DESIGN OF WIDE APERTURE MAGNETS FOR FAIR - SUPER FRS ENERGY BUNCHER DESIGN OF WIDE APERTURE MAGNETS FOR FAIR - SUPER FRS ENERGY BUNCHER ( Present Status- October 2012 ) VECC FAIR MAGNET TEAM Kolkata, INDIA

OUTLINE INTRODUCTION DIPOLE QUADRUPOLE SEXTUPOLE - Physics design - Engineering design - Thermal design & safety - Status

Physics design DIPOLES

Specification of Dipole Magnet 5 Number of magnets3 Bending angle (deg) 30  Curvature radius R [m] Maximum field [T]1.6 Average operating field [T]1.15 Minimum field [T]0.15 Ramp rate DC Magnets ∆t rise (Sec)120 Effective length [m]2.43 Field quality (over aperture)±3 X Useable horizontal aperture [mm]±380 Useable vertical gap [mm] ±100 Superconducting Dipole Magnets NuSTAR Week 2012, VECC

30 0 Dipole seen from the mid-plane

NuSTAR Week 2012, VECC7 Meshed geometry for field calculation (TOSCA) No. of nodes = 5 million Calculation time ~ 3 hrs

Magnetic field Simulation 8 Quality achieved in design= ± 2.1 x Coil positional accuracy: ± 1 mm Pole gap accuracy: 240 ± 0.1 mm NuSTAR Week 2012, VECC

Internal Purcell filter - Brings down the field deviation by an order of magnitude - Brings down the field deviation by an order of magnitude - Improves the field uniformity as a result - Improves the field uniformity as a result

Unconventional Purcell filters

Magnetic field simulation result 13 Maximum field: 1.6 T Current required: 196 A Maximum Impedance: 85 H Maximum stored energy: 1.4 MJ NuSTAR Week 2012, VECC

QUADRUPOLES

SLParametersUnitShort Magnet Long Magnet 1Number of magnets33 2Max. gradient (TDR)T/m Gradient field Quality (TDR)+8* aGradient field Quality (Physics Design)+8.5* * Usable Horizontal Aperture (TDR)mm± 300 5Pole Radiusmm350 6Effective Length (TDR)m Overall Lengthm1.98 8Current at max fieldA200 9 Ramp rate, DC Magnets, (  t rise ) (TDR) sec120 Specifications of Quadrupoles

Long Quadrupole

1/16 th symmetric portion for field calculation

Dimensions – Long Quadrupole

Field specifications of quadrupole

3D Magnet Geometry

≤ ± uniformity ≤ ± ≤ ± uniformity

Maximum coil field maximum field gradient

Short Quadrupole - Purcell filter is at the middle

SEXTUPOLE

Unit Number of magnets3 TypeHexapole magnet Design Superferric magnet Max. hexapole component T/m 2 15 Effective length Lm0.800 Useable horizontal aperture mm+300 Useable vertical aperture mm+200 Pole radiusmm350 Ramp ratet rise = 120 sec Details of sextupole

COIL MAGNETIC FIELD LOADING CONDITION : 1. COIL ENERGISED AT 300 AMPS.

Engineering Design of Superconducting Dipole Magnets for FAIR Project

 Engineering design Conductor, coil, iron Magnetic force and stress Cryostat, coil stress analysis He chamber, supports links, their stress Radiation shield, OVC, Heat load estimation Cool-down analysis Quench analysis Relief system analysis Assembly and testing Important issues 38NuSTAR Week 2012, VECC

Dipole magnet 39NuSTAR Week 2012, VECC

Superconductor 40 Conductor specificationDataUnit Superconducting strandsNb-Ti Dimension1.17 x 1.93mm Dimension with insulation1.43 x 2.24mm Filament diameter62µm Number of filament55 Dia. of core wire0.63mm Cu: Super conductor10.8 RRR117±11 Insulation thickness0.31 x 0.26mm Critical current 4.2K, 1.6T Current density1133A/mm 2 Nb-Ti Conductor NuSTAR Week 2012, VECC

Coil 41 Epoxy- impregnated coil Number of turns: 40 (H) x 24 (V) Coil Cross-section: 72.9 mm x mm NuSTAR Week 2012, VECC

