document 764 pages
Magnet Design Requirements
Note: Part of Magnet Specification document
Bid document 764 pages

9. Solenoid magnet with cryo-can and electronics racks
Solenoid magnet and Cryogenics
Solenoid magnet with cryo-can
and electronics racks

10. Hall B Detector magnets
CLAS12 Detector Magnets in the Hall
Hall B Detector magnets
Torus Magnet
Solenoid magnet

11. Solenoid Magnet in operational position
Solenoid Magnet in the Hall in operational position
Solenoid Magnet in operational position

12. 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

13. 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.

14. Solenoid Dimensional Space
Magnet Design Constraints
Solenoid
Dimensional
Space

15. CND and CTOF & HTCC around Solenoid magnet
Magnet Design Constraints
CND and CTOF & HTCC around Solenoid magnet

16. CTOF Detector around Solenoid magnet
Magnet Design Constraints
CTOF Detector around Solenoid magnet

17. Conductor Decision
The conductor is SSC cable (Outer dipole design) soldered in a copper channel.

18. Conductor Decision
The cable is made of 36 strands fabricated into a Rutherford style form with 1.01o keystone.

19. Conductor Decision

20. 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

21. Main Parameters of current design are:
Design Meets Specifications
Main Parameters of current design are:

22. 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

23. 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.

24. Back-up Slide
Back-up Slide

25. 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.

26. Magnet Design Constraints
Magnet Specification