@article{article,
  author = {T. W. Morgan and M. Balden and J. G. A. Scholte and S. Roccella and J. H. You},
  title = {The influence of ELM-like loading on tungsten under slow transient conditions in Magnum-PSI},
  abstract = {ITER is anticipated to operate with occasional slow transients, resulting in an increase in expected heat loads to the divertor from 10 to 20 MW m-2 and thus in the surface temperature increasing to > 2000 degrees C. At the same time mitigated ELMs may be expected to strike the surface. To investigate the consequences of this, two sets of experiments were carried out in Magnum-PSI, representing the first experiments to explore this regime. In the first set, seven ITER-like tungsten monoblocks were exposed to either hydrogen plasma, or impurity-seeded hydrogen plasma at a surface temperature of 2050 degrees C. Simultaneously five of the seven monoblocks were exposed to 105 ELM-like pulses using a 1 ms duration laser at an energy density of 0.1 - 0.19 MJ m-2. Very strongly roughened and cracked laser exposed areas with localized melted regions were observed. These areas protruded several hundreds of micrometers above the original surface. In the second experiment, three tungsten plates, with either small, large or no castellations cut into the surface, were exposed to a hydrogen plasma at 2100 degrees C with a wider range of ELM-like pulse numbers (102 - 105) and energies (0.13 - 0.31 MJ m-2). The surface was found to evolve by roughening and pre-crack formation towards similar strongly protruding roughened structures as pulse number increased, while increasing the transient energy resulted in increasing the fraction of surface melting observed in the loaded region. Mass loss measurements of the plates indicated that erosion was significant, between 0.05-0.13 nm per pulse for the different plates. Extrapolating these results to ITER suggests that this mass loss rate would be relatively high and would constitute a significant tungsten source.},
  year = {2026},
  journal = {Nuclear Fusion},
  volume = {66},
  pages = {in press},
  doi = {10.1088/1741-4326/aeaefe},
  language = {eng},
}