8 Feb 99 Quasi-symmetry - Boyd Blac kwell 1 Quasi Symmetric Stellarators Boyd Blackwell, ANU • History of Stellarator Optimisation – sigma optimisation, j || minimisation • Quasi-Symmetry – QHS, QAS, QOS, QBS • The (US)NCSX, a QAS machine • Flexibility – in transform and spectrum • Real Time Surface Calculations • QAS Design studies
Quasi Symmetric Stellarators Boyd Blackwell, ANU. History of Stellarator Optimisation sigma optimisation, j || minimisation Quasi-Symmetry QHS, QAS, QOS, QBS The (US)NCSX, a QAS machine Flexibility in transform and spectrum Real Time Surface Calculations QAS Design studies. Introduction. - PowerPoint PPT Presentation
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8 Feb 99 Quasi-symmetry - Boyd Blackwell 1
Quasi Symmetric StellaratorsBoyd Blackwell, ANU
• History of Stellarator Optimisation– sigma optimisation, j|| minimisation
• Quasi-Symmetry– QHS, QAS, QOS, QBS
• The (US)NCSX, a QAS machine
• Flexibility– in transform and spectrum
• Real Time Surface Calculations
• QAS Design studies
8 Feb 99 Quasi-symmetry - Boyd Blackwell 2
Introduction• Stellarator: magnetic surfaces generated entirely by
currents external to plasma
• Nested magnetic surfaces– magnetic field cover nested surfaces before closing on
themselves
• Rotational transform: twist per turn (=1/q), generated by:
• Application: heliac configuration studies and QAS flexibility winding studies
• 3D spline calculation of B from large arrays (~100MB)
• linear combination of arrays for TFC, Ring provide instant adjustment of current ratios and configurations
• variable geometry conductors not allowed, but simplified model can be evaluated on top of accurate model of the rest of the geometry.
• Traces at ~20K steps/second surfaces in secs.
– BLINE code by Antony Searle
• Demonstration at Remote Data Access Poster
Real Time 3D B Field and Surface Calculations
8 Feb 99 Quasi-symmetry - Boyd Blackwell 11
Conclusions
• Quasi helical symmetry consistent with high transform and good orbits.
• Quasi axi-symmetry consistent with low aspect ratio, but requires internal currents to generate enough transform - at high pressure, these currents are approximated by the bootstrap current
• QO is a weaker condition than QA, QH– QO optimization of QAS? Best of both?
• Flexibility is possible with Qsym, but often other parameters degrade (esp. symmetry)
• H-1NF has comparable helical and toroidal components (mixed helicity), but is optimised for flexibility.