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For experimental campaigns on the National Ignition Facility (NIF) to be successful, they must obtain useful data without causing unacceptable impact on the facility. Of particular concern is excessive damage to optics and diagnostic components. There are 192 fused silica main debris shields (MDS) exposed to the potentially hostile target chamber environment on each shot. Damage in these optics results either from the interaction of laser light with contamination and pre-existing imperfections on the optic surface or from the impact of shrapnel fragments. Mitigation of this second damage source is possible by identifying shrapnel sources and shielding optics from them. It was recently demonstrated that the addition of 1.1-mm thick borosilicate disposable debris shields (DDS) blocks the majority of debris and shrapnel fragments from reaching the relatively expensive MDS's. However, DDS's cannot stop large, fast moving fragments. We have experimentally demonstrated one shrapnel mitigation technique showing that it is possible to direct fast moving fragments by changing the source orientation, in this case a Ta pinhole array. Another mitigation method is to change the source material to one that produces smaller fragments. Simulations and validating experiments are necessary to determine which fragments can penetrate or break 1-3 mm thick DDS's. Three-dimensional modeling of complex target-