Separatrix: Difference between revisions

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[[File:Geometry.png|400px|thumb|right|Sketch of tokamak geometry, including separatrix]]
A separatrix is a boundary between domains with distinct dynamical behaviour (phase curves) in a dynamical system.
A separatrix is a boundary between domains with distinct dynamical behaviour (phase curves) in a dynamical system.
<ref>[http://eom.springer.de/s/s084540.htm Separatrix (Encyclopaedia of Mathematics)]</ref>
<ref>[http://eom.springer.de/s/s084540.htm Separatrix (Encyclopaedia of Mathematics)]</ref>
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In the fusion context, the term refers to the trajectories of the magnetic field lines and is used to describe:
In the fusion context, the term refers to the trajectories of the magnetic field lines and is used to describe:
* In the case of a [[Divertor|divertor]] configuration in [[Tokamak|tokamaks]], or a similar situation in other devices: the boundary between closed and open field lines, separating the toroidally confined region from the region where field lines connect to material surfaces.
* In the case of a [[Divertor|divertor]] configuration in [[Tokamak|tokamaks]], or a similar situation in other devices: the boundary between closed and open field lines, separating the toroidally confined region from the region where field lines connect to material surfaces. In the case of a 'double null' configuration, two separatices can be distinguished: the main (primary) and secondary separatrix. Only the main separatrix truly separates the regions of closed and open field lines.  
* The boundary between the inside of a [[Magnetic island|magnetic island]] and the surrounding region.
* The boundary between the inside of a [[Magnetic island|magnetic island]] and the surrounding region.