Isotope exchange by Ion Cyclotron Wall Conditioning on JET

The isotopic exchange efficiencies of JET Ion Cyclotron Wall Conditioning (ICWC) discharges produced at ITER half and full field conditions are compared for JET carbon (C) and ITER like wall (ILW). Besides an improved isotope exchange rate on the ILW providing cleaner plasma faster, the main advantage compared to C-wall is a reduction of the ratio of retained discharge gas to removed fuel. Complementing experimental data with discharge modeling shows that long pulses with high (∼240 kW coupled) ICRF power maximizes the wall isotope removal per ICWC pulse. In the pressure range 1–7.5 × 10⁻³ Pa, this removal reduces with increasing discharge pressure. As most of the wall-released isotopes are evacuated by vacuum pumps in the post discharge phase, duty cycle optimization studies for ICWC on JET-ILW need further consideration. The accessible reservoir by H₂-ICWC at ITER half field conditions on the JET-ILW preloaded by D₂ tokamak operation is estimated to be 7.3 × 10²² hydrogenic atoms, and may be exchanged within 400 s of cumulated ICWC discharge time