Conventional divertor technologies may be insufficient for a fusion reactor environment. The Super-X Divertor (SXD) is an advanced concept that employs extreme manipulation of the diverted magnetic field in an effort to moderate the plasma conditions at the target. The layout for the SXD incorporated into the proposed upgrade to MAST is presented, along with preliminary results from boundary plasma transport modelling with the SOLPS 2D fluid code. The fraction of exhausted power required to be radiated in reactor-scale devices will be significantly higher than in ITER (~70%) 1 , with DEMO design studies 2 indicating values of 90% or greater. It is unclear if impurity seeding of the plasma edge, in conjunction with a conventional divertor geometry, can achieve such high radiative fractions without significantly degrading core energy confinement 3 . When examining this problem in the context of divertor design, it is useful to review the operational requirements for high performance: heat flux and thermal cycling tolerance (to avoid melting, brittle fracture, or “blooming” in the case of carbon), erosion resistance (low plasma temperatures at the targets to minimise physical sputtering), particle control (impurity retention, pumping of hydrogen and helium), preservation of material properties (thermal conductivity and integrity), and mitigation of uncontrolled fuel retention (tritium trapping). Note that it is necessary to meet all of these objectives in a reactor-scale device, unlike in most present-day tokamaks – this is mentioned here explicitly because discussions have a tendency to focus on power handling alone. During the design process, there are several “actuators” or “control tools” available for manipulating the boundary plasma, in an effort to meet the above requirements: magnetic geometry, layout of structures, choice of plasma facing material, thermal engineering, particle injection (gas, small pellets, etc.), pumping, and to a lesser extent, electrical biasing of the targets. The Super-X Divertor (SXD) focuses primarily on optimising the first item in the list. The basic idea is reviewed in Section 2 and the MAST Upgrade specific implementation is discussed in Sections 3. Section 4 contains a few comments devoted to justifying the additional cost and effort associated with an SXD.