Integrated Tokamak Modelling Task Force Research Articles

Conceptual integrated approach for the magnet system of a tokamak reactor

In the framework of the reflexion about DEMO, a conceptual integrated approach for the magnet system of a tokamak reactor is presented. This objective is reached using analytical formulas which are presented in this paper, coupled to a Fortran code ESCORT (Electromagnetic Superconducting System for the Computation of Research Tokamaks), to be integrated into SYCOMORE, a code for reactor modelling presently in development at CEA/IRFM in Cadarache, using the tools of the EFDA Integrated Tokamak Modelling task force. The analytical formulas deal with all aspects of the magnet system, starting from the derivation of the TF system general geometry, from the plasma main characteristics. The design criteria for the cable current density and the structural design of the toroidal field and central solenoid systems are presented, enabling to deliver the radial thicknesses of the magnets and enabling also to estimate the plasma duration of the plateau. As a matter of fact, a pulsed version DEMO is presently actively considered in the European programmes. Considerations regarding the cryogenics and the protection are given, affecting the general design. An application of the conceptual approach is presented, allowing a comparison between ESCORT output data and actual ITER parameters and giving the main characteristics of a possible version for DEMO.

The European Integrated Tokamak Modelling (ITM) effort: achievements and first physics results

A selection of achievements and first physics results are presented of the European Integrated Tokamak Modelling Task Force (EFDA ITM-TF) simulation framework, which aims to provide a standardized platform and an integrated modelling suite of validated numerical codes for the simulation and prediction of a complete plasma discharge of an arbitrary tokamak. The framework developed by the ITM-TF, based on a generic data structure including both simulated and experimental data, allows for the development of sophisticated integrated simulations (workflows) for physics application. The equilibrium reconstruction and linear magnetohydrodynamic (MHD) stability simulation chain was applied, in particular, to the analysis of the edge MHD stability of ASDEX Upgrade type-I ELMy H-mode discharges and ITER hybrid scenario, demonstrating the stabilizing effect of an increased Shafranov shift on edge modes. Interpretive simulations of a JET hybrid discharge were performed with two electromagnetic turbulence codes within ITM infrastructure showing the signature of trapped-electron assisted ITG turbulence. A successful benchmark among five EC beam/ray-tracing codes was performed in the ITM framework for an ITER inductive scenario for different launching conditions from the equatorial and upper launcher, showing good agreement of the computed absorbed power and driven current. Selected achievements and scientific workflow applications targeting key modelling topics and physics problems are also presented, showing the current status of the ITM-TF modelling suite.

Synthetic Diagnostics in the European Union Integrated Tokamak Modelling Simulation Platform

The European Union Integrated Tokamak Modelling Task Force (ITM-TF) has developed a standardized platform and an integrated modeling suite of codes for the simulation and prediction of a complete plasma discharge in any tokamak. The framework developed by ITM-TF allows for the development of sophisticated integrated simulations (workflows) for physics application, e.g., free-boundary equilibrium with feedback control, magnetohydrodynamic stability analysis, core/edge plasma transport, and heating and current drive. A significant effort is also under way to integrate synthetic diagnostic modules in the ITM-TF environment, namely, focusing on three-dimensional reflectometry, motional Stark effect, and neutron and neutral particle analyzer diagnostics. This paper gives an overview of the conceptual design of ITM-TF and preliminary results of the aforementioned synthetic diagnostic modules.

A New Simulation Framework Based on the Kepler and Scicos Open-Source Software for the Design and Qualification of Tokamak Control Algorithms: First Test Case Results

Plasma control is recognized to be a crucial issue for the achievement of ITER objectives. One of the most challenging tasks for the preparation of the ITER operation will therefore be the design and qualification of a variety of control algorithms. This highlights the need for a simulation platform capable of supporting the design, integration and test of advanced control algorithms on complex physics models. With this aim, a generic multi-purpose “flight” simulator (GMFS) is being developed at IRFM (Institut de Recherche sur la Fusion par confinement Magnétique), CEA Cadarache, France.The GMFS is based on Kepler, a free interdisciplinary open-source Java software. Kepler will be used as a simulation platform to test and improve control algorithms before their actual use in the real control system. The physics and engineering codes complementary to the control algorithms will be supplied by the EFDA Integrated Tokamak Modelling Task Force (ITM-TF). The GMFS will be benchmarked, at the beginning, on the Tore Supra Tokamak.In this paper we will report on a test case suitable to demonstrate the feasibility of a part of GMFS, namely the development of workflows where to create and verify ITER plasma boundary feedback control algorithms. It consists of: a) derivation of a linear plasma response model; b) design of a control diagram under the ScicosLab/Scicos open-source software; c) porting of the diagram under Kepler; d) substitution of the Kepler controller with a controller generated by a special Scicos extension; e) substitution of the simplified static linear model with the free-boundary equilibrium code CEDRES++.The test case demonstrated the feasibility of employing Kepler, ScicosLab/Scicos and other expressly-made codes in view of the conception of valuable instruments for the active control of ITER and it can be considered as a first step in this direction.

