This award supports an experimental study of energy transport in collision-dominated ultracold plasmas. Ultracold plasma can serve as a model system for extremely dense and hot plasmas generated in laser-driven nuclear fusion experiments, which create matter that is hotter than the Sun and more dense than solid metal. Improved understanding of such plasmas would enable faster progress towards development of nuclear fusion energy sources, as well as address national nuclear security priorities. This research project will test portions of the detailed computer models used to predict transport processes in hot, dense plasmas by conducting precision laser measurements to create small-scale ultracold plasmas and measure everything about them – how the ions collide, how energy is transferred, and how the plasma approaches equilibrium. These small-scale plasmas are prepared with adjustable shapes and with different kinds of atoms, sometimes in combination with strong magnetic fields, so that transport processes in them will mimic the transport processes that occur in hot, dense plasmas. Testing the computer models and highlighting ways they can reach higher fidelity will help advance plasma science in the national interest. Radiation-hydrodynamic codes successfully capture the temperature, density, and neutron yield of high energy laser experiments that are designed to produce plasmas close to the hydrodynamic limit. However, many current and planned experiments are far from t