EFDA 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia...

EFDA

10th 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


AssociationEuratom

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


AssociationEuratomMeasurement requirements

Measurement Parameter Condition Range ΔT or ΔF

ΔX or Δk Accuracy (2σ)

Plasma current Ip Default 0-1 MA 1 ms Integral 10 kA

1-17.5 MA 1 ms Integral 1 %

Ip Quench 17.5-0 MA 0.1 ms Integral 30% +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


dZ/dT of current centroid

Default 0-5 m/s 1 ms - 0.05 m/s (noise) + 2 % (error)

Low (m,n) MHD modes,

Sawteeth, Disruption precursors

Mode complex

amplitude at wall

TBD DC – 3 kHz

(0,0)<(m,n)< (10,2)

10%

High frequency macro

instabilities (Fishbones,

TAEs)

Fishbone-induced

perturbations in B,T,n

TBD 0.1-10 kHz

(m,n)=(1,1) -

TAE mode-induced

perturbations in B,T,n

TBD 30-300 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


AssociationEuratom

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


AssociationEuratom

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


AssociationEuratom

HF coils

Slide 6

Present design features

usable at up to 2 MHz measure both: equilibrium field andfluctuation related to plasma instabilities

heat shield – protection from the plasma, prevent from interfering with

other circuitsShield - 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=0.1m2

two toroidal arrays of 20 coils (with non-uniform distribution) located at Z=ZMAG30cm, each coil with effective area (NA)EFF=0.1m2

Anna Encheva


AssociationEuratom

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


AssociationEuratom

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


AssociationEuratom

Measurement Parameter Condition Range ΔT or ΔF ΔX or Δk Accuracy (2σ)


Main plasma gaps, Δsep

Ip > 2 MA, full bore

- 10 ms - 1 cm


Divertor channel location

Default - 10 ms - 1 cm


dZ/dT of current centroid

Default 0-5 m/s 1 ms - 0.05 m/s (noise) +

2 % (error)

Low (m,n) MHD modes,

Sawteeth, Disruption precursors

Mode complex

amplitude at wall

TBD DC – 3 kHz (0,0)<(m,n)< (10,2)

10%

Locked Modes Br(mode)/Bp 10-4 - 10-2 1 ms (m,n)=(2,1) 30%

Backups:


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 requirementsMHD saddles

Anna Encheva


AssociationEuratomLocation 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=ZMAG80cm

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: , lj)

redundancy is sufficient as saddle loops are permanent

where is ZMAG? need to optimise positioning of saddle loops as different magnetic equilibria are expected

effective area of each saddle loop (NA)EFF ~1.5m2

lower than previous DDD estimate (~5m2)

Anna Encheva


AssociationEuratomPresent 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 (∆ZMAG, *-

correction)

Anna Encheva


AssociationEuratom

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


AssociationEuratom

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


AssociationEuratom

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/cc0.4 W/cc

1.0 W/cc

Construction of divertor coils similar to in-vessel coils

Better cooling proposed coil effective area

~0.5m2, corresponding to ~50V volume constraint (2x10x10x10

cm3) 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


AssociationEuratom

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


AssociationEuratom

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


AssociationEuratom

Diamagnetic loop system

Slide 17

Range βp = 0.01÷3

Accuracy 5% at βp = 1

Plasma current (MA)

Diamagnetic flux

Flux error for 5%

Ratio to total toroidal flux

17 MA 3 Wb 150 mWb 8x10-4

1 MA 10 mWb 2 mWb 10-5

Achieved in present devices 5x10-5

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


AssociationEuratom

Slide 18


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 ?

