ICRF scenarios for ITER’s half-field phase

transcript

19th Topical Conference on RF Power in Plasmas, Newport, 2011 1/34

ICRF scenarios for ICRF scenarios for ITER’s half-field phaseITER’s half-field phase

E. Lerche, D. Van Eester and JET-EFDA contributorsE. Lerche, D. Van Eester and JET-EFDA contributors

19th Topical Conference on RF power in Plasmas, Newport 201119th Topical Conference on RF power in Plasmas, Newport 2011

ICRF scenarios for ITER’s half-field phase

E. Lerche1, D. Van Eester1, J. Ongena1, M.-L. Mayoral2, T. Johnson3, T. Hellsten3, R. Bilato4, A. Czarnecka5, R. Dumont6, C. Giroud2, P.

Jacquet2, V. Kiptily2, A. Krasilnikov7, M. Maslov8, V. Vdovin9 and JET EFDA Contributors*

JET-EFDA, Culham Science Centre, Abingdon, OX14 3DB, UK

1 LPP-ERM/KMS, Association Euratom-‘Belgian State’, TEC Partner, Brussels, Belgium2 Euratom-CCFE Fusion Association, Culham Science Centre, UK

3 Fusion Plasma Physics, Association Euratom-VR, KTH, Stockholm, Sweden4 Institut für Plasmaphysik (MPI)-Euratom Association, Garching, Germany

5 Institute of Plasma Physics and Laser Microfusion, Warsaw, Poland6 CEA(IRFM)-Euratom Association, Saint-Paul-lez-Durance, France

7 SRC RF Troitsk Institute for Innovating and Fusion Research, Troitsk, Russia8 Centre de Recherches en Physique des Plasmas, Association EURATOM-Conf. Suisse, Lausanne, CH

9 RNC Kurchatov Institute, Nuclear Fusion Institute, Moscow, Russia

*See the Appendix of F. Romanelli et al., paper OV/1-3, IAEA Fusion Energy Conference, Daejeon, 2010

Outline

- Motivation ICRF scenarios for initial operation phase of ITER (non-activated, half-field)

- Summary of main results of JET experiments (H plasmas)

N=1 H majority ICRH

N=2 3He ‘large minority’ ICRH

- Preliminary modelling of half-field ICRH scenarios

H plasmas: N=1 H majority ICRH

4He plasmas: (Standard) N=1 H ‘minority’ ICRH Impact of H concentration (H-pellet’s)

- Summary & Discussion

Outline

N=1 H majority ICRH

ITER half-field H plasmas (L-mode)

Plasma: ~80%H, (He3) , 2%Be, …

B0=2.65T, IP=7.5MA (L-mode)

Auxiliary power:• 16.5MW H-NBI (elec/ion = 80/20)• 15.0MW ECRH• 10MW ICRH (elec/ion = 50/50)

n 3x1019/m3

T 8-10keV

ASTRA [A.Loarte, P.Lamalle]

ICRH (?)

ICRF scenarios for ITER at B0=2.65T

N=2 He3

(N=2 D)N=3 D

N=1 H (~40MHz)

N=2 3He (~53MHz)

(either H or 4He plasmas)

Outline

N=1 H majority ICRH

JET experiments in H plasmas at B0=2.65T

ITER ITER

JET JET

N=1 H majority ICRH [f=42MHz, Bo=2.65T]

N=2 3He ‘minority’ ICRH [f=51MHz, Bo=2.65T]

• B0=2.65T (ITER), IP=1.5MA (<<ITER)

• Similar Ne but lower T than ITER

• ICRF power up to 6MW (ITER 10MW)

• NBI: D-beams instead of H-beam (ITER non-active phase)

L2L1=L2

JET experiments in H plasmas at B0=2.65T

Outline

N=1 H majority ICRH

N=1 Hydrogen majority ICRH (f=42MHz)

Initial remarks:

• Low absorptivity scenario

• Electron absorption dominant

• No He3 !

