Superconducting solenoid for MPD detector on heavy-ion collider NICA at JINR (Dubna)

Presented byEvgeny K. Koshurnikov

CERN September 27, 2011

2

Superconducting solenoid of Multi-Purpose Detector (MPD)

• The main component of the Multi-Purpose Detector (MPD) on heavy-ion collider NICA is a large 0.5 T superconducting solenoid. It has to provide resolution for transverse momenta over the range 0.1 3 GeV/c. ‑

• The magnet is designed as a superconducting solenoid with a flux return iron yoke and with aluminium stabilized coil implying an inner winding method and circulating indirect cooling.

• The magnet has to be commissioned in 2017.

3

General view of MPD

The magnet inner dimensions are chosen as a compromise between the time of flight requirements to length of tracks to be sufficient for good particle identification and track reconstruction precision on one side, and the needs in homogeneous magnetic field and reasonable cost of the magnet on the other side.

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Interface requirements

The solenoid aperture volume is determined by arrangement of the

inner detectors ΔZ=5.24m; Ø=4m

• Requirement for cryostat radiation transparency is not considered• It takes pole taper bores 14°- acceptance for two future forward spectrometers• Important requirement! The installed electrical capacity in Dubna is very limited. So

the decision was taken for benefit of superconducting winding

5

Magnetic field requirements

• Rated magnetic field in the aperture 0.5T • High level homogeneity dictates requirements for the magnet

geometry stability under action of the magnetic forces and after magnet transportation to assembly area and back

Radial magnetic field component

0z , mmzmax 1500= dz

B

BInt

z

rmaxz

z=

mmInt 0.775|<|

mmrmm 1100<<350 Radial magnetic field

component

0z , mmzmin 1500= dz

B

BInt

z

rminz

z=

mmInt 0.775|<|

mmrmm 1100<<350

• Magnetic field requirements are optimized for momentum resolution of particles.

• Requirement for integral of radial component of the magnetic field

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MPD Solenoid DesignDistinctive features of the magnet• high field homogeneity in the tracker area, • heavy weight and large dimensions of the system.Accepted concept is the well proved design• Solenoid with a thin winding, pure aluminum stabilized NbTi superconductor,

indirect cooling of the coil, and flux return iron yoke• Yoke geometry stability is secured by the rigidity of two support rings joined by

twelve flux return legs (this design is analogues to STAR magnet yoke design)• Two correcting coils with higher linear current density at the ends of the main coil

and trim coils on the poletipsOther magnet features • The magnet doesn’t have doors. The poles are being inserted in axial direction • Inner detectors are fixated on the yoke support rings. So the inner shell of the

cryostat is not loaded by addition weight of the detectors

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Main solenoid parameters

Rated current, kA 1.44Rated induction, T 0.5 ТMaximal designed current, kA 1.59Maximal flux density in the coil at maximal designed current [T] 0.61Current density in aluminium matrix of the corrective/main coil conductor for designed current, A/mm2 50.2/46.6

Total current (Amp-turns) at the rated induction [ MA] 2.18Stored energy at the rated induction [ MJ] 7.9Decentering forces acted on the coil- axial force, kN/cm- radial force, kN/cm

371.07

Number of turns (main section of the SC coil and in the correcting sections) 1512=758+2 x 377Inductivity of the SC coil [H] 7.3Inductivity of the trim coil [H] 0.0038

Rated/Maximal current density in the trim coil at the nominal induction [А/mm2] 1.467/1.89

Total current (Amp-turns) in the trim coil at the nominal induction [kA] 97

MAGNETIC FIELD CALCULATIONS

OPERA-3D and FE-2D software, original FORTRAN and Mathcad – based computer

codes

FE TOSCA model(1.8 10∙ 6 ÷ 5 10∙ 6 nodes)

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MAGNET OPTIMIZATION

• The goal of optimization is minimization of the integral of the radial component of magnetic induction keeping minimal values of main and corrective coil current density difference and current density in the trim coil with help of Mathcad – based computer code

• Optimization parameters are: Relation of current densities of corrective and main sc coils JCORR / JSC, Trim coil current density JTRIM SC coil current density JSC.

• Two first parameters are independent and the last parameter depends on the first two parameters trough the average magnetic induction in TPC area.

max

0)(

)(Z

Z

dzzBz

zBrInt

1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 2600 27000.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

J CO

RR/ J

SC [

%]

140

120

80

60

40

20

100

0

Int(Br/Bz) J

CORR/ J

SC

TPC boundary Coil end

Int(

Br/

Bz)

[mm

]

ZC [mm]

SC corrective coil center positiondependence for radial component integral in the TPC area and relationof sc coils current densities

Very high homogeneity of magnetic field and very low integral of radial component for the TPC area are achieved

Intmax = 0.17 mm< 0.775 mm

|δ| < 0.12%

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SC solenoid coil

• One layer coil is wound on the inside of the structural aluminum alloy Al5083 cylinder • Indirect cooling by force two-phase helium• Two corrective coils with the current density about 6% higher than in central coil • Radial conductor size and aluminium cylinder thickness provides acceptable temperature rise after a

quench and keeping of the coil shape under gravity. Radial deformation of the coil loaded by gravity, magnetic pressure and radial decentering force <0.5mm

• Maximal radial magnetic pressure 0.12 MPa, maximal axial compression force 470 kN.

