SMITER for IMAS

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Leon Kos¹, Gregor Simiˇc¹, Matic Brank¹, Dejan Penko¹, Richard A. Pitts², Simon D. Pinches², Wayne Arter³

1Faculty of Mechanical Engineering, University of Ljubljana Aˇskerˇceva 6, 1000 Ljubljana, Slovenia

2 ITER Organization, Route de Vinon-sur-Verdon - CS 90 046 - 13067 St Paul Lez Durance Cedex - France

3 Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, OX14 3DB, Oxfordshire, U.K.

ABSTRACT

The SMITER Graphical User Interface (GUI) is a simulation framework integrated into SALOME, an open-source platform allowing the combination of numerical solvers from different physical domains. The SMITER GUI provides a user-friendly interface to the SMITER (SMARDDA for ITER) suite which contains modules that allow import of CAD objects, meshing, python scripting, fast and accurate shadowing calculations, and prediction of the power deposition by the plasma on first wall and divertor plasma-facing components (PFCs), together with data analysis and visualization. The SMITER GUI has been further developed and extended with additional features and additions. One significant improvement is the integration of the ITER Integrated Modelling and Analysis Suite (IMAS) with SMITER. IMAS is a framework that is being actively developed and used by the ITER organization and EUROfusion community.

The main goal of the integration of IMAS with SMITER was to set the foundations for interoperability between SMITER and the IMAS databases or Interface Data Structures (IDSs) that provide a uniform means of data archival and retrieval within the IMAS framework. This allows SMITER to use the IMAS IDSs to store the meshed geometry needed as input by the SMITER GUI to run the case computations. Moreover, the mesh and output results can be saved directly to IDSs if needed. To provide these new capabilities additional interface SMITER GUI utilities have been developed which provide tools for data conversion and transformation between the IDSs and the mesh files.

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1 INTRODUCTION

SMITER [1] is a recently developed field line tracing environment with verified kernel and user-friendly framework for simulations of the power deposition mapping on plasma-facing components (PFCs) and verification of surface shape suitability of ITER tokamak first wall pan- els and divertor components. One of the SMITERs essential purposes is to determine possible solutions towards the critical and demanding issue of management and control of PFC heat fluxes in ITER as an actively cooled fusion device.

SMITER features a sophisticated Graphical User Interface (GUI) based on an open-source platform SALOME [2] that uses SMARDDA [3] kernel. Furthermore, it is composed of several independant and interoperable modules for pre- and post processing that are based on SALOME processing framework. Pre-processing modules provides the creation, import, visualization, modification of geometric CAD models and generation of meshes from the CAD models. Post- processing modules allow result analysis ParaView visualization module and data export to different file formats.

The GUI framework provides the user with features for SMITER field-line case simulation setup and computation such as:

• import and export of CAD models in many different formats including industry standard STEP and IGES, which are regularly used in all commercial CAD software,

• CAD model defeaturing, surface extraction, grouping and other CAD model modification features,

• triangular mesh generation with different algorithms and hypotheses with re-meshing at different densities,

• visualization in 3D with integrated ParaView visualization tool,

• data analysis with 2D and 3D predefined plots of case setup,

• Python scripting for additional user defined processing and geometry generation,

• batch processing within closely coupled compute cluster, remote job submission, or local workstation processing without GUI.

• Parallel MPI support for large and time demanding power calculations,

• saving study and results in form of hierarchical data files (HDF) for single file reuse.

Presently, the development of SMITER continues and the list of the available features is constantly being extended. One of the latest enhancements is the integration of Integrated Modelling & Analysis Suite (IMAS) within SMITER framework. This allows the user to use IMAS Python library in SMITER-GUIs Python scripting environment and to manage the IMAS databases and their contents. Moreover, a set of utilities written in Python programming lan- guage were developed and added to GUI that enable reading and writing of IMAS IDS databases and thus represent an advanced alternative to the traditional way of storing and importing data in a form of local data files. In this article, we present the main aspects of SMITER integration with IMAS that performs these functions.

