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 (but still safe) ICRF power maximizes the wall isotope removal per ICWC pulse. In the pressure range 1 to 7.5¥10­5 mbar, the removal efficiency reduces with increasing discharge pressure. As most of the isotopes are recovered 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 larger than 7.3¥1022 hydrogenic atoms, and may be exchanged within 400s of cumulated ICWC discharge time.