UMD Plasma Seminar

Plasma Physics Seminar

Fall 2025 Schedule

September 3rd, Wed. 3:30PM ERF 1207, Large Conference Room	Open
September 10th, Wed. 3:30PM ERF 1207, Large Conference Room	Open
September 17th, Wed. 3:30PM ERF 1207, Large Conference Room	Open
September 24th, Wed. 3:30PM ERF 1207, Large Conference Room	Open
October 1st, Wed. 3:30PM ERF 1207, Large Conference Room	Open
October 8th, Wed. 3:30PM ERF 1207, Large Conference Room	Ida Ekmark, Chalmers University Optimization of runaway electron mitigation by massive material injection in ITER and SPARC During tokamak disruptions, strong electric fields can arise which are sufficient to cause electron runaway, whereby electrons are accelerated continuously. In future large-current tokamaks, such as ITER and SPARC, significant runaway electron generation is expected, due to the runaway generation being exponentially sensitive to the pre-disruption plasma current. Should the beam of runaway electrons come in contact with the tokamak wall, its energy can be almost instantly deposited deep into the wall. During disruptions, high heat loads can also arise from heat being transported into the wall when the magnetic surfaces are broken up during the thermal quench. Additionally, if the current decay is too fast or too slow, electromechanical forces caused by eddy or halo currents can cause forces and torques on the tokamak structure. While all of these unwanted aspects of a disruption can individually be addressed by massive material injection, they pose conflicting requirements on the injected material quantity and composition. In this talk, we investigate disruptions mitigated with combined deuterium and noble gas injection in ITER and SPARC. We use multi-objective Bayesian optimization of the densities of the injected material, taking into account limits on the maximum runaway current, the transported fraction of the heat loss, and the current quench time. Regions in the injected material density space corresponding to successful mitigation are found for both machines when optimizing pure deuterium plasma scenarios. When optimizing deuterium-tritium plasma scenarios, on the other hand, simultaneous mitigation of runaway current, transported heat loss and electromechanical forces appear more challenging for ITER than for SPARC.
October 15th, Wed. 3:30PM ERF 1207, Large Conference Room	Sophia Sanchez-Maes, University of Maryland 3D Particle-in-Cell Simulations of Reconnection-Driven Particle Acceleration and Their Implications for Sagittarius A Flares The brightest X-ray flares from Sagittarius A* (Sgr A) reveal extreme episodes of particle acceleration. Explaining observed spectra requires electrons accelerated to Lorentz factors in the range of hundreds of thousands to millions, which is beyond what traditional approaches have demonstrated in this context. Magnetic reconnection offers a compelling mechanism, capable of efficiently accelerating particles to high energies. However, two-dimensional (2D) particle-in-cell (PIC) simulations have intrinsic limitations: particle motion is confined within plasmoids, restricting energy gain. Acceleration in 2D reconnection typically saturates near the plasma magnetization limit, falling short of the energies required to explain the brightest X-ray flares. In contrast, 3D reconnection introduces additional degrees of freedom, allowing particles to escape plasmoids and enhancing acceleration efficiency. To connect reconnection physics with observed Sgr A flare spectra, we perform 3D PIC simulations spanning a range of magnetic guide field strengths (Bg/B0), and investigate the resulting particle acceleration and synchrotron spectra. We find that the guide field plays an important role: a strong guide field limits particle energies and softens the spectrum, while a weak or absent guide field in 3D produces overly hard power-law slopes. Intermediate guide field strengths yield particle distributions more consistent with those observed during X-ray flares from Sgr A. These initial results suggest that reconnection-mediated acceleration can plausibly power the IR and X-ray variability observed near the Galactic Center's supermassive black hole. The strength of the guide magnetic field may further regulate whether flare emission extends into the X-ray, consistent with the fact that all Sgr A X-ray flares have IR counterparts, but not all IR flares produce observed X-rays.
