Investigation of the high-energy x-ray spectrum of pinhole point-projection backlighters*

Laser-produced hot electrons may present many undesirable effects in high-energy-density physics experiments. In particular, the secondary production of high-energy x-rays produces a background that reduces the signal-to-noise. Experiments were performed to study the hot electron-induced high-energy x-ray background present in pinhole point-projection x-ray backlighters. In these experiments, bremsstrahlung x-ray spectrometers (BMXS) were used to measure the high-energy x-ray signal from the backlighter targets. The response of the BMXS diagnostic is capable of retrieving both the continuous x-ray spectrum and a best fit of the hot electron temperature describing the hot electron energy distribution. We will present the inferred hot electron temperatures and discuss how the x-ray spectra depend on backlighter and pinhole substrate material. Additionally, we will discuss the x-ray spectra angular dependence. Lastly, we will discuss the effect of the background on the quality of x-ray radiographic data.