.3.018002 sf vv

Anna Encheva


AssociationEuratom

Slide 19


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 clips2 compensation coilsadditional poloidal field compensation loops

Obstacle

Diamagnetic loop contour

Compensation coil

Anna Encheva


AssociationEuratom

Slide 20


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


AssociationEuratom

Slide 21


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


AssociationEuratom

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-sectionTemperature: 200°CEffective area: 2.0 m2

Issues: Available space 7x57x250mm3

Radial dimension is small coil sizing difficultRequirements:

Measurement Parameter Condition Range T or F X or k Accuracy (2)

1. Plasma Current Ip

2. Plasma Pos & Shape

9. Low (m,n) MHD Modes Sawteeth, Disrupt. Precursors

Default1 - 17.5 MA

0 - 1 MA

Ip quench 17.5 - 0 MA

1 ms

1 ms

0.1 ms

Integral

Integral

Integral

10 kA

1%

30% + 10 kA

Main plasma Gaps sep

Divertor channel location(r dir.)

Default

-

-

10 ms

10 ms

1 ms

-

-

-

1 cm

2 cm

0.05m/s (noise)+2% (error)

Ip Quench -

0 - 5 m/s

10 ms

Mode complex amplitudeat wall

-

2 cm

Ip > 2MA full bore

- 10 ms - 1 cmDefault

Ip Quench

dZ/dt of current centroid

Default TBD DC - 3kHz(0,0) <(m,n)

<(10,2)10%

Ph.Moreau Slide 22

TORE SUPRA


AssociationEuratomProgress made in TWP2004 task

Number of coils defined : 60 Bnorm + 60 Btang

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

243248250

57

55

50

7 9

50535759

Bnorm cross section Btang cross section

Investigate winding issues

Error assessment using VV EM and movement models

Performance analysis of ex-vessel Bnorm and Btang coils (EFIT)

Technical review EFDA TWP 2004 task

Future work : EFDA TWP 2005 task

Ph.Moreau Slide 23

TORE SUPRA


AssociationEuratom

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 inTFC casing, coil OD is 12mm

Temperature: 4.0K

Sensitivity: typ. 800 mV s / MA

Issues: Available space, joints

Requirements :

Measurement Parameter Condition Range T or F X or k Accuracy (2)

1. Plasma Current Ip

2. Plasma Pos & Shape

Default1 - 17.5 MA

0 - 1 MA

Ip quench 17.5 - 0 MA

1 ms

1 ms

0.1 ms

Integral

Integral

Integral

10 kA

1%

30% + 10 kA

Main plasma Gaps sep

Divertor channel location(r dir.)

Default

-

-

10 ms

10 ms

1 ms

-

-

-

1 cm

2 cm

0.05m/s (noise)+2% (error)

Ip Quench -

0 - 5 m/s

10 ms -

2 cm

Ip > 2MA full bore

- 10 ms - 1 cmDefault

Ip Quench

dZ/dt of current centroid

Ph.Moreau Slide 24

TORE SUPRA


AssociationEuratomProgress made in TWP2004 task

Rogowski routing in TFC is defined

Number of joints as low as possible: One joint at the top ofTFC, another one at the bottom of TFC

Stress analysis during cool-down / warm-up cycles andplasma operation Selection of material (former and cable)

Rogowski design and model have been done

Former having a double screw groove – regular winding



Rogowski : Stainless steel former model

two layers:

1st layer diameter 11 mm

2st layer diameter 9 mm

Routing constrains: 100m radius of curvature

Ph.Moreau Slide 25

TORE SUPRA


AssociationEuratomTORE 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


AssociationEuratom

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 Bnorm and Btang).

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 byspot welded joints

Temperature: 300°C

Issues: Subjected to plasma and nuclear heatingContinuous flux loops interrupted by 9 welded joints

Ph.Moreau Slide 27

TORE SUPRA


AssociationEuratom

Section for removal

Contact plate

Flux loop

Connection

Support plate

Joint soldered tosupport plate

Progress made in TWP2004 task

9 special welded joints allowing 3 replacements by remote handling


Source of errors have been investigated

Define the thermal gradient along the cable (TIEMF effect)

Measurement errors assessment using VV EM and movement models


Open issues

Ph.Moreau Slide 28

TORE SUPRA

EFDA 10 th Meeting of the ITPA Topical Group on Diagnostics 10-14 April, 2006, Moscow, Russia...

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