Diagnostics for FIRE: A status report

Abstract

The mission for the proposed fusion ignition research experiment (FIRE) device is to “attain, explore, understand and optimize fusion-dominated plasmas.” Operation at Q⩾5, for 20 s with a fusion power output of ∼150 MW is the major goal. Attaining this mission sets demands for plasma measurement which are at least as comprehensive as on present tokamaks, with the additional capabilities needed for control of the plasma and for understanding the effects of the alpha-particles. Because of the planned operation in advanced tokamak scenarios, with steep transport barriers, the diagnostic instrumentation must be able to provide fine spatial and temporal resolution. It must also be able to withstand the impact of the intense neutron and gamma irradiation. There are practical engineering issues of minimizing radiation streaming while providing essential diagnostic access to the plasma. Many components will operate close to the first wall, e.g., ceramics and mineral insulated cable for magnetic diagnostics and mirrors for optical diagnostics; these components must be selected and mounted so that they will operate and survive in fluxes which require special material selection. The measurement requirements have been assessed so that the diagnostics for the FIRE device can be defined. Clearly, a better set of diagnostics of alpha-particles than that available for TFTR is essential, since the alpha-particles provide the dominant sources of heating and of instability-drive in the plasma.