ITER STEADY-STATE OPERATIONAL SCENARIOS

IAEA LT W55/DOE-JAERI TPTE Joint Workshop onPhysics needs for high beta steady state tokamak

JAERI Naka, Ibaraki, Japan,24 November 2003

A.R. Polevoi for ITER IT and HT contributors

ITER-SS 1

OUTLINE:

(1) Definitions

(2) Basis for choice of operational parameters

(3) Transport simulations for ITER

(4) Types of SS scenarios proposed for ITER

SS Type-I: NB + LH CD

SS Type-II: NB + EC CD

(5) Discussion on physics needs

Projection of experimental scenarios to ITER

Experimental demonstration of feasibility

DEFINITIONS

Steady State scenario

= scenario with full noninductive current drive

ITER Hybrid reference scenario

= scenario with partial noninductive current drive with Q > 5 and duration of the current flat top t > 1000 s

ITER Steady State reference scenario

= scenario with full noninductive current drive with Q > 5 and duration of the current flat top t > 3000 s

BASIS FOR CHOICE OF OPERATIONAL PARAMETERS

(2.1) CD systems for ITER are defined PCD,ITER :

NB 33 MW 2 NBIs with 1 MeV D

EC 20 MW 170 GHz

LH 40 MW (20 + 20) 5 GHz

(2.2) For ITER divertor configuration and pumping

system power flux to SOL should be limited Psep < Pmax,ITER ( ~ 100 MW)

(for more accurate parametric dependence see ITER PDD)

BASIS FOR CHOICE OF OPERATIONAL PARAMETERS

(2.3) Plasma contamination by He can be relatively small */e < 2 [1] for ITER reference inductive scenario

(2.4) Codes for CD simulation are benchmarked vs some experiments and can be used for CD predictions

(2.5) Transport model for SS and hybrid operation in present day experiments is not identified yet

• [1] Kukushkin et al NF 43 (2003) 716

TRANSPORT SIMULATIONS FOR ITER

(3.1) To find the requirements for transport HHy,2 = ? which provide

SS operation 100% Noninductive CD with the ITER CD tools and

Pfus/PCD = Q > 5; PCD < PCD,ITER

(3.2) To study whether such operation can be stable against NTMs, ballooning, MHD modes, RWMs:

N < ITER-wall

(3.3) To use He pumping and recycling consistent with SOL/divertor simulations with B2/Eirene

(3.4) To study whether such operation is compatible with ITER divertor loads:

Psep < Pmax,ITER ~ 100 MW

(3.5) Taking account of density limit

TYPES OF SS SCENARIOS PROPOSED FOR ITER

SS TYPE-I

GOAL: qmin > 2 RS to avoid NTMs

TOOLS: NB CD + edge LH CD

~50% Ibs / ~ 50% ICD

(+): Moderate requirements for confinement HHy,2 = 1.3-1.4

(-): Low li3 ~ 0.6

=> N close to ITER-wall => narrow operational space

with pressure peaking p(0)/<p>

SS TYPE-II

GOAL: qmin > 1 WS to avoid ST

high li3 to increase stability

TOOLS: NB CD + EC CD

~50% Ibs / ~ 50% ICD

(+): High li3 ~ 0.9

=> stable n = 1

(-): Higher HHy,2 = 1.5-1.6 is required -NTM stability ?

-n = 2, 3 stability ?

SS TYPE-I: qmin > 2 RS , NB+LH CD

Suggested transport: Ion neoclassical at the edge pedestal and RS areas, D = e = i

0

5

10

15

20

25

30

0.0 0.2 0.4 0.6 0.8 1.0

T, keV

X

1

0

n

e

, 10

20

m

-3

T

e

T

in

e

Fig. 1 Plasma temperature and density profilesfor ITER SS Type-I scenario 4.1.1 fromTable I calculated with ASTRA.

0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.2 0.4 0.6 0.8 1.0

j, MA/m

2

X

10

0

q

j

bs

j

tot

j

nb+lh

q

Fig. 2 Current density and safety factor profi lesfor ITER SS Type-I s cen ario 4.1.1 fromTable I c alcu lated with ASTRA.

TABLE I: ITER PLASMA PARAMETERS FOR THE SS TYPE-ISCENARIOS [1]

Ip = 9 MA, B = 5.17 T, a/R = 1.85/6.35 m, k95 = 1.84, d95 = 0.4

Scenario N 4.1.1 4.1.2 4.1.3

qmin/ q95 2.43/5.13 2.25/5.14 2.12/5.16N 2.56 2.7 2.82p(0)/< >p 2.7 2.9 3.1lI3 0.63 0.69 0.72<Te>/<Ti>,keV 10.5/11 10.8/11.7 11/12<ne>,10

19m-3 6.74 “ “n/nG 0.83 “ “Wth/Wfast, MJ 255/50 264/53 273/60HH98 (y,2) 1.3 1.36 1.41Q 5 5.42 5.7PNB/PLH, MW 34/33.7 34/31 34/29P fus, MW 338 352 361P los, MW 97 94.5 93<Zeff> 2.17 2.22 2.2

