Production and characterization of large plasmas from gas bag targets on Nova

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Abstract
Large plasmas are created by illuminating gas‐filled thin‐walled balloon‐like targets using the Nova laser [E. Campbell et al., Rev. Sci. Instrum. 57, 2101 (1986)]. The targets consist of a 5000–6000 Å skin surrounding 1 atm of neopentane, which, when ionized, becomes a plasma with an electron density of 1021 electrons/cm3. X‐ray images of the gas bag target are used to evaluate the size and uniformity of the plasma by comparison with L A S N E X [R. M. More, J. Quant. Spectrosc. Radiat. Transfer 27, 345 (1982)] simulations. The gas bags are heated with converging and diverging beam spots. The most uniform plasmas are created by illuminating the target with large converging beam spots that overlap to cover most of the surface of the gas bag. The gas bag plasma is heated to a peak temperature of approximately 3.5 keV, with 25 kJ of 3ω laser light in a 1 ns square pulse.