Bonnin, X.

Coster, D.

Counsell, G.

Kaveeva, E.

Kirk, A.

Rozhansky, V.

Schneider, R.

Voskoboynikov, S.

English

MPG.PuRe

First Results from B2SOLPS5.0 Plasma Edge Modelingfor the MAST Spherical TokamakV. Rozhansky1, E. Kaveeva1, S. Voskoboynikov1, G. Counsell2, A. Kirk2, D. Coster3,X. Bonnin4, R. Schneider41St.Petersburg State Polytechnical University, Polytechnicheskaya 29, 195251St.Petersburg, Russia2EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon, OX143DB, UK3Max-Planck Institut für Plasmaphysik, EURATOM Association, D-85748 Garching,Germany4Max-Planck Institut für Plasmaphysik, EURATOM Association, D-17491 Greifswald,GermanyIntroductionModeling of the edge plasma for the MAST spherical tokamak was performed with theB2SOLPS5.0 code with drifts and currents for L-mode regimes. Two shots were analyzed:shot 5498 corresponds to a quasi single-null (SND) divertor configuration (distancebetween two separatrixes 8 mm), while shot 7138 (distance between two separatrixes 1mm) corresponds to a quasi connected double-null divertor configuration (CDN).Simulation resultsThe transport coefficients used in the simulations are chosen to match the experimentaldata and are given in table 1. They are independent on radius and poloidal angle. Theanomalous viscosity coefficient Dnmi=η . The plasma density, the ion and electrontemperatures at the inner boundary are also given in table 1. These temperatures werechosen to provide the experimental heat flux (PLOSS) from the core divided equallybetween the electron and ion channels. The gas puff sparticles /100.6 21⋅=Γ  for bothshots was imposed at the outer midplane. Calculated and measured profiles of electrontemperature and ion saturation current along the plates are shown in Figs.1-2 for shot7138. The comparison between the (TS) data and calculated density and electrontemperature profiles at the inner mid-plane for shot 5498 is shown in Fig.3.Table 1 cross field transport and core parameters used in the simulationShot Dm2s-1κe/nem2s-1κi/nem2s-1ne|core1019m-3Te|coreeVTi|coreeVPLOSSkW5498 1.5 2.5 2.5 1.8 90 100 4207138 1.0 2.5 1.5 1.8 120 188 50030th EPS Conference on Contr. Fusion and Plasma Phys., St. Petersburg, 7-11 July 2003 ECA Vol. 27A, P-3.91Since the position of the separatrix is not exactly defined the calculated curves wereshifted to match the experimental ones. The matching of the slopes of calculated andobserved profiles is reasonable. The Dα signal in the equatorial mid-plane for the sameshot is shown in Fig. 4. The corresponding profiles for shot 7138 are very similar.As seen from the comparison, the simulation reproduces the experimental data.The accuracy is determined by the restrictions of the fluid model for neutrals used inB2SOLPS5.0 similar to other tokamaks, e.g. ASDEX Upgrade. In particular, flux-limitingcorrections in perpendicular neutral heat and particle fluxes are important for MAST.Note, however, that there is no much flexibility in choosing the transport coefficientssince the matching to all experimental data imposes rather severe restrictions on theirvalues. As in the experiment, the main energy flux goes to the outer divertor plates. Theratio of energy flux to the outer plates and the energy flux to the inner plates is 2.5 for shot5498 and 2.7 for shot 7138. This ratio could be amplified if the ballooning nature of thetransport coefficient was assumed.The radial electric field profiles at the outer mid-plane are shown in Figs. 5-6 fortwo shots. In the core region the radial electric field is close to the neoclassical electricfield, as in ASDEX-Upgrade [1]. The value of the electric field in MAST is significantlysmaller, while the shear of the poloidal BE ×  drift is of the same order due to the smallertoroidal magnetic field at the outer mid-plane. In the scrape-off layer the poloidal BE ×drift is nearer to the poloidal sound speed than in ASDEX Upgrade especially at the outerpart of the SOL. The parallel velocity at the outer mid-plane is negative (in the co-currentdirection), its poloidal