Measuring shock-bang timing and ρR evolution of D3He implosions at OMEGA

New experimental results describing the dynamics of D3He capsule implosions, performed at the 60 beam direct-drive OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], are presented. The capsules, nominally 940 μm in diameter and with 20–27 μm thick CH shells, were filled with 18 atm D3He gas and irradiated with 23 kJ of UV light. Simultaneous measurements of D3He burn history, DD burn history, and several time-integrated D3He proton energy spectra provided new results, such as shock-bang timing, shock-burn duration, evolution of the ion temperature, and evolution of ρR and ρR asymmetries. The shock-bang time measurements, when compared to calculation using the 1D LILAC code [J. Delettrez et al., Phys. Rev. A 36, 3926 (1987)], indicate that a varying flux limiter is required to explain the data, while the measured shock-burn duration is significantly shorter than 1D calculations, irrespective of flux limiter. The time evolution of ion temperature [Ti(t)] has been inferred from the ratio of the DD and the D3He burn histories, and a constant temperature is observed during the compression phase. The discrepancy between experimental data and 1D simulations during the final stages of the compression burn indicates that mix is significant, especially for the 20 and 24-μm capsule implosions. Evolution of ρR and ρR asymmetries show that the average ρR grows by a factor of ∼4–5 from shock-bang to compression-bang time, and that ρR asymmetries (l=1), primarily driven by capsule convergence, grows ∼2 times faster than the average ρR growth.