Reflection Atomic and Molecular Spectroscopy in the Scrape-Off … · 2014. 12. 16. · Atomic and...

Mem

ber

of th

e H

elm

holtz A

ssocia

tion

S. Brezinsek | Institut für Energie und Klimaforschung – Plasmaphysik | Forschungszentrum Jülich

S. Brezinsek, G. Sergienko, A. Pospiesczyk

M.F. Stamp, A. Meigs

Atomic and Molecular Spectroscopy in the

Scrape-Off Layer of High Temperature Fusion Plasmas

- Results from TEXTOR and JET -

IAEA Atomic, Molecular and Plasma-Material

Interaction Data for FS&T

S. Brezinsek | Institut für Energie und Klimaforschung - Plasmaphysik | Forschungszentrum Jülich 16.12. 2014 No 2

Plasma-Surface Interaction Processes

Scrape-off layer Reflection

Confined plasma

Erosion

Deposition, mixing

and co-deposition of

fuel (retention)

Separatrix

Plasma-facing material

Processes depend on material mass, projectile mass, material mix and concentration, impact

energy (Ein), impact angle (a), surface roughness and temperature (Tsurf)

Here: focus on recycling, erosion and impurity fluxes in the SOL and edge layer


Plasma-Facing Materials

Low-Z: strong wall erosion (also at low Ein)

Sputtering Yields

High-Z: low sputtering / mainly by impurities

energetic threshold for each species

Steady-state divertor

conditions Transients

(ELMs)

detached attached divertor

… from all-C to Be/W mix ….


Particle-Flux Determination

e p

= * 1

4 n A A ij

Line emission

n A n n A ik k i

A e Exg e

*

£

å = < > s u

with B as branching ratio:

B = £ å A A ik ik k i

/

I h

n r n r dr tot A e Exg e

r

r

= < > ò B n

p s u

4

2

( ) ( )

Particle flux <=> number of ionisation events

d

dr

d n

dr n r n r

A A A

A e I e

G = = - < > ( )

( ) ( ) u

s u

G A A e I e

r

r

n r n r dr = < > ò ( ) ( ) s u

1

2

G B A tot

A e I e r

r

r

A e Exg e r

r

r

I

h

n r n r dr

n r n r dr

=

< >

< >

ò

ò 4

1

2

1

2 p

n

s u

s u

( ) ( )

( ) ( )

( )

( ) 1

Assumption of a fully ionising plasma & almost constant local plasma conditions

in the region of emission. Otherwise corrections factor or full rate coefficients.

G B X

A tot I

h =

4 p

n

I e < > s u

Exg < > s ue

= B tot I

h 4 p

S


Outline

§ Introduction

§ Hydrogen spectroscopy

§ D2 molecules in front of W PFCs

§ Tritium molecules in JET

§ Hydrocarbon spectroscopy

§ Molecular break-up chain

§ Effective sputtering yields

§ Beryllium spectroscopy


§ Chemical-assisted physical sputtering

§ Tungsten spectroscopy

§ In-situ W source calibration

§ Effective W sputtering yields

§ Summary


Fulcher-a Spectroscopy

§ Fulcher-a routinely used for vibrational population and plasma analysis [see talk by U. Fantz]

§ Impact of material on D2 population and release studied in TEXTOR (Te~30-100eV) and labs

TEXTOR

D2reference

spectrum

(Te~30eV)

(S. Brezinsek et al. JNM

PFR 2008)

Q(0-0)-branchQ(1-1)-branch

Q(2-2)-branch

Q(3-3)-branch

Q(4-4)-branch

Q(5-5)-branch

605 610 615 620600 625 630 635 640

0

1

2

3

4

5

6

600.0 602.0 604.0 606.00

4

6

2

JET-ILW

D2 spectrum

in outer divertor

(Te~30eV)

wavelength [nm]

Inte

nsit

y [

arb

. u

nit

s]


D2 Recycling in JET W Divertor

0 1 2 3 4 50

100

200

300

400

500

600

700

800

900

1000

1100

1200

D2 (d

3P)

Tro

t [K

]

vibrational quantum number

0 1 2 3 40.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

D2 (d

3P

-) line inegrated density (sum v=0-19)

(4.20±0.25) 1012

m-2

measurement

fit Tvib=6088K±(2548K/1408K)

popu

latio

n

vibrational quantum number

§ Contribution of reflected ions (neutralised at the PFC) is larger for W than for C PFCs

§ Increase in atom-to-molecule ratio of the recycled deuterium

§ Strong variation of surface temperature is changing the fuel content AND release species

§ Non-Boltzmann population in the vibrational ground state measured – different population

to previous JET-C measurements. Detailed analysis started.

JPN 87456-58

G. Sergienko et al.


JET-C T2 in Trace Tritium Experiment

§ Detailed studies of D2, H2, HD rovibrational population in TEXTOR, JET-C, AUG etc.

