Studies of Target Implosion Using K-Shell Absorption Spectroscopy of an Embedded Titanium Layer

LLE Review, Volume 79 139 In laser-imploded target studies, the measurement of shell compression and uniformity is essential to understand target performance. Previously we have used targets in which a titanium-doped layer was incorporated into the target shell. The doped layer provided a variety of diagnostic signatures (absorption lines, K-edge absorption, Kα imaging) for determining the areal density and density profile of the shell around peak compression.1–5 In this article we apply some of these methods to demonstrate the improvement in target performance when implementing SSD6 (smoothing by spectral dispersion). In particular, we study slow-rising laser pulses (for low-adiabat implosions), where the effect of SSD smoothing is more pronounced. In addition, we introduce a new method for studying the uniformity of imploded shells: using a recently developed5 pinhole-array x-ray spectrometer we obtain core images at energies below and above the K-edge energy of titanium. The nonuniformity of such images depends on the nonuniformity of both the emitting core and the absorbing shell; however, the ratio between the images above and below the K edge essentially depends on the nonuniformity of the shell alone. Finally, we compare the results with those of 1-D LILAC simulations, as well as 2-D ORCHID simulations, Studies of Target Implosion Using K-Shell Absorption Spectroscopy of an Embedded Titanium Layer