Solutions of several theory and technique problems in high-space-resolving hotspot electron temperature diagnosis techniques in inertial confinement fusion

Abstract

In implosion experiments, bremsstrahlung radiation ratios of broad-energy-band x-ray emission intensities (sampled by Ross pair) and narrow-energy-band x-ray emission intensities (sampled by multilayer) are typically used to extract the hotspot electron temperature. The latter method could potentially be more accurate because it does not require any additional theoretical arithmetic. However, the boundary conditions of the energy band, drastic influence on the measured electron temperature resulting from response differences of recording devices in the energy band, evident impact from uncertainties of the detector aiming, and coordinate interrelations for the two narrow-energy-band x-ray images have not been explored. These problems should be overcome to obtain the accurate hotspot electron temperature using the narrow-energy-band x-ray emission intensities method. This study solves the problems indicated above by exploring a diagnosis technique to extract the accurate hotspot electron temperature. In particular, we determine that the effect of the response differences and uncertainties could be ignored when the width of the sampled narrow energy band is approximately ±0.5 keV in the linear spectrum response regions of the imaging plate, and the reflectivity of the multilayer is uniform and constant in that energy band and the viewing field of the detector (≥±110 µm). This study is the first to consider the linear spectrum response of the imaging plate in different energy regions, eliminating the effect of the response differences. Finally, the maximal emission intensities in the two recorded-energy-band x-ray images can be used for coordinate interrelation.