§ T2 injection in the main chamber and local observation of molecular emission

§ Injected amount of 2.5mg is recycled/pumped in JET-C. A fraction ends up in the divertor

PFCs (CFC) and can be detected as TD and T2 Fulcher-a emission

§ Tritium surface content down to 0.1% of recycling flux measurable via DT molecules

A. Pospieszczyk et al. J. Nucl. Mater. 2007


Outline

§ Introduction











§ In-situ W calibration


§ Summary S. Brezinsek et al. JNM 2007


Hydrocarbon Break-up

S. Brezinsek et al.

JNM 2007

TEXTOR hydrocarbon injection experiments:

§ CD, CD+, C2, D2, Db, Dg,!CI, CII, CII lines

§ Comparison with HYDKIN and ADAS

§ Production efficiency between 20 and 100%

§ Break-up chain & excited states

C2C2C 2

CHCD

CHCD

CII

CII

CII

CIICIII

HeI CII

CIIDg

Da(sat.)

Db

Da

CD Douglas-Herzberg+

CH+

CD+

CH+

CD+

C2 C2

[nm]

difference spectra

CD Gerö-band

inte

nsit

y

[arb

. u

nits

]

C Swan band2


Simple plasmas in TEXTOR (3.0-4.0 1018m-3 and 60-65eV at the LCFS)

Injection in the SOL, gas inlet 1.5cm -2cm behind the LCFS

Isotope experiment – surface influences minimised

Hydrocarbon Break-up Footprints: CD & C2

S. Brezinsek et al.

JNM 2007


Outline

§ Introduction













§ Summary Radius [m]

He

igh

t[m

]

#82626

at 11s

KS3 view

HFS LFS

a)2.0 2.5 3.0 3.5 4.0

2.0

1.0

0.0

-1.0


§ Determination of Be sputtering yields in limited configuration to verify data base

and ERO code used for ITER Be wall life-time predictions [D. Borodin PS2014].

§ Spectroscopy averages over observation spot (Tsurf, ion flux, geometry)

§ Dominant self-sputtering observed at high electron temperatures / impact energies

§ Energetic threshold at low impact energies

Effective Beryllium Sputtering Yields

S. Brezinsek et al.

Nucl. Fusion 2014

0.1

10

1

0 10 20 30 40

(eff.)

Tota

l B

e s

pu

tteri

ng y

ield

Electron temperature (eV)

Be self

sputtering

JET

Pulse No:80319–23

80272, 74

ERO

max

min Experiment (i)low Tbase

high Tbase

limiter

plasmas divertor

plasmas

D. Borodin et al.

Physica Scripta


Chemical Assisted Physical Sputtering of

Be via BeDx

S.Brezinsek

Nucl. Fusion 2014

as function of the Be tile temperature

§ Comparison of BeD A-X band, BeI and

BeII provides dissociation path

§ Dominant BeD + e ->Be + D + e (75%)

over BeD + e-> BeD+ + 2e (25%)

§ With increase of Tsurf inreasing release

of D2 => less D in stored in Be!


causes an increase of the net source

§ Lower binding energy of Be in the D

supersaturated Be surface likely

§ Physical sputtering process which releases

from near surface molecules: BeDx, x=1,2,3

§ Energetic threshold at low impact energies –

not like carbon chemistry!

§ Confirms Molecular Dynamics predictions [C.

Börkas] and PISCES results [D. Nishijima PPFC 2008]


Material Migration: Main Chamber

HFS LFS

SOL flows

Ions

CXN

Ions

CXN

Limiter configuration

§ At high Ein: Be sputtering yield (JET-ILW) is larger

than C sputtering yield (JET-C)

§ Moderate increase of total limiter source (25%)

with respect to C in JET-C

§ Campaign averaged erosion rate at centre tile:

Spectroscopy : 4.1x1018 Be/s gross erosion

Post-mortem analysis: 2.3x1018 Be/s net erosion

§ Majority of eroded Be remains in the main

chamber and is redistributed on limiter/wall

A: Widdowson Phys. Scr. 2013

S. Brezinsek IAEA2014,

ICFRM2013

I. Bykov PSI2014


Divertor configuration

§ Sputtering at recessed wall at low Te / impact

energies (Ein<10eV) and by CX neutrals

§ At low Ein: Be sputtering yield (JET-ILW) is lower

than total C sputtering yield (JET-C)

§ Factor 4-5 smaller primary source with ILW (Be in

JET-ILW vs. C in JET-C)

§ Absence of low energy erosion in the ILW case

(chemical erosion in case of C in JET-C!)

§ Majority of eroded Be transported in SOL towards

inner divertor.

