42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/1

Comparison of RF-heated withNBI-heated ELMy H-mode plasmas

in JET

R.V. Budny1, M. de Baar2, C.S. Chang7, D.R. Ernst1, A. Gondhalekar3, C. Gowers3, K. Gunther3, P. Lamalle4,

G. Maddison3, D. McDonald3, F. Nave3, J. Ongena4, R. Perkins1, E. Righi5, G. Saibene5, R. Sartori5,M. Stamp3, J.D. Strachan1, W. Suttrop6 , R. White1, K.-D. Zastrov3, and staff involved in the

EFDA-JET work program

1Princeton Plasma Physcis Laboratory, Princeton University, Princeton, NJ, USA2FOM Institute for Plasma Physics Rijnhuizen, Nieuwegein, NL

3UKAEA-Cullam, Abingdom, England4Ecole Royale Militaire, Brussels, Belgium

5EFDA, Garching, Germany6IPP, Garching, Germany

7Courant Institute, New York University, NY, NY, USA

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/2

Outline

Motivation

Experiment

Modeling and Results

Discussion and Future Plans

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/3

Conclusions

Motivation

ICRH – heated ELMy plasmas are suggested for reactor startup

But NB-heated ELMy plasmas have better diagnostics and better performance in present-day experiments

To what extent are NB and ICRH ELMy’s comparable?

Goals

Compare global and local parameters for ICRH and NBI ELMy’s

Compare results with Ion Temperature Gradient theory

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/4

Results from experiment

Matched pair of ICRH and NBI heated ELMy plasmas

Heating power lower than desired (close to L-mode)

VTor for RF in Co-Ip direction, similar in shape to that of NBI, but 15% magnitude

Power deposition in ICRH more central, similar to that expected by alpha heating

Higher central Zeff with ICRH

Results from theory

Near the mid-radius, R/LTi close to R/Lcrit for ICRH and NBI

Peak γlin similar for ICRH and NBI

Peak ωExB and ωExB / γlin smaller for ICRH

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/5

Matched pair of plasmas:

4

2

2

1

02

1

0

0

00.8

0.4

018 20 22

Time (s)24 26

4

8

(MW

)(M

J)(1

020/m

2 )(a

.u.)

(a.u

.)

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BTF = 2.8T IP = 2.5MA GGreenwald → 85%PRF

PNBI

WDia

nel

H89

H97

Hα

Pulse No: 50502 with ICRH

Pulse No: 50632 with NBI

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/6

Measured toroidal rotation rate from CX

Rotation factor of 6 lower with ICRF

80

60

40

20

00 0.5

XTo

roid

al r

otat

ion

rate

(kr

adia

ns/s

)1.0

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Pulse No: 50632(High power NBI)

Pulse No: 50502(ICRH + Low power NBI)

24.1s

23.1s

20

10

024 25

Time (s)

Toro

idal

rot

atio

n ra

te (

krad

ians

/s)

26

Pulse No: 50502

NBI

2.99m3.08m3.18m

+

+++

+

+

3.27m3.36m3.46m

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/7

Toroidal rotation rate measurements of Ni27consistent with CX measurements

20

10

5

15

022 24

NBI for 50497 & 50498

Time (s)26

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Pulse No:50497Pulse No:

50498

Pulse No: 50502Pulse No: 50503

NBI for 50502NBI for 50503

(k/r

ads/

s)

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/8

2D contours from TRANSP usingSPRUCE ICRH model

Well focused heating on resonance rear axis

2

Re {Er} RF Power deposition

1

0

–1

–2

1 2 3Major radius (m)

4 5

Antenna

Hei

ght (

m)

Pulse No:50502

@ 24.15s

2

1

0

–1

–2

1 2 3Major radius (m)

4 5

Antenna

Hei

ght (

m)

Pulse No:50502

@ 24.15s

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42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/9

Distribution function of hydrogen minorityin Pulse No: 50502

nH/ne ≈ 1-2% in approximate agreement with measurements

1000

100

10

1

0.10 0.5

Toroidal flux label X

(keV

)1.0

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Measured (NPA)

23.1s

Pulse No: 50502 C11 (1%)

Pulse No: 50502 C06 (3%)

26.1s

400

1011

1012

1013

High Energy NPA measurements Central RF tail temperature

800 1200Hydrogen energy (keV)

Line

-inte

grat

ed d

istr

ibut

ion

func

tion

22.80 – 23.20sT⊥ (0) = 315keV

25.30 – 25.90sT⊥ (0) = 204keV

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/10

H Concentration in the edge increases in time

0.07

0.05

0.0420 22 24

Time (s)26

JG00

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0.06

HH

+D

Pulse No:50497 Pulse No:

50498

Pulse No:50502

Pulse No:50503

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/11

ICRH Heating power deposition to thermal plasmacan simulate alpha heating

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0

0.15

0.10

0.05 Pion

Pe

0.2 0.40 0.6 0.8 1.0

Toroidal flux label X

NBI Pulse No: 50632 C03 @ 24.1s

(MW

/m3 )

0

1.0

0.5

Pion

Pe

0.2 0.40 0.6 0.8 1.0

Toroidal flux label X

ICRH Pulse No: 50502 C03 @ 24.1s

(MW

/m3 )

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/12

Ion temperature gradient near the critical valueat mid radius

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01

100

10

0.5 1.0Toroidal flux label X

01

100

10

0.5 1.0Toroidal flux label X

ICRH (Pulse No: 50502 C08 @ 24s) NBI (Pulse No: 50632 C03 @ 24s)

RLTcrit, impurity

RLTcrit, impurity

RLTcrit

RLTcrit

RLTi

RLTi

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/13

Microturbulence growth rate, frequency and flow rate

Turbulence suppression ratio ωExB / γlin small for ICRH, large for NBI

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0

80

60

40

20

3.4 3.6 3.8Major radius (m)

NBI Pulse No: 50632 C03 @ 24.1s

ωExB

γlin

ωlin /10

0

80

60

40

20

3.4 3.6 3.8Major radius (m)

|ωE

xB| (

krad

ians

/s)

|ωE

xB| (

krad

ians

/s)

ICRH Pulse No: 50502 C03 @ 24.1s

ωExB

γlin

ωlin /10

42nd APS DPP Meeting, Quebec City Canada R V Budny 23–27 October 2000 JG00.293/14

DiscussionThe turbulence suppression ratio ωExB / γlin appears to be paradoxically small for ICRHplasmas

Candidate explanations:ωExB / γlin is not a good indicator of microturbulence and transport suppression

VPol is larger than Vneoclassical and thus ωExB is larger

γlin is not a good indicator of the amount of microturbulence and transport

Future plans

Improve the ITG analysis to include non-linear effects, TEM branch, etc

Continue the experiment at higher heating power to produce plasmas with more reactorrelevant conditions and lower torque from the diagnostic NBI

Apply theories of ICRH-induced rotation