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 divertor to vary. This enables all the relevant dimensionless plasma parameters to be matched in a scaled experiment, while reducing the required heating power and target heat flux. This modification preserves the important ratio of neutral mean free path to divertor plasma width, but mismatches the less important ratio of neutral mean free path to divertor depth. In the second step, we consider the problem of approximate generalized similarity in existing tokamaks with constrained divertor depths. A least squares similarity fitting approach is described and applied for different transport assumptions. It shows that existing tokamaks can approximate the dimensionless parameters of the ITER divertor very closely