TOMCAT #79332: B=2.67T, f=42.50MHz

Typical N=1 H pulse (f=42MHz)

JPN 79335

• Weak energy response to RF power step (low absorbtivity)

• Considerable radiation losses (Prad / PICRH ≈ 1/3)

ICRF Heating efficiency

RF Power absorption

electrons

ions = 0.3-0.4

Heating efficiency increases

with plasma temperature

(CXRS)

TOMCAT

electrons

ionsAbs

PICRH dependence

1 PINI = 1.3MW NBI2 PINIs = 2.6MW NBI

~0.1keV/MW ~0.1keV/MW

Poor performance compared

to similar (H)-D ICRF expts.

(H)-D (JET)

~1keV/MW

Central temperatures

B0=2.7T

RF acceleration (NPA)

Horizontal neutral particle analyzer (KR2)

PRF=2.5MW PRF=5MW

• No clear effect of ICRF on D distribution

• (Hints of fast H with E~200keV in KF1)

Very modest tails if compared with minority ICRH experiments

SKIP if NEEDED

Outline

N=1 H majority ICRH

N=2 He3 ICRH (f=51MHz)

Initial remarks:

• Low absorptivity scenario

• Largely dominant electron heating at low X[He3]

• Ion heating enhanced for higher X[He3]

• D-beams: N=2 / 3 parasitic absorption

TOMCAT

X[3He]=5%

#79357: B=2.66T, f=51.50MHz

Typical N=2 He3 pulse

JPN 79359

elec elec + ion

X[He3]

• X[3He]<20%: only elec heating

• X[3He]>20%: elec + ion heating

• Large radiation losses (Prad / PICRH ≈ 1/2)

JPN 79359

nkTe+nkTi

Global heating efficiency (Wpla)

• 2x larger heating efficiency at X[3He]=20% (w.r.t. 5-10%) • Efficiency increase is due to enhanced ion absorption

ICRF heating efficiency

TOMCAT

elecsionstotal

X[He3] dependence (2 PINIs , PICRH ~ 2.5MW)

• (Equilibrium) plasma energy and

temperature increase with X[3He]

(PICRH ~ 2.5MW)Overall performance increase

PICRH dependence (1 PINI, X[He3]=10-18%)

~0.25keV/MW ~0.2keV/MW

Central temperatures

(H)-D (JET)

~1keV/MW

• Better performance than N=1 H maj. expts.

• Poor performance compared to similar

(H)-D ICRF expts.

B0=2.7T

Horizontal NPA (KR2)He3

• Dominant 3He RF acceleration for E<160keV

• Dominant (N=3) RF acceleration of D (beam) ions for E>160keV[V.Kiptily, to appear in PPCF]

Impurities: N=1 H vs. N=2 He3

0 1 2 3 4 5 6

N=2 He3N=1 H

2 e (1

*m2 /s

Ni 26 (KT7D)

Higher impurity content in N=2 3He discharges

[A.Czarnecka, to appear in PPCF]

0 1 2 3 4 5 60

6N=2 He3N=1 H

C 4 (KT7D)

I/n2 e (1

2 /s *

0 1 2 3 4 5 60,0

2,0N=2 He3N=1 H

C 6 (KT7D)

I/n2 e (1

2 /s *

C6 C4 • Higher radiation from plasma edge / divertor

• Confirmed by 2D bolometric tomography

Summary of JET experiments

N=1 H ICRH

N=2 He3 ICRH

• Low heating efficiency ( = 0.15 – 0.4, increasing with X[He3])• Largely dominant electron heating for low X[He3] (mainly LD + TTMP) • Ion absorption proportional to X[He3]: dominant for X[He3] > 20% • Fast He3 (up to 250keV) detected by NPA

• Clear parasitic D absorption with PNBI>5MW

• Poor global heating: ~0.2keV/MW

• Strong plasma-wall interaction (Prad/PICRH ≈ 1/2, impurities, etc…)

• Low heating efficiency ( = 0.3 - 0.4)

• Dominant electron heating: pe 2 x pi (LD + TTMP)

• Modest H acceleration (up to 50keV) registered by NPA• Negligible parasitic N=2 D absorption• Poor global heating: ~0.1keV/MW

• Considerable plasma-wall interaction (Prad/PICRH ≈ 1/3)

Outline

N=1 H majority ICRH

Preliminary ITER modelling

• Objectives:

- Intuitive picture of relative RF absorptivity (SPA) of the various heating scenarios

