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Nuclear-pumped lasers (NPL) are lasers in which excited active laser environment caused by nuclear reaction. Such lasers need ionizing radiation shielding for mixed neutron and gamma fields. In this work, a shielding system for NPL was designed for an NPL that uses 10B(n,α)7Li. In fact, we have used MCNPX 2.6.0 Monte Carlo code and the thermal neutron flux as 1 × 1016 n.cm-2.s-1 for excitation reaction. Such a large neutron flux can be obtained from a reactor source or a heavy ion accelerator. For this work, 10B fuel is covered on the surface of a rectangular cube aluminum shell by using the Monte Carlo method. In the design of the shielding, combinations with different materials have been used with various arrangements in three layers. According to the simulation, the arrangement of Fe2B-BPE-Pb is a suitable protection compound for such lasers. [ABSTRACT FROM AUTHOR]

A transport model for a transverse electron beam-pumped semiconductor laser has been developed. The model incorporates spatial dependencies of the power deposition from the beam as well as a three-dimensional model of the gain medium and the field intensity of the photons produced by stimulated emission in the oscillation cavity. This model accounts for spatial inhomogeneities and has been solved for a variety of pumping strengths. The model was developed so that it can be benchmarked with electron beam pumping. The dominant mechanisms for the production of electron–hole pair production within the semiconductor material is similar to the dominant mechanisms for the production of electron–hole production using ion beams. Thus, the model can be extended to fission fragment ion pumping of semiconductor lasers in order to model a nuclear-pumped laser/reactor system. [ABSTRACT FROM AUTHOR]

We irradiated the soft x-ray laser (SXRL) pulses having a wavelength of 13.9 nm, a duration time of 7 ps, and fluences of up to 27 mJ/cm2 to aluminum (Al) surface. After the irradiation process, the modified surface was observed with the visible microscope, the scanning electron microscope, and the atomic force microscope. The surface modifications caused by the SXRL pulses were clearly seen, and it was found that the conical structures having about 70-150 nm in diameters were formed under a single pulse shot. The conical structures were formed in the features with the average depth of about 40 nm, and this value was in accordance with the attenuation length of the SXRL beam for Al. However, those conical structures were deconstructed under the multiple pulse shots exposure. Thermomechanical modeling of SXRL laser interaction with Al surface, which explains nanostructure surface modification, was provided. [ABSTRACT FROM AUTHOR]

A novel x-ray laser (XRL) application, aimed at understanding the microscopic effects involved in formation of laser-induced damage in optical materials exposed to high-power sub-ns laser pulses, is presented. Standard fused silica substrates with permanent damage threshold below 20 J/cm2, when irradiated by 438 nm laser pulses, were probed in situ by a neonlike zinc XRL at 21.2 nm. The probing beamline employed a double Lloyd’s mirror x-ray interferometer, used in conjunction with an imaging mirror to achieve magnification of ∼8. In conjunction with an array of in situ optical diagnostics, the main question addressed is whether the damage on the rear surface of the beamsplitter is transient or permanent. The second issue, examined by both the x-ray interferometric microscopy and the optical diagnostics, is whether a local rear-surface modification is associated with nonlinear effects such as self-focusing or filamentation of the damaging laser beam in the bulk. [ABSTRACT FROM AUTHOR]

Presents information on a study which developed a two-dimensional model to determine the coupled fluid dynamic and charged particle transport behavior of a flowing gas, nuclear pumped laser cavity. Methodology of the study; Results; Conclusions.