Cooling tube length 80 m , diameter 18 mm

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Main parameters of the conductor Superconductor NbTi/Cu Stabilizer Pure Al RRR of stabilizer 1000> NbTi/Cu wire diameter, mm 1.2 Configuration (NbTi/Cu) 1:0.9 Filament diameter about 20 µm Number of filaments about 2000 Twist pitch about 20 mm RRR of copper matrix > 100 Bare SC cable cross-section in the main and correcting sections, mm2 (3.2 х 12.0) & (3.0 х 12.0)

Edge radius, mm 0.3 Insulated SC cable cross-section in the main and correcting sections, mm2 (3.6 х 12.4) & (3.4 х 12.4)

Insulation material Half lapped prepreg fiberglass tape of 0.1 mm (after compression)

Critical current density at 4.2 K and 5 T, A/mm2 2700 Length of the conductor, km 21 Weight of the conductor, kg 850

Aluminium stabilized conductor with central sc wire Ø1.2 mm

The critical parameters of the conductor for low inductions were chosen on the base of approximation expressions L. Bottura. “A practical fit for the critical surface of NbTi”. CERN, LHC Project Report, MT-16, 1999.The design current 1.59kA is ~40% along the load line to the conductor capability at the temperature 4.5 K. The maximal current corresponds to a temperature 7.2 K leaving a temperature margin of greater than 2.7 K at the maximal induction 0.61 T at the coil end. MQE ~1 J/cm3

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Influence of technological deviations on the magnet parameters

Nature of deviationChange of the

integral of radial component [mm]

Axial/radial force on the shifted unit [kN]

Current density in the trim1/ trim2 coils

[А/mm2]Axial shift of SC coil

by 10 mm 0.16 36/0 1.39/1.59

Radial shift of SC coil by 10 mm 0.01 0/2.7 1.467/1.467

Symmetric axial shift of the poles by

+5 mm each0.04 890/0 1.536/1.536

Radial shift of the pole by 5 mm 0.02 940/137 1.467/1.467

Radial deformation of the coil Δ = 10 mm 0.02 0/0 1.467/1.467

Axial shortening of the SC coil by 1% 0.31 0/0 1.753/1.753

Complex axial deviation* 0.52 34.3/0 (SC coil) 1.68/1.89

* Cumulative effect of all axial deviations given in the previous lines of the table

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Cryostat design

Stainless steel cryostat: to=16mm/ti=13mm. Maximal overpressure– 0.7 Bar.

Cryostat supports

Control Dewar

2x12 radial ties

6 axial ties

Inner radius, m 2.02Outer radius, m 2.36Length, m 5.7

Inner radius, m 2.02Outer radius, m 2.36Length, m 5.7

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Cryogenic system

• Heat load at T=4.5 K, W 46 • Heat load on the Control Dewar

heat exchanger, W 123• Refrigerating capacity (including • thermal screen), W

220• Forward flow, g/s 9.8• Return flow, g/s

9.58• The flow trough the current leads, g/s 0.22• Steam-content in the inlet/outlet of

heat exchanger, % 5/ 23• Pressure drop in the cooling tube, kPa 4.7• Gaseous Helium flow for thermal screen, g/s 2.9

«Linde» Refrigerator LR 140, 210 - 255 W at 4.5K

Forced Two-Phase cooling systemHelium circuit parameters

Cryostatting cycle in T-S diagram

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Yoke Assembly at the factory and in the Experimental building

Part count

Weight Sum

Iron Yoke Support ring, ton 2 20.9 41.8Barrel beam, ton 12 17.2 206.4Pole tip inner ring, ton

2 14 28

Pole tip outer ring, ton

2 14.4 28.8

Yoke support, ton 2 17.5 35Pole support, ton 2 31.7 63.4Trim coil, ton 2 0.75 1.5Total (weight of the yoke):

405

Cryostat & coil Vacuum vessel, ton 1 26.4 26.4Thermal shield, ton 1 1.3 1.3Coil+Support cylinder, ton

1 6.3 6.3

Total (cryostat+coil) 34Grand total (magnet

weight)440

Weights of the magnet main parts

Incircle radius of the yoke, m 2.4Circumcircle radius of the yoke, m 2.67Interpole distance, m 5.24Length of the yoke, m 6.4

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Assembly/Operation conditions

Parking Position

Operation Position

Rails for magnet and platform transportations

Platforms for equipment and electronics

Magnet poles on their rails

Assembled magnet

Accelerator ring

Iron yoke and cryostat with assembledinner detectors

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Moving and Supports Systems Yoke movement – 2 hydraulic cylindersPole insertion – 2+2 cylindersYoke supports – 6 cylinders

• The magnet has: Two hydraulic horizontal drive cylinders for translation of the detector, which have positional

feedback gages of the pistons. Controller which allows operation of each cylinder either independently or synchronously.