- Parametric scans for preliminary optimization

• More ‘rigorous’ numerical efforts

[R. Budny, IAEA2010, to appear in NF2011]

1D TOMCAT code

[Van Eester, PPCF98]

Outline

N=1 H majority ICRH

• E+ 0 @ =H (‘screening’)

• Low absorptivity scenario (= 0.3 - 0.4)

• Dominant electron heating (broad absorption)

• Higher TH helps ion absorption

• Possible 3He absorption (if present)

E+ electric field

Fundamental H majority ICRH (42MHz)

TH 8keV

TH 25keV

• Higher TH yields higher absorption (ions)

• Higher ne yields higher absorption (elecs)

• pe = pi @ TH 20keV

Parametric scan

L-mode 2: T =8/10keVn=34 (00)

ITER ITER

• Larger E+ at =2He3

• Low absorptivity scenario (= 0.25 - 0.4)

• Dominant electron heating (broad absorption)

• Ion heating enhanced at higher X[3He]

• Possible N=1 H (N=2,3 D) absorption

N=2 3He ‘minority’ ICRH (53MHz)

X[3He]=4%

X[3He]=25%

E+ electric field

• Higher X[3He] yields higher absorption (ions)

• Higher ne yields higher absorption (elecs)

• pe = pi @ X[3He] 30%

Parametric scan

L-mode 2: T =8/10keVn=34 (00)

ITER ITER

Do we have an ICRH scenario for H plasmas?

N=2 H majority ICRH at 1/3 nominal field (B0=1.8T)

(N=3 D)

E+ electric field

pH = 70%

pe = 30%

• Full single-pass absorption (=1) • Dominant ion heating• But ECRH out of range, confinement (?)• Could be used for fast particle studies

Outline

N=1 H majority ICRH

N=1 H–4He minority ICRH (42MHz)

• Good absorption scenario (= 0.7 – 1.0)

• Dominant ion heating (for moderate X[H])

• Ion absorption decreased at higher X[H]

n=34 (00) L-mode 2 E+ electric field

L-mode 2: T =8/10keV L-mode 1: T =4/5keV

• Ion absorption is reduced at higher X[H] (‘screening effect’)

• This effect is stronger at lower temperatures (L-mode 1):

• Operating at high k// phasing (00) helps

• Accounting for tail formation does not alter the behaviour at high X[H]

• No MC absorption (1D and 2D)

n=34 (00) n=34 (00) n=60 (0)

Comparison with 2D wave codes

• Electron absorption slightly overestimated in 1D calculations

• Unlike for the H plasmas (touchy), for the better absorbing (H)-D scheme 2D calculations are converged

EVE code [R.Dumont, NF2009]

X[H]=5% X[H]=45%E+ E+

PabsPabs

SPA vs. heating efficiency

pla=0.5 loss=0.1

Simple multi-pass model

(H plasmas)

(4He plasmas)loss=0

N=1 H majority ICRH

N=2 3He–H ICRH

• Moderate absorptivity (~0.5) → significant PWI? [seen in JET]

• Dominant electron heating [seen in JET]

• Increasing temperature favours ion heating [seen in JET] but pe=pi @ 25keV

• Increasing density favours overall heating (electron heating dominant)

• Low absorptivity (~0.3) significant PWI? [seen in JET]

• Largely dominant electron heating except for high X[He3] [seen in JET]

• Increasing X[He3] favours ion heating [seen in JET] but pe=pi @ X[He3]~30%

• Increasing temperature has small effect

• Increasing density favours overall heating (electron heating dominant)

Summary of ITER modelling

N=1 H-4He ICRH

• Good single-pass absorption (0.7) with dominant ion heating (X[H]<25%)

• ICRF efficiency lower for larger X[H], partic. at lower temperature (L mode-1)

• This effect can be compensated with higher k// phasing (00)

H plasmas:

• Both ICRF scenarios proposed for ITER’s half field phase in H suffer from low power absorptivity with dominant electron heating:

- N=1 H majority requires high plasma temperatures

- N=2 3He requires large X[3He] for efficient ion heating

• This DOES NOT mean that they are not suited for the commissioning of the ICRF system, but the power may be limited (enhanced PWI)

• One possible ICRF scenario with good ion absorption is N=2 H majority at 1/3 of the nominal B0 (but ECRH is out of range)

4He plasmas:

• (H)-4He minority ICRH is OK for moderate X[H] (<40%)

• At higher X[H] the ion absorption is jeopardized, particularly at low T

• Operating at higher k// phasing (e.g. 00) helps recovering good absorption in general (but lower coupling)

Final remarks

Wave modelling:

• Low absorption H-plasma scenarios require further modelling (touchy!)

