A new era of fusion research has started with ITER being constructed and DEMO for power demonstration on the horizon. However, the fusion nuclear science needs to be developed before DEMO can be designed. One of the most crucial and most complex outstanding science issues to be solved is the plasma surface interaction (PSI) in the hostile environment of a nuclear fusion reactor. Not only are materials exposed to unprecedented steady-state and transient power fluxes, but they are also exposed to unprecedented neutron fluxes. Both the ion fluxes and the neutron fluxes will change the micro-structure of the plasma facing materials significantly even to the extent that their structural integrity is compromised. New devices have to be developed to address the challenges ahead. Linear plasma-material interaction facilities can play a crucial role in advancing the plasma-material interaction science and the development of plasma facing components for future fusion reactors.