Oxygen Emission Measurements Using a Double Crystal von Hamos Spectrometer for Electron Collimation Experiments

Electron Fast Ignition (EFI) is a promising method for improving energy deposition in Inertial Confinement Fusion by using a high-power, short-pulse laser that generates an electron beam to ignite a pre-compressed fuel core. However, beam divergence limits energy transfer. This investigation explores electron collimation using self-generated magnetic fields via resistive return currents. At the Jupiter Laser Facility, the Titan Laser is focused on a coaxial copper/PMMA target with ~10% oxygen concentration. Resistivity is both material- and temperature-dependent, making it essential to characterize heat transfer within the target. A time-integrated oxygen spectrometer is designed and constructed to probe the surface cladding temperature. The spectrometer uses a double crystal von Hamos geometry, designed to have a spectral range spanning K-alpha and He-beta lines. Analysis of spectral line ratios can be used to determine the temperature in this region. Combined with spectroscopic measurements from higher-Z elements, the temperature profile normal to electron propagation can be established, from which the resistivity gradient and its impact on electron collimation can be inferred.