Woodruff School of Mechanical Engineering
NRE 8011/8012 and MP 6011/6012 Seminar
Nuclear & Radiological Engineering and Medical Physics Programs
Materials Challenges for Fusion
Mr. Juergen Rapp
Oak Ridge National Laboratory
Thursday, February 4, 2016 at 11:00:00 AM
Boggs Building, Room 3-47
Dr Miniami Yoda
The availability of future fusion devices such as FNSF and DEMO greatly depends on long lifetimes of plasma facing components in their divertors. The development of those plasma facing components and materials requires facilities able to test them under reactor relevant conditions. This includes relevant divertor plasma parameters (ne~1021m-3, Te=1-15eV) plasma fluxes of 1024 m-2s-1, lifetime relevant fluence of ~1030-1031 ions/m2, high PFC ambient temperature and relevant displacement damages as a result of neutron irradiation. Unfortunately, no existing facility, whether toroidal or linear plasma device, is able to conduct the testing under those conditions. Hence the development of plasma-material interaction science and the technology of plasma facing material components will require new facilities. Since next-stage development of plasma facing materials, underpinned by a fundamental understanding of how prototypical plasmas interact with surfaces, are critical to future fusion systems, new experimental facilities capable of carrying out this research are required. This paper presents the design, early development and testing of a facility addressing this need. The Material-Plasma Exposure experiment (MPEX), a superconducting magnet, steady state device is proposed to address the above mentioned conditions. This facility as designed will have the unique feature of being able to conduct accelerated lifetime tests of tungsten plasma facing components, where the net erosion yield for divertor plasmas with Te=10-15 eV has to be reduced to 10-6 by effective re-deposition processes to achieve the required lifetime. MPEX will utilize a new high-intensity plasma source concept based on RF technology. 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). Proto-MPEX has achieved electron densities of more than 4x1019m-3 with a large diameter (13cm) helicon antenna at 100 kW power. First heating with microwaves resulted in a higher ionization represented by higher electron densities on axis, when compared to the helicon plasma only without microwave heating.
Juergen Rapp is a Senior R&D Staff member at the Oak Ridge National Laboratory in the Fusion and Materials for Nuclear Systems Division since 2011 leading the program for the advanced plasma generator MPEX. He received his MS and PhD in Electrical Engineering from the University of Wuppertal, Germany in 1991 and 1995 respectively. He started his early career on the TEXTOR tokamak at the Research Center in Juelich, Germany (1995 to 1999). From 1999 to 2007 he worked mainly at the Joint European Torus (JET) at Culham, U.K. in various activities: Scientific Coordinator, Session Leader, Physics Officer and as Head of Operations in the European Fusion Development Agreement (EFDA)-JET Close Support Unit. From 2007 to 2011 he was Program Leader and Head of the Plasma Surface Interactions Division in the FOM Institute for Plasma Physics in Nieuwegein, The Netherlands. In 2011 he was appointed as Part-time Professor at the Technical University of Eindhoven, The Netherlands. Presently he serves on FESAC, the ITER STAC, the DIII-D PAC, the US BPO council and the IEA Executive Committee for the IA on development and research on plasma-wall interaction facilities for fusion reactors. Dr. Rapp authored and co-authored more than 350 publications, of which more than 130 in peer-reviewed journals, cited more than 3000 times.