The effect of a saturated kink on the dynamics of tungsten impurities in the plasma core

Ferrari, Hugo; Farengo, Ricardo; Clauser, C.

doi:10.1088/1361-6587/aaf7e6

Cited by 7 publications

(4 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An additional mechanism responsible for expelling heavy/high-Z impurities is a saturated n/m = 1/1 mode destabilized by excessive ECRH power inside of q = 1 surface driving a strong outward convection of heavy/high-Z ions inside of a displaced core [4,15,[17][18][19][20]. A description of this phenomenon by available transport models in non-axisymmetrical geometry is still incomplete [21,22].…”

Section: Introductionmentioning

confidence: 99%

Understanding core tungsten (W) transport and control in an improved high-performance fully non-inductive discharge on EAST

Shi¹,

Chen²,

Bourdelle³

et al. 2022

Nucl. Fusion

View full text Add to dashboard Cite

The behavior of heavy/high-Z impurity tungsten (W) in an improved high-performance fully non-inductive discharge on EAST with ITER-like divertor (ILD) is analyzed. It is found that W could be well controlled. The causes of no W accumulation are clarified by analyzing the background plasma parameters and modeling the W transport. It turns out that the electron temperature (T_e) and its gradient are usually high while the toroidal rotation and density peaking of the bulk plasma are small. In this condition, the modeled W turbulent diffusion coefficient is big enough to offset the total turbulent and neoclassical pinch, so that W density profile for zero particle flux will not be very peaked. Combining NEO and TGLF for the W transport coefficient and the impurity transport code STRAHL, not only the core W density profile is predicted but also the radiated information mainly produced by W in the experiment can be closely reconstructed. At last, the physics of controlling W accumulation by electron cyclotron resonance heating (ECRH) is illustrated considering the effects of changed T_e by ECRH on ionization balance and transport of W. It shows that the change of ionization and recombination balance by changed T_e is not enough to explain the experimental observation of W behavior, which should be attributed to the changed W transport. By comparing the W transport coefficients in two kinds of plasmas with different T_e profiles, it is shown that high T_e and its gradient play a key role to generate large turbulent diffusion through increasing the growth rate of linear instability so that W accumulation is prevented.

show abstract

Section: Introductionmentioning

confidence: 99%

Understanding core tungsten (W) transport and control in an improved high-performance fully non-inductive discharge on EAST

Shi¹,

Chen²,

Bourdelle³

et al. 2022

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…It is, therefore, vital to acquire a good understanding of impurity transport and to develop methods for controlling the concentration of W in tokamak core plasmas. A large number of experimental [11][12][13][14][15], theoretical [16][17][18][19][20] and numerical [21][22][23][24] studies have provided important results on these complex processes, but the domain is still open as shown by very recent papers [25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Effects of the parallel acceleration on heavy impurity transport in turbulent tokamak plasmas

Vlad¹,

Palade²,

Spineanu³

2021

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

A process specific to the dynamics of the heavy impurities in turbulent tokamak plasmas is found and analyzed. We show that the parallel stochastic acceleration is strongly coupled to the perpendicular transport and generates a radial pinch velocity. The interaction is produced with the hidden drifts, a quasi-coherent component of the motion that consists of a pair of average radial velocities in opposite directions. The parallel acceleration breaks this symmetry and yields a radial average velocity that can be in the inward or outward direction. The pinch is generated in three-dimensional turbulence, in the presence of a poloidal average velocity. It is significant only for heavy, high Z ions. The transport of the tungsten ions is analyzed in the frame of the minimal test particle model that yields this pinch mechanism. We use a semi-analytical method and numerical simulations. The scaling laws of the pinch velocity and of the diffusion coefficient are found and analyzed in order to drive a clear physical image of these non-linear effects. We conclude that the pinch produced by the non-linear interaction of the parallel accelerated motion with the perpendicular transport is rather strong for the heavy impurities.

show abstract

“…A huge experimental [1][2][3][4][5][6][7][8][9], theoretical [10][11][12][13] and numerical [14][15][16][17] effort was directed in the last decades to the understanding of W ion transport and dynamics. In spite of important achievements, this domain is still open as shown by many very recent papers [18][19][20][21][22]. The complex transport process includes neoclassical and turbulent effects, which generate specific phenomena that are not observed for light ions.…”

Section: Introductionmentioning

confidence: 99%

Turbulent transport of the W ions in tokamak plasmas: properties derived from a test particle approach

Palade¹,

Vlad²,

Spineanu³

2021

Nucl. Fusion

View full text Add to dashboard Cite

A detailed analysis of a special type of turbulent pinch mechanism for tungsten (W) ions is presented. It is based on the numerical simulation of ion trajectories in a complex test-particle model that contains realistic representations of the turbulence and of the confining magnetic field, plasma rotation, ion collisions, the polarization drift and the parallel stochastic acceleration. The origin of the pinch is a special type of order generated by an average poloidal velocity V p superposed on the E × B stochastic drift. It consists of a pair of radial symmetric drifts, the hidden drifts (HDs), that exactly compensate. The polarization drift and the parallel acceleration drive radial pinch velocities V x by destroying the perfect anti-symmetry of the HDs. These phenomena that were found in simplified models are theoretically validated here in a realistic model of W ion transport. The main conclusion of the paper is that this turbulent mechanism can be experimentally relevant for a large domain of parameters, which cover both existing plasmas and ITER conditions, and it can be responsible for an important amount of the W ion accumulation.

show abstract

The effect of a saturated kink on the dynamics of tungsten impurities in the plasma core

Cited by 7 publications

References 20 publications

Understanding core tungsten (W) transport and control in an improved high-performance fully non-inductive discharge on EAST

Understanding core tungsten (W) transport and control in an improved high-performance fully non-inductive discharge on EAST

Effects of the parallel acceleration on heavy impurity transport in turbulent tokamak plasmas

Turbulent transport of the W ions in tokamak plasmas: properties derived from a test particle approach

Contact Info

Product

Resources

About