Impurity transport in JETFunded under: FP2-FUSION 10C
Impurity transport has been studied in JET using the laser blow-off technique. Results are presented for ohmic, L-mode and H-mode plasmas. In all cases impurity transport was found to be small inside r/a of about 0.3, with values for D of roughly 0.03-0.3 m2/s, close to neoclassical predictions. Outside r/a of about 0.4, the transport was much faster than neoclassical, with values for D of about 0.3-0.6, 3-5 and 0.8-1.2 m2/s in H-mode, L-mode and ohmic plasmas, respectively. These values apply only between sawtooth crashes. During the sawtooth phase itself (roughly 100 micro-sec.) the transport is greatly perturbed over the central region, allowing the impurities to leave or enter this region quickly. In ohmic plasmas, the impurity confinement time was between 250 and 350 ms. This value was reduced to 150-200 ms in L-mode plasmas, due to an increase of D in the anomalous transport region. During H-mode plasmas, on the other hand, very long impurity confinement times, of the order of several seconds, were observed. This was explained by a sharp increase of the ratio V/D in a thin region near the plasma edge and a general reduction of D in the outer half of the plasma radius.
Bibliographic Reference: Report: JET-P(91)36 EN (1991) 14 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199111581 / Last updated on: 1994-12-02
Original language: en
Available languages: en