S. Krat JNM 2014

S. Brezinsek PSI2014, IAEA2014

M. Mayer et al.

Global Material Migration in JET-ILW

Fair balance between Be eroded (21 g) in

main chamber and Be deposited (28 g) in

divertor after first year of ILW operation


Outline

outer

divertor

2D camera and

filter

WI at 400.9nm

inner

divertor

SOL

SOL

PFR

SOL

TEXTOR W limiter

JET W divertor

§ Introduction













§ Summary


WC

toroidalpoloidal

radial

80 mm120 mm

curvature: 70 mm

height: 37mm

§ Twin Limiter experiment with variation of impact energies of impinging impurities

§ Determination of the W sputtering yield and the impurity composition

§ Effective S/XB values from corresponding WF6 injections (into comparable plasmas)

TEXTOR Experiments:

W Sputtering and WF6 Injection

§ WF6 injection experiment with gas inlet and negligible limiter surface

§ Well-known amount of W injected / direct dissociation at about Te~0.1eV

§ Prompt re-deposition minimised / no impact from local deposition of W


TEXTOR: Comparison of W Atoms

from Sputtering and Injection

§ Is W from WF6 dissociation representative for W from sputtering?

§ No difference in line shape of different WI and WII lines

§ Line ratios of WI lines with same lower level comparable in sputtered and injected W

§ WII lines measured and quantified in WF6 injections

S. Brezinsek Phy. Scripta 2011


Inverse Photon Efficiencies for WI

§ Multimachine fit of effective S/XB values for 400.9 nm applied for quantification of W fluxes

§ Contrast to AUG data which uses constant 20 (but works only in the range od 5-15 eV)

§ JET outer divertor hotter and has larger ELM energy drops (higher Te)

Different methods:

§ Weight loss

§ Spectroscopy

§ WF6 injection

§ W(CO)6 injection

S. Brezinsek ITPA 2012 steady-state ELMs


Effectice S/XB for Different WI Lines

Modelling:

ADAS/Mons data

(O‘Mullane/

Palmeri et al.)

Experiment:

TEXTOR data

(Brezinsek/Laengner)


JET: Effective Tungsten Sputtering Yields

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

0 20 40 60 80 100

Te [eV]

GG

Wio

n/

ASDEX Upgrade

JET, density steps

JET, density ramp

TEXTOR

5.7% C4+

4.0% C4+

2.0% C4+

1.0% C4+

0.5% Be4+

0.5% Be2+

R. Dux JNM 2009

G.v. Rooij JNM 2013

§ General W sputtering well described by Be ions / slight shift in energetic threshold

§ Plasma cooling by N2/Ar seeding till Ein drops below threshold [AUG R.Neu JNM 2011/Giroud

2014]

Increasing N

Competition between higher impurity flux

and local cooling in seeded discharges

G. v. Rooij,

JNM 2013

Increasing N

Plasma cooling leads to reduction of the W

source down to physical sputtering threshold

Plasma cooling


JET: ELM-induced Tungsten Sputtering

§ H-mode plasmas have energetic transients (ELMs) which hit the target at impact

energies of 1keV or above

§ Residual W in seeded plasmas determined by ELMs (Be+D+N impact) [Guillemaut

PPCF]

N2 seeded

discharge

S. Brezinsek et al.

PSI 2014

§ Prediction of residual W source in ITER in H-mode plasmas

ASDEX: Dux et al.,

J Nucl Mat 2009


S. Brezinsek et al.

Chemical Assisted Physical Sputtering of W ?

WD A-X transition

Q branch

Garvey et al.

J. Phys. Chem. 1988

TEXTOR:

§ Molecular emission solely in W sputtering

experiment and not with WF6 injection

§ Molecular emission identified in high spectral

resolution as WD molecules

§ Surface reaction responsible for WD:

Chemical assisted physical sputtering

§ fast D impacts on D saturated W surface

and releases WD

§ C, O impacts on D saturated W surface

and releases WD

JET:

§ WD identified,

but poor

resolution

inte

nsity [

arb

. units]

l [A]

JPN 85326


Summary

§ D2 d-a transition: Recycling flux

=> understood and good set of data (EIRENE)

=> impact of surface confitions / material needs to be investigated

§ BeD A-X band : Chemical-assisted physical sputtering / recombination

=> empiric set of S/XB values

=> more work required

§ WD A-X band : Swift chemical sputtering

=> just identified => no S/XBs


§ ND A-X band : Volume or surface reaction

=> identified => S/XBs?


§ CN, N2, N2+, CD, C2 in minor quantities. Hydrocarbons well documented.

§ Atomic and molecular species in the scrape-off layer of tokamaks

observed

§ Focus on species related to ITER materials, fuelling and seeded species

Reflection Atomic and Molecular Spectroscopy in the Scrape-Off … · 2014. 12. 16. · Atomic and...

Documents

Transcript of Reflection Atomic and Molecular Spectroscopy in the Scrape-Off … · 2014. 12. 16. · Atomic and...