A microfocus X-ray fluorescence spectroscopy beamline (BL-16) at the Indian synchrotron radiation facility Indus-2 has been constructed with an experimental emphasis on environmental, archaeological, biomedical and material science applications involving heavy metal speciation and their localization. The beamline offers a combination of different analytical probes, e.g. X-ray fluorescence mapping, X-ray microspectroscopy and total-external-reflection fluorescence characterization. The beamline is installed on a bending-magnet source with a working X-ray energy range of 4-20 keV, enabling it to excite K-edges of all elements from S to Nb and L-edges from Ag to U. The optics of the beamline comprises of a double-crystal monochromator with Si(111) symmetric and asymmetric crystals and a pair of Kirkpatrick-Baez focusing mirrors. This paper describes the performance of the beamline and its capabilities with examples of measured results.

A study of silver, chromium, stainless-steel, and indium thin films prepared by subnanosecond laser deposition in vacuum is reported. We compare the laser ablation in vacuum at the weak- and tight-focusing conditions of a Ti:sapphire laser beam and analyze the nanoparticles synthesized in the latter case using absorption spectroscopy, x-ray fluorescence, atomic force microscopy, and scanning electron microscopy. Our results show that the nanoparticle formation can be accomplished using long laser pulses under tight-focusing conditions.

A comparative experimental study of soft x-ray emission from laser-irradiated Au–Cu mix-Z targets of different atomic compositions has been performed. Plasma was produced from planar targets using second-harmonic laser pulses from an Nd:glass laser at a focused intensity of ∼1013 W cm−2. Radiation intensity in the spectral region ∼15–150 Å and integrated x-ray yield for mix-Z target were observed to be higher than those for individual elements. The maximum conversion occurred for an atomic composition of Au 0.43–Cu 0.57. These observations are consistent with the variation of Rosseland mean opacity with atomic composition calculated using a screened hydrogenic average atom model.

In this paper, we present a comparative study of the laser energy absorption, soft x-ray emission (in the water window region: 2.3–4.4 nm) and hard x-ray emission (in the 2–20 keV range) from planar aluminum and nanohole alumina of 40 nm average diameter, when irradiated by Ti:sapphire laser pulses. The laser pulse duration was varied from 45 to 500 fs, and the focused intensity on the target ranged from ∼3 × 1016 W/cm2 to 3×1017 W/cm2. The x-ray yield enhancement from the nanoholes shows an increased coupling of the laser energy to the target. The effect of laser pulse duration on the x-ray emission was also studied, where a resonance like phenomenon was observed. The laser energy absorption measurements in the nanoholes showed a marginal enhancement in absorption as compared to planar Al. The integrated keV x-ray yield, from nanohole alumina and planar Al, at an intensity of 3 × 1017 W/cm2, was 25 and 3.5 μJ, respectively. The results can be explained by considering the hydrodynamic expansion of the laser irradiated structure and field enhancement in the nanoholes.

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Conversion efficiency and spectral broadening of the K-α line emitted from planar titanium targets irradiated with ultra-short laser pulses of high intensity Near complete absorption of the energy of intense ultra-short laser pulses (45 fs, intensity $1.6 Â 10 16 to 2.5 Â 10 17 W/cm 2 ) is observed in carbon nanotubes deposited on a planar molybdenum substrate. The hollow structure of the nanotube plasma facilitates resonant electric field enhancement during its ionization phase. This resonantly enhanced localized field at a density much larger than the critical density n c leads to efficient hot electron generation, which results in enhanced K a emission of Mo at 17.5 keV. It is observed that for nanotubes, depending on the degree of hollowness, there is an optimum laser intensity for maximum x-ray enhancement compared to a planar uncoated target.

A systematic study of structure and thermal stability of a [(Mo/Y/) x 5] soft x-ray multilayer (ML) mirror prepared by electron beam evaporation system has been performed by means of x-ray reflectivity (XRR) and grazing incidence x-ray diffraction (GIXRD). The GIXRD patterns show that the Mo and Y layers are polycrystalline in nature. The obtained XRR patterns confirm the very good quality of the ML stack. Isochronal thermal annealing up to the temperature of 400 °C leads to a decrease in interface roughness which in turn results in sharpening of the ML interfaces. Further elevating the annealing temperature above 400 °C oxidizes the Y layers and the interface roughness increases. Thus increase in interface roughness beyond this temperature can be understood in terms of evolution of yttrium oxide, which significantly affects the ML structural properties. The modulation structure is well maintained even after annealing at 600 °C, which confirms very good thermal stability of the Mo/Y ML mirror. Our results demonstrate that low-temperature annealing (up to 400 °C) is an effective method to improve the quality of an as deposited Mo/Y soft x-ray ML mirror. Diffuse scattering measurements show very good correlation with the XRR fitting parameters.