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2 IMAS

The ITER Integrated Modelling & Analysis Suite (IMAS) [4,5] provides a framework for both the computation of various fusion codes describing plasma operations in ITER tokamak and research activities on the ITER tokamak experiment. The IMAS is based on an underlying Physics Data Model (PDM) that allows the coupling of codes via standardized database structures, named IDS (Interface Data Structures) [6–8]. The IDSs are a rich and complex standardized hierarchical transferable databases or data structures, consisting of tree-like data structure units that provide standardized data archival and retrieval together with straightforward data sharing and distribution. Each IDS is a segment of so-calledData Dictionary[9], an extensive database description or data container under which all IDSs are categorized as children, as seen in Fig. 1.

Figure 1: The presentation of Data Dictionary root with the IDSs currently supported by SMITER, namelywallandequilibrium, and appendededge profilesIDS as an addition to the

list of supported IDSs, together with the first and the last IDSs in the list of the IDSs, amns dataandwaves. The Data Dictionary consists of about 40 different IDSs that are

constantly being improved and updated.

The IDSs were developed with a purpose of creating a database that is capable to store a wide amount of physical quantities such as grid geometry description of tokamak and tokamak components, plasma equilibrium, heating and fuelling sources, a full description of the plasma state in a form of the electron temperature, ion temperature, electron density, ion density, etc., and system data relevant to tokamak fusion reactors including ITER. Those databases are set as tree-like structured entities with each structure being set to store specific data relevant to tokamak and fusion processes. Furthermore, the IDSs can be easily shared with other users working

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remotely on the same HPC cluster and are accessible with several programming languages (For- tran, C++, Java, Python, and Matlab). The IDSs are stored in the local database with the use of MDSplus [10], a set of software tools for data acquisition and storage and a methodology for management of complex scientific data.

To sum up, the IDSs provide a more advanced alternative to the traditional way of using local files on PC for data storage and it proves to be more efficient when dealing with a larger amount of files. Furthermore, the IDSs simplify the data tracing, conservation and allow straightforward data comparison and case repeatability. Moreover, the integration of IMAS within SMITER is further favoured due to the IMAS and its IDS database segments being presently progressively established as a standardized way of storing any ITER tokamak related data for all ITER parties, including the EUROfusion Consortium and its members. Presently, the IMAS is available only for users on ITER HPC and EUROfusion Gateway HPC, however, for local installations, the SMITER is setup and installed with its own IMAS build, meaning that IMAS is compiled from ITER GIT repository and included directly in SMITER.

3 DEVELOPED IMAS UTILITIES FOR SMITER

The newly developed set of standalone IMAS utilities for SMITER allow the users means by which they can archive and access a portion of data relevant to SMITER workflow to IDSs such as grid geometry - meshes and equilibrium magnetic data.

3.1 Grid geometry - meshes

The grid (or mesh) is an assemblage of multiple connected elements, provided through their geometry data, which as a whole represents a discrete approximation of geometry of a real- life physical object, required for solving physical or mathematical problems like fluid flow and heat transfer, producing virtual presentations of simulations intended for analysis of simulation results and other computing related work in connection with the real-life object.

Figure 2: The presentation of the General Grid Description (GGD) tree structure found in the Data

Dictionary and its IDSs. As the structure is very extensive only the first-level tree nodes are presented.

Full structure can be found in Data Dictionary description [6].

In SMITER, meshes are manda- tory for case description and can be either imported from mesh files such as VTK, STL, MED or gener- ated from the provided CAD models using SMESH module and its mesh generation utilities. IMAS integrated in SMITER enables to store these meshes to the IDS database underlying structure called Gener- alized Grid Description (GGD) [6–

8] that serve specifically for the storage of grid geometry relevant data in a structured and standardized way. The GGD (see Fig.2 structure is consistent and it is present in the IDSs that require storage of various multidimensional grid geometries.

