The Material Plasma Exposure eXperiment (MPEX)

Note the different day of the week. The availability of future fusion devices such as a Fusion Nuclear Science Facility (FNSF) or DEMO greatly depends on long operating lifetimes of plasma facing components in their divertors. ORNL is designing the Material-Plasma Exposure eXperiment (MPEX), a superconducting magnet, steady state device to address the plasma material interactions of fusion reactors. MPEX will utilize a new high-intensity plasma source concept based on RF technology. This source concept will allow the experiment to cover the entire expected plasma conditions in the divertor of a future fusion reactor. It will be able to study erosion and re-deposition for relevant geometries with relevant electric and magnetic fields in-front of the target. The source system consists of a helicon antenna for high density plasma production. The electrons are heated by microwaves either with 28 GHz EBW, or 105 GHz with 2nd harmonic X-mode ECH. 105 GHz Upper Hybrid collisional damping is explored as well. Ions are heated in the 7-9 MHz ICRF range via a magnetic beach approach. The total heating power will be up to 800 kW. MPEX is being designed to allow for the exposure of a-priori neutron-irradiated samples. In this concept, targets will be irradiated in ORNL’s High Flux Isotope Reactor (HFIR) or possibly at the Spallation Neutron Source (SNS) and then subsequently (after a sufficiently long cool-down period) transferred to MPEX and exposed to fusion reactor relevant plasmas. The pre-design of MPEX will be presented. MPEX is being developed in a staged approach with successively increased capabilities. After the initial development step of the helicon source and ECH system the source concept is being tested in the Proto-MPEX device (100 kW helicon, 200 kW EBW, 30 kW ICRH). Results from the plasma source development on Proto-MPEX will be presented.