SIMILARITY IN DIVERTOR STUDIES

The similarity of divertor tokamaks is studied in two steps. First, in the context of a toroidal divertor simulator, we modify the 'isolated divertor' approach of Lackner to allow the field line angle in the di vertor to vary. This enables all the relevant dimensionless plasma par ameters to be matched in a scaled experiment, while reducing the requi red heating power and target heat flux. This modification preserves th e important ratio of neutral mean free path to divertor plasma width, but mismatches the less important ratio of neutral mean free path to d ivertor depth. In the second step, we consider the problem of approxim ate generalized similarity in existing tokamaks with constrained diver tor depths. A least squares similarity fitting approach is described a nd applied for different transport assumptions. It shows that existing tokamaks can approximate the dimensionless parameters of the ITER div ertor very closely.