We describe an experimental method to measure the gate profile of an x-ray framing camera and to determine several important functional parameters: relative gain (between strips), relative gain droop (within each strip), gate propagation velocity, gate width, and actual inter-strip timing. Several of these parameters cannot be measured accurately by any other technique. This method is then used to document cross talk-induced gain variations and artifacts created by radiation that arrives before the framing camera is actively amplifying x-rays. Electromagnetic cross talk can cause relative gains to vary significantly as inter-strip timing is varied. This imposes a stringent requirement for gain calibration. If radiation arrives before a framing camera is triggered, it can cause an artifact that manifests as a high-intensity, spatially varying background signal. We have developed a device that can be added to the framing camera head to prevent these artifacts. [ABSTRACT FROM AUTHOR]

A concept for the IRM fast periodic-pulse reactor, which can be used as an ignition module for high-power nuclear-pumped lasers, is presented. The periodic-pulse operating regime of IRM is examined. The results of calculations of the parameters of the IRM which is under development are compared with the main characteristics of IBR-2. It is shown that IRM holds promise for use in high-power nuclear-pumped lasers. [ABSTRACT FROM AUTHOR]

We predict high-gain x-ray lasing in molecular nitrogen by ultrafast core ionization with an x-ray free-electron laser source. To estimate the spectral and temporal output of this molecular x-ray laser, we solve generalized Maxwell-Bloch equations, keeping track of the electronic and nuclear degrees of freedom. The spectrum of the amplified x-ray emission shows a strong dependence on the gain-length product. Whereas the emission at small gain length is similar to the relatively broad x-ray fluorescence band, the spectrum is determined by a single frequency in the linear gain region. The vibrational wave packet dynamics during the x-ray emission process is examined. By preparation of the initial vibrational quantum state, the x-ray emission frequency can be tuned within the fluorescence band. The present scheme is applicable to other homo- and heteronuclear diatomic systems, thereby extending the spectral range of coherent x-ray radiation sources based on amplification on bound transitions. [ABSTRACT FROM AUTHOR]

The experience gained in operating a demonstration nuclear-pumped laser in stand B (Physics and Power- Engineering Institute (FEI)) with a pulsed ignition reactor based on the U BARS-6 reactor is analyzed. It is shown that laser block → ignition reactor neutron feedback coupling greatly limits the parameters of the pump pulse from the amplifier. A method is proposed for decreasing the feedback by replacing U with the threshold fissile element Np in the ignition reactor. Such a reactor will increase by approximately 15-fold the energy and power of the pump pulse in the laser block of the demonstration reactor of the nuclear-pumped laser in stand B. [ABSTRACT FROM AUTHOR]

Experiments to study the light emission from plasma produced by particle beams are presented. Fundamental aspects in comparison with discharge plasma formation are discussed. It is shown that the formation of excimer molecules is an important process. This paper summarizes various studies of particle beam induced light emission and presents the first results of a direct comparison of light emission induced by electron- and ion beam excitation. Both high energy heavy ion beam and low energy electron beam experiments are described and an overview over applications in the form of light sources, lasers, and ionization devices is given. [ABSTRACT FROM PUBLISHER]

We discuss an opportunity to achieve amplification without inversion in a three-level cascade scheme using an effective unidirectional pumping via bidirectional incoherent pump. Analytical solution to the population and the coherence are obtained in the steady-state regime. With a proper choice of the parameters, obtained here, the possibility for amplification without inversion is presented. [ABSTRACT FROM PUBLISHER]

Abstract: Coherent population transfer between nuclear states using X-ray laser pulses is studied. The laser pulses drive two nuclear transitions between three nuclear states in a setup reminding of stimulated Raman adiabatic passage used for atomic coherent population transfer. To compensate for the lack of γ-ray laser sources, we envisage accelerated nuclei interacting with two copropagating or crossed X-ray laser pulses. The parameter regime for nuclear coherent population transfer using fully coherent light generated by future X-Ray Free-Electron Laser facilities and moderate or strong acceleration of nuclei is determined. We find that the most promising case requires laser intensities of 1017–1019 W/cm2 for complete nuclear population transfer. As relevant application, the controlled pumping or release of energy stored in long-lived nuclear states is discussed. [Copyright &y& Elsevier]

Abstract: LASERIX is a high-power laser facility leading to High-repetition-rate XUV laser pumped by Titanium:Sapphire laser. The aim of this laser facility is to offer Soft XRLs in the 30–7nm range and auxiliary IR beam, which could also be used to produce synchronized XUV sources. In this contribution, the main results concerning both the development of XUV sources and their use for applications (irradiation of DNA samples) are presented, as well the present status and some perspectives for LASERIX. [Copyright &y& Elsevier]