(1) AL L SU CH SCENARIOS REQUIRE S RW M STABILIZATION

(2) ACTI VE RW M STABILISATION IS POSSIBLE

(3) ROTATION REQUIRED FOR RMW STABILISATION AT q=3IS ~ 2 TIMES HIGHER, THAN PREDICTED BY MODELLING[2], [3], BUT UNCERTAINT Y O F PREDICTION IS TOOHIGH

[1] A.R.Polevo i et al, 19 th IAE , A Ly 20on 02, IAEA- -CN 94/CT/P-08[2] Y.Li , u e tal, tob e publishe d i nNF;[3] .M Ch , u G A report

FEASIBILITY OF TYPE-I SCENARIO(-) low inductance li3 ~ 0.6 => low no wall limit N < 2.5

STABLE OPERATIONAL SPACE SHRINKS WITH PRESSURE PEAKING

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2

2 2.5 3 3.5 4 4.5

a

w

/a

N

a

,w ITER

/a

2

1

1

2

3

3

FIG.4 Stabilising wall position aw/a vs. for q=const scan of SS operational points 4.1.1, 2, 3 from Table I at a = 1.85 m. No-wall ideal MHD stability limits are shown by vertical dashed lines. aw,ITER/a 1.375.

Lines 1,2,3 correspond to 4.1.1, 4.1.2, 4.1. 3 from the Table I with different pressure peakednss:

p(0)/<p> = 2.7, 2.9, 3.1

SS TYPE-II: qmin > 1 WS , NB+ECCD

Suggested transport: D = e = 0.5 i ~1+ 3x2 and ion neoclassical at the edge pedestal D = e = i = i,neo

0

10

20

30

40

50

0 0.2 0.4 0.6 0.8 1

T, keV

X

n

e

, 10

20

m

-3

0

1

n

e

T

e

T

i

Fig. 5 Plasma temperature and density profilesfor ITER SS Type-II scenario 4.3.2 fromTable II calculated with ASTRA

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

j, MA/m

2

X

q

0

10

j

ec

j

nb

j

tot

j

bs

q

2

4

6

8

Fig. 6 Current density and safety factor profi lesfor ITER SS Type-II sce nario 4.3.2 fromTable II c alcu lated with ASTRA.

(1) N IN ALL SCENARIOS IDEAL n=1 KINKS ARE STABLE (2) SCENARIOS CAN REQUIRE CONSIDERATION OF THE NTM STABILIZATION

TABLE II: ITER PLASMA PARAMETERS FOR THE SS Type-II SCENARIOS Scenario N 4.3.1 4.3.2

Ip, MA 9 “

a / R, m 2 / 6.2 1.85 / 6.35

HH98(y,2) 1.57 1.5

Pfus, MW 267 266

Plos, MW 88 86

PNB/PEC, MW 33/20 33/20

<ne>,1019m-3 5.36 5.33

n/nG, a.u. 0.77 0.66

li3, a.u. 0.77 0.8

IBS/Ip, % 46.8 43.7

INB/Ip, % 48.4 49.3

IEC/Ip, % 4.75 (q = 2) 7.0 (q = 1.5)

N, a.u. 2.7 2.67

<nHe>/<ne>,% 1.3 1.4

<nAr>/<ne>,% 0.12 0.1

q(0)/qmin/q.95 2.23/1.52/5.62 1.6/1.45/5.25

DISCUSSION ON PHYSICS NEEDS

Projection of experimental scenarios to ITER

(5.1) Pressure and q profiles, N are similar to those required for ITER SS operation.

Thus, at least the ideal stability features and active RWM control do not require extrapolation

(5.2) In ITER heating of electrons dominates Pe > Pi , Ti/Te ~ 1 is expected

In experiments with N and HH similar to ITER Pe < Pi, Ti/Te > 1.

Thus, projection to ITER with Ti/Te ~ 1 (rather than with Ti/Te > 1) with the same N and HH is required to avoid overestimation of Pfus ~ Ti

2 (and Q) and underestimation of ICD~ Te

DISCUSSION ON PHYSICS NEEDS

Constraints from SOL/DIV simulations (B2/EIRENE)

For ITER divertor configuration and pumping system power flux to SOL should be compatible with divertor constraints (Pmax,ITER ~ 100 MW ) (for more accurate parametric dependence see ref. [1,2] )

Plasma contamination by He can be relatively small */e < 2 [1]

Core fuelling saturates with increase of the separatrix density. Thus, ITER operation requires dominant core fuelling [1]. Pellet injection is suggested as a major source of the core fuelling.

Thus, the experimental scenario can be considered as ITER relevant if results of projection to ITER fulfil:

(5.3) Psep < Pmax,ITER (5.4) with moderate contamination by He.(5.5) scenario should be compatible with pellet fuelling

[1] Kukushkin et al NF 43 (2003) 716[2] ITER PDD

DISCUSSION ON PHYSICS NEEDS

Experimental demonstration of ITER SS feasibility

For experimental support of the ITER SS scenarios feasibility the following directions are suggested:

I. Data supply for validation of transport which fulfil the SS requirements

II. Data supply for validation of predictive capabilities of CD codes

III. Demonstration of active control of instabilities

IV. Demonstration of compatibility with pellet fuelling

V. ITER relevant discharges should be selected taking account of limitations and rules (5.1 - 5.5) discussed in a previous section