Speaker
Description
Controlling the Plasma-Material Interactions (PMI) is one of the key issues to be resolved for the success of machines like ITER and SPARC and the following generation of the magnetic fusion devices. The Divertor Material Evaluation System (DiMES) was a workhorse of PMI research at the DIII-D tokamak for about three decades and still remains one of the leading material testing facilities in the world with exceptional diagnostic coverage.
The DiMES program was started in 1992 as a collaborative project between General Atomics, Sandia National Laboratories and Argonne National Laboratory [1]. The DiMES manipulator was fabricated and installed on DIII-D in 1995 [2]. Since then DiMES contributed to over 100 publications in scientific journals and numerous presentations at US and international conferences. DiMES allows inserting material samples up to ~5 cm in diameter in the lower outer divertor of DIII-D, typically flush with the divertor tile surface. Samples elevated about the surface and angled towards the incident plasma fluxes are used to achieve reactor-relevant heat fluxes of over 10 MW/m2. Since DIII-D has all-C (graphite) plasma facing components (PFCs), the initial DiMES studies concentrated on studies of C erosion/deposition [3]. Alternative PFC options were also investigated, e.g. experiments with Li were conducted in 2003. A sample heating capability was added in 2004, allowing studies of the temperature effects on C erosion/deposition and diagnostic mirror coating with C [4]. As the magnetic fusion community moved away from C PFCs and C was excluded from the ITER design, DiMES was used to test high-Z PFC materials including W, V, Mo, Ta and Zr, first in thin coatings [5], then in bulk, including the leading edge effects.
One of the main strengths of the DiMES program lies in a worldwide network of collaborating institutions. In recent years, DiMES has become the primary point for the industry engagement at DIII-D, fueled by a rapid growth in the fusion private industry community. Details of the industry collaborations will be covered in a companion presentation by F. Effenberg et al.
[1] C.P.C. Wong et al, J. Nucl. Mater. 196-198 (1992) 871
[2] C.P.C. Wong et al, J. Nucl. Mater. 258-263 (1998) 433
[3] D.G. Whyte et al., Nucl. Fusion, 41 (2001), 1243
[4] D.L. Rudakov et al., Phys. Scr. T128 (2007) 29
[5] D.L. Rudakov et al., Fusion Eng. Des. 124 (2017) 196
Work supported by the US DOE under DE-FC02-04ER54698