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Nuclear Component Testing (NCT) FNT-5 Plasma facing surface performance C. H. Skinner, PPPL

Nuclear Component Testing (NCT) FNT-5 Plasma facing surface performance C. H. Skinner, PPPL. Tungsten is the only solid material that is expected to have an adequate erosion lifetime for DEMO.

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Nuclear Component Testing (NCT) FNT-5 Plasma facing surface performance C. H. Skinner, PPPL

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  1. Nuclear Component Testing (NCT) FNT-5Plasma facing surface performanceC. H. Skinner, PPPL • Tungsten is the only solid material that is expected to have an adequate erosion lifetime for DEMO. • The present performance base on which hopes for practical fusion power are founded is based on carbon machines. • Tungsten has known problems with impurity influx that could impact fusion performance. • Goal: Reliable plasma facing components (PFCs) to enable continuous Q ~ 20 operation in Demo. Comparison of measured values for the sputtering yield at normalized incidence for Be (closed squares), C (open squares), and W (closed triangles) by deuterium ions with results from analytic modelling of physical sputtering [Eckstein, W., et al., Sputtering Data, Rep. IPP 9/82, Max- Planck-Institut fuer Plasmaphysik (1993).] (dotted lines). The experimental data were obtained from the weight loss of polished samples after ion bombardment. The divergence between experimental points and modelling for carbon at low energies is due to chemical effects not included in the model. From Federici et al., Nucl. Fus. 41 (2001) 1967.

  2. R&D Gaps (NCT-FNT-5 ) • Successful operation with tungsten PFCs requires control of impurity influx and core tungsten concen-trations should be less than ~1e-5 • Positive results so far from ASDEX-U with 100% W PFCs. Tungsten is planned for JET ITER-like wall project. • Testing in a long-pulse, high heat flux tokamak, is a required intermediate step to qualify the durability and tritium retention properties of W for NCT. • A NCT facility using W PFCs would provide an integrated opportunity to test, research, and develop the knowledge base needed to enable Demo design using W PFCs. Operational regime of a fusion plasma for different impurity concentrations. The p=5 contour includes the effect of helium ash with a helium confinement time of 5x the energy confinement time. The inner countours indicate the burn region for the stated carbon and tungsten impurity concentrations. [From T Putterich Ph.D. Thesis IPP 10/29 April 2006 “Investigations of Spectroscopic Diagnostic of High-Z Elements in Fusion Plasmas’]

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