Challenges to a foundational understanding of the plasma-material interface in plasma-burning nuclear fusion reactors
Although progress has been made in the last half-decade in establishing an understanding of plasma-material interactions (PMI), there remain critical knowledge gaps, particularly when it comes to predicting the behavior at the plasma-material interface under reactor-relevant fusion plasma conditions in a future plasma-burning neutron-dominated environment. The plasma-material interface is considered to be one of the key scientific gaps in the realization of nuclear fusion power. At this interface, high particle and heat flux from the fusion plasma can limit the material’s lifetime and reliability and therefore hinder operation of the fusion device. This region is critical to operation of a nuclear fusion reactor since material can be emitted both atomistically (e.g. through evaporation, sputtering, etc.) and/or macroscopically (i.e. during transients events, such as disruptions or edge localized modes). The environmental conditions at the plasma-material interface of a future nuclear fusion reactor interacting will be extreme. The incident plasma will carry heat fluxes of the order of 100’s of MWm-2 and particle fluxes that can average 1024 m-2s-1. The fusion reactor wall would need to operate at high temperatures near 800 C and the incident energy of particles will vary from a few eV ions to MeV neutrons. Another challenge is the management of damage over the course of time. Operating at reactor-relevant conditions means the wall material would need to perform over the course of not just seconds or minutes (i.e. as in most advanced fusion devices today and in the near-future), but from months to years. Therefore, the plasma-material interface would be a dynamic, evolving, reconstituted region of material that is constantly eroded and re-deposited a million times over, creating conditions that go well beyond our currently limited understanding of materials damage. This talk will focus on outlining both the challenges and promises of PMI research in nuclear fusion today and the prospects for possible solutions for future plasma-burning fusion reactors. The talk will in part summarize the recent DOE Fusion Energy Sciences Workshop on Plasma-Material Interactions and also highlight some of the recent work in Prof. Allain’s RSSEL group at UIUC.
Directed irradiation synthesis: manipulating matter in nanoscale self-organized systems
Deciphering self-organization mechanisms of nanostructures (e.g. nanodots, ripples) on compound semiconductors and silicon via low-energy ion-beam assisted plasma irradiation is critical to manipulate functionality in nanostructured systems. By operating at ultra-low energies near the damage threshold, irradiation-driven defect engineering can be optimized (e.g. 10-500 eV). Tunability of optical, electronic, magnetic and nuclear detection properties is realized by reaching metastable phases controlled by irradiation. This talk summarizes emerging research that exploits irradiation-driven materials modification with applications in: nanophotonics, nanoelectronics, biomaterials and nuclear detection. Furthermore advances of in-situ analysis conducted during modification to correlate tunable irradiation synthesis and device performance will be summarized.
Prof. Jean Paul Allain completed his Ph.D. degree from the Department of Nuclear, Plasma and Radiological Engineering at the University of Illinois, Urbana-Champaign. He received a M.S. degree in Nuclear Engineering from the same institution. Prof. Allain joined Argonne National Laboratory as a staff scientist in 2003 and joined the faculty in the School of Nuclear Engineering at Purdue University in Fall of 2007 with a courtesy appointment with the School of Materials Engineering. Prof. Allain joined the faculty at the University of Illinois at Urbana-Champaign in the Department of Nuclear, Plasma, and Radiological Engineering in Fall of 2013. He is an affiliate faculty with the Department of Bioengineering, the Micro and Nanotechnology Lab, and the Beckman Institute for Advanced Science and Technology. Prof. Allain is the author of over 180 peer-reviewed and proceedings papers in both experimental and computational modeling work in the area of plasma and ion-surface interactions. Prof. Allain’s research includes developing in-situ and in-operando surface structure and composition characterization of complex surfaces under low-energy irradiation designing function at the nanoscale and mesoscale. Prof. Allain has been recipient of numerous awards including the DOE Early Career 2010 Award, the Research Excellence Award in 2011 and the Fulbright Award in 2015.