October 22nd, Wed. 3:30PM ERF 1207, Large Conference Room	Yi-Min Huang, Goddard Space Flight Center Magnetic Chaos, Reconnection, and Dissipation: A New Look at Coronal Heating The constant shuffling of coronal loop footpoints by photospheric convection entangles the Sun's magnetic field, leading to a complex topology. In Parker's influential coronal heating model, this entanglement produces a large number of small-scale magnetic reconnection events, or "nanoflares," which are thought to heat the corona to millions of degrees. This work uses Parker's model as a testbed to investigate whether chaotic magnetic fields-a generic feature of such 3D systems-naturally facilitate fast reconnection by exploiting the sensitivity of field line mapping to non-ideal effects. Furthermore, we present an extension of these simulations that incorporates two-fluid physics to explore if the overall energy dissipation is sensitive to the detailed microphysics of the reconnection process. Our results shed new light on the fundamental link between large-scale external forcing and small-scale energy release in the solar corona.
October 29th, Wed. 3:30PM ERF 1207, Large Conference Room	Will Fox, University of Maryland Magnetized high-energy-density plasmas and plans for the UMD High Energy Plasma Laboratory Laser heated plasmas are important for fusion, industry, and experiments on fundamental phenomena important in plasma astrophysics. I will present recent results on the generation and dynamics of magnetic fields in laser-plasmas plasmas. Magnetic fields are important for modifying the particle and heat transport in these plasmas, and for example mediate the generation of collisionless shocks. I will present results observing the self-generation of magnetic fields by the Biermann battery and Weibel instability processes, including the first tomographic 3-D reconstruction of magnetic fields in laser-solid interaction. Together these paint a picture that magnetic fields are ubiquitously self-generated in these plasmas and should be considered in transport modeling. Finally I will present plans for the UMD High Energy Plasma Laboratory, currently under construction, which will allow new experiments on all these phenomena. It will feature a frequency-doubled Nd:glass laser capable of delivering 35 J in 1.5 ns at 532 nm at a repetition rate of one shot per minute and with an arbitrary temporal waveform. It will cooperate with a new 100-TW Ti:Sapphire laser in the neighboring Laboratory for Intense Laser-Matter Interactions for combined short- and long-pulse experiments such as radiography. We describe the status of the facility, plans for the initial diagnostic suite, and scoping studies of the first experiments. The diagnostics will include proton and electron radiography for electromagnetic field measurements, optical probing of plasma density via interferometry and angular filter refractometry, and kinetic measurements via Thomson scattering. Initial experiments will study magnetic reconnection and particle acceleration, magnetic field generation by the Biermann battery and Weibel instabilities, and the Nernst effect and extended magnetohydrodynamics in laser-heated magnetized gas jets.
November 5th, Wed. 4:00PM ERF 1207, Large Conference Room	Artur Perevalov, University of Maryland Thermonuclear fusion in the Centrifugal Mirror Fusion Experiment (CMFX) The Centrifugal Mirror Fusion Experiment (CMFX) is an experimental machine located in IREAP. The project is led by UMBC in partnership with UMCP. The primary goal of the project is to explore whether the centrifugal magnetic mirror design is capable of achieving the confinement parameters that are relevant for reactor-level fusion. In this talk, I will explain the basics of centrifugal magnetic mirror confinement and show the experimental results of the machine operation. Included in the results are a series of experiments with deuterium that yielded measurable amounts of fusion neutrons. I will show the observed scaling of the fusion power as a function of control parameters.
November 12th, Wed. 3:30PM ERF 1207, Large Conference Room	Open
November 19th, Wed. 3:30PM ERF 1207, Large Conference Room	APS DPP meeting
November 26th, Wed. 3:30PM ERF 1207, Large Conference Room	Thanksgiving Recess
December 3rd, Wed. 3:30PM ERF 1207, Large Conference Room	Emily Lichko, Naval Research Laboratory
December 10th, Wed. 3:30PM ERF 1207, Large Conference Room	Open

Contact Information: Marc Swisdak or Ian Abel