Experimental study of tungsten transport properties in T-10 plasma

Abstract

First experimental results of tungsten transport investigation in OH and ECRH plasmas in the T-10 tokamak with W-limiter and movable Li-limiter are presented. It is shown that tungsten tends to accumulate (a joint process of cumulation and peaking) near the plasma axis in ohmic regimes. The cumulation of W is enhanced in discharges with high values of the parameter that coincides with accumulation conditions of light and medium impurities in T-10 plasmas. Experiments with Li-limiter show the immeasurable level of Li3+ (0.3–0.5% of ne) of T-10 CXRS diagnostics because of the low inflow of Li with respect to other light impurities. Nevertheless, the strong influence of lithium on inflow of light and tungsten impurities is observed. In discharges with lithized walls, vanishing of light impurities occurs and values of are obtained. It is also shown that the tungsten density in the plasma center decreases by 15 to 20 times while the W inflow reduces only by 2 to 4 times. In lithized discharges with high γ, the flattening of the tungsten density profile occurs and its central concentration decreases up to 10 times during the on-axis ECRH. This effect is observed together with the increase of the W inflow by 3 to 4 times at the ECRH stage.

Nonlinear Problems of Equilibrium Charge State Transport in Hot Plasmas

“…But only they determine the equilibrium transport along with the resulting stationary density distributions. The corresponding similarities of the equilibrium rate ratios can be suspected in experiments, e.g., when there is an apparently similar stationary density profiles of the central accumulation of C [29,30], Ar [31,32] and W [1,33].…”

Nonlinear Problems of Equilibrium Charge State Transport in Hot Plasmas

“…But only they determine the equilibrium transport along with the resulting stationary density distributions. The corresponding similarities of the equilibrium rate ratios can be suspected in experiments, e.g., when there is an apparently similar stationary density profiles of the central accumulation of C [27,28], Ar [29,30] and W [1,31].…”

“…  Z n  , for example, of C and Ar are well known from experiments (see, e.g., in [27][28][29][30][31][32]). The profiles   Z n  can be (i) peaked in the plasma core, (ii) almost flat, or (iii) slightly hollow.…”

The Influence of Tungsten Impurity Accumulation on T-10 Ohmic Discharges Stability

“…В качестве экспериментального значения радиационных потерь были использованы результаты измерения датчиков AXUV. В работе [13] было показано, что в относительно чистых разрядах (Z эф ≤ 3) излучение в центральной области шнура (ρ ≤ 0,5) практически полностью формируется ионами вольфрама, что гарантирует применимость 2 Всего зарегистрировано несколько сотен разрядов с присутствием данного эффекта. В ходе развития W-цикла можно выделить следующие этапы, по многим признакам совпадающие с отмече нными в [2,3]:…”

“…Как видно на рис. 3, г, это приводит к исходному слабому обострению профиля радиационных потерь rad W ( ), P r как результату прямой связи [13]. Описанные этапы могут в дальнейшем многократно повторяться в разряде, заканчиваясь, как правило, срывом тока.…”