1. EFDA 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Progress on the design of various magnetic sensors for ITER: diamagnetic and flux loops, high-frequency coils, in-vessel and divertor coils, ex-vessel coils, and external Rogowskis Anna Encheva for the CRPP team Ecole Polytechnique Fédérale de Lausanne (EPFL) Centre de Recherches en Physique des Plasmas Association Euratom-Confédération Suisse CH-1015 Lausanne Switzerland

2. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Slide 2 Outline  ITER Measurement requirements  Location within or outside the vessel  Design features  Open design issues  Research activities withing EFDA TWP 2005 High frequency coils MHD Saddle loops Diamagnetic loops Divertor coils Ex-vessel coils Ex-vessel Rogowskis In-vessel flux loops Anna Encheva

3. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Measurement requirements MeasurementParameterConditionRangeΔT or ΔF ΔX or ΔkAccuracy (2σ) Plasma currentIpDefault0-1 MA1 msIntegral10 kA 1-17.5 MA1 msIntegral1 % Ip Quench17.5-0 MA0.1 msIntegral30% +10 kA Plasma position and shape Main plasma gaps, Δsep Ip>2 MA, full bore -10 ms-1 cm Ip Quench-10 ms-2 cm Divertor channel location Default-10 ms-1 cm Ip Quench-10 ms-2 cm dZ/dT of current centroid Default0-5 m/s1 ms-0.05 m/s (noise) + 2 % (error) Low (m,n) MHD modes, Sawteeth, Disruption precursors Mode complex amplitude at wall TBDDC – 3 kHz (0,0)<(m,n) < (10,2) 10% High frequency macro instabilities (Fishbones, TAEs) Fishbone- induced perturbation s in B,T,n TBD0.1-10 kHz (m,n)=(1,1)- TAE mode- induced perturbation s in B,T,n TBD30-300 kHz n=10 - 50- Main system:  Low (m,n) MHD modes, sawteeth, disruption precursors  High frequency macro instabilities Backups:  Plasma current  Plasma position and shape Slide 3 HF coils Anna Encheva

4. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Slide 4 HF coils Location within the vessel Located in the gap between blanket module and wall  distributed along poloidal contours  in 6 sectors  displaced by 60° toroidally * The scaled drawing could be found on: http://ftp.itereu.de/cad/html/  In order to cover up to m ~ 10, 20 high frequency coils were primary foreseen.  Only 18 high frequency coils are placed in each sector, due to the restriction to one/blanket module in the main chamber.  their proximity to the plasma is the same as the equilibrium coils  measures the flux change through the area of its windings without subsequent integration  the measured quantities is thus the time rate of change of the magnetic field in a locally rather restricted area Anna Encheva

5. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom HF coils Slide 5 Present design features  for avoid short-circuiting between the two layers of windings - ceramic is grooved with one layer of deep and one layer of shallow grooves which cross each other  for high bandwidth a wide gap is constructed  coil supports are insulated to reduce eddy currents  for reducing the internal coil capacitance – larger winding pitch  for minimizing stray fields and avoiding noise in the signal - even number of layers and windings is necessary  for getting a high induced voltage signal – effective area of the coil has to be large Anna Encheva

6. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom HF coils Slide 6 Present design features  usable at up to 2 MHz measure both: equilibrium field and fluctuation related to plasma instabilities  heat shield – protection from the plasma, prevent from interfering with other circuits Shield - connected to the vessel ground the coils has to be fully isolated from the casing  bobbin - made of stainless steel layer and copper strips  proposed implementation (minimum physics):  one poloidal array of ~20 coils (with non- uniform distribution) covering both low- and the high-field side on 3 machine sectors for redundancy, each coil with effective area (NA)EFF=0.1m 2  two toroidal arrays of 20 coils (with non- uniform distribution) located at Z=Z MAG  30cm, each coil with effective area (NA)EFF=0.1m 2 Anna Encheva

7. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom HF coils Slide 7 Open design issues  Choice of conductor Molybdenum or Tungsten or other material, having:  Good winding properties  Withstanding high temperatures  Coil effective area Now in total 0.075 sq.m. or larger?  Good frequency response within a wide operational range  Withstanding electromagnetic loads by full disruption mode 200 T/s  M.Roccella, ITER_D_22JQLY, May 2003 10 kHz ÷ 1MHz  Withstanding high temperatures Max. 600°C Anna Encheva

8. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom HF coils Slide 8 Work plan 2006  Transient electromagnetic analysis:  full disruption mode : 200T/s  induced voltage  Dynamic harmonic electromagnetic analysis:  induced eddy currents  amplitude - frequency response characteristics  Coupled field analysis:  Thermal analysis:  nuclear heating rate in the coil materials  temperature distribution in the coil structure  Structural analysis:  thermal loads  stress-strain distribution Anna Encheva

9. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom MeasurementParameterConditionRangeΔT or ΔFΔX or ΔkAccuracy (2σ) Plasma position and shape Main plasma gaps, Δsep Ip > 2 MA, full bore -10 ms-1 cm Ip Quench-10 ms-2 cm Divertor channel location Default-10 ms-1 cm Ip Quench-10 ms-2 cm dZ/dT of current centroid Default0-5 m/s1 ms-0.05 m/s (noise) + 2 % (error) Low (m,n) MHD modes, Sawteeth, Disruption precursors Mode complex amplitude at wall TBDDC – 3 kHz(0,0)<(m,n)< (10,2) 10% Locked ModesB r (mode)/B p 10 -4 - 10 -2 1 ms(m,n)=(2,1)30% Backups:  Plasma position and shape Main system:  Locked modes  Low (m,n) MHD modes, sawteeth, disruption precursors If necessary: MHD saddles as backup measurements for the equilibrium reconstruction Slide 9 Measurement requirements MHD saddles Anna Encheva

10. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Location within the vessel  Mounted on the inner wall of vacuum vessel  Exist on 9 machine sector pairs (40° apart toroidally)  Poloidally – 8 loops mounted on each sector  Saddle loops are permanent Slide 10 MHD saddles proposed implementation (general): toroidal distribution: 4 sets of ~15 saddle loops with non-uniform distribution at Z=Z MAG  80cm 2 sets on low-field side + 2 sets on high-field side toroidal positioning optimised for control of natural error field (TF ripple with/out ferrite inserts) poloidal distribution: 1 set of ~20 saddle loops in >3 sectors non-trivial role of  *-correction (loops shrink: , l j ) redundancy is sufficient as saddle loops are permanent where is Z MAG ? need to optimise positioning of saddle loops as different magnetic equilibria are expected effective area of each saddle loop (NA) EFF ~1.5m 2 lower than previous DDD estimate (~5m 2 ) Anna Encheva

11. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Present design features  Loops of 2mm mineral insulated cable  attached to the vessel at frequent intervals via resistance-welded clips  Choice of MI cable  Research activity, CIEMAT and SCK-CEN MHD saddles Slide 11 Open design issues:  design changes are required to satisfy full-scope physics requirements (∆Z MAG,  *-correction) Anna Encheva

12. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Divertor coils Slide 12 Measurement requirements  measurement of separatrix-wall gaps and reconstruction of equilibria (plasma shape and position)  improve the reconstruction accuracy near the X-point  this set of coils is essential to the reconstruction of divertor configuration Plasma Position and Shape:  Main plasma gaps with time resolution  10 ms and accuracy 1-2 cm  Divertor channel location (  10 ms, 1-2 cm)  dZ/dt of current centroid for range of  5 m/s, time resolution 1 ms and accuracy 0.05 m/s (noise) + 2% (error) Measured quantity:  Magnetic field (normal and perpendicular to diverter cassette elements) at coils locations. Anna Encheva

13. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Slide 13 Divertor coils Location within the vessel * The scaled drawing could be found on: http://ftp.itereu.de/cad/html/  Position in the vessel: divertor cassette  Location: 72 (6x6x2) coils on 6 divertor cassettes  ports 02, 04, 08, 10, 14, 16 (6 position)  System: pairs of equilibrium coils normal and tangential to the mounting surfaces of selected cassettes  6 coils with an axis perpendicular to divertor cassette elements  6 separate coils at equivalent positions with an axis parallel to divertor cassette elements Anna Encheva

14. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Slide 14 Divertor coils Present design features * Reference: G.Mazzone et al., Final Report on the Revision of ITER divertor design, 2003 Nuclear heating in St.St. at coils locations 0.5 W/cc 2.1 W/cc 2.5 W/cc 1.0 W/cc 0.4 W/cc 1.0 W/cc Construction of divertor coils similar to in-vessel coils Better cooling proposed coil effective area ~0.5m 2, corresponding to ~50V volume constraint (2x10x10x10 cm 3 ) less severe than by in-vessel coils for coils on pos.1,5,6  in-vessel tangential and normal coils design suitable coils on high heat flux region pos.2,3  re-optimization of coil shape different EM environment and screening, specially under divertor dome Anna Encheva

15. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Slide 15 Divertor coils Open issues Design of in-vessel equilibrium coils as basis for preliminary divertor coils design Choice of materials to minimize parasitic EMFs Winding wire selection (MIC, bare wire, ceramic coated wire) Divertor layout  identification of available space on divertor cassette  optimization of coil’s position, shape and orientation Wiring and connectors Estimation of mechanical errors (thermal expansion, EM forces) Anna Encheva

16. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Divertor coils Slide 16 Work plan 2006 Identification of available space on divertor cassette (A.Martin, ITER IT) Re-design the present in-vessel coils for the position 2 and 3, under the divetor dome Dynamic harmonic electromagnetic analysis Thermal FE analysis Anna Encheva

17. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Diamagnetic loop system Slide 17 Range β p = 0.01÷3 Accuracy 5% at β p = 1 Plasma current (MA) Diamagnetic flux Flux error for 5% Ratio to total toroidal flux 17 MA3 Wb150 mWb8x10 -4 1 MA10 mWb2 mWb10 -5 Achieved in present devices5x10 -5 accuracy is highly demanding estimation of mechanical errors is needed definition of compensation methods ITER accuracy requirements Anna Encheva Main system:  Plasma energy  Toroidal magnetic flux

18. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Slide 18 Diamagnetic loop system ITER frequency requirements f = 1 kHz flux is attenuated by vessel eddy currents by a factor of: poloidal time constant Achieved in present device ~ 300 (TCV, time const. 5.3ms,10kHz) Bandwidth is highly demanding Importance of vessel eddy current compensation Are the compensation coils adequate ? Advantage of a double loop set-up ? Anna Encheva

19. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Slide 19 Diamagnetic loop system Location and design 3 sets mounted on the inner vessel wall, separated by 120°: 2 diamagnetic loop, wired in parallel (to circumvent obstacles) Attached to the wall by spot welded clips 2 compensation coils additional poloidal field compensation loops Obstacle Diamagnetic loop contour Compensation coil Anna Encheva

20. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Slide 20 Diamagnetic loop system Method for performance analysis Identify and describe sources of mechanical errors (2005) construction misalignements and assembly errors in sensors construction misalignements in PF and TF coils, VV deformation under EM forces in PF and TF coils deformation after thermal expansion of VV Quantifying mechanical errors requires: magnetic field mapping (2006) thermal expansion modelling of VV (2006) modelling of VV deformation under EM forces modelling of eddy currents in VV (2006) Anna Encheva

21. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Slide 21 Diamagnetic loop system Diamagnetic loop status in short Assessment of ITER measurement requirements: very demanding Methodology to perform comprehensive performance analysis (requires modelling tool for various ITER components) Feasibility of alternative set-up to be studied (double loop) Anna Encheva

22. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Ex-vessel tangential and normal coils: specifications overview Ex-vessel tangential and normal coils is a backup set measuring plasma current, plasma equilibrium and plasma low frequency MHD activity. Location :On the outer VV skin in a poloidal cross-section Temperature : 200°C Effective area : 2.0 m 2 Issues : Available space 7 x 57 x 250mm 3 Radial dimension is small  coil sizing difficult Requirements : Ph.Moreau Slide 22 TORE SUPRA

23. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Progress made in TWP2004 task  Number of coils defined : 60 B norm + 60 B tang  Choice of conductor : insulated copper wire (  0.25mm)  Coil design  Electrical parameters have been defined (resistance, inductance, capacitance, cut-off frequency, etc.)  Sources of errors have been identified 243 248 250 57 5550 B norm cross sectionB tang cross section  Investigate winding issues  Error assessment using VV EM and movement models  Performance analysis of ex-vessel B norm and B tang coils (EFIT)  Technical review EFDA TWP 2004 task  Future work : EFDA TWP 2005 task Ph.Moreau Slide 23 TORE SUPRA

24. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Ex-vessel continuous Rogowski: specifications overview Ex-Vessel continuous Rogowski is a separate backup measuring the plasma current and giving relevant information on current flowing through the vessel. Location :In 14.5mm diameter groove cut in TFC casing, coil OD is 12mm Temperature : 4.0K Sensitivity : typ. 800 mV s / MA Issues : Available space, joints Requirements : Ph.Moreau Slide 24 TORE SUPRA

25. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Progress made in TWP2004 task  Rogowski routing in TFC is defined  Number of joints as low as possible: One joint at the top of TFC, another one at the bottom of TFC  Stress analysis during cool-down / warm-up cycles and plasma operation  Selection of material (former and cable)  Rogowski design and model have been done  Former having a double screw groove – regular winding  Electrical parameters have been defined (resistance, inductance, capacitance, cut-off frequency, etc.)  Technical review EFDA TWP 2004 task Rogowski : Stainless steel former model two layers: 1 st layer diameter 11 mm 2st layer diameter 9 mm Routing constrains: 100m radius of curvature Ph.Moreau Slide 25 TORE SUPRA

26. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom TORE SUPRA Slide 26  Refine the design and former selection (easy bending)  Rogowskis in two parts Define the joints  Assess Rogowski’s accuracy and source of error  Future work : EFDA TWP 2005 task Ex-vessel continuous Rogowski: specifications overview Ph.Moreau

27. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Inner vessel partial and continuous flux loops: specifications overview Continuous and partial flux loops contribute as the main set-up to plasma equilibrium calculation (with in-vessel B norm and B tang ). The continuous loops supply loop voltage and are supplementary set to get plasma current. Partial flux loops are also a supplementary set measuring plasma MHD activity. Location :Inner surface of the VV Number :4 continuous flux loops + 6 sets of 20 saddle loops Design: 2mm MIC Mechanic :Attached to the VV by spot welded joints Temperature : 300°C Issues : Subjected to plasma and nuclear heating Continuous flux loops interrupted by 9 welded joints Ph.Moreau Slide 27 TORE SUPRA

28. 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia Association Euratom Section for removal Contact plate Flux loop Connection Support plate Joint soldered to support plate Progress made in TWP2004 task  9 special welded joints allowing 3 replacements by remote handling  Electrical parameters have been defined (resistance, inductance, capacitance, cut-off frequency, etc.)  Source of errors have been investigated  Define the thermal gradient along the cable (TIEMF effect)  Measurement errors assessment using VV EM and movement models  Technical review EFDA TWP 2004 task  Open issues Ph.Moreau Slide 28 TORE SUPRA