hydrocarbon spectroscopy on eu tokamaks

1Institut für PlasmaphysikAssoziation EURATOM-Forschungszentrum Jülich

ITPA - DSOL - Toronto S. Brezinsek

TEC

Hydrocarbon spectroscopy on EU tokamaks

S. Brezinsek on behalf of the EU task forcefor Plasma-Wall Interaction

presented by V. Phillips

TEXTOR: Photon efficiencies for different types of hydrocarbons in ionising plasmas

HYDKIN: Measured and calculated photon efficiencies in different devices

AUG: Chemical erosion and photon efficiencies under detached plasma conditions

JET: Chemical erosion yielded in higher hydrocarbons

TF-E



TECTEXTOR– Photon Efficiencies for Hydrocarbons: CD4

Aim: Measure D/XB values without contamination from deposited and re-eroded hydrocarbons.

Comparison with HYDKIN and ERO calculations

D/XBExp. =36D/XBHYDKIN=46D/XBERO=32

CD A-X band(CD from CD4)



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CxHy in D plasmas: Te=35 eV, ne=2.2*1018m-3 at the emission locationCxDy in H plasmas: Te=45 eV, ne=1.8*1018m-3 at the emission location

CH A-X band (Gerö band) C2 d-a band (Swan band)

Brezinsek et al. PSI 2006

TEXTOR: Effective Photon Efficiencies for CxHy, CxDy



TECTEXTOR: CD+ Observed in Hot Edge Plasmas

TEXTOR benchmark experiment with CD4: 20 % of theoretically expected

CI 909.5 nm per C observed 50 % of theoretically expected

CII at 426.7 nm per C+ observed 20 % of theoretically expected

Dper H observed

l / nm

0.0

0.2

0.4

0.8

420.0 425.0415.0 430.0 435.0inte

nsity

/ ar

b. u

nits

T 3500 Krot»

TEXTOR #93964

CD A-X bandmodelling

CD

=> CD+ identified in TEXTOR plasmas=> break-up via molecular ions important



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Part of the dissociation chain (CH4):

CH4+

CH4

CH3+

CH3 CH2 CH C

CH2+ CH+ C+ C2+

Reaction kinetic analysis with HYDKIN (Reiter 2006) for CH4

Te=45 eV

CH+

CH

HYDKIN: CH+ vs. CH in the Hydrocarbon chain

Te=5 eV

CH

CH+

Hot limiter plasma (TEXTOR)Cold divertor plasma (AUG, JET)



TECHYDKIN: Effective Photon Efficiencies for Methane

Comparison of measured effective photon efficiencies with HYDKIN calculations (const. plasma, no deposition, no transport)

• Janev-Reiter database is reliable in the range between 5 eV and 100 eV• Detailed comparison with the aid of erosion and deposition models necessary




TECz

/ m

1.0 1.5 2.0R / m

OSP sweep

injectionintrinsic

-1.25

-0.75

-0.50

S4=1.594 m

T4

S3

NP

S4

S2=0.541 mS3=1.038 m

S1=0.000 m

S1

T1LP9

ISP sweep

injection intrinsic

-1.00

T3=1.170 mT4=1.242 m

valve

S2

T3

LP1NP: Neutral Pressure GaugeLP: Langmuir Probe

VOL

T1=0.395 m

VOLT3

ROV18

ROV16

ROV15 (blind)

ROV14

ROV13

ROV12

ROV11

T4

ROV17

AUG: Hydrocarbon Injection in Detached Plasmas

• L-mode discharges with outer divertor detachment• Injection of CH4 and C2H4 in the SOL, Separatrix and PFR

in the volume: Te=1.2 eV, ne=3*1020m-3 at the target (separatrix): Te=2.3 eV, ne=4*1018m-3



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Brezinsek et al. PFCM 2006

AUG: Photon Efficiencies in Detached Plasmas

Intrinsic CD A-X spectrum --- attached plasma ---

Intrinsic CD A-X spectrumwith strong BD contamination

--- detached plasma ---

CH A-X spectrum from injection and CD A-X intrinsic background

--- detached plasma ---

CH A-X spectrum from injection and CD A-X intrinsic background

--- attached plasma ---



TECAUG: Erosion Yields in Detached Plasmas

Decrease of CH and C2 light much stronger than increase of D/XB=> Significant decrease of the hydrocarbon flux in detachment

D/XB for CH from CH4: 18+-/7D/XB for CH from C2H4: 47 +/-19D/XB for C2 fromC2H4: 407 +/-134

Measured D/XB values are higher than in attached plasmas and higherthan predictions with HYDKIN!

Ychem=3.2*10-2 (ion flux only)

Ychem=2.9*10-3 (atom and ion flux)

Erosion yield at the separatrix for detached conditions:

Reduced influx is largely compensated by lower plasma outflux. => Consideration of neutral outflux to the target is important!

Erosion yield in line with Roth-formula: Ychem=2.5*10-3 (atom and ion flux)



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2.20 2.40 2.60 2.80 3.00 3.202.20 2.40

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6

53

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#63253

t2

t3

t1

KS3I KS3O

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he

ight

[m

]

major radius [m]

GIM 10OSP sweep

#63250

KS3 - integrated photon fluxes

loc

al T [e

V]

e

time [s]22 23 24 25

021

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loc

al n

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n mapped on GIM10 location

e

T mapped on GIM10 location

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PFREFIT

#63250

KY4D #63253

2

3

16

24

SOL

Circumferential injectioninto the attached outer divertor:i) Discharge with C2H4 injectionii) Discharge with H2 injection

Nearly identical local plasma conditions

Assumption: symmetric and homogenous injection

Brezinsek et al. EPS 2005

JET: CxHy Contribution to the Erosion Yield



TECJET: CxHy Contribution to the Erosion Yield

• Most reliable value for Ychem is achieved when the strike point is at GIM10

• Toroidal inhomogeneity of gas injection module included (=> information from tracer experiments)

• Bypass in the outer divertor considered!

Photon efficiencies and erosion yield lowered in comparison to first analysis (EPS 2005)

• D/XB for C2 Swan band from C2H4 about 75• Ychem associated to higher hydrocarbons about 0.6%

SOL

sweep

#63253KS3O

0.25

0.50

0.75

1.00

1.25

1.50

1.75

PFRsweep

YC

2Hy [

%]

impinging ion flux (at GIM10) [10 ions s m ]23 -1 -2

chem

KY4D

EFIT

0.4 0.8 1.2 1.60.0




TECSummary

TEXTOR:- Photon efficiencies for different hydrocarbons- Information about hydrocarbon catabolism- Detection of CH+ in the hot edge plasma

AUG:- Photon efficiencies for CH in detached plasma conditions - Hydrocarbon particle flux reduction in detached plasmas- Neutral flux to the target important for yield determination

JET:- Circumferential injection in the outer divertor - Erosion which yielded in C2Hy lower than previously deduced

HYDKIN:- Janev & Reiter data base reliable for ionising conditions- Normalised D/XB values deduced in different machines and compared with HYDKIN

hydrocarbon spectroscopy on eu tokamaks

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