profile is shown in Fig. 7 for shot 7138.Conclusions1.First simulations of spherical tokamak MAST were performed with B2SOLPS5.0 code.2.Results of the simulations are in reasonable agreement with probe measurements of theelectron temperature and saturation current at the divertor plates, with the radial profilesof Dα signal at the outer mid-plane and with the mid-plane density and electrontemperature profiles obtained from a Thomson scattering (TS) system.3.The core radial electric field in the vicinity of the separatrix is close to the neoclassicalvalue, as obtained previously for ASDEX Upgrade.References1. V. Rozhansky et al Nucl. Fus. 42 (2002) 1110.Acknowledgements This work was funded jointly by the United Kingdom Engineering and PhysicalSciences Research Council and by EURATOM.30th EPS Conference on Contr. Fusion and Plasma Phys., St. Petersburg, 7-11 July 2003 ECA Vol. 27A, P-3.91 2 of 4Fig.1. Electron temperature profiles along the divertor plates. Comparison of B2SOLPS5.0 results withprobe measurements for shot 7138.122 124 126 128048121620  experim ent codeprivate regionSOL T e,eVdistance along the plate, cm (a) Inner upper plate-135 -130 -1250481216202428 expe rim en t codep riva tereg ionS O L T e,eVd is tan ce  a lo ng  the  p la te ,cm(c) Inner lower plate11 0 12 0 13 0 14 0 15 004812  ex pe r im e n t co depr iva tere g io nS O L Te,eVd is ta n ce  a lon g  th e  p la te , cm(b) Outer upper plate1 1 0 1 2 0 1 3 0 1 4 00481 2  e x p e r im e n t c o d ep r iv a tere g io nS O L T e,eVd is ta n c e  a lo n g  th e  p la te ,  c m(d) Outer lower plateFig.2. Ion saturation current profiles along the divertor plates. Comparison of B2SOLPS5.0 results withprobe measurements for shot 7138.122 124 126 1280481216SOL private region experiment code j sat , kA / m 2distance along the plate, cm(a) Inner upper plate-135 -130 -125 -1200481216S O Lprivate  reg ion experim ent code j sat , kA / m 2d istance a long  the  p la te , cm(c) Inner lower plate120 130 14002468SOLprivate region experim ent code  j sat , kA / m 2distance along the p la te, cm(b) Outer upper plate110 120 130 14002468SOLprivate region  j sat , kA / m 2distance along the plate, cm experiment code(d)Outer lower plate30th EPS Conference on Contr. Fusion and Plasma Phys., St. Petersburg, 7-11 July 2003 ECA Vol. 27A, P-3.91 3 of 40.1 0.2 0.3 0.4 0.50.05.0x10181.0x10191.5x10192.0x10192.5x1019separatrix High resolution TS Low resolution TS code profile n e , m - 3Radial coodinate (Y), mFig.3 (a). Comparison of calculated density profileand TS data at the inner midplane for shot 5498.1.2 1.3 1.4 1.50.02.0x10204.0x10206.0x10208.0x10201.0x10211.2x10211.4x1021coreSOLseparatrix  Emissivity, photons  m-3 s-1Radial coordinate (Y) , m experiment codeFig.4. Radial profile of Dα emission at the outermidplane. Code calculation for shot 5498.-0.04 0.00 0.04 0.08-4-2024innerseparatrixSOLcore E(code)  E(NEO)Radial electric field (kV/m)Radial coordinate Y, (m)Fig.6. Radial electric field profile for shot 5498.0.1 0.2 0.3 0.4 0.504080120160200240280separatrix High resolution TS Low resolution TS code profile Te , eVRadial coodinate (Y), mFig.3 (b). Comparison of calculated electrontemperature profile and TS data at the innermidplane for shot 5498.-0.04 0.00 0.04 0.08-4-2024innerseparatrixSOLcore E(code)  E(NEO)Radial electric field (kV/m)Radial coordinate Y, (m)Fig.5. Radial electric field profile for shot 7138.0 1 2 3 4 5-40-20020lower plateupper plateoutermidplaneshot #7138Parallel velocity (km/s)Poloidal coordinate X, (m)Fig.7. Poloidal profile of parallel velocity in theouter SOL for shot 7138.30th EPS Conference on Contr. Fusion and Plasma Phys., St. Petersburg, 7-11 July 2003 ECA Vol. 27A, P-3.91 4 of 4

First Results from B2SOLPS5.0 Plasma Edge Modeling for the MAST Spherical Tokamak

https://pure.mpg.de/pubman/item/item_2137666_3/component/file_3311237/P3_091.PDF

First Results from B2SOLPS5.0 Plasma Edge Modeling for the MAST Spherical Tokamak

Abstract

Similar works

Full text

Available Versions

MPG.PuRe