How to do wall conditioning in ITER ?

# Btor cycles is limitedGDC inefficient in BDrawbacks of ECWC, Taylor

Ion cyclotron wall conditioning (ICWC)

J. Roth

General aims of wall conditioning:

Plasma initiation- Impurities, fuel removal

Control of discharge content- Isotopic ratio

ITER : Tritium removal

Ion Cyclotron Wall Conditioning (ICWC) on JET

V. Philipps, A. Lyssoivan, D. Douai, R. Pitts, C. Schueller, T. Loarer, G. Sergienko, S. Brezinsek, J. Ongena, M. Mayoral …

ICWC compatible with permanent magnetic fieldICWC seems suitable – at least in C machines – for removal of impurities and tritium control by isotope exchange (TEXTOR, Tore Supra and AUG)

RF plasma production : He-D2 ICWC

Simulate D2-ICWC in ITER full field conditions using JET A2 ICRF antennas : BT=3.3 T and frequencies ~25 MHz and ~29 MHz thus simulating ITER operation at BT=5.3 T and 40 MHz and 46.6 MHzSimulate ITER RF conditions at full field JET only!

-Optimise poloidal homogeneity (and penetration of the ICWC-plasma into the divertor throat) using a second frequency-Optimise RF power coupling (phasing of antenna straps, gas pressure and composition, antenna phasing, in particular for safe antenna operation-Check consistency with codes (deposition profile by TOMCAT/METS )

PWI : pure D2 ICWC

1) Assess the efficiency of ICWC for T-removal on large size tokamak with divertor2) Compile a reference dataset with a C-based PFCs for later comparison with the ILWJET : only machine with Be operation unique information for active phase in ITER!

-Optimise isotopic exchange efficiency : pressure, gas-composition, RF-power waveform after breakdown-Optimize duty-cycle (RF on/ RF off).-Test plasma re-start after ICWC

ITER DCR-080 (2007) : ICWC as a functional requirement for the main ICRH system ITPA experiment-2009 - SOL/Div group

Goals and rationales

ICWC discharge optimisation (RF part + preparation of PWI experiment)

Reference ICWC discharge

Preloading by 2 hours H2-GDC

with H+)=6.1013 cm-2.s-1 total fluence = 4,4.1017 H/cm2

~ accessible reservoir in JET: 1023 D

Reference H2-ohmic shot [H]/([H]+[D])

10 D2-ICWC shots to perform change-over

Reference D2 ohmic shots [H]/([H]+[D])

- test of ohmic plasma initiation after ICWC

- repeated for changeover HD

Diagnostics

- Neutral Particle Analyser : CX neutrals + isotopic ratio in ref ohmic shots

- OES

- Detailed exhaust gas composition by mass spectrometry

- AGHS after cryo-pumps regeneration

- pressure gauges

- + others : Langmuir, Penning gauges,…

Present strategy

-5 0 5 10 15 200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

time (sec.)

n H/[

n H+

n D]

#43447

#43485

nH/[nH+nD] in ohmic shots (by means of NPA)

after 15+3’ ICWC

Reference ohmicshot before ICWC

-5 0 5 10 15 200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

time (sec.)

n H/[

n H+

n D]

#43447

#43485

nH/[nH+nD] in ohmic shots (by means of NPA)

-5 0 5 10 15 200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

time (sec.)

n H/[

n H+

n D]

#43447

#43485

nH/[nH+nD] in ohmic shots (by means of NPA)

after 15+3’ ICWC

Reference ohmicshot before ICWC