[en] Study of x-ray conversion efficiency in laser produced plasmas and its optimization with respect to laser and target parameters has drawn considerable attention of research workers in the last few years. An important reason for this motivation is the use of sub-keV x-ray emission as a driver for the inertial confinement fusion. Here, experimental measurements of the spectral distribution of keV x-ray energy conversion of the M-shell emission from gold plasma produced by a 4 GW, 5 nS Nd:glass laser are presented. At a laser intensity of 2 x 10¹³ W/cm², the overall x-ray yield for 2.0 ≤ hν ≤ 3.6 keV is determined to be 0.1% of the laser energy. The effect of the keV x-ray spectral distribution on radiation preheat is discussed

[en] A spectroscopic study of ablation from moderate and high Z layered targets of aluminium and gold in the laser intensity range 10¹¹-10¹³ W/cm² of Nd:glass laser is presented. Ablation thickness of 0.5 micron of aluminium and 0.1 micron of gold is determined at laser intensity of 5 x 10¹¹ and 3 x 10¹² W/cm² respectively. Ablation pressures of 0.24 M Bar for aluminium and 0.15 M Bar for gold target are obtained from the measured values of mass ablation rate and angular distribution of ion velocity. A substantially large lateral energy loss for the gold target has been inferred from measurements of ablation depth, x-ray emission and plasma expansion velocity. (author). 21 refs, 4 figs

[en] The Laser Plasma Division at the Centre for Advanced Technology is engaged in a variety of R and D activities on laser-plasma interaction with special emphasis on laser-matter interaction at ultra-high intensities. An important aspect of our future work is studies in laser-plasma based acceleration using an elaborate infrastructural set-up of ultra-fast laser and plasma diagnostic systems and recently acquired 10 TW, 50 fs Ti: Sapphire laser system. This paper presents outline of the planned studies in this field. (author)

[en] A comparative study of ablation from moderate and high-Z layered targets of aluminum and gold in the laser intensity range 10¹¹--10¹³ W/cm² of a neodymium glass laser is presented. A substantially large lateral energy loss for high-Z target is observed from measurements of ablation depth, x-ray emission, and plasma blow-off

[en] The K-α and K-β x-ray emission (at 8.05 keV and 8.9 keV respectively) produced from a copper target by the impact of 25 keV hydrogen (H⁺) and nitrogen (N⁺) ion beams, and 200 keV for argon (Ar⁺⁸) beams from an electron cyclotron resonance ion source (ECRIS), has been studied experimentally. The K-α x-ray line intensity exhibited an increase with increasing ion beam energy with a scaling law I_K-α∝E^γ, where the scaling exponent γ was 4.0, 4.2, and 4.1 for hydrogen, nitrogen, and argon ion beam respectively. The results can be explained by considering the K-shell ionization cross-section for ion impact. The peak to background ratio of x-ray line intensity was observed to increase rapidly with the ion beam energy and highest ratio of 6×10⁵ was observed for hydrogen ions. The study is important for optimizing ECRIS for generating a low cost, long life x-ray source for applications in material science

[en] An enhanced spatial smoothing of ablative motion of thin plastic foil targets coated with high atomic number ablators such as gold or aluminium, irradiated by a spatially modulated Nd:glass laser beam was observed. Optical shadowgraphy coupled with double foil technique was used to observe the laser-irradiated foil motion. Laser irradiance used for the experiments was in the range of 10¹¹ - 10¹³ watts/cm². A 60-80 per cent enhancement in the smoothing was observed for a laser beam modulation (width 75-150 μm) at the target surface. (author)

[en] We have measured the x-ray emission intensity from plasmas created from a number of targets with atomic number (Z) in the range 6< or =Z< or =73 using a 1-GW, 5-ns neodymium glass laser. The variation of x-ray intensity with laser intensity (Phi) was observed to depend on the target atomic number and showed a scaling of Phi/sup α/ where α varies from 1.9 to 2.8 for different elements. The observed scalings were found to be consistent with a self-regulating model for plasma heating

[en] A simple and compact x-ray luminosity time-of-flight spectrometer for measurements of the velocity distribution of highly charged ions in laser-produced plasmas is presented. The spectrometer is based on making time- and space-resolved measurements of x-ray line emission from these ions in the expansion zone. Design, operation, and performance of this system are described. The spectrometer is useful in studying processes of interaction between highly charged ions and buffer gases, and nonthermal behavior of laser-produced plasma expansion

[en] A simple method of generating multi-keV, monochromatic, twin x-ray point sources based on laser-driven vacuum diode is presented. Electrons from a laser-produced aluminum plasma cathode were accelerated towards two point-tip titanium anodes placed symmetrically with respect to the cathode. Temporal and spatial characterizations of the K-shell x-ray emission from the twin anodes are carried out. Each source (∼300 μm diameter) emits ∼10⁹ Ti Kα (hν≅4.51 keV) photons in a pulse of ∼20 ns duration with a peak brightness of ∼4x10¹⁸ photons/cm² s sr. Single-shot twin x-ray shadowgrams of physical objects were recorded at a distance of several centimeters from the two sources. Such a system may be useful for single-shot stereoradiography for differential imaging in the multi-keV energy region

[en] A study of the ion expansion characteristics in plasmas created from carbon, copper, and gold targets using a 1-GW, 5-ns neodymium glass laser is presented. The ion expansion velocity is found to vary with the distance of the probe from the target and the variation is observed to be different for low and high atomic number (Z) targets. Analysis shows that the strikingly different variation for low and high Z targets is a manifestation of their different recombination characteristics during plasma expansion