Magnets Y.C. Saxena Institute for Plasma Research 1/16/2007 IPR Peer Review 15-17 Jan 2007 1
Magnet Development Program driven by Laboratory Scale Experiments ADITYA Tokamak SST-1 Tokamak 1/16/2007 IPR Peer Review 15-17 Jan 2007 2
BASIC EXPERIMENTS IN TOROIDAL ASSEMBLY (BETA) Vertical Field Coils Helmholtz Coil Configuration Inner Dia: 230 Cms No.Turns: 10 ( 5 G @ 100 A) Toroidal Field Coils Picture Frame Coil (ETP Copper) 16 Numbers, 3 turns each Width of each leg: 5 Cms Radial & Vertical aperture 50 Cms B 0 : 1 kg at 5 ka 0.38 mh ; 10 mω Resistance: 350 mω ; Inductance : 1.3 mh 1/16/2007 IPR Peer Review 15-17 Jan 2007 3
Large Volume Plasma Device Uniform Magnetic Field Field Uniformity (< 1% variation) Axial extent : 1.5 m Radial Extent: 1.6 m B max (G) (at 300 A) 150 ETP Copper (Water Cooled) Double pancakes Two sets of circular coils Type A (ID 2.3m; OD 2.375m) Type B (ID 2.9m; OD 2.975m) 1/16/2007 IPR Peer Review 15-17 Jan 2007 4
Solenoid for test stand 6T @ 75 A Sixth order compensated Self protecting Warm bore : 256 mm MF NbTi wire 0.559 mm dia 54 filaments 45 micron dia Cu:Sc :: 1.34:1 (Cu 142 RRR) 1000 turns/layer; 42 layers 1/16/2007 IPR Peer Review 15-17 Jan 2007 5
ADITYA Copper Magnets SST-1 SC Magnets + Copper for Ohmic system 1/16/2007 IPR Peer Review 15-17 Jan 2007 6
TF COILS for ADITYA TOKAMAK PARAMETERS OF TF COILS Number of coils 20 Turns per coil 6 Length (mm) 1260.0 Radial Aperture (mm) 780.0 Vertical aperture (mm) 940.0 Width coil (mm) 1030.0 Resistance: (m ) 5.04 Inductance (mh) 4.0 Max. Stored energy (MJ) 5.0 Peak current (ka) 50.0 Picture Frame Coils Magnetic Fux Density B 0 (T) : 1.5 1/16/2007 IPR Peer Review 15-17 Jan 2007 7
ADITYA TOKAMAK Central Solenoid: Designed for 0.6 Vs flux storage; 3.2 T field in bore at 20kA current per turn; 17mm x 15mm conductor with 6.4mm dia bore; two in hand winding; 174 turns; 6 layers 1/16/2007 IPR Peer Review 15-17 Jan 2007 8
Parameter TR1 TR2 TR3 TR4 BV1 BV2 No. of coils 1 2 2 2 2 2 Turns/coil 174 56 3 4 60 22 ID (cm) 17.5 28 121 150 30 155 OD (cm) 27.5 49 124 156 54 171 17mm x 15mm conductor with 6.4mm dia bore; two in hand double pancakes for TR coils One conductor double pancake winding BV coils 1/16/2007 IPR Peer Review 15-17 Jan 2007 9
SST-1 MAGNET SYSTEM Requirements: Confinement, Shaping and Equilibrium Fields Ohmic Flux Storage Feed-Back Control Supercondcting Magnets: Toroidal Field (TF) Coils : Poloidal Field (PF) Coils : 16 Nos. 9 Nos. Copper Magnets (Water Cooled) : Ohmic Transformer (TR) Coils : 7 Nos. Poloidal Field (PF ) Coils ( in-vessel): 2 Nos. Position Control Coils ( in-vessel) : 2 Nos. Figure 1: A cross-section of SST-1 tokamak. (1 -Support Structure; 2-TR2 Coil ; 3-VF Coil; 4 -TR3 Coil; 5-PF5 Coil; 6-PF4 Coil; 7 -PF1, PF2 & PF3 Coils; 8-TR1 Coil; 9- Vacuum Vessel; 10 -PF6 Coil; 11-Feedback Coil; 12-PFC; 13 -TF Coil; 14- Cryostat; 15- LN2 Panels) 1/16/2007 IPR Peer Review 15-17 Jan 2007 10
PARAMETERS Total No. of Coils : 16 Turns per Coil : 108 Current per turn (3T Field): 10 ka Max. Field at Conductor: SUPERCONDCTING MAGNETS: TF Coils 5.1 T Maximum Field Ripple : 0.35% Total Inductance : 1.12H Total Stored Energy: TF COIL Winding Pack: D-Shaped; 6 Double Pancakes X-section: 194x144 mm 2 Dimensions: 2.59 m 1.53 m 56MJ Consolidated by VPI & encased in SS316L case Conductor: NbTi based CICC 1/16/2007 IPR Peer Review 15-17 Jan 2007 11
TF MAGNETS CASINGS TF winding packs are encased in casings made of SS316L Each of the Casing consist of Inner ring, outer rings & two side plates Inter coil supports are provides on inner and outer legs 1/16/2007 IPR Peer Review 15-17 Jan 2007 12
Assembly of TF coils TF coils nosed and bolted on in-board side to form a toroidal vault Outer Inter coils supports (2 #each ) provided between adjacent coils Coil Casings insulated from each other. Casings and inter-coils structures support PF coils 1/16/2007 IPR Peer Review 15-17 Jan 2007 13
