Thomas Jefferson National Accelerator Facility Pg. 1 Renuka Rajput Ghoshal John Hogan Ruben J. Fair Probir K. Ghoshal Cesar Luongo Latifa Elouadrhiri Jefferson Lab Jefferson Lab CLAS12 Superconducting Solenoid magnet Requirements and Design Evolution

Thomas Jefferson National Accelerator Facility Pg. 2 Introduction Physics requirements Magnet Design Constraints Conductor Decision Cooling choices Design meets specifications Design iterations Path forward Outline

Thomas Jefferson National Accelerator Facility Pg. 3 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 High electron polarization Beam Power: 1MW Beam Current: 90 µA Max Enery Hall A-C: 10.9 GeV Max Energy Hall D: 12 GeV Introduction: Jefferson Laboratory

Thomas Jefferson National Accelerator Facility Pg. 4 Optimized for exclusive and semi-inclusive reactions Large coverage in and  angles Small angle capabilities Capable to operate at luminosity of cm -2 sec -1 Particle ID up to high momentum for e - /π -, π/K/p, γ/π o separation Good momentum & angle resolution for use of missing mass techniques Operate Polarized Target Optimized for exclusive and semi-inclusive reactions Large coverage in and  angles Small angle capabilities Capable to operate at luminosity of cm -2 sec -1 Particle ID up to high momentum for e - /π -, π/K/p, γ/π o separation Good momentum & angle resolution for use of missing mass techniques Operate Polarized Target Introduction: CLAS12 Technical Scope

Thomas Jefferson National Accelerator Facility Pg. 5 CLAS 12 MM CND

Thomas Jefferson National Accelerator Facility Pg. 6 CLAS12 – Physics Requirements 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 CTOF SVT Solenoid HTCC Torus LTCC FTOF PCAL EC DC Torus Solenoid

Thomas Jefferson National Accelerator Facility Pg. 7 Central Detector – Space and Field Requirement CND CTOF MM SVT

Thomas Jefferson National Accelerator Facility Pg. 8 Note: Part of Magnet Specification document Bid document 764 pages Solenoid Magnet Design Requirements

Thomas Jefferson National Accelerator Facility Pg. 9 Solenoid magnet with cryo-can and electronics racks Solenoid magnet and Cryogenics

Thomas Jefferson National Accelerator Facility Pg. 10 Hall B Detector magnets CLAS12 Detector Magnets in the Hall Torus Magnet Solenoid magnet

Thomas Jefferson National Accelerator Facility Pg. 11 Solenoid Magnet in operational position Solenoid Magnet in the Hall in operational position

Thomas Jefferson National Accelerator Facility Pg. 12 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 1 st ramp (90% of nominal is “Good Enough”) Biggest problem: Missing links between the above 2 perspectives Magnet Concept and design from various perspectives

Thomas Jefferson National Accelerator Facility Pg. 13 Magnets from various perspectives Magnet Engineer-3 rd 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. Magnet Concept and design from various perspectives

Thomas Jefferson National Accelerator Facility Pg. 14 Solenoid Dimensional Space Magnet Design Constraints

Thomas Jefferson National Accelerator Facility Pg. 15 CND and CTOF & HTCC around Solenoid magnet Magnet Design Constraints

Thomas Jefferson National Accelerator Facility Pg. 16 CTOF Detector around Solenoid magnet Magnet Design Constraints

Thomas Jefferson National Accelerator Facility Pg. 17 The conductor is SSC cable (Outer dipole design) soldered in a copper channel. Conductor Decision

Thomas Jefferson National Accelerator Facility Pg. 18 The cable is made of 36 strands fabricated into a Rutherford style form with 1.01 o keystone. Conductor Decision

Thomas Jefferson National Accelerator Facility Pg. 19 Conductor Decision

Thomas Jefferson National Accelerator Facility Pg. 20 Vendor chose to conduction cool the magnet using a minimum volume of Liquid Helium. Pros and cons of conduction cooling: Pros Low requirement of liquid Helium (very good choice for small labs and universities) 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 Cooling Choices

Thomas Jefferson National Accelerator Facility Pg. 21 Main Parameters of current design are: Design Meets Specifications

Thomas Jefferson National Accelerator Facility Pg. 22 Detector shielding induces unbalanced axial forces on solenoid Axial support added to design Design Iterations: Cryogenic Cooling Design Original DesignOptimized Design PressureAtmSub-atm LHe temp4.2K3.6K Temp Margin1.12K1.71K SC Correction coils Original DesignOptimized 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

Thomas Jefferson National Accelerator Facility Pg. 23 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. Summary

Thomas Jefferson National Accelerator Facility Pg. 24 Back-up Slide

Thomas Jefferson National Accelerator Facility Pg. 25 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. Abstract

Thomas Jefferson National Accelerator Facility Pg. 26 Design Option 1 Design options

Thomas Jefferson National Accelerator Facility Pg. 27 Design Option 2 Design options

Thomas Jefferson National Accelerator Facility Pg. 28 Corrector coils- Initial Design ETI Corrector Coil Design Details (Initial Design) The “worst realistic” cases are calculated to result in a Z gradient of 33.4 ppm on 48mm DSV, and X/Y gradients of 42.1 ppm on 48mm DSV. At 5T, these equate to 167  T and 210  T respectively. ETI has designed shims fitting within the envelope allowed (208mm  z  596mm, mm  r  mm). ETI has used 0.6mm (bare) monofilament wire with I c of 5T, 4.2K. (The local field is 4.12T). The shims are designed to achieve the required strength at 50A. Z comprises 71 turns per half, 638m total. X and Y each comprise four double-layered saddles, 2  111 turns per saddle, 551m per saddle. X and Y saddles each span less than 90 degrees, so they can be laid up in the same layer.

Thomas Jefferson National Accelerator Facility Pg. 29 Initial Corrector coil Design Corrector coils- Initial Design

Thomas Jefferson National Accelerator Facility Pg. 30 Corrector coils- Initial Design Trim/Corrector Coils Incorporated into Design X,Y & Z Trim Coils assembled onto OD of Intermediate Coils Two X-Y Gradient (Saddle) & Two Z Gradient (Solenoid) Trims Coils

Thomas Jefferson National Accelerator Facility Pg. 31 Magnet Specification Magnet Design Constraints