Resources for... William & Mary
William & Mary W&M menu close William & Mary

Fall 2022


September 9, 2022 (Friday) 4:00-5:00p.m. 
Speaker: Greg Smith, Jefferson Lab
Host: D. Armstrong
Title:   The proton's weak charge and the neutron skin of aluminum: Results & Perspectives
Abstract: The Jefferson Lab Qweak experiment provided the first measure of the proton’s weak charge to test for physics beyond the standard model at the TeV scale. I will briefly review the experiment and summarize the final results for the weak charge Qw(p), the weak mixing angle sin2θw, and the mass reach 𝜆 for new physics of coupling strength g. By including results from atomic parity-violation in Cesium, the e-q couplings for the u and d quarks were also obtained. Some aspects of the liquid hydrogen target, the highest power ever used in a scattering experiment, will be discussed including its exceptionally small boiling response to the 2.2 kW of beam heating used in the experiment. Frank insights into some of the target’s design decisions will be given, including performance/safety tradeoffs. Finally, as a consequence of one of those tradeoffs, newly published results for the 27Al neutron skin thickness ∆Rn-p are presented. These provide a baseline for the use of the electroweak method in recent measurements of ∆Rn-p in 208Pb, which constrain the nuclear symmetry energy in models of neutron stars but are in some tension with non-electroweak determinations.

September 16, 2022 (Friday) 4:00-5:00p.m. 
Speaker: Edward Thomas Jr., Auburn University Alabama
Host: Mordijck and Sher
Title: Using magnetic fields and microgravity to explore the physics of dusty plasmas 
Abstract: Over the last three decades, plasma scientists have learned how to control a new type of plasma system known as a “complex” or “dusty” plasma.  These are four-component plasma systems that consist of electrons, ions, neutral atoms, and charged, solid, nanometer- to micrometer-sized particles.  The presence of these microparticles allow us to “tune” the plasma to have solid-like, fluid-like, or gas-like properties.  This means that dusty plasmas are not just a fourth state of matter – they can take on the properties of all four states of matter. 
From star-forming regions to planetary rings to fusion experiments, charged microparticles can be found in many naturally occurring and man-made plasma systems.  Therefore, understanding the physics of dusty plasmas can provide new insights into a broad range of astrophysical and technological problems.  This presentation introduces the physical properties of dusty plasmas – focusing on how the small charge-to-mass ratio of the charged microparticles gives rise to many of the characteristics of the system.  In particular, dusty plasmas can be used to study a variety of processes in non-equilibrium or dissipative systems such as self-organization and energy cascade as well as a variety of transport and instability mechanisms.  This presentation will discuss results from our studies of dusty plasmas in high (B ≥ 1 T) magnetic fields using the Magnetized Dusty Plasma Experiment (MDPX) device at Auburn University and in microgravity experiments using the Plasmakristall-4 (PK-4) laboratory on the International Space Station.

September 23, 2022 (Friday) 4:00-5:00p.m. 
Speaker: Hyun-Tak Kim, Elect. & Telecom. Inst. South Korea
Host: M. Qazilbash
Title: Mechanism and applications of the Mott transition in vanadium dioxide (VO2)
Abstract: Revealing the mechanism of the metal-insulator transition (MIT) induced by a change of on-site electron-electron interaction (Mott transition), is one of the important contemporary issues in condensed matter physics. Applications of the Mott transition span cutting-edge technologies such as neuromorphic devices, high-sensitivity photon detection, and MIT quantum bits (qubits). We have long studied the mechanism of the Mott transition in a representative material vanadium dioxide (VO2) with the metallic electronic structure of half filling (3d1). In this talk, we will show the experimental results for both the mechanism and applications of the Mott transition and prospects for future research. We demonstrate observations of the monoclinic and correlated metal (MCM) phase before the structural phase transition for proving the Mott transition in VO2 films.. As applications of the MIT for non-boolean computing, the negative differential resistance (NDR) switching and the measured MIT oscillation are shown in VO2-based devices. Moreover, a high-sensitivity MIT photon detector using NDR switching is displayed. These applications form the basis of Mitronics (MIT + electronics). Furthermore, in future we shall explore the relationship between the Mott transition and the emergence of the metal phase on the surface of topological insulators.

September 30, 2022 (Friday) 4:00-5:00p.m. 
Speaker: Elton Smith, Jefferson Lab
Host: J. Stevens
Title: Can you stretch a pion?
Abstract: Electromagnetic polarizabilities are fundamental properties of composite systems such as molecules, atoms, nuclei and hadrons. They measure how easy it is to stretch a system using electromagnetic forces. Hadrons, such as nucleons and pions, are extremely stiff, which means that deformations are very small and difficult to measure precisely. However, pion polarizabilites are rigorous predictions of Chiral Perturbation Theory in the chiral limit and therefore represent desirable targets for exploration. We will describe two experiments in Hall D at Jefferson Lab that utilize a new technique to measure pion polarizabilities, the Primakoff photo-production of charged and neutral pion pairs using linearly polarized 6 GeV photons on a 208Pb target. The experimental run was completed in summer of 2022, and we will present a first look at the data.

October 21, 2022 (Friday) 4:00-5:00p.m. 
Speaker: Zhenghan Wang, Microsoft State Q
Host: E. Rossi

November 18, 2022 (Friday) 4:00-5:00p.m. 
Speaker: Daniel Andruczyk, University of Illinois
Host: S. Mordijck
Title: Can using liquid lithium as a Plasma Facing Component (PFC) drive a path to a viable fusion power plant
Abstract: The promise of using fusion reactions to produce the energy we need in the future is recently gaining much attention. Scientists and engineers have been in pursuit of this “Holy Grail” of energy for 70 years and now than ever it seems that fusion is within reach, at least on an experimental demonstration level. But to truly achieve a steady state working fusion power plant there is on major hurdle that needs to be overcome. Plasma Material Interactions (PMI). The materials we build these machines is extremely important. Several issues effect the materials that are used, the heat fluxes seen by parts of a fusion reactor can reach over 100 MWm-2 in some cases. This is more than double the surface heat flux of the Sun. Or the interactions with energetic ions, neutrals and neutrons can cause surface morphology changes (DPA, transmutation, fuzz, bubbles, blisters), ejection of material into the plasma, recycling of cold neutral gas back into the plasma and fuel depletion through implantation into the material. The current standard is to use solid metals that can try and withstand many of these issues, for example tungsten, carbon. But these all suffer in one shape or form from some or all of these problems. However, there is potentially a solution. Liquid metals and in particular liquid lithium, pose several solutions to many of the problems. As a liquid its self-healing and can possibly handle the large heat fluxes seen in the divertor. Its chemical reactivity means that it will essentially trap most impurities and fuel ions and neutrals that come out of the plasma. It reduces the recycling rate of the wall and thus can increase the performance of plasmas and reducing instabilities. That is not to say that there are technological challenges of liquid lithium, and these are all under investigation. This talk will focus on PMI challenges faced by solid materials and how liquid lithium can solve many of these issues as well as the challenges faced by using liquid metal systems. It will focus on a lot of the solutions being investigated at UIUC and the plasma, fusion and PMI program at the Center for Plasma Material Interactions.