Impact of impurities on zonal flow driven by trapped electron mode turbulence

Abstract

The impact of impurities on the generation of zonal flow (ZF) driven by collisonless trapped electron mode (CTEM) turbulence in deuterium (D)-tritium (T) plasmas is investigated. The expression for ZF growth rate with impurities is derived by balancing the ZF potential shielded by polarization effects and the ZF modulated radial turbulent current. Then, it is shown that the maximum normalized ZF growth rate is reduced by the presence of the fully ionized non-trace light impurities with relatively flat density profile, and slightly reduced by highly ionized trace tungsten (W). While, the maximum normalized ZF growth rate can be also enhanced by fully ionized non-trace light impurities with relatively steep density profile. In particular, the effects of high temperature helium from D-T reaction on ZF depend on the temperature ratio between electron and high temperature helium. The possible relevance of our findings to recent experimental results and future burning plasmas is also discussed.

Effects of Micro-turbulence on the Removal of Helium Ash in Deuterium–Tritium Plasmas

“…While, these parametric dependence of PVS are weak. Combined with the effects of helium ash on CTEM instability in the previous work [25], we point out that the effects of helium ash are different for different types of micro-instabilities. (ii) The total flux of helium ash driven by CTEM turbulence is outward.…”

“…This outward Ĉz is because the diffusion mechanism dominates over the convection as show in Figs. 7, 8 and 10 of [25]. Moreover, outward Ĉz is increased when we steepen the density profile of helium ash, increase T z (i.e., decrease of s z due to fixed T e ¼ T i ) and f T (i.e., more T ions in D-T plasmas).…”

“…For a better comparison, we further compare the temperature and density profile of helium ash as well as isotopic effects on micro-instabilities in Table 2 based on Refs. [23][24][25] and Figs. 1,2,3and4 in this paper.…”

“…Based on the analytical results, we have studied the role of ITG [23], PVS [24] and CTEM turbulence [25] on the removal of helium ash, respectively. The variation of helium ash flux with parameters (such as R=L nz , T z and f T ) has been given in the ITG and PVS turbulence dominated plasmas.…”

“…In this paper, we study the effects of helium ash on ITG and PVS instabilities based on the analytical results in [23,24], and compare with those on CTEM instability [25]. The presence of helium ash significantly affects micro-instabilities, due to the consideration of both dilution effects and the density profile of ash.…”