Ústavu fyziky plazamtu - detail projektu 00180

Integrované modelování tokamaku s rovnováhou s volným rozhraním – optimalizace scénáru a regulace
ID projektu:	GP13-38121P
Poskytovatel:	Grantová agentura České republiky
Období:	01.02.2013 - 31.12.2013
Hlavní řešitel:	Ing. Jakub Urban, Ph.D.
Cíle projektu: Integrované (transportní) simulace jsou stežejní pro výzkum fúze s magnetickým udržením. Konkrétne pro ITER a budoucí zarízení poskytují predpovedi pro operacní scénáre. V kontextu integrovaných simulací hrají kódy s rovnováhou s volným rozhraním duležitou roli. V porovnání s bežnejšími kódy s pevným rozhraním respektují vlastnosti a omezení daného zarízení, predevším systému poloidálního pole, takže poskytují realistický vývoj rovnováhy plazmatu. Zároven jsou ale obtížnejší. Budeme vyvíjet pokrocilé nástroje pro integrované simulace výboju v tokamacích. Budeme vycházet ze soucasné práce na integraci kódu FREEBIE (rovnováha s volným rozhraním) a CRONOS (transport). Vyvinuté metody budou dále využity pro EFDA ITM projekt, zejména pro simulace ITER scénáru. Plánujeme použít metody teorie rízení pro optimalizace scénáru s pomocí rychlého transportního kódu.
Dosažené výsledky: Overview A procedure for benchmarking multiple free boundary equilibrium (FBE) codes has been developed in a wide international collaboration. Several benchmarks have been carried out using codes FREEBIE, CEDRES++ and DINA-CH, showing a reasonable agreement of the results. The results were presented at an international conference (APS DPP meeting). The FBE-transport coupling has been further developed for both CRONOS and ITM. However, the coupling scheme still has numerical issues. FREEBIE has been coupled to METIS, thus forming a tightly integrated FBE tokamak simulator, which is to be exploited for fast simulations and optimizations. First integrated simulations for the COMPASS tokamak have been performed using METIS. Several discharges have been analysed in order to authenticate different diagnostics and derive unmeasured quantities. Suitable equilibrium quantities have been used in support of modelling relativistic electron generation in the WEGA stellarator by a lower-hybrid antenna (paper accepted to Physics of Plasmas). In collaboration with CCFE Culham, UK, a new version of the equilibrium reconstruction code EFIT has been released and applied to COMPASS (paper submitted to Nuclear Fusion). Free-boundary equilibrium inter-code benchmark Free-boundary equilibrium (FBE) codes have in principle never been thoroughly benchmarked against each other. Moreover, several new codes, including FREEBIE, appeared only recently. Hence, it is highly appropriate to create a standard inter-code benchmarking procedure for FBE codes. We have developed a complex procedure, which consists of several problems, organised into six groups: 1) vacuum description, 2) static equilibrium, 3) open loop evolution of plasma with zero resistivity, 4) open loop evolution with realistic resistivity (requires current diffusion), 5) closed loop evolution with a feedback control, 6) transient events benchmarks. Each groups consists of multiple tasks, focused on ITER and future devices. Very important here is a correct, consistent definition of inputs and outputs. Quantitative measures, based on the ITM CPO (consistent physical object) standard, for comparing the results have been proposed. Benchmarks from groups 1 – 4 have already been carried out using FREEBIE, DINA-CH and CEDRES++. Problems that do not require a coupled current diffusion equation (CDE) solver, i.e. those in groups 1 – 3, yield reasonably agreeing results, i.e. within ~5 % error bars. On the other hand, coupled FBE-CDE simulation with FREEBIE or CEDRES++ coupled to CRONOS revealed that numerical issues still exist in the coupling scheme. In particular, small changes in the inputs or numerical parameters cause significant differences in important results (the vertical displacement event growth rate, for example). Free-boundary equilibrium coupling to transport solvers The numerical issues in the current FBE-CDE coupling scheme initiated further optimizations; however, the results are not satisfactory yet. This algorithm is used for CRONOS, ITM (ETS) and METIS. METIS (Minute Embedded Tokamak Integrated Simulator) is an elaborated all-in-one tokamak simulator based on scaling laws and suitable simplifications. Its coupling to FREEBIE creates a unique tool for efficient tokamak simulation with a realistic (free-boundary) equilibrium. At the moment, the coupling is actively developed. First proof-of-principle simulations have been successfully carried out. ITM development An FBE workflow has been created and used for benchmarks of FREEBIE against CEDRES++ and CHEASE. FREEBIE has been incorporated into a recent ETS-C workflow, using the same interface as CEDRES++. A new project for a generic controller interface, ITMCONTROL, was started. Such a tool is necessary (not only) for FBE simulations. Based on structured input and Python expressions, synthetic diagnostics, actuators and arrays of MIMO PID controllers can be easily created. This projects is under an active development. Other activities A theory for a recent experimental observation of relativistic electrons (in MeV range) on the small stellarator WEGA was developed by V. Fuchs, J. Seidl and collaborators. In this theory, certain equilibrium parameters, such as the safety factor and the magnetic field, are required. The modelling has demonstrated—by employing a relativistic Fermi-Ulam map as well as direct integrals of the equation of motion—that MeV electrons can indeed be generated by stochastic interactions with the lower-hybrid wave if the phase of the electron-field interactions are random. Results have been accepted for publication to Physics of Plasmas [V. Fuchs et al., Relativistic Fermi-Ulam Map: Application to WEGA Stellarator Lower Hybrid Power Operation]. We also participated in the development of the equilibrium reconstruction code EFIT, particularly its MPI-based parallel version. (Equilibrium reconstruction is a differently posed free-boundary equilibrium problem.) A new version of EFIT has been released and applied to the COMPASS tokamak. Comparisons with the previous version are on-going. A paper [L.C. Appel et al., Equilibrium reconstructions on multiple tokamaks] has been submitted to Nuclear Fusion.
Související výsledky:
Urban J., Appel L.C., Artaud J., Faugeras B., Havlíček J., Komm M., Lupelli I., Peterka M.: Validation of equilibrium tools on the COMPASS tokamak. Engineering and Design. [October] (2015) 998-1001. [ Link ] [Symposium on Fusion Technology 2014(SOFT-28)/28./. San Sebastián, 29.09.2014-03.10.2014]
Fuchs V., Laqua H.P., Seidl J., Krlín L., Pánek R., Preinhaelter J., Urban J.: Relativistic Fermi-Ulam map: Application to WEGA stellarator lower hybrid power operation. Physics of Plasmas 21 [6] (2014) 061513-061513. [ Link ] [Twentieth Topical Conference on Radio Frequency Power in Plasmas. Sorrento, 25.06.2013-28.06.2013]
Urban J., Pipek J., Hron M., Janky F., Papřok R., Peterka M., Duarte A.S.: Integrated Data Acquisition, Storage, Retrieval and Processing Using the COMPASS DataBase (CDB). Fusion Engineering and Design 89 [5] (2014) 712-716. [ Link ] [Ninth IAEA TM on Control, Data Acquisition, and Remote Participation for Fusion Research. Hefei, 06.05.2013-10.05.2013]