• (H)-4He ICRF scenario well converged but further simulations at high X[H] welcome

Integrated scenario modelling:

• Use experimental heating efficiencies / SPA’s obtained for assessing which T can actually be expected in ITER’s half-field H-plasma phase

• Use realistic power absorption profiles in all cases (broader elec. absorption)

Final remarks

Experiments:

• High X[H] ICRH experiments in 4He plasmas (B0=2.65T, f=42MHz)

Discussion

JET ITER (prelim.)

N=1 H ICRH

• Low heating efficiency (= 0.3-0.4)

• Electron heating dominant (pe/pi=2)

• Pre-heating helps overall absorption

• Considerable plasma-wall interaction

• Reasonable heating efficiency (= 0.5)

• Electron heating dominant except for TH>40keV

• Higher ne and higher Te enhance absorption• ??

N=2 He3 ICRH

• Low heating efficiency (= 0.15-0.45) depending on X[He3]

• Elec. heating dominant for low X[He3]; • Ion heating dominant for X[He3]>20%

• NBI pre-heating helps (but parasitic D absorption)

• Strong plasma-wall interaction

• Low heating efficiency (= 0.2-0.4) depending on parameters • Electron heating dominant throughout

• Higher X[He3], higher ne or higher Te enhance overall efficiency:

• ??

EXTRAS

Impurities: N=1 H vs. N=2 He3 (KS3)

Bolom Zeff

0 1 2 3 4 5 6

N=2 He3N=1 H

I/n2 e (

2 /s *

Ni 26 (KT7D)

0 1 2 3 4 5 60

6N=2 He3N=1 H

Cr 22 (KT7D)

2 e (1

*m2 /s

Higher impurity content in N=2 3He discharges

[A.Czarnecka, to appear in PPCF]

Impurities: N=1 H vs. N=2 He3 (KT2/7)

VUV spectroscopy (KT2/KT7)

N=2 3He

0 1 2 3 4 5 60

6N=2 He3N=1 H

C 4 (KT7D)

2 e (1

*m2 /s

0 1 2 3 4 5 60,0

2,0N=2 He3N=1 H

C 6 (KT7D)

2 e (1

0-20 P

2 /s *

• Higher radiation losses in N=2 3He scenario come from plasma edge / divertor

• Confirmed by 2D bolometric tomography

coax • Larger k// yields higher absorption

• pe / pi roughly independent of k//

Effect of antenna phasing

[A. Messiaen NF2010]

Fundamental H majority ICRH (42MHz)

• Low X[3He]:

Larger k// yields higher

absorption (elecs only)

X[3He]=4%

X[3He]=30%

Effect of antenna phasing

Fundamental H majority ICRH (42MHz)co

• High X[3He]:

Low k// → ion heating

Large k// → elec. heating

Effect of H dillution (4He contamination)

N=1 H majority ICRH

Preliminary modelling shows same tendency (but weaker)

Important to re-assess experimentally

X[4He] X[4He]

(PICRF=5MW)

no NBI1 PINI

Wdia NPA on H

Plasma dilution

Horizontal NPA (KR2)3He

• Relatively modest acceleation of 3He ions (E<160keV) (hints on KF1 E<260keV)• Clear RF acceleration of D (beam) ions above beam source energy

RF acceleration (ion losses)

Scintillator probe (KA3)

• Main losses come from RF accelerated D beam ions

• Small fast 3He losses (No hints fast 3He detected by -spectroscopy)

[V.Kiptily]

Simple comparison with other scenarios

H minority in D (ILA)

PICRH(MW)T

~1keV/MW

N=1 D majority (B0=3.3T, f=25MHz)

~0.5keV/MW

N=1 H majority

T/P 0.1keV/MW

N=2 He3

T/P 0.2keV/MW

ICRF scenarios for ITER’s half-field phase

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