The 11th International Surface X-ray and Neutron Scattering (SXNS) Conference was held on July 13-17, 2010, on the Northwestern University (NU) campus, in Evanston, Illinois (http://www.sxns11.northwestern.edu/) and hosted by the NU Materials Research Science and Engineering Center. This biennial conference brought together a community of 164 attendees from 16 countries. The field now makes use of a broad range of new experimental capabilities that have been made possible through the development of increasingly brilliant X-ray and neutron sources around the world, including third generation synchrotron sources, neutron reactor and spallation sources, as well as the recent development of X-ray lasers. [ABSTRACT FROM AUTHOR]

An overview of recent advances in applications of currently the most energetic X-ray laser at 21 nm is given. The unique parameters of this half-cavity based X-ray laser such as record output energy of 10 mJ, highly symmetric beam, robustness and reproducibility, have made it possible to carry out a number of multidisciplinary scientific projects featuring novel applications of intense coherent X-ray radiation. Selected results obtained in these experiments are reviewed, including X-ray laser probing of dense plasmas, measurements of transmission of focused soft X-ray radiation at intensities of up to 1012 W cm-2, measurements of infrared laser ablation rates of thin foils, and ablative microstructuring of solids. [ABSTRACT FROM AUTHOR]

Abstract: A low-threshold passively continuous-wave (CW) mode-locked Nd:YVO4 solid-state laser was demonstrated by use of a semiconductor saturable absorber mirror (SESAM). The threshold for continuous-wave mode-locked is relatively low, about 2.15W. The maximum average output power was 2.12W and the optical to optical conversion efficiency was about 32%. The pulse width was about 15ps with the repetition rate of 105MHz. [Copyright &y& Elsevier]

Coulomb corrections to the action function and rate of multiphoton ionization of atoms and ions in a strong linearly polarized electromagnetic field are calculated for high values of the Keldysh adiabaticity parameter. The Coulomb corrections significantly increase the ionization rate for atoms (by several orders of magnitude). An interpolation formula proposed for ionization rate is valid for arbitrary values of the adiabaticity parameter. The high accuracy of the formula is confirmed by comparison with the results of numerical calculations. The general case of elliptic polarization of laser radiation is also considered. [ABSTRACT FROM AUTHOR]

Abstract: We report on gain-saturated operation of the 11.9nm X-ray lasing line in Ni-like Sn using the grazing-incidence pumping scheme (GRIP). The experiments were done with 2-ps duration pump pulses and energies up to 5J. Strong gain saturation with multi-microjoule output was measured for the Sn laser at a grazing angle of 30° and a pump pulse energy of 3J. This was achieved with a 4.5%, 2-ps duration prepulse 2.4ns ahead of the main pulse and also incident at grazing incidence. Increasing laser output was observed at GRIP angles up to 45°. At this angle, the minimum energy required for saturated lasing was determined as ∼2J. [Copyright &y& Elsevier]

We carry out a theoretical investigation to clarify the dynamic property of photo-created nano-sized ferroelectric cluster observed in the paraelectric BaTiO3 as a real time correlation of speckle pattern between two soft X-ray laser pulses, at just above the paraelectric-ferroelectric phase transition temperature. Based on a model with coupled soft X-ray photon and ferroelectric phonon mode, we study the time-dependence of scattering probability by using a perturbative expansion approach. The cluster-associated phonon softening as well as central peak effects are well-reproduced in the phonon spectral function via quantum Monte Carlo simulation. Besides, it is found that the time-dependence of speckle correlation is determined by the relaxation dynamics of ferroelectric clusters. Near the transition point, cluster excitation is stable, leading to a long relaxation time, while at high temperature, cluster structure is subject to the thermal fluctuation, ending up with a short relaxation time. [ABSTRACT FROM AUTHOR]