Simulation of the neutral beam deposition within integrated tokamak modelling frameworks

The NEMO (NEutral beam MOdelling) code for simulating neutral beam ionization during neutral beam injection (NBI) in tokamak plasmas has been developed for implementation in integrated modelling frameworks and is presented. Integrated modelling of fusion plasmas is becoming increasingly important, both for preparation and analysis of experiments in large devices. Moreover, it should play a crucial role for the design of future fusion reactors. In a modern context, integrated modelling requires codes that are (i) flexible in terms of their interfaces, i.e. can be adapted for different simulation environments, (ii) machine independent; i.e. they should not contain hard coded information on a particular device to be simulated; (iii) optimized for speed of execution, (iv) verified and validated. The NEMO code has been specially designed to meet these requirements. The code is based on the physics concept outlined by Feng et al (1995 Comput. Phys. Commun. 88 161–72) and is a completely modular program: it works with any input NBI geometry and can be coupled to any external Fokker–Planck calculation for evaluating the distribution function of the injected species, i.e. it can provide source terms for both Monte Carlo codes and codes using finite difference/elements methods. The NEMO code has already been integrated with the CRONOS integrated modelling suite (Artaud et al 2010 Nucl. Fusion 50 043001) and the European Integrated Tokamak Modelling Task Force (ITM-TF)b https://www.efda-itm.eu/index.html. The basics of the code are described in this paper along with an illustration of its integration in the ITM-TF simulation platform. A crucial aspect is the verification of the code, the results of benchmarks carried out with other NBI codes for JET and ITER discharges are thereby presented.

Simulation and high performance computing—Building a predictive capability for fusion

The Integrated Tokamak Modelling Task Force (ITM-TF) is developing an infrastructure where the validation needs, as being formulated in terms of multi-device data access and detailed physics comparisons aiming for inclusion of synthetic diagnostics in the simulation chain, are key components. As the activity and the modelling tools are aimed for general use, although focused on ITER plasmas, a device independent approach to data transport and a standardized approach to data management (data structures, naming, and access) is being developed in order to allow cross-validation between different fusion devices using a single toolset. Extensive work has already gone into, and is continuing to go into, the development of standardized descriptions of the data (Consistent Physical Objects). The longer term aim is a complete simulation platform which is expected to last and be extended in different ways for the coming 30 years. The technical underpinning is therefore of vital importance. In particular the platform needs to be extensible and open-ended to be able to take full advantage of not only today's most advanced technologies but also be able to marshal future developments. As a full level comprehensive prediction of ITER physics rapidly becomes expensive in terms of computing resources, the simulation framework needs to be able to use both grid and HPC computing facilities. Hence data access and code coupling technologies are required to be available for a heterogeneous, possibly distributed, environment. The developments in this area are pursued in a separate project—EUFORIA (EU Fusion for ITER Applications) which is providing about 15 professional person year (ppy) per annum from 14 different institutes. The range and size of the activity is not only technically challenging but is providing some unique management challenges in that a large and geographically distributed team (a truly pan-European set of researchers) need to be coordinated on a fairly detailed project level. The 2009 Work programme of ITM-TF organizes 240 individuals from 24 different associations providing about 60 ppy in total. Remote participation and collaborative tools and facilities as the ENEA sponsored Gateway have proven indispensible to meet this challenge.The current status of ITM-TF and EUFORIA is presented and discussed.

Enabling remote access to projects in a large collaborative environment

In the context of the Integrated Tokamak Modelling Task Force, a large number of software projects are made available to the task force members, including developers and end-users. This has been achieved through a combination of tools and technologies. The front-end is represented by a Java based portal system exposing a PHP project management system, GForge. These two applications are linked by a single sign-on mechanism, Shibboleth [1], and through secure HTTP [2] request rewriting, where appropriate. Furthermore, the underlying storage facility is an OpenAFS [3] distributed file system and the user base comes from both a network information server and an LDAP [4] directory. Security mechanisms are those of a distributed system, with multiple access points and protocols used for reading and writing data. The present paper presents the challenges of integrating these different technologies and programming languages into a single, working, application presented to its users as a web portal. Chaining of the tools is explored through the user perspective, with an in-depth overview of the background transitions between the various systems involved with regard to security requirements for the front-end nodes and the policies as seen by the users.

A generic data structure for integrated modelling of tokamak physics and subsystems

The European Integrated Tokamak Modelling Task Force (ITM-TF) is developing a new type of fully modular and flexible integrated tokamak simulator, which will allow a large variety of simulation types. This ambitious goal requires new concepts of data structure and workflow organisation, which are described for the first time in this paper. The backbone of the system is a physics- and workflow-oriented data structure which allows for the deployment of a fully modular and flexible workflow organisation. The data structure is designed to be generic for any tokamak device and can be used to address physics simulation results, experimental data (including description of subsystem hardware) and engineering issues.

Integrated tokamak modelling: Infrastructure and Software Integration Project

The Infrastructure and Software Integration Project must provide the hardware and software environment for the European integrated tokamak modelling taskforce to build and simulate a comprehensive fusion device. Several frameworks have been evaluated in 2006 and this paper reports on the current status of the gateway, the data communication system, the Web portal and the various ITM applications. The first version will be delivered in 2007, prefiguring the next decades’ tools.