Iron NuSTAR Week 2012, VECC42 Plate thickness: < 30 mm

Magnetic Stress Analysis NuSTAR Week 2012, VECC43 Magnetic force on Coil Total force on all coils Fx : kN Fy: kN Fz: kN Maximum Von-Mises stress in Iron 3 MPa

Cryostat Design 44NuSTAR Week 2012, VECC Fill-box Beam tube Vertical support Hz. support Outer Vacuum Chamber

Coil stress analysis Pre-stress NuSTAR Week 2012, VECC45 Contour Plot of Total DisplacementContour Plot of Stress Intensity

Coil stress analysis Pre-stress NuSTAR Week 2012, VECC46 Contour Plots of SigX after Pre-stress

Coil stress analysis Thermal stress NuSTAR Week 2012, VECC47 Contour Plots of Total Displacement Contour Plots of stress intensity Important is to see no loss of contact after cool-down, so that no coil movement when under magnetic force

Helium chamber 48NuSTAR Week 2012, VECC

Support link 49 Vertical link E Glass-epoxy link Horizontal link Thermal intercept Radiation shield NuSTAR Week 2012, VECC

Support link Design 50 Parameters Unit Horizontal Support links (4 nos.) Vertical support links (8 nos.) Length from bobbin to thermal intercept mm Length thermal intercept to vacuum chamber mm 36 (2 nos.) and 101 (2 nos.) 52 Height of cross sectionmm4720 Width of cross sectionmm3013 Maximum Force during operationN2 x x 10 5 Material: E Glass Epoxy Composite (σy: 2000 MPa) NuSTAR Week 2012, VECC

Stress Analysis 51 A] Thermal load: Cool-down from 300 K to 4.5 K B] Structural load: Internal Pressure = 5 bar a Maximum deformation = 7.4 mm Maximum Tensile stress for Horizontal support links =900 MPa Vertical support links = 400 MPa NuSTAR Week 2012, VECC

Stress analysis for transportation 52 Max. deformation = 0.5 mm Max. Von-Mises stress = 30 MPa Impulse loading for transportation Vertical acceleration = 2*g Horizontal acceleration = 1.5*g 1.5*g 2*g NuSTAR Week 2012, VECC

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Outer Vacuum Chamber 54 vacuum chamber Port extensions Material : SS316LN Operating Pressure < mbar Force on Support ports due to Cool-down Thickness of side wall : 15 mm ( Standard Followed: ASME, Section-VIII, Div- 1, Appendix 13)Max. Von-Mises stress = 80 Mpa NuSTAR Week 2012, VECC

Heat load Minimization 55 Vacuum requirement: mbar Number of MLI on radiation shield: 20 Number of MLI on LHe chamber: 10 NuSTAR Week 2012, VECC

Heat load estimation 56 ComponentsUnit LHe Chamber at 4.5 K Radiation shield at 80 K Support Links (12 no.)Watt Current leads (1 pair)Watt0.52 Vent PortWatt Instrumentation PortWatt Radiation from outer shields Watt TotalWatt NuSTAR Week 2012, VECC

Cool-down Analysis 57 ProcessRadiation Shield LHe Chamber During Cool-down Helium flow K Time required: 2.5 h Plant capacity K Time required: 10 days Steady StateHelium flow KLiquid Helium flow 3.4 lit/h Liquid Helium poured into the chamber to reach 4.5 K Cool down the Radiation shield at 80 K by cold Helium gas flow. NuSTAR Week 2012, VECC

Superconductivity of Coil Operating Point: Maximum field: 1.6 T Current density: 1133 A/ mm 2 Temperature: 4.5 K Temperature margin: 2.5 K For NbTi Superconductor: Critical field: 14.5 T Critical Temperature: 9.2 K Critical Current density: 6720 A/ mm 2 Superconductor 58NuSTAR Week 2012, VECC

Coil magnetic field NuSTAR Week 2012, VECC59 Maximum coil field: 1.64 T

Cryostability of Coil For single conductor- cryo-stable. For potted coil- not cryo-stable. LHe Pool boiling curve LHe

Quench of Superconducting Coil Quench without dump resister : Maximum Voltage: 8.2 kV Maximum Temperature: 110 K Minimum Quench Energy: 7 J 61NuSTAR Week 2012, VECC Self-protecting magnet ?

