Imploding Cryogenic Shell Nonuniformity Measurements on OMEGA by Self-Radiography

Radiographs of pure DT cryogenic imploding shells will help to validate progress toward ignition-scalable performance of inertial confinement fusion implosions. Imploding cryogenic D₂ and DT shells can be radiographed with the core spectral emission, progressively from hν ≈ 1 keV to ≈2 keV, from the deceleration phase through peak compression. Utilizing the distinct spectral dependences of hydrogen continuum emissivity and opacity, shell optical‑thickness variations can be distinguished from core structure. This technique does not require shell additives, as used in previous applications of implosion self-radiography. Demonstrations with simulated data show that this technique is remarkably well suited to cryogenic implosions. Specifically, emission and absorption are well localized to the core and shell, respectively. Also, shell self-backlighting can be used near peak compression, unlike externally backlit radiography, where self-emission is a background signal that overwhelms the backlighter near peak compression.