Correlating X-ray emissions and Target EM fields in Laser-Driven Ion Acceleration

Laser-driven-ion-acceleration is widely used to generate MeV-energy particle sources. A commonly used mechanism in Proton Fast Ignition, for instance, is Target-Normal-Sheath-Acceleration (TNSA). During this process, X-rays are emitted and strong electric fields responsible for ion acceleration are established. Recent results from TNSA proton acceleration studies have shown that accepted models underestimate the ion energies achieved in experiment. We examine this phenomenon by taking the characteristic X-ray emissions from the hot-electron beam as a signature of the ion-accelerating TNSA fields. We present a simulation framework capable of reproducing K-alpha signals detected from the foil targets. We consider electron and photon interactions in the foil, as well as the refluxing behavior of electrons. The simulation is used to model and iteratively adjust properties of the ion-accelerating fields to match measured X-ray signatures. We aim to provide new constraints on the strength, structure, and evolution of the TNSA fields surrounding the laser-irradiated target.