Geometry of drift surfaces near the magnetic separatix in a tokamak with poloidal divertor

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Abstract
High-energy particle drift orbits near the magnetic separatix have been studied in order to analyse the divertor target plate heat load by the superthermal ions. It was found that the particle flux profile usually has three maxima at the toroidal drift facing divertor plate and two at the opposite one. It is shown that toroidal field ripple due to discreteness of the toroidal coils produces a ripple well region near the divertor X-point and as a consequence can change the distribution of the escaping particles over the target plates. The convective flux of the ripple-trapped particles provides noticeable toroidal asymmetry of the particle flux profile, even at a very small ripple value of -3. JET parameters have been considered as an example, but the results obtained are also applicable to a tokamak reactor.