• At every stage of movement the free ends of the cylinders are fixed on the floor. The detector is translated of 1.5m and after that the pistons repositioned in new positions on the floor for the next step of translation.

Hilman Rollers

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Solenoid Coil Quench Protection

symmetry: 1/2 in axial and 1/32 in azimuthal direction

QUENCH model of electric circuit

R1 = 1.3 10∙ -3 OhmR2 = 0.3145 OhmS1 opens when Vnz>1 Volt

QUENCH FE design model

Quench processes were modeled by means of Vector Fields Software

Protection Circuit

MODELLING OF THE COIL PROTECTION

QUENCH, TEMPO and ELEKTRA modules of the OPERA-3D software

Detail of FE QUENCH model (2.5 10∙ 6 nodes)

Al cylinder

Insulation

Yoke pole

Air

SC coil

Quench-back effect is seen (60 sec after quench starts)

Temperature distribution: 40 sec after quench starts

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RESULTS OF THE QUENCH TRANSIENT ANALYSISEnergy extraction to the external dump

resistor Energy extraction without active

protection

Parameter With protection Without protection

Maximal temperature (design current 1590 A) , Tmax [K] 24 112 (100 for Al6061)

Maximal temperature difference in the coil, ΔTmax [K] 14 93

Maximal radial temperature difference in insulation, ΔTrmax [K] 4 30

Maximal voltage on the normal zone, Vmax [Volt] 19 230

Energy dissipated in the coil, W [MJ] 0.43 8.98

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Yoke deflected mode under action of gravity and magnetic forces

1

X

Y

Z

-.539E-03

-.422E-03

-.306E-03

-.189E-03

-.718E-04

.450E-04

.162E-03

.279E-03

.395E-03

.512E-03

Maximal pole to pole approach distance < 2 х 0.5 mm for rated solenoid current andfor ANY combination of the magnet support reactions The magnetic force applied to the pole = 960kN.

1

X

Y

Z

-.002167

-.001924

-.001681

-.001438

-.001194

-.951E-03

-.708E-03

-.465E-03

-.222E-03

.216E-04

Maximal vertical deflection of the support cradles when magnet is rested on two supports <1mm

Maximal stresses (membrane+bending) are located in the Yoke cradles Normal operative condition , MPa [169] 43Violation of Normal operative Conditions , MPa [234] 56

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Stress in the Cryostat Shells

1

X

Y

Z

.266116

4.266

8.266

12.266

16.266

20.266

24.265

28.265

32.265

36.265

1

X

Y

Z

-.001399

-.001244

-.00109

-.936E-03

-.781E-03

-.627E-03

-.472E-03

-.318E-03

-.164E-03

-.936E-05

Operative magnet on two diagonal supports.

Equivalent stress in the cryostat shell

Magnet transportation . Two diagonal supports

Vertical deformation of the cryostat shell

Conclusion

• The most critical features of the magnet of Multi-Purpose Detector (MPD) :

low value of integral of radial component of magnetic induction

large overall dimensions and heavy weight • The solenoid design provides very rigid fixation of

the yoke and cryostat parts. The mutual positions of the solenoid parts are secured against action of gravity and magnetic forces after multiple magnet transportations to beam/parking position and removing/insertion of the poles .

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THANK YOU FOR YOUR ATTENTION!

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DELPHI [1] ALEPH [2] BABAR [3] CDF [4] MPD (CERN) (CERN) (SLAC) (Fermilab) (JINR)

Year completed 1988 1986 1997 1984 2014 Central field, T 1.2 1.5 1.5 1.5 0.5 Field inhomogeneity in the tracker area, % 0.1 0.4 2 1 0.1 Stored energy, MJ 110 137 25 30 7.9 Total Amp.Turns, MA 7.6 8.56 5.12 5.75 2.17 Current density, A/mm 2 46.3 40 47 64 34 (32) Current, kA 5.0 5.0 4.6 5.0 1.23 Aluminum stabilized conductor cross section, mm 2 244.5 353.6 204.9 203.89 )122.3(123 Inner bore, m 5.2 4.96 2.8 2.86 4 Coil length, m 6.8 7 3.46 5 5.3 Yoke incircle outer diameter, m 9.36 5.84 9.5 5.34 Yoke length, m 10.6 6 7 6.4 Total magnet weight, t 2640 580 2000 451 Cold mass, kg 25000 4900 5570 6265 Thermal load at 150 W 100 W 52 35 30 W 4.5 K, W +1.25 g/sec +1.25 g/sec +0.156 g/sec