The resonant driving of nuclear transitions by super-intense X-ray laser fields is studied, considering parameters of upcoming high-frequency coherent light sources. Photoexcitation for a broad range of nuclei initially in the ground state or in a long-lived isomeric state is investigated. The theoretical formalism employed can appropriately account for dipole electric as well as higher multipolarities of the laser-driven nuclear transitions. As an application, we calculate reaction rates for isomer triggering with intense X-ray lasers using realistic parameters for the coherent light source and ion accelerator facilities. A comparison shows that isomer triggering via coupling to the atomic shell is more efficient than via photoexcitation with laser light for the present X-ray laser intensities. [ABSTRACT FROM AUTHOR]

It is shown experimentally that, when the residence time of the lasing mixture in a laser unit increases from 60 to 120 min, the lasing threshold grows and the energy parameters of the laser degrade. The latter effect is associated with impurity gas accumulation. Impurities are found to variously influence the operating characteristics of the lasing media considered in this paper. [ABSTRACT FROM AUTHOR]

Abstract: We have modelled an experiment performed at the LULI facility (Ecole Polytechnique, Palaiseau, France). This experiment was devoted to the measurement of the temporal coherence of the transient Ni-like silver X-ray laser at the wavelength of 13.9nm. In population kinetics studies of saturated lasers, it is necessary to account for the interaction between the X-ray laser electric field and the lasing ions. To this end, we have used the Maxwell–Bloch formalism in the paraxial approximation. The Zeeman sublevels (JM) associated with the lower lasing level (J =1) are not identically affected by the X-ray laser field. As a result, their populations are different. However, elastic collisions between free electrons and lasing ions have the opposite effect: they tend to restore equilibrium between the sublevel populations. Therefore, elastic collision rates obtained in the distorted wave approximation have been included in the rate equations. Refraction of the X-ray beam, due to electron density gradients, is taken into account by using a ray-trace code which works as a post-processor of the hydro-code EHYBRID. We have checked that the Voigt profile is a good approximation for lasing lines in Ni-like ions. This allowed us to implement a subroutine calculating the Voigt profile in the Maxwell–Bloch code. Whilst the FWHM of the spontaneous emission profile is 12mÅ, the amplified X-ray line shows a smaller width of ∼3mÅ. This is known as the gain narrowing effect. We notice the saturation of the line-width for a propagation length of 2–3mm. Comparison with experiment is discussed. [Copyright &y& Elsevier]

We report the output characteristics of a saturated capillary discharge 46.9?nm Ne-like Ar soft x-ray laser obtained with relatively low main discharge current of less than 20?kA, with the lowest being 9?kA. The 20?cm long and 3?mm diameter alumina capillary channel was filled with argon in the region 0.1-0.4?mbar and was driven by a current pulse with a quarter-cycle duration of about 40?ns. The laser pulse duration generated was about 1.3?ns, with a gain coefficient of 1.2?cm?1. [ABSTRACT FROM AUTHOR]

The amount and distribution of energy deposition in the cylindrical cells of nuclear-pumped lasers excited by products of the 3He( n, p)3H nuclear reaction are investigated theoretically. Calculation results for three neutron energy distributions, as well as the energy deposition distributions inside the laser cell at helium-3 initial pressures of 1 and 2 atm, are presented. [ABSTRACT FROM AUTHOR]

We discuss the demonstration of gain-saturated high repetition rate table-top soft X-ray lasers producing microwatt average powers at wavelengths ranging from 13.9 to 33 nm. The results were obtained heating a precreated plasma with a picosecond optical laser pulse impinging at grazing incidence onto a precreated plasma. This pumping geometry increases the energy deposition efficiency of the pump beam into the gain region, making it possible to saturate soft X-ray lasers in this wavelength range with a short pulse pump energy of only 1 J at 800-nm wavelength. Results corresponding to 5-Hz repetition rate operation of gain-saturated 14.7-nm Ni-like Pd and 32.6-nm line Ne-like Ti lasers pumped by a table-top Ti:sapphire laser are reported. We also discuss results obtained using a 1 ω1054-nm prepulse and 2 ω527-nm short pulse from a Nd:glass pump laser. This work demonstrates the feasibility of producing compact high average power soft X-ray lasers for applications. [ABSTRACT FROM AUTHOR]

