Effects of plasma shape on laser blow-off injected impurity transport in TCV

Abstract

The extreme shaping capabilities of the TCV tokamak have been used to investigate the effect of the plasma geometry on the confinement of non recycling trace impurities injected by means of the laser blow-off technique. The progression of the injected Silicon in the core of

Local effects of ECRH on argon transport in L-mode discharges at ASDEX Upgrade

“…This leads to flat or hollow central impurity density profiles and to a global decrease in impurity density for the same amount of impurity atoms injection. The evaluated transport coefficients confirm results from previous studies using independent methods [2,3,4,5,6,7,8,9] and, additionally, show that the diffusivity enhancement and the rise of an outward convection are strongly localized around the ECRH deposition radius. While the local increase of the convection velocity was clearly shown in [3] whereas others have seen a more global effect on the convection velocity profile, the diffusion coefficients in all of these cases does not exhibit such localized increase around the position of deposition of ECRH (or ICRH).…”

“…For the most centrally heated case (10c), the central D reaches values up to one order of magnitude higher than the reference case, while the mixed heating case (10b) exhibits an increase of D up to a factor 6 at ρ ∼ 0.45, just outside the ECRH deposition radius. The maximum convection velocity is also found around the ECRH deposition radius: convection partially confirm previous experimental findings obtained using different analysis methods [3,4,5,6,7,8,9]. What is striking and novel of these results is the strong localization of these effects around the ECRH deposition position.…”

Effects of ECRH power and safety factor on laser blow-off injected impurity confinement in TCV

“…Remarkably, in the JET-Tore Supra studies, the total energy confinement time exceeded the impurity energy confinement time by a factor of 2.5 on average, whilst for TCV experiments, as reported here and previously [5], the impurity confinement time is the larger with The 1-D simulation code STRAHL [22,23] has been used to estimate the transport parameters D edge and v edge of the impurities for two injections in plasmas whose currents were respectively below and above the threshold. The simulation technique is identical to that described in Refs.…”

“…[5]. The global impurity confinement time imp τ is defined as the time constant of the exponential decay of the line integrated SXR signals, following the peak of the pulse produced by the introduction of the impurities into the plasma.…”

Core impurity transport in Alcator C-Mod L-, I- and H-mode plasmas

“…The results of the full magnetic field scan are shown in Fig.11, along with a curve proportional to B T .18 , a scaling which was derived from a regression analysis of C-Mod data [43]. This scaling is in contrast to the observations from Alcator C [29] and TCV [38] which showed a marked drop in the impurity confinement time as the toroidal magnetic field was increased. The relatively strong plasma current dependence of impurity confinement and weak dependence on magnetic field suggest that the inverse rotational transform q is not the governing parameter.…”