Plasmaphysik Seminar

# Initial Operation of the Wendelstein W7-X Stellarator

## by Glen Anthony Wurden (Los Alamos National Labs(LANL-PP))

Tuesday, May 23, 2017 from to (Europe/Berlin)
at GSI Darmstadt ( KBW 2.28 )
 Description Wendelstein 7-X , a new superconducting (NbTi) stellarator at the Max Planck Institute for Plasma Physics in Greifswald, has recently completed (Dec. 2015 to March 2016) its first operating period (OP1.1), after 19 years of design and construction. It is designed to test a quasi-isodynamic magnetic confinement geometry of the Helias (helical advanced stellarator) type, eventually with steady-state (pulses up to 30 minutes) deuterium plasmas. Scientists and engineers from more than 20 institutions around the world collaborate at the facility. First plasma, in helium, was achieved on Dec. 10, 2015, while the first hydrogen plasma occurred on Feb. 3, 2016, attended by numerous notables from the political and scientific communities. Plasma performance increased steadily with the application of various wall conditioning techniques, culminating in hydrogen plasmas of up to 6 seconds in duration with 4 MJ of input energy, up to 4 MW of heating power (ECRH), plasma densities in the range of 1-4 x 1019 m-3, central electron temperatures of 7-12 keV, ion temperatures of 1-2 keV, all while using graphite limiters at the plasma boundary. During the first part of 2017, graphite wall armor was added in the vessel, along with inertially cooled graphite divertors, replacing the initial (simple) limiters at the plasma boundary. The next 6 month operating phase (OP1.2a) will begin in August 2017, and will test the magnetic island divertor concept, with input energies of up to 80 MJ, heating powers of 8-10 MW, and pulse lengths of 10 seconds at full power, or 80 seconds at reduced power. An extensive set of diagnostics was available, even during the first operation, and results have now been presented in a variety of forums. This talk will highlight initial physics results and future plans.