X‐ray imaging of uniform large scale‐length plasmas created from gas‐filled targets on Nova

We report on the production and characterization of large scale‐length plasmas created by illuminating gas‐filled thin‐walled balloonlike targets using the Nova laser. The targets consisted of a 5–6000 A skin surrounding 1 atm of neopentane which when ionized becomes a plasma with 1021 electrons/cm3. Results are presented from x‐ray imaging used to evaluate the uniformity of the plasma. The most uniform plasmas were produced by illuminating the target with large converging beams that overlapped to cover most of the surface of the gas bag. An alternate focus geometry using small beam spots resulted in a less uniform plasma with low density holes in it.