We present a systematic method to absolutely calibrate detector efficiency vs photon energy using a laser produced plasma broadband x-ray source, a gold standard calibrated detector, and transmission gratings (TGs) as dispersive elements. Calibration uses one calibrated TG and a calibrated gold standard detector on one channel and a second calibrated TG and a detector to be calibrated on the other channel. Both channels simultaneously view the laser-produced plasma x-ray source from the same angle with respect to the laser beam and the planar target normal. Image plate detectors are calibrated for the first time at photon energies below 700 eV. Single shot simultaneous calibration of several detectors is possible, making this method an efficient and practical way to periodically calibrate detectors, using in-house capabilities of laser laboratories.

High-temperature, high-density experiments require a simultaneous understanding of temporal and spectral regions. The spectral x-ray streak camera (SXSC) is a new high-temporal-resolution spectral x-ray diagnostic system that allows researchers to differentiate between soft and hard x-ray regions. The diagnostic offers three spectral channels with a wide spectral range, one direct channel that includes a filter and two indirect channels that include both mirrors and filters. The opto-mechanical design positions the filtered radiation at three different locations along the streak photo-cathode (PC) slit to provide time-dependent spectral channels with pico-second temporal resolution. A moderate spatial resolution (150-700 μm) is achieved using slits perpendicular to the PC slit, while the slit width is optimized according to the central channel wavelength (for each channel). The diagnostic system covers a spectral range of 30-500 eV for the mirror channels and >1300 eV for the direct channel. The temporal and spatial axes of the streak camera are calibrated with respect to a sequence of x-ray pulses. The SXSC diagnostic system is tested and analyzed using Marshak-wave emission from an SiO2 foam that was heated by a laser-beam irradiated halfraum. The SXSC results are compared to measurements from an x-ray diode array with similar spectral channels.

A new approach for the spectral reconstruction of time-dependent emission of soft x-ray sources based on the measurement of filtered x-ray diode array systems is suggested. Two reconstruction methods, based on this approach, are demonstrated using both simulated and measured data. The methods use the filtered x-ray diode measurement together with a co-aligned, time-integrated, spectrally resolved measurement, such as transmission grating spectroscopy. The additional experimental information allows for high accuracy spectral reconstruction, even for plasmas far from local thermodynamic equilibrium where the traditional reconstruction methods may miss some important source spectral features. For the demonstrated cases, the accuracy of the new reconstruction methods is better than 10% for the energy dependent flux and 1% of the total flux, which is higher than the accuracy of previous methods and better than the accuracy of the measurement itself.

Calibration of soft x-ray diagnostics is a challenge due to the lack of laboratory-size calibrated sources. An in situ calibration method for newly developed x-ray mirrors, is presented. The x-ray source is produced by laser-matter interaction, and twin transmission gratings which create two identical dispersion lines. The gratings have a sinusoidal transmission function, which produces a highly precise high-orders free spectrum. An x-ray mirror interacts with one of the dispersion lines, and the mirror efficiency curve as a function of wavelength is extracted. Mirror efficiency shows good agreement with the literature, and evidence of water layer may justify the need of in situ calibration.

Laser experiments of the plasma jet formation using nanosecond laser pulses with low energy, i.e., <20 J, are presented. Planar and cratered gadolinium and aluminum targets are irradiated with laser intensities of several 10(14) W/cm(2). Spatially-resolved time-integrated X-ray spectra were recorded in the spectral range from 7 to 10 angstrom. A jet-like structure is obtained from aluminum targets with a preformed crater, which is not seen in planar target irradiation. For gadolinium, a jet is observed from both planar and preformed cratered targets, suggesting that the collimation is dominated by radiative cooling. A radiation-hydrodynamics code coupled to a non-LTE ionization code was used to model the plasma. The calculated plasma emission was found to be consistent with the experimental results. (C) 2013 Elsevier B.V. All rights reserved.

