Solid tungsten Divertor-III for ASDEX Upgrade and contributions to ITER

ASDEX Upgrade became a full tungsten experiment in 2007 by coating its graphite plasma facing components with tungsten. In 2013 a redesigned solid tungsten divertor, Div-III, was installed and came into operation in 2014. The redesign of the outer divertor geometry provided the opportunity to increase the pumping efficiency in the lower divertor by increasing the gap between divertor and vessel. In parallel, a by-pass was installed into the cryo-pump in the divertor region allowing adapting of the pumping speed to the required edge density.Safe divertor operation and heat removal becomes more and more significant for future fusion devices. This requires developing 'tools' for divertor heat load control and to optimize the divertor design. The new divertor manipulator, DIM-II, allows retracting a relevant part of the outer divertor into a target exchange box without venting ASDEX Upgrade. Different front-ends can be installed and exposed to the plasma. At present, front-ends for probe exposition, gas puffing, electrical probes and actively cooled prototype targets are under construction.The installation of solid tungsten, the control of the pumping speed and the flexibility for testing divertor modifications on a weekly base is a unique feature of ASDEX Upgrade and offers together with the extended set of diagnostics the possibility to investigate dedicated questions for a future divertor design.

[1]  Y. R. Martin,et al.  Plasma wall interaction and its implication in an all tungsten divertor tokamak , 2007 .

[2]  J. Contributors,et al.  ELM-induced transient tungsten melting in the JET divertor , 2015 .

[3]  H. Greuner,et al.  High heat flux facility GLADIS:: Operational characteristics and results of W7-X pre-series target tests , 2007 .

[4]  K. Lüddecke,et al.  The ASDEX upgrade digital video processing system for real-time machine protection , 2013 .

[5]  A. Loarte,et al.  Experimental study of divertor plasma-facing components damage under a combination of pulsed and quasi-stationary heat loads relevant to expected transient events at ITER , 2011 .

[6]  J. Linke,et al.  Performance of different tungsten grades under transient thermal loads , 2011 .

[7]  R. H. Bulmer,et al.  Sustained Spheromak Physics Experiment (SSPX): design and physics results , 2012 .

[8]  L. Giannone,et al.  Partial detachment of high power discharges in ASDEX Upgrade , 2015 .

[9]  R. Neu,et al.  A solid tungsten divertor for ASDEX Upgrade , 2011 .

[11]  J. Linke,et al.  Investigation of the impact of transient heat loads applied by laser irradiation on ITER-grade tungsten , 2014 .

[12]  J. Contributors,et al.  Bulk tungsten in the JET divertor: Potential influence of the exhaustion of ductility and grain growth on the lifetime , 2013 .

[13]  Gerald Pintsuk,et al.  Clamping of solid tungsten components for the bulk W divertor row in JET—precautionary design for a brittle material , 2009 .

[14]  H. Greuner,et al.  FEM investigation and thermo-mechanic tests of the new solid tungsten divertor tile for ASDEX Upgrade , 2013 .

[15]  H. Greuner,et al.  Experiences with tungsten coatings in high heat flux tests and under plasma load in ASDEX Upgrade , 2009 .

[16]  R. Dux,et al.  Controlled tungsten melting and droplet ejection studies in ASDEX Upgrade , 2011 .