JPP is holding weekly meetings in the Frontiers of Plasma Physics Colloquium series
Organisers: Cary Forest and Alex Schekochihin
For information on how to join the Colloquium please sign up here.
Upcoming speakers are listed below.
Past talks are listed here.
Speaker: Young Dae Yoon, Asia Pacific Center for Theoretical Physics - Chaired by: Nuno Loureiro, Editor, JPP
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Date/Time: Thursday 7th August 2025, 4PM BST/11AM EDT
Title: Interaction between coherent whistler waves and energetic particles in the magnetosphere and its exploitation for runaway electron suppression in tokamaks
Abstract: Recent spacecraft observations indicate that whistler mode chorus subelements are extremely coherent, i.e., are monochromatic and phase-aligned. In such cases, popular diffusion mechanisms such as the quasi-linear mechanism that requires a broadband wave spectrum are invalid, and coherent wave-particle interactions must be examined. It is shown that the vector relativistic equation of motion of a particle under a circularly polarized electromagnetic wave can be reduced to a scalar conservative equation of motion of a resonance mismatch parameter. This equation of motion involves a conserved pseudo-energy in a pseudo-potential, whose shape if double-welled can lead to a rapid, extreme scattering, which is often observed in the magnetosphere. This mechanism can then be leveraged to construct a "momentum firewall" for hazardous runaway electrons in tokamaks, wherein the accelerating electrons are prevented from gaining parallel momentum upon hitting the firewall and are instantaneously scattered in momentum space. This method is further verified by self-consistent particle-in-cell simulations.
Speaker: Rebecca Masline, Massachusetts Institute of Technology, USA - Chaired by: Paolo Ricci , Associate Editor, JPP
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Date/Time: ;Thursday 21st August 2025, 4PM BST/11AM EDT
Title: Helium enrichment and tritium burn efficiency in simulations of divertor plasmas
Abstract: Efficient removal of helium ash is a critical requirement for the operation of fusion power plants, as its accumulation can dilute the core fuel and degrade plasma performance. While past studies suggested that helium exhaust in devices like ITER could be managed effectively through divertor optimization and conventional cryopumping, a detailed understanding of helium behavior in the edge and divertor plasma remains limited, as helium transport through the edge plasma is complex and fundamentally different from other impurity species. With the emergence of more sophisticated numerical modeling tools and renewed focus on D-T burning plasmas, revisiting helium transport in current magnetic confinement devices is necessary for planning and designing fusion pilot plants. This study uses SOLPS-ITER to model a helium-seeded discharge from the DIII-D tokamak, analyzing the transport, recycling, and enrichment of helium in the divertor. In addition to characterizing helium dynamics, the results are interpreted in terms of the Tritium Burn Efficiency (TBE), a recently proposed metric linking helium exhaust fraction to tritium fuel utilization in steady-state burning plasmas. By assessing the compatibility of TBE assumptions with detailed edge plasma simulations, this work provides insight into the practical viability of TBE as a reactor design and performance metric.
Speaker: Christopher Ridgers, University of York, UK - Chaired by: Louise Willingale, Associate Editor, JPP
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Date/Time: Thursday 28th Aug 2025, 4PM BST/11AM EDT
Title: TBC
Abstract: TBC.
Speaker: Daniel Verscharen, MSSL, University College London, UK - Chaired by: Thierry Passot, Associate Editor, JPP
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Date/Time: Thursday 11th September 2025, 4PM BST/11AM EDT
Title: Multi-scale kinetic physics of the electrons in the heliosphere
Abstract: Electrons are a subsonic plasma species in the solar wind. Their kinetic behaviour is - to a much greater extent than the proton behaviour - the result of an interplay between global properties of the heliosphere and local plasma processes. The global properties of the heliosphere include the interplanetary electrostatic potential, the large-scale interplanetary magnetic field, and the density profile of the plasma. The local plasma processes include collisions, wave-particle interactions, and turbulence. Through this interplay, the electron distribution function develops interesting kinetic features that are observable in situ. In addition to a quasi-Maxwellian core, the distribution exhibits suprathermal populations in the form of the strahl and halo components as well as cut-offs due to loss effects in the interplanetary potential. I will discuss the multi-scale processes that shape the electron distribution in the solar wind, the interaction of electrons with local structures such as compressive waves and magnetic holes, and the impacts of these structures on the global electron transport in the heliosphere. The regulation of the electron heat flux is of particular interest in this context. I will support these results with observations from Solar Orbiter and Parker Solar Probe.