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  • Momentum losses by charge exchange with neutral particles in H-mode discharges at JET
    Versloot, T.W. ...
    The effect of a neutral density background on the toroidal angular momentum and kinetic energy profiles has been investigated in JET. Under equivalent conditions but with increasing gas fuelling ... during the flat top phase, it has been observed that both the edge rotation and temperature decrease. The increase in electron density was not sufficient to compensate the rotation andtemperature loss such that both energy and momentum confinement times are significantly reduced. The edge localized mode behaviour is observed to be significantly affected by the increased neutral influx. A simple 1.5D fluid model has been used to qualitative capture the neutral transport response within the plasma, followed by a forward model of the passive charge-exchange (CX) emission of carbon to obtain a corrected radial neutral density profile. It has been found that the neutral density is sharply attenuated over the edgeregion, with similar edge magnitudes in both the non-fuelled (Ž0žne ~ 1.2 m s-1) and maximum fuelled case (Ž0žne ~ 2.5 m s-1). Discharges with reversed-B operation exhibited even higher normalized neutral fluxes related to first orbit effects and increased wall interactions. Over the full neutral influx range, a decrease in pedestal thermal Mach number from 0.25 to 0.14 wasobserved. Increased neutral penetration up to the pedestal top (rža ~ 0.9) due to multiple CX interactions is obtained from the interpretive model. Underthese multiple neutral-ion interactions, the impact on the CX loss of angular momentum is larger compared with the CX energy loss. The drag torque was seen to increase up to 10% of the total applied torque, while energy losses appeared to be smaller. The accuracy of this global approach method is unfortunately limitedč however, the estimated momentum sink was found comparable to the torque required to explain the discrepancy between observed global energy and momentum confinement.
    Source: Plasma physics and controlled fusion. - ISSN 0741-3335 (Iss. 6, Vol. 53, 2011, 065017-1-065017-15)
    Type of material - article, component part
    Publish date - 2011
    Language - english
    COBISS.SI-ID - 25290279

source: Plasma physics and controlled fusion. - ISSN 0741-3335 (Iss. 6, Vol. 53, 2011, 065017-1-065017-15)
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