SUPERCONDCTING MAGNETS: PF Coils Support single & double null equilibria Triangularity ( 0.4-0.7), Elongations ( 1.7-1.9), l i (0.75-1.4), p ( 0.01-0.85) & slot divertor configuration Limiter operation during Plasma current ramp up Coil type # coil s Coil Radi us ( m) Verti cal Locati on ( m) Wi ndi ng Cr osssecti on ( mm 2 ) # t ur ns PF1 1 0. 45 0. 0 71x320 80 PF2 2 0. 45?0. 43 71x163 40 PF3 2 0. 50?0. 93 136x380 192 PF4 2 1. 72?1. 03 85x136 40 PF5 2 2. 01?0. 65 85x136 40 PF6 2 1. 35?0. 35 100x100 16 1/16/2007 IPR Peer Review 15-17 Jan 2007 14
COPPER MAGNETS (WATER COOLED) Ohmic Transformer (TR) Coils : 7 # Vertical Field (VF) coils : 2 # PF Coils 2 # Position Control Coils (in-vessel): 2 # Parameters of Ohmic Transformer Coils # Radius (m) Turns (#) X-section (mm 2 ) Center (m) TR1 1 0.20 672 120 2600 0.00 TR2 2 0.49 40 195 95 1.40 TR3 2 2.42 3 58 23 0.73 Conductor for the copper coils The TR1 & TR2 coils of the Ohmic transformer. The transformer has a flux storage of 1.4 Vs with field strength of 8 T in the TR1 bore. 1/16/2007 IPR Peer Review 15-17 Jan 2007 15
Conductor for SST-1 Superconducting Magnets Cable-in-conduit-conductor (CICC) selected for both TF and PF coils: Low A.C. loss Good heat transfer characteristics High rigidity Moderate cost NbTi based CICC has been designed taking into account all the events typical of SST-1 operations on SC Magnets: Plasma Current disruptions Vertical displacement events Plasma break down and current start-up Current in Control coils 1/16/2007 IPR Peer Review 15-17 Jan 2007 16
Conductor for SST-1 Superconducting Magnets Conductor Characteristics Conductor type : CICC Dimensions : 14.8 14.8 mm 2 No. of Strands : 135 Cabling Pattern : 3 3 3 5 Last stage wrapped (half overlap) with 25 m thick SS304 tape. Strand Specifications Material : NbTi in Cu Strand Dia : 0.86 mm Filament Dia. : 10 µm Filaments per strand : 1272 Cu : NbTi : : 5 : 1 Cu RRR : 100 Hysterisis Cu NbTi Cu Twist Pitches: I stage : 40 mm; II stage : 75 mm III stage: 130 mm; Losses : <100 mj cm -3 Strand Cross-section Strand Characteristics: I c @4.5K; 5T : 232A IV stage: 290 mm Index n : 45 Conduit Material : SS 304L (0.1 V / cm criteria) Conduit thickness : 1.5 mm Void Fraction : 36 % Hysterisis I c @ 5T, 4.2K : 36 ka loss : 33.5 mj cm -3 I op @ 5T, 4.5K : 10 ka (±3T; 4.2K) CICC Cross-section 1/16/2007 IPR Peer Review 15-17 Jan 2007 17
Pre-qualification tests on CICC strands Parameters Design Values Qualification Test Results Virgin Strand Extracted * Strands I c @ 5T;4.2K 272 A 273 A 262 A n @ 5T 25 46 45 Hysteresis Loss 3T (mj/cm 3 -strand) 100 36.5 32.7 RRR of Cu ~100 108 92 Filament Breakage 0% 0% Cu:SC 4.98:1 4.98:1 *Strands extracted from first stage triplets of sample length of CICC 1/16/2007 IPR Peer Review 15-17 Jan 2007 18
Tests on CICC strands 700 Ic (A) 600 500 400 300 200 100 0 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 Temperature (K) Data, 2T Fit, 2T Data, 3T Fit, 3T Data, 4T Fit, 4T Data, 5T Fit, 5T Data, 6T Fit, 6T Data, 7T Fit, 7T Data, 7.5T Fit, 7.5T Data, 8T Fit, 8T Critical Current Vs Temperature for different Magnetic Fields Hysteresis for 3T field in VSM at 4.2K 1/16/2007 IPR Peer Review 15-17 Jan 2007 19
MODEL COIL TEST Test Objectives: To establish suitability of CICC for both TF and PF coils of SST-1. To estimate the limiting parameters in different operational scenario of SST-1 Design Drivers for Model Coil : Simulation of 5 T DC Field over a length of more than 0.7 m with CICC at 10 ka ( SST-1 TF coil Maximum Field) Hydraulic path similar to SST-1 TF DP path ( SST-1 TF coil flow path) Ampere-turn similarity to SST-1 PF3 ( Relevant to SST-1 Start-up scenarios) Winding current density 36 A mm -2 ( TF operating current density) Pancake to pancake transition with `r 200 mm ( half of highest TF curvature) Controlled normal zone initiation to investigate normal zone propagation characteristics ( Dump constant validation in TF magnets) Flow conditions similar to SST-1 flow conditions ( Cryo-stability validations) Disturbances similar to SST-1 scenarios 1/16/2007 IPR Peer Review 15-17 Jan 2007 20