Relief system analysis of LHe Chamber Pressure rise due to Quench and Loss of Vacuum 62 Heat dump rate in LHe due to vacuum loss: 16.5 kW Heat dump rate in LHe during Quench: 61.4 kW Total heat dump in LHe: 78 kW Total liquid He volume: lit Total He gas volume: 1.8 lit Vent port size: DN 50 Maximum Pressure: 3.5 bar NuSTAR Week 2012, VECC

The materials involved AssemblyMaterialWeight (kg) Superconducting coilNbTi600 Helium chamberSS316LN2,100 Radiation shieldETP Copper140 Vacuum chamberSS316LN1,680 Elliptical beam tubeSS316LN100 Magnet iron-coreCR steel (1010)110,000 Total weight115 T 63NuSTAR Week 2012, VECC

Magnetic field analysisMechanical design of the magnet Fabrication of laminated iron core Materials, Fixtures & Tools Punching laminations Stacking and pressing Solidification in oven End block machining Half yoke stamping and welding Fabrication of coil Superconductor, moulds, vacuum impregnation facility Coil winding Vacuum impregnation Test of insulations Fabrication of cryostat Fabrication of helium chamber Forging of SS plates Welding of the chamber MachiningCryo-shocking Helium leak testing Fabrication of radiation shield Cutting of the copper plates Riveting of the plates Brazing/solderin g of the cooling channels Fabrication of vacuum chamber Forging of SS plates Welding of the chamber MachiningHelium leak test 64 DESIGN & FABRICATION STEPS NuSTAR Week 2012, VECC

Integration & test Integration of coil with the helium chamber Helium chamber closing and cryo-shocking followed by vacuum test MLI wrapping on helium chamber and assembly with radiation shield and vacuum chamber Global helium leak test Integration of cryostat with magnet iron Cool-down and boil off rate measurement Magnetic Field measurements Magnetic field corrections Installation at FAIR site Final acceptance test at FAIR site 65 ASSEMBLY & TESTING STEPS NuSTAR Week 2012, VECC

Issues related to these magnets Quality of magnetic field – 3 x To achieve this, the pole gap tolerance required is ± 0.1 mm !! In a 115 T magnet, how to achieve this? Inductance of magnet is too high (85 H) ! Resulting 8 kV voltage in coil. Not possible to have a self- protecting magnet. 110 T iron, big issue is transportation? Take in pieces and assemble at site ! What is the limit of size of each piece? Assembly at site? Facilities for handling to be available ! Testing – at factory? Assembly of this big magnet is a issue at any factory. Testing with LHe, mostly not available at factory. Warm testing may have to be done at factory. Cold testing at site ? Corrections, if any??? NuSTAR Week 2012, VECC66

Engineering Design of quadrupole magnet

Conductor Properties Superconducting Strands : NbTi Filament diameter : µm Ratio of Cu and no Cu : 15.7:1 Critical current Ic : 600 K & 4 T Operating temperature Top : 4.2 K Operating current Iop : 300 A RRR of Cu in strand : > 80 Current density : A/mm 2   Conductor & Coil geometry 2.24 mm mm Coil Geometry Total NI required : Aspect ratio (approx.): 2.32:1 Packing Factor : 0.86 Min. Bending Radius at corner: 43 mm Total No. of turns; 984 Cross Section of the coil: 100mmX43mm COIL(Quadrupole) No. of Columns : 38, No of rows : 26

Iron core Iron core Material: Laminated Iron Material: Laminated Iron Hyperbolic pole contour Hyperbolic pole contour Lamination Thickness : 0.5mm Thickness : 0.5mm Weight : 6.5 kg Weight : 6.5 kg

Iron Lamination (Two halves)

Fx =213.4 kN Fy = kN Fb = 162 kN Fa = 140 kN Coil Support Details

Coil in Assembled Condition Magnet Wt: 21 T Approx

Nodal Distribution of Lorentz Force (N) Von Mises Stress (Pa) contour in coil Key parameters for analysis 2D plain strain coupled electromagnetic structural analysis Element :Solid 96 3 Translational DOF are constrained along straight portion of the long arm Load due to Lorentz Force only is considered