Using the fully relativistic version of the Korringa–Kohn–Rostoker method for electronic structure calculations within local spin density functional theory, the magnetic and spectroscopic properties of Co clusters deposited on Pt(111) have been investigated. Of central interest was the role of spin–orbit coupling, since it influences the spontaneous formation and orientation of magnetic moments and gives rise among other things to the occurrence of orbital magnetic moments, magnetic anisotropy energy and magnetic circular dichroism in X-ray absorption. The results have been complemented by calculations of the exchange coupling parameters Jij used within Monte Carlo simulations on the basis of the extended classical Heisenberg Hamiltonian. This allowed us to simulate the magnetic properties at finite temperatures, which are of central importance for applications. [ABSTRACT FROM AUTHOR]

A nonstationary gasdynamic model of sealed laser and luminescent cells pumped by uranium fission fragments is developed. This model extends the earlier 1D model of gas dynamics in cells of flat geometry to the case of cells with buffer volumes and allows analysis of gasdynamic processes for the energy deposition step distribution over the laser cell length. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Plasma conditions for the Ni-like Ag, Cd, In, Sn, Sb X-ray lasers and the Ne-like Fe, Co, Ni, Cu, Zn X-ray lasers are studied, using a one-dimensional hydrodynamic code. The results suggest that the main hydrodynamic characteristics and plasma conditions of these Ni-like X-ray lasers and their corresponding partner Ne-like X-ray lasers are similar. This similarity enables us to predict the performance of some Ni-like X-ray lasers using rather simple simulations of their partner Ne-like X-ray lasers. [ABSTRACT FROM AUTHOR]

Recent advances in accelerator, laser, and undulator technology have created the possibility of constructing a national user facility based on an intense free-electron laser at extreme ultraviolet and X-ray wavelengths. MIT is exploring the construction of such a facility at its Bates Laboratory site, 20 miles north of Cambridge. The science that is foreseen spans many disciplines including atomic and fundamental physics, condensed matter physics and materials sciences, femtochemistry, structural biology, and various fields of engineering. The source we propose, and the experimental methods it will spawn, will generally be qualitatively new and have high impact in many fields of science and technology. The strength of the science and technology base in the northeast region, and in particular at MIT, make this a superb location for such a national user facility. [Copyright &y& Elsevier]

The Ni-like Ag x-ray laser at 13.9 nm (4d→4p, J=0→1) is numerically studied, using a one-dimensional hydrodynamic code coupled with an atomic physics code. The effects of the drive laser intensity, pulse duration, and delay time on the performance of the Ni-like Ag x-ray laser are investigated. A saturated x-ray laser output could possibly be generated for a short plasma length under the optimized drive pulse configuration. The analysis of the plasma conditions, including the evolution of gain in time and space, the electron temperature and the electron density, contribute to further understanding of the process of Ni-like x-ray lasers. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The distribution of the two-dimensional gas velocity inside ion-irradiated laser cells is considered for low ion energy deposits into the gas. It is shown that, if the energy deposit is smoothly nonuniform, the twodimensional motion has two quasi-one-dimensional components: the longitudinal gas velocity is practically uniform across the cell and depends on the transversely averaged energy deposit, while the transverse velocity component depends on the difference between the local energy deposit and energy deposit averaged over the transverse direction. [ABSTRACT FROM AUTHOR]

A general method of calculating the energy deposition by fission fragments in nuclear-pumped lasers is presented. A specific case of a cylindrical cell is considered. [ABSTRACT FROM AUTHOR]

Optical nonuniformities in the nuclear-pumped gas lasers are calculated. The nonuniformities are formed due to inhomogeneous energy deposition by the fission fragments from thin plane uranium layers that irradiate the laser active gas. The results of calculations agree with experimental data. [ABSTRACT FROM AUTHOR]

Demonstrates optically pumped lasers with active layers of indirect-gap of aluminum (Al)[subx]gallium(Ga[sub1-x]arsenic(As) operating up to room temperature. Measurement of emission wavelength at 609nm and 20K and 639nm at 300k respectively; Indication of a weak sensitivity on the lattice temperature of the laser threshold; Determination of the parameters of the electron-hole plasma with the use of gain spectroscopy.

