Optimization of x‐ray sources for proximity lithography produced by a high average power Nd:glass laser

We measured the conversion efficiency of laser pulse energy into keV x rays from a variety of solid planar targets and a Xe gas puff target irradiated using a high average power Nd:glass slab laser capable of delivering 13 ns full width at half‐maximum pulses at up to 20 J at 1.053 μm and 12 J at 0.53 μm. Targets were chosen to optimize emission in the 10–15 A wavelength band, including L‐shell emission from materials with atomic numbers in the range Z=24–30 and M‐shell emission from Xe (Z=54). With 1.053 μm a maximum conversion of 11% into 2π sr was measured from solid Xe targets. At 0.527 μm efficiencies of 12%–18%/(2π sr) were measured for all of the solid targets in the same wavelength band. The x‐ray conversion efficiency from the Xe gas puff target was considerably lower, at about 3%/(2π sr) when irradiated with 1.053 μm.