VonMises Stress (Pa) on magnet LOADING CONDITION : 1. THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

Von-Mises Stress on Coil LOADING CONDITION : 1. THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

LHe Vessel LHe Vessel i. i. Structural Load Transportation Inertia load Cool Down iv. iv. Cryogen pressure Warm Warm condition ii. Pre stress load Design Code used: ASME Sec VIII, Div I Detail Analysis Done by: ANSYS code iii. Thermal stress

Von Mises Stress in helium vessel (2D) ( Pa) Key parameters for analysis 2D plain strain coupled electromagnetic structural analysis Element :Plane 13 X & Y axis are defined as symmetry plane Cryogen Pressure, Thermal Stress and Self Weight are taken as load.

Helium Vessel Material: 316LN

LHe Vessel Beam Pipe Cryostat : Inside View

Thermal Radiation Shield

Wt: 30 T (Approx)

The loads that are coming on the outer vacuum chamber are: Pressure load (due to vacuum inside) Force transferred through the links due to magnet weight Inertial Loads during transport and lifting. Outer Vacuum Chamber

Design for External Pressure Material SS 304 External Pressure = bar Vessel ID = 1942 mm Vessel length = 1900 mm Thickness t = 8 mm Vessel OD = 1958 mm L/D 0 = 0.97 D 0 /t = Factor A = and B = 5500 psi = 3.79E7 Pa (from the chart ASME code) Allowable Pressure P = B/(D 0 /t) = 1.55E5 Pa Circumferential Compressive Stress f = A*E = 7.0E7 Pa

Design for Internal Loads (Magnet Weight) Von Mises StressTotal Deformation

Buckling: Various Mode Shapes

Buckling Six mode shapes were considered. Participation factor for each mode is evaluated. Participation factor is factor of safety over the applied load for buckling. The high values of participation factor shows that the buckling won’t occur under the applied loads. ModeLoad Multiplier

Design for inertial load (Lifting) Lifting by fixing the legs Acceleration value = g Von Mises StressStress Concentration

ENGINEERING DESIGN OF SEXTUPOLE MAGNET

COIL NODAL FORCE LOADING CONDITION : 1. THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

IRON MAGNETIC FIELD LOADING CONDITION : 1. THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

TOTAL DISPLACEMENT LOADING CONDITION : 1. THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

IRON DISPLACEMENT LOADING CONDITION : 1.THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

IRON STRESS LOADING CONDITION : 1.THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

COIL DISPLACEMENT LOADING CONDITION : 1.THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

COIL STRESS LOADING CONDITION : 1.THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

COIL FORMER STRESS LOADING CONDITION : 1. THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

Stress on Helium Vessel (2D) LOADING CONDITION : THERMAL LOADING : COOLDOWN FROM 300K TO 4 K.

OUTER CYLINDER, INNER CYLINDER & END FLANGE STRESS LOADING CONDITION : 1.THERMAL LOADING : COOLDOWN FROM 300K TO 4 K. 2. COIL ENERGISED AT 300 AMPS.

THERMAL DESIGN

Total Heat Load at 4.5K Sources of heat Load: Thermal radiation from 50K to 4.5K Conduction through: 1.Support Links 2.Current leads 3.Vent port 4.Refrigeration port 5.Instrumentation port

Radiation heat Load : W Conduction Load: Support Links: 0.25x8=2 watt Current Lead : watt/pair at full current Vent port : 0.27 watt Refrigeration port : 0.03 watt/barrier Instrumentation : 0.1 watt Total heat load at 4.5K:3.87 watt

SAFETY

Quench propagation of quadrupole coil

Coil Temperature and voltage in case delay in actuation of trigger circuit

Pressure transient after loss of vacuum and quench for different rupture disc size

Protection Resistance : Ohm

Issues related to multipole magnets Large weight for a single magnet. Maximum weight is around 32Ton. Installation and handling of these magnets have to be thought. Physical gap between magnets? Detail field quality requirement are not available for Sextupole. Magnetic measurement – Rotating coil for such wide aperture magnets are not available. Testing with LHe, mostly not available at factory. What are the possibilities of shimming the magnets? NuSTAR Week 2012, VECC 110