THE SIMPLE MAP FOR A SINGLE-NULL DIVERTOR TOKAMAK

We present the simple map for a single-null divertor tokamak. The simp le map is an area-preserving map based on the idea that magnetic held lines are a single-degree-of-freedom time-dependent Hamiltonian system , and that the basic features of such systems near the X-point are gen eric. We obtain the properties of this map and the resulting footprint s of field lines on the divertor plate. These include the width of the stochastic layer, the edge safety factor, the area of the footprint a nd the amount of magnetic flux diverted. We give the safety factor pro file, the average and median values of strike angles, lengths end the Liapunov exponents. We describe how the effects of magnetic perturbati ons can be included in the simple map. We show how the map can be appl ied to the problem of the determination of heat flux on the divertor p late in tokamaks.