There are now two standalone utilities available in SMITER that

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utilize IMAS databases for mesh storage and retrieval purposes. Previously, those tools were developed to a stage that enabled them to work only with the essential tokamak 3D wall grid geometry [8] and grid geometry of other components relevant to the tokamak wall. With further improvements, they were developed to a stage that they allow storage of grid geometry such as vacuum vessel and other structures to the IDS. These meshes can then be read and used in the same or another SMITER study.

The latest available SMITER tools included in the framework that translate meshes are:

• SMESH2IDS, a tool developed for storing the selected meshes directly to IDS. Single IDS can hold multiple meshes at once.

• IDS2SMESH, a tool developed for reading the grid geometry data out from the IDS and uses the same data to construct the mesh for SMITER SMESH module, as seen in Fig. 3.

Presently, those two utilities support meshes consisting of generally used 1D, 2D and 3D elements such as triangles, quadrilaterals, tetras and hexahedrons and wall and edge profiles IDSs. Few of beforehand prepared IDSs, containing the meshes, are available in SMITER sources for examples and tutorial purposes. The placement of the SMESH2IDS and IDS2SMESH in the SMITER workflow is presented in Fig. 4.

Figure 3: The SMITER Graphical User Interface displaying meshes obtained from the IDS using IDS2SMESH utility. Those meshes are case-ready for the SMITER limiter case.

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3.2 Magnetic equilibrium data

Magnetic equilibrium data represent the data relevant to the plasma equilibrium and all its quantities and attributes. The common method of storing such data is in a form of a G-EQDSK file format [11]. Moreover, the G-EQDSK file commonly contains the definition of the flux function, required by GEOQ code to produce NURBS-approximation of flux gradients, overlay flux function contours with silhouette wall (limiter) and last closed flux surface (LCFS).

Figure 4: SMITER data workflow with IMAS utilities. SMESH module computed meshes can be stored to IDS with SMESH2IDS utility while the IDS2SMESH is used to read the meshes out from the IDS into SMITER. Similarly, the G-EQDSK format files can be easily stored and

read to/from IDS with the EQDSK2IDS and IDS2EQDSK utility.

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Two new standalone tools that utilize IMAS databases for equilibrium magnetic data storage and retrieval purposes are now available in SMITER:

• EQDSK2IDS, a tool developed for reading the equilibrium data out from the local G- EQDSK format file and then storing the same data to the IDS.

• IDS2EQDSK, a tool developed for reading the equilibrium data out from the IDS and creating the G-EQDSK format file that can be used by SMITER for case preparation.

The main part of the equilibrium data found in the G-EQDSK file correspond to theequi- librium IDS as the purpose of this data tree structure is to store the description of tokamak equilibrium. The remaining, smaller part of the equilibrium data is relevant to the limiter and it correspond to thewallIDS which purpose is to store the description of the tokamak torus wall and other tokamak components and it contains an appropriate structure intended for the storage of the limiter relevant data. The placement of the EQDSK2IDS and IDS2EQDSK tools in the SMITER workflow is presented in Fig. 4.

4 CONCLUSION

The presented additions contribute to the overall usability and the compatibility of IMAS with SMITER and provide a convenient way of storing the tokamak fusion reactor related 3D grid geometries and equilibrium data to IDS. Furthermore, IMAS integrated in the SMITER framework allows us to run different codes in a coupled mode though IDS structures. The newly developed tools intended for mesh handling, represented in this paper, have the potential to be further improved to a support mesh storage in other corresponding IDS if required, as many of the IDSs contain the GGD structure. Furthermore, the SMITER usage of IMAS databases could be extended with additional tools if required for storage of any other fusion related data required by SMITER.

ACKNOWLEDGMENTS

This work was partially conducted under an ITER contract for the development of the SMITER field line tracing software environment (contract number: IO/16/CT/4300001401).

The views and opinions expressed herein do not necessarily reflect those of the ITER Organi- zation.

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