Page History

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• Obtaining documentation
  • Automatically generated (type dd_doc command to see list of IDSes similar to this on picture above)
  • Accessed on following >>page<< of EUROfusion portal (more user-friendly GUI)
  • Most recent version of Data Dictionary can be found here: imas-3.24.0
  • It is also possible to view documentation directly from NX session using following command: firefox $IMAS_PREFIX/share/doc/imas/html_documentation.html 
• Description of IDS contains:
  • List of all IDSs. For each of them, a detailed documentation:
  • Full path name: name of all variables of the IDSs, with their path in the structure. Replace “/” by the structure operator in a programming language, e.g. “%” in Fortran, “.” in C++, Matlab, Java, Python
  • Description
  • Definition
  • Units in []
  • In {}, whether it is STATIC (constant over a range of pulses, e.g. machine configuration), CONSTANT (constant over the pulse or the simulation), or DYNAMIC (time-dependent within the pulse or the simulation)
  • Data_Type: indicates whether it is a string, an integer or a real, and its dimension (0D, 1D, 2D, …)
  • Coordinates: for each dimension, the full path name to the related coordinate. If the dimension simply refers to a quantity not present in the Data Model, it is indicated as “1…N”

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Time is of course a key physical quantity in the description  of a tokamak experiment. Present day integrated modelling codes all have their workflow based on time evolution. Time has however a hybrid status because of the large differences in time scales in the various physical processes. For instance, the plasma force balance equilibrium (which yields the surface magnetic topology) or Radio Frequency wave propagation are established on very fast ime scales with respect to other processes such as macroscopic cross-field transport. Therefore such physical problems are often considered as “static” by other parts of the workflow, which need to know only their steady-state solution. In fact such a configuration appears quite often in the physics workflows: a physical object that varies with time during an experiment (e.g., the plasma equilibrium) can also be considered as a collection of static time slices, and the other modules in the workflow will need only a single static time slice of it to solve their own physical problem at a given time. 

Each time slice is located at given index. When you are looking for a time slice, there are three possible ways of finding "correct" time slice.

• 1 : CLOSEST_SAMPLE
  the returned IDS is the stored IDS whose time is closest to the passed time;
• 2 : PREVIOUS_SAMPLE
  the IDS whose time is just before the passed time is returned.
• 3 : LINEAR INTERPOLATION
  the values of the time-dependent return IDS fields are computed according to a linear interpolation between the corresponding values of the IDSs just before and after the passed time;

05.1.2.5. Occurrences

There can be multiple instances, or “occurrences” of a given IDS in a database entry . These occurrences can correspond to different methods for computing the physical quantities of the IDS, or to different functionalities in a workflow (e.g. store initial values, prescribed values, values at next time step, …). For modelling tokamak experiments, multiple source terms are needed because many different heating/fuelling/current drive mechanisms are commonly used simultaneously. In present  day integrated modelling codes, this is usually done by pre-defining in the data structure slots for each of the expected heating methods. Moreover, the way to combine these source terms is also usually pre-defined, though present codes have some possibility to tune their workflows with a set of flags – still within a pre-defined list of possible options. In view of providing a maximum flexibility of the workflow (which can also be something completely different from the usual “transport” workflows), we have to abandon this strategy and go for multiple IDS occurrences. For each physical problem we have defined a IDS type that must be used to exchange information related to this problem. While the elementary IDS structure is designed for a single time slice, we have gathered all time slices referring to the same physical object in an array of IDS time slices. This array is the unit which is manipulated when editing workflows. We now introduce the possibility to have in a workflow multiple IDS occurrences, i.e. multiple occurrences of arrays of IDSs of the same type.

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