ITPA-9, Avila, Spain, 7-10. 01. 2008

Impact of ICRF on impurity production in TEXTOR

Presented by Marek Rubel

Alfvén Laboratory, Royal Institute of Technology, Association EURATOM – VR, Stockholm, Sweden

in co-operation with

B. Emmoth, P. Wienhold, Ph. Mertens, V. Philipps

E. Fortuna, M. Pisarek and W. Zieliński

Outline:

• Collector probe data

• Analysis of deposits from ICRF antenna grill

Impact of ICRF on impurity production Collector probe data (1)

Probe exposure in time-resolved mode to ICRF heated pulses.• Time resolution: 125 ms• Probe position: 25 – 85 mm in the SOL; data presented for 37 mm.

Message:

• Increase of metal (Ni, Cr, Fe) impurity fluxes during ICRF heated pulses.

• Increased deposition rates are measured also for deuterium and oxygen.

Metal Deposition Rates

0

0,2

0,4

0,6

0,8

1

1,2

0 2 4 6 8

Discharge Time [s]

De

po

sit

ion

ra

te [

10

e1

4 c

m-2

s-1

]

INCONEL METALS

ICRF ICRF

Single discharge

Two discharges

00 2 42

Plasma current and density

Impact of ICRF on impurity production Collector probe data (2)

Probe exposure in time-resolved mode to ICRF heated pulses

Message:Increase of metal (Ni, Cr, Fe) impurity fluxes during ICRF heated pulses.

Metal Deposition Rates

0

0,2

0,4

0,6

0 1 2 3 4

Discharge Time [s]

Dep

osi

tio

n R

ate

[10e

14 c

m-2

s-1

]

23756-7

ICRF

Two discharges

1.8 3.4 5.0

ICRH, An-1

5.1 4.6 12.8

4.3 1.1 8.8

ICRH, An-2

5.1 6.9 13.0

Heating Si1015 cm-2s-1

B1014 cm-2s-1

Me1013 cm-2s-1

Impact of ICRF on impurity production Collector probe data (3)

Probe exposure in time-integrated mode to Ohmic and ICRF pulses

Message:Increase of all impurity fluxes during ICRF heated pulses.

Co-deposits on ALT-II and antenna grill

1. ALT-II 2. ICRF antenna

Antenna grill

2m

2m

Deposition zone on ALT-II

ElementElement Limiter Limiter ALT-IIALT-II AntennaAntenna Grill Grill

C 75-80 24-27

O 10-15 15-17

Fe ~1 20-23

Si 1-10 23-28

B 3-10 -

Cr - 6-7

D* 9-12 3-5

Composition of co-deposits:Deposition zone on limiter and antenna grill

Messages:

Differences in the content of elements

• More light elements – C and B - on ALT-II toroidal belt limiter

• Prevalence of heavy elements on the antenna grill

Distribution of elements in co-deposits on the toroidal belt limiter

Message:Heavier elements embedded in an uniform carbon matrix.

C

Fe

Si

Distribution of elements in co-deposits from the antenna grill

Message:Distinct separation of elements in co-deposits from the antenna.

• Increase of impurity fluxes in the SOL during ICRF phase.

• ICRF-induced modification of the SOL (edge temperature, electric sheath, ion trajectories) influence the structure and composition of co-deposits.

• The increase of deuterium atomic density (1.5-3 times) and ion energies (up to 5 times) cause preferential removal of carbon from co-deposits on the antenna.

Concluding Remarks