The first stage of the petawatt excimer laser project started at the P.N. Lebedev Physical Institute, implements a development of multiterawatt hybrid GARPUN-MTW laser facility for generation of ultra-high intensity subpicosecond ultraviolet (UV) laser pulses. Under this project, a multi-stage e-beam-pumped 100-J, 100-ns GARPUN KrF laser was upgraded with a femtosecond Ti:Sapphire front-end, to produce combined subpicosecond/nanosecond laser pulses with variable time delay. Attractive possibility to amplify simultaneously short and long pulses in the same large-scale KrF amplifiers is analyzed with regard to the fast-ignition, inertial confinement fusion problem. Detailed description of hybrid laser system is presented with synchronized KrF and Ti:Sapphire master oscillators. Based on gain and absorption measurements at GARPUN amplifier and numerical simulations with a quasi-stationary code, we are predicting that 1.6 J can be obtained in a short pulse at hybrid GARPUN-MTW Ti:Sapphire/KrF laser facility, combined with several tens of joules in nanosecond pulse. Amplified spontaneous emission, which is responsible for the pre-pulse formation on a target, was also investigated: its acceptable level can be provided by properly choosing staged gain or loading the amplifiers by quasi-steady laser radiation. Fluorescence and transient absorption spectra of Ar/Kr/F 2 mixtures conventionally used in KrF amplifiers were recorded to find out the possibility for femtosecond pulse amplification at the broadband Kr 2 F (4 2 G ! 1,2 2 G) transition, which benefits in 100 times higher saturation energy density than for KrF (B ! X) transition.
This is a theoretical study of argon plasma under conditions, where Ne- and Na-like ionization stages are dominant. Balance equations are generalized to treat 37 3l states of Ne-like ion and 37 adjacent series of Rydberg states of Na-like ion simultaneously. This allows us to include in the kinetics a diffusion-like motion of the state of the system "Ne-like ion plus one electron" through the multitude of excited levels spread over an energy region of 50 eV. The populations Ni - i (i = (1, ..., 37)) of the Ne-like ion states are introduced explicitly; those of adjacent 37 Rydberg series are accounted for through continuous functions Ni(ε). These functions describe the population distribution within each Rydberg series dependent on the Rydberg electron enegy ε. The elementary processes of the collisionalradiative model connecting all Ne- and Na-like states, as well as processes of redistribution of populations inside each Rydberg series, are accounted for. The rate coefficients for all processes within the Ne-like residue have been calculated previously, using a detailed many-body relativistic theory. The dielectric capture cross sections and autoionization probabilities are presented as analytical continuation of the collisional excitation cross sections. The excited-excited states transitions are included. The rest of the processes are treated in a simple semiclassical approximation. The Lotz formula is generalized by unambiguous analytical continuation to cover the case of bound-bound transitions between Rydberg states of Na-like ions. The radiation reabsorption in a long plasma cylinder is included through Biberman-Holstein coefficients for all transitions. The inclusion of Na-like states, accounting for diffusion-like processes, increases the population inversion for the "lasing candidates" by at least a factor of two for a wide range of plasma conditions. This is important for the ionization equilibrium too. Besides, the functions Ni(ε) bear diagnostic information. Detailed calculations have been done for the homogeneous steady-state Maxwellian plasma. The role of transient processes in the population inversion creation is under discussion.
The conventional model of a cermet in the dielectric regime-metallic islands in a dielectric matrix-is shown to be inapplicable to cermets made by the authors by sputtering Pt-Si02 composites in an Ar-02 plasma. A significant proportion of the metal is incorporated into the dielectric matrix, and the compositional fluctuations appear to be much more gradual than is consistent with the conventional metal island model. Further evidence in support of this interpretation is given by the AC properties of the Pt-Si02 cermet films. t Present address:
Soil, tree stems, and ecosystem carbon dioxide fluxes were measured by chambers and eddy covariance methods in a paludified shallow-peat spruce forest in the southern taiga of European Russia (Tver region, 56 • N 33 • E) during the growing seasons of 2002-2012. The site was established in 1998 as part of the EUROSIBERIAN CARBONFLUX project, an international field experiment examining atmosphere-biosphere interaction in Siberia and European Russia. In all years the observed annual cumulative net ecosystem flux was positive (the forest was a source of carbon to the atmosphere). Soil and tree stem respiration was a significant part of the total ecosystem respiration (ER) in this paludified shallow-peat spruce forest. On average, 49% of the ER came from soil respiration. We found that the soil fluxes exhibited high seasonal variability, ranging from 0.7 to 10 µmol m −2 s −1 . Generally, the soil respiration depended on the soil temperature and ground water level. In drought conditions, the soil respiration was low and did not depend on temperature. The stem respiration of spruces grew intensively in May, had permanently high values from June to the end of September, and in October it dramatically decreased. The tree stem respiration in midsummer was about 3-5 µmol m −2 s −1 for dominant trees and about 1-2 µmol m −2 s −1 for subdominant trees. The respiration of living tree stems was about 10-20% of the ER.
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