Design of the Fusion Ignition Research Experiment (FIRE) plasma facing components

A design study of a Fusion Ignition Research Experiment (FIRE) is underway to investigate and assess near term opportunities for advancing the scienti fic understanding of self-heated fusion plasmas. The emphasis for the FIRE program is on understanding the behavior of plasmas dominated by alpha heat ing (Q greater than or equal to 5). Study activities have focused on the te chnical evaluation of a compact, high field, highly shaped tokamak. One of the key issues for the design is to find suitable plasma facing components (PFCs). We have investigated a variety of plasma edge and divertor conditio ns ranging from reduced recycling high heat flux conditions (attached) to r educed heat flux detached operation. The inner divertor detaches easily whi le impurities must be added to the outer divertor to achieve detachment. Th e outer divertor and private space baffle will have to be actively cooled. The plasma-facing surface of the divertor is tungsten bonded to a CuCrZr he at sink. The remainder of the PFCs are beryllium coated copper attached to the vacuum vessel. Plasma current disruptions impose strong constraints on the design. Appreciable PFC surface melting and evaporation and onset of "p lasma shielding" are expected. The forces induced on the PFC due to disrupt ions determine the size of the attachment of the PFC to the vacuum vessel.