We report far-field profile measurements of an optical-field-ionized high-order harmonic-seeded soft x-ray laser. We show that the beam transverse profile can be controlled between a regular Gaussian shape and a Bessel profile exhibiting several rings via the infrared laser pump intensity. These experimental data are supported by a complete numerical modeling including a two-dimensional plasma amplifier simulation and a two-level soft x-ray amplification using a Maxwell-Bloch treatment. This model takes into account the experimental high-order harmonic wavefront and intensity before it is numerically amplified. [ABSTRACT FROM AUTHOR]

A highly coherent 13.9 nm x-ray laser (XRL) is generated under an oscillator-amplifier configuration using a new tape target system and a driver laser system with a 0.1 Hz repetition rate. The output energy is comparable to the XRL generated with a silver-deposited slab target, and the pointing stability using the new tape target system is better than conventional slab targets. [ABSTRACT FROM AUTHOR]

The influence of the temperature of an active medium on the output characteristics of a directly nuclear-pumped laser on atomic transitions in xenon has been studied. It is shown that the quenching of generation before reaching a maximum of the pumping neutron flux is caused primarily by the temperature dependence of the reaction rate constant for the dissociation of heteronuclear ArXe+ ions upon collisions with buffer gas atoms. [ABSTRACT FROM AUTHOR]

An efficient, widely tunable, narrow-bandwidth, green-pumped, noncritical phase-matched lithium triborate based optical parametric oscillator (OPO) is applied to coherent anti-Stokes Raman scattering (CARS) spectroscopy and microscopy. The tunable signal beam (740–930 nm) of the OPO is combined with the fundamental of a Nd:YVO4 pump laser (1064 nm, 15 ps) to obtain high resolution vibrational spectra of molecules around the CH vibrational stretch (2700–3100 cm-1). The straightforward and convenient tunability of the OPO is demonstrated by CARS microscopy for the identification of different polymer microparticles on the same substrate. [ABSTRACT FROM AUTHOR]

Abstract: We are developing a cryogenic bolometer to measure the total energy of the linear coherent light source (LCLS) free electron X-ray laser to be built at the Stanford Linear Accelerator Center. The laser will produce ultrabright X-ray pulses in the energy range between 0.8 and 8keV with ∼1012 photons per ∼200fs pulse at a repeat interval of 8ms, and will be accompanied by a halo of spontaneous undulator radiation. The bolometer is designed to determine the total energy of each laser pulse to within <0.1%, taking into account thermal and mechanical stress to prevent melting in the LCLS beam due to its high energy density. We propose to use a magnetoresistive Nd(1− x )Sr x MnO3 sensor array at the metal–insulator transition, where the composition x is adjusted to produce the desired transition temperature. We discuss design considerations and material choices, and present numerical simulations of the thermal response. [Copyright &y& Elsevier]

Time-resolved x-ray photoelectron spectroscopy is used to probe the nonsteady-state evolution of the valence band electronic structure of laser heated ultrathin (50 nm) copper. A metastable phase is studied using a 527 nm wavelength 400 fs laser pulse containing 0.1–2.5 mJ laser energy focused in a large 500×700 μm2 spot to create heated conditions of 0.07–1.8×1012 W cm-2 intensity. Valence band photoemission spectra are presented showing the changing occupancy of the Cu 3d level with heating are presented. These picosecond x-ray laser induced time-resolved photoemission spectra of laser-heated ultrathin Cu foil show dynamic changes in the electronic structure. The ultrafast nature of this technique lends itself to true single-state measurements of shocked and heated materials. [ABSTRACT FROM AUTHOR]