Description
In the central hotspot approach to inertial confinement fusion, the hotspot serves as the spark plug, initiating thermonuclear burn at the core of the fusion fuel. The hotspot conditions are highly sensitive to drive asymmetries, hydrodynamic instabilities, and impurities. Measuring the history of the hotspot in fusion experiments, from formation to the final density and temperature conditions, is important for furthering understanding of the implosion process and assessing fusion performance. To achieve this, the multi-monochromatic X-ray imager (MMI) can be used to record time-gated, spectrally resolved images of the hotspot dynamics. Doping the gaseous core with trace amounts of Ar enables the extraction of electron density and temperature in the hotspot as well as the shell areal density, all as a function of time. A forward analysis methodology is presented using a collisional-radiative and spectral synthesis code. The synthetic data is compared with MMI measurements of implosions reaching peak compression on the OMEGA laser system. The analysis enables the extraction of two-dimensional maps of electron density and electron temperature, further aiding the understanding of the implosion physics via comparison with radiation-hydrodynamic simulations.