3MT Department Winners

Inertial confinement fusion (ICF) involves initiating nuclear fusion reactions by imploding a small fuel pellet, causing the fuel to reach high densities and temperatures. A novel triple-shell pellet design has been proposed that is composed of three concentric spherical shells encasing an inner volume of Deuterium-Tritium fuel. This design, an alternative to the more widely tested single shell design, addresses different physics constraints. For example, the triple shell's inner-most shell is composed of a heavy metal allowing it to trap electromagnetic radiation inside the fuel, which minimizes radiative losses. Additionally, the other shells smooth out small irregularities that form during the implosion process, such as Rayleigh-Taylor (RT) instabilities. To perform its intended purpose, the optimal physical dimensions of each shell must be determined, including shell radii and thicknesses. This research presents the results of a Bayesian optimization procedure that uses one-dimensional (1D) radiation-hydrodynamic simulations to determine the optimal triple shell design parameters. This procedure advances the research in triple shell designs by determining dimensions that best avoid hydrodynamic instability growth and optimize the total energy output of implosions. The optimization process began by generating a set of simulation data by randomly querying simulations from parameter space. This initial dataset was used as the starting point for a Bayesian optimization algorithm. The yield optimized design specifying the radius and thickness of each shell is p_in=271.47, p_th=48.438, d_in=491.48, d_th=21.193, a_in=893.01, a_th=206.99 in units of microns. When fielded in ICF experiments, a capsule with parameters outlined in this paper will produce high energy output and low RT instability presence in implosions.

We study the expansion velocity and ion temperature evolution of ultracold neutral plasmas (UNPs) of calcium atoms under the influence of a uniform magnetic field that ranges up to 200 G. In the experiments, we use a magneto-optical trap (MOT) to capture the neutral atoms and laser-induced fluorescence (LIF) to take images of the plasma. We vary the magnetic field strengths and the initial electron temperatures and observe the plasma evolution in time. We compare the ion temperature evolution to the theory introduced in the paper by Pohl et. al. [Phys. Rev. A 70, 033416 (2004)]. The evolution of the gradient of expansion velocity suggests the presence of ion acoustic waves (IAWs). We speculate that our measurements showing that the ion temperature remains relatively high throughout the evolution is a biproduct of the IAW.

In ultracold neutral plasma research, it is necessary to have an imaging system that guarantees a known magnification. Early experimentation concluded that a simple imaging system consisting of identical lenses guarantees 1:1 imaging when the lenses are well aligned and the image is resolved. The purpose of this experiment is to develop a model describing the impact object position and alignment have on the magnification and confirm this model through experimentation. To achieve this, images of the 1951 USAF resolution test chart, a \SI{50}{\micro\metre} pinhole, and a \SI{100}{\micro\metre} pinhole are taken using the imaging system for different alignments and compared to a mathematical model derived from an ABCD matrix calculation. Magnification values for the images are calculated and fitted to the mathematical model, predicting the alignment of the system. The results of this experiment confirm the model when the lens pair separation is equal to or less than $2f$. However, when the lens separation is greater than $2f$, the agreement between the experiment and model decreases for the 50 $\mu$m pinhole.