Radiation cooling of laser-produced aluminum plasmas by highly ionized gold atoms was studied experimentally. The plasma was produced by irradiating 500-μm-diam glass spheres coated with two layers of aluminum and an intermediate gold layer of varying thickness. The 24-beam Omega laser system at a laser wavelength of 351 nm and intensity in the range (2–3)×${10}^{14}$ W/${\mathrm{cm}}^2$ was used to produce the plasma. Electron temperatures were determined spectroscopically by measuring the 1s-2p–to–1$s^2$-1s2p line ratio in Al xiii and Al xii. With no gold layer the electron temperature of highly ionized aluminum is found to be close to 1400 eV. The introduction of a 0.01-μm layer of gold reduced the electron temperature to approximately 1100 eV, and with a 0.05-μm gold layer it was reduced to 700 eV. A gold layer also reduced the temperature of the sodium plasma produced from the glass as measured using Na x and Na xi line ratios. Time-resolved x-ray measurements showed additional evidence of cooling. Measurements of total x-ray emission and radiative energy calculations from a hydrodynamic code showed a 50% increase in radiated energy with the addition of 0.05-μm gold layer.

• Received 22 May 1989

DOI:https://doi.org/10.1103/PhysRevA.40.4564