A series of experiments conducted on the HELEN laser system [M. J. Norman et al., Appl. Opt. 41, 3497 (2002)], into thermal x-ray generation from hohlraum targets using 527 nm ($2\omega$) wavelength laser light, has shown that it is possible to exceed radiation temperatures previously thought limited by high levels of superthermal or hot electron production or stimulated backscatter. This Letter questions whether the assumptions traditionally applied to hohlraum design with respect to hot plasma filling and the use of $2\omega$ light are too conservative.

• Received 8 August 2004

DOI:https://doi.org/10.1103/PhysRevLett.94.055006