Comparison of solenoids similar to the MPD solenoid

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RESULTS OF OPTIMIZATION

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T=4.5 K (safety factor 2) Load, Watt

Radiation 20.5

Support conduction 9

Chimney and Control Dewar 10

Conductor joints and wires 2

Eddy current losses in the Al cylinder 12

Total (normal/transient regime): 41.5/53.5

T=77 K (safety factor 2)

Radiation 398

Shield supports conduction 73

Heat intercepts of the coil supports 140

Total: 611

Current leads (safety factor 1.5)

Operation current 0.22 g/sec

Zero current 0.094 g/sec

Heat Loads

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Deformation of the coil loaded by gravity, magnetic pressure and radial decentering force

Radial displacements

The maximal radial deviation of the coil shape doesn't exceed 0.5 mm

Coil space fixation by 2 x 12 radial ties

Two 45 mm thickenings on both ends of the support cylinder

The origin of decentering force: 20 mm vertical off-center coil displacement

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Maximal stresses (membrane+bending)

Yoke beams Magnet transportation , MPa [169] 5,5

Normal operative condition , MPa [169] 3,6

Violation of Normal operative Conditions , MPa [234] 7,5

Cryostat outer shell and flanges/ Cryostat supportsMagnet transportation , MPa [169] 30,6/64,1Normal operative condition , MPa [169] 9,7/24,4Violation of Normal operative Conditions , MPa [234] 36,3/97,5

Yoke Support Rings & PolesNormal operative condition , MPa [169] 10,3Violation of Normal operative Conditions , MPa [234] 11,0

Yoke cradles Normal operative condition , MPa [169] 43,4Violation of Normal operative Conditions , MPa [234] 55,5

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Maximal axial deformation of the yoke under action of gravity and magnetic forces

Maximal pole to pole approach distance < 2 х 0.5 mm for rated solenoid current andfor ANY combination of the magnet support reactions

Uz1<0.36mm

1

X

Y

Z

-.539E-03

-.422E-03

-.306E-03

-.189E-03

-.718E-04

.450E-04

.162E-03

.279E-03

.395E-03

.512E-03

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Yoke footprint vertical deflection 1

X

Y

Z

-.002167

-.001924

-.001681

-.001438

-.001194

-.951E-03

-.708E-03

-.465E-03

-.222E-03

.216E-04

1

X

Y

Z

-.002167

-.001924

-.001681

-.001438

-.001194

-.951E-03

-.708E-03

-.465E-03

-.222E-03

.216E-04

Maximal vertical deflection of ANY combination of the support point lost <0.94mm

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Stresses in the coil

• Tensile stress in aluminium 5083 support cylinder under action of differential thermal contraction and magnetic pressure=26 MPa < al=92MPa

• Local axial tensile stress conductor/insulation because of differential thermal contraction =6 MPa (Axial prestress = 10MPa/162 ton)

• Local shear stress conductor/insulation because of differential thermal contraction τ=12 MPa

• Equivalent stress in the aluminium matrix of the conductor=11 MPa (plastic deformation is considered)

Thermomechanical stresses in the coil on the conductor/insulation boundaries

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Local radial tensile stress up to =13 MPa > ins=10MPa

Local shear stress τmax=12 MPa > τ=7MPa

Local axial tensile stressmax=16 MPa > ins=10MPa

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Axial and Radial Passages for Cabling and Tubing

35

Yoke Deflected Mode FE Computations

Step-by-step load application in the process of FE computation:Gravity load. The poles are not mountedGravity load. The poles are mountedGravity load. The poles are mounted. Magnet is rested on two diagonal support pointsGravity load. The poles are mounted. Magnet is rested on two diagonal support points. Magnetic forces.

Six magnet support points. Operative regime - Normal ConditionsThe pressure in two diagonal hydraulic mountings is 20% higher than in all other mountings. Operative regime - Normal ConditionsTwo diagonal magnet supports. Operative regime – Violation of Normal Conditions

M48 studs2 x 72 pcs.Initial M48 stud tightening force 295 kN

Two critical Studs M48

M24/M42/M48 (magnet is in the beam position) Normal operative conditions , MPa [708] 388/571/533Emergency conditions , MPa [1000] 1200/580/1110

ActionM24 → M27At least 2x3 beam/ring radial contacts