Model Coil test set up for SST-1 CICC Main parameters of Model Coil Main Parameters of Pulsed Simulation Coils 1/16/2007 IPR Peer Review 15-17 Jan 2007 21
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Results of Model Coil Tests Static characterization test Static Test: MC Charge slowly up to 12 ka (6.2 T) at He flow rate of 0.5 g/s (SST-1 flow rate >1.2g/s) Response of Model coil to the perturbations at different operational currents 1/16/2007 IPR Peer Review 15-17 Jan 2007 23
Results of Model Coil Tests Current Sharing Temperature Measurements Stability against sinusoidal perturbations ( 0.025 T; 125 ms duration) at 0.5 g/s 1/16/2007 IPR Peer Review 15-17 Jan 2007 24
Results of Model Coil Tests Stability against fast transients (disruption like disturbances) Stability against combined ( longitudinal + transverse) disturbances at (a) 0.85 g/s (b) 1.2 g/s. CICC IS SUITABLE FOR SST-1 TF AND PF MAGNETS WITH VARIOUS PHYSICAL REQUIREMENTS SPECIFIED IN SST-1 1/16/2007 IPR Peer Review 15-17 Jan 2007 25
Insulation System for Superconducting magnets Electrical tests : Inter-turn insulation at 1 kvdc Insulation resistance between turns Insulation resistance on main insulation 2 kv AC 50 Hz proof resistance for 1 min. Thermal cycling test: 10 cycles of Heating at 160 0 C for 15 minutes in an electrical oven followed by quenching in liquid Nitrogen at minus 196 0 C for 5 minutes. After thermal cycling all electrical tests were done. The samples passed all the electrical tests with degradation in performance below 5% after the thermal cycling. No mechanical cracks were observed. 1/16/2007 IPR Peer Review 15-17 Jan 2007 26
CICC Spool CICC Shaping 1/16/2007 Take-up spool for double pancakes IPR winding Peer Review 15-17 Jan 2007 TF Double-pancake winding machine 27
Dummy TF double pancake 1/16/2007 VPI Mould for TF coils IPR Peer Review 15-17 Jan 2007 28
Casings for TF Coils 1/16/2007 IPR Peer Review 15-17 Jan 2007 29
Superconducting Magnets Consolidation 1/16/2007 IPR Peer Review 15-17 Jan 2007 30
Superconducting Magnets Consolidation 1/16/2007 IPR Peer Review 15-17 Jan 2007 31
Winding machine for PF1,P2 and PF3 coils Winding of PF1 in progress 1/16/2007 Winding former for PF4 and PF5 IPR coils Peer Review 15-17 Jan 2007 Winding of PF5 in progress 32
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Joints for Superconducting Cable Joint Characteristics Shake Hand Soldered Overlap type Overlap length: 320 mm Copper RRR : 10 Solder Alloy : 95 Sn 05A (cable space) Solder Alloy : 60 Pb 40Sn (termination) Series cooled with the magnet winding pack 1/16/2007 IPR Peer Review 15-17 Jan 2007 35
Secondary Loop Hall sensor Primary coil CICC Joint 1/16/2007 IPR Peer Review 15-17 Jan 2007 36
Experimental Validation of the Joints (principle) Contactor Normally closed I 4.2 K PS R d L p Ls R j I Secondary current Current Primary current 1/16/2007 t t IPR Peer treview t 15-17 Jan 2007 37 1 2 3 4 Time
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Sensors and Quench Detection in SCMS Sensor Placement of the sensor Purpose of the sensor Voltage taps (PTFE shielded twisted pair cable) Flow meters (Venturi meters) Temperature Sensors (Cernox) Hall probes (Semiconductor chip based) Linear displacement transducers Across the superconducting magnets (# 300) At the inlet of each TF and PF coils (# 19) TF & PF Coil Inlet and Outlets, Support rings & Cantilever (# 173) In the bore of TF coils (# 2) On the 4 quadrants of support ring and 4 TF coils (# 8) Quench detection Flow measurements and secondary quench detector Temperature Measurement Direction and intensity measurements of magnetic field. Displacement measurement cool down & warm up of cold mass 1/16/2007 IPR Peer Review 15-17 Jan 2007 40
TF coil cool down 1/16/2007 IPR Peer Review 15-17 Jan 2007 41
Ion Deflection Magnet for NBI system 1/16/2007 IPR Peer Review 15-17 Jan 2007 42
Future Directions: Nb 3 Sn Technology Proto type TF coils Proto type Central Solenoid Jointless winding Test facility 1/16/2007 IPR Peer Review 15-17 Jan 2007 43