A novel fabrication method for soft x-ray transmission grating and other optical elements is presented. The method uses focused-ion-beam technology to fabricate high-quality free standing grating bars on transmission electron microscopy grids. High quality transmission gratings are obtained with superb accuracy and versatility. Using these gratings and back-illuminated CCD camera, absolutely calibrated x-ray spectra can be acquired for soft x-ray source diagnostics in the 100-3000 eV spectral range. Double grating combinations of identical or different parameters are easily fabricated, allowing advanced one-shot application of transmission grating spectroscopy. These applications include spectroscopy with different spectral resolutions, bandwidths, dynamic ranges, and may serve for identification of high-order contribution, and spectral calibrations of various x-ray optical elements.

Detailed spectroscopic identification and analysis of lines emitted by Ni-like ions may infer on plasma parameters, such as electron density, temperature, and ionization state. Spatially, resolved X-ray spectra of samarium laser produced plasma were recorded in the 7 to10 angstrom wavelength range. Measured line intensity ratios of Ni-like 3d-5f, 3p-4d, 3p-4s, and 3s-4p transitions were used for electron density diagnostic as a function of the distance from the target. Calculations using Hebrew University Lawrence Livermore Atomic Code show that these ratios are not very sensitive to the electron temperature in the range from 500 to 1000 eV. Self-absorption of some lines is found to be important at electron densities higher than 10(21)cm(-3). The inferred ranges of electron density and temperature are found to be consistent with results of hydrodynamic simulations and models of ionization in plasma.

Spatially-resolved time-integrated X-ray spectra of laser produced iron plasma were recorded, in the spectral range from 10 to 12 angstrom. The newest version of the atomic code HULLAC was used alongside a radiation-hydrodynamics code to model the plasma and generate simulated spectra for comparison with the experimental one. The spectra were found to be characterized by line emission from Li-like Fe XXIV ions, with 2s-3p and 2p-3d dominant transitions. Ionization stage, electron temperature and density were inferred from spectroscopic measurements. Good agreement was found between the parameters obtained from the radiation-hydrodynamics code and the detailed atomic code. (C) 2011 Elsevier B. V. All rights reserved.

Spatially-resolved time-integrated X-ray spectra of laser produced samarium plasma were recorded; in the spectral range from 7 to 10 A. The spectrum of samarium is characterized by the prominent pattern of transitions 3d - nf (n = 4-7) belonging to Co-like (Sm35+), Ni-like (Sm34+) and Cu-like (Sm33+) ions. Spectral lines of Mn-like (Sm37+) to Zn-like (Sm32+) were identified. The appearance of these ionization stages as a function of distance from the target was measured. Transfer of the dominant ion stages to lower stages with increasing distance from the original target surface was demonstrated, probably indicating dielectronic recombination. The Hebrew University Lawrence Livermore Atomic Code was used to generate emission spectra for comparison with the experimental ones.A radiation-hydrodynamics code coupled to three non-Local Thermal Equilibrium ionization and equation of state models with different approaches for dielectronic processes was used to model the plasma. The simulated plasma ionization and electron densities and temperatures were found to be consistent with the experimental results. (C) 2011 Elsevier BM. All rights reserved.

A unique scheme for remote detection of explosives has been demonstrated. High detection sensitivity was achieved by an exclusive combination of two processes: Explosive vapor detection by PLP/LIF (pulsed laser photodissociation/laser-induced fluorescence) with vapor concentration enhancement by remote evaporation. The basic PLP/LIF method was demonstrated on TNT in the vapor phase with a detection sensitivity higher than 1 ppb m. Remote vapor enhancement improves detection capability by about three orders of magnitude enabling remote detection of explosives with extremely low vapor pressures. Remote detection of RDX, PETN and C4 from several meters is presented. Updated experimental results and calculations show that the enhanced PLP/LIF method is a promising tool for detection distances of up to ten's of meters.

High power Nd:YAG laser rods may easily exceed their fracture strength as a result of thermally induced tensile stress. Strengthening of such rods is achievable at elevated temperatures by wet chemical, etching in concentrated orthophosphoric acid or in a mixture of phosphoric and sulfuric acids. In the present study, the etching rates of Nd:YAG in both etchants were determined as a function of temperature. The calibration curves thus obtained enabled the controlled removal of the outer "damaged" layer of lasing elements. Four-point flexure strength measurements were performed on deep etched and on non-etched YAG slabs. The measurements showed a 3.5 fold increase in the strength of the etched slabs. Weibull analysis treatment was carried out on the basis of our fracture data.