Predictive SOLPS-ITER simulations to study the role of divertor magnetic geometry in detachment control in the MAST-U Super-X configuration

Nuclear Fushion

article

O. Myatra¹  B. Lipschultz²  D. Moulton¹  K. Verhaegh¹  B. Dudson³  S. Orchard¹  A. Fil¹  C. Cowley¹ 

[1] Culham Centre for Fusion Energy, Culham Science Centre;York Plasma Institute, University of York;Lawrence Livermore National Laboratory

关键词: tokamak divertor;    detachment control;    MAST-U;    Super-X;    SOLPS-ITER;   

DOI  :  10.1088/1741-4326/acea33

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

The SOLPS-ITER code has been utilised to study the movement of the detachment front location from target towards the X-point for MAST-U Super-X plasmas. Two sets of detached steady state solutions are obtained by either varying the deuterium ( D ₂) fuelling rate or the nitrogen ( N ) seeding rate to scan the corresponding 'control' parameters of outboard midplane density, n_mathrm{u} , and the divertor impurity concentration, f_mathrm{I} . At seeding and fuelling rates ∼10 ×and ∼5 ×that required to start detachment at the divertor target, the detachment front only reaches ∼50% of the poloidal distance to the X-point, l_mathrm{pol} , corresponding to a region of strong parallel gradients in the total magnetic fieldB . The region of strong total field gradients correlates with where the detachment front location becomes less sensitive to control parameter variation. This result is qualitatively consistent with the predictions of a simple, analytic detachment location sensitivity (DLS) model (Lipschultzet al2016Nucl. Fusion56056007) which is based in a scaled parallel-to- Bspace,z . While the DLS model predictions are in agreement with SOLPS-ITER results in terms of where the front location becomes less sensitive to controls (i.e. in the region of strong parallel gradients inB ), the DLS model predicts a higher sensitivity in the region of weak parallel gradients inBdownstream as compared to the simulation results. Potential sources of differences between the SOLPS-ITER and DLS model predictions were explored: The DLS model does not include energy sinks beyond radiation from a single impurity nor cross-field energy transport. Momentum and particle balance are also not included in the DLS model. The tight opening into the divertor for flux surfaces could lead to variations in plasma-neutral pressure balance as the detachment front reaches that region, exactly how this affects the front movement needs further investigation.

【 授权许可】

Unknown