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TJ-II:Magnetic coordinates: Difference between revisions
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First, vacuum equilibrium calculations from VMEC. These are then used to obtain magnetic flux co-ordinates ''(ψ, θ, φ)''. A set of routines is available to perform the corresponding co-ordinate transforms.<ref>[[File:TJ2 Library V2.pdf| TJ-II Library Manual, Informe Técnico del CIEMAT Nº 963]]</ref> The drawback of the VMEC calculations is (a) that magnetic islands are ignored, and (b) that only a limited number of configurations is available. | First, vacuum equilibrium calculations from VMEC. These are then used to obtain magnetic flux co-ordinates ''(ψ, θ, φ)''. A set of routines is available to perform the corresponding co-ordinate transforms.<ref>[[File:TJ2 Library V2.pdf| TJ-II Library Manual, Informe Técnico del CIEMAT Nº 963]]</ref> The drawback of the VMEC calculations is (a) that magnetic islands are ignored, and (b) that only a limited number of configurations is available. | ||
Second, magnetic field line calculations using the Biot-Savart Law. The approximate magnetic flux is recovered from an interpolation procedure. A set of routines is available to perform the corresponding co-ordinate transforms. More information can be found in [ | Second, magnetic field line calculations using the Biot-Savart Law. The approximate magnetic flux is recovered from an interpolation procedure. A set of routines is available to perform the corresponding co-ordinate transforms. More information can be found in files [http://www-fusion.ciemat.es/cgi-bin/dir/dirnew.cgi?manuals/geometry_TJII/ g3d_readme.doc and g3d_gridfile.doc]. Since the latter procedure is more flexible and generally applicable than the VMEC-based calculations, the latter is preferred. | ||
It should be noted that these co-ordinate transforms are approximate and not error-free. The errors in the vacuum field calculation are due to three sources: | It should be noted that these co-ordinate transforms are approximate and not error-free. The errors in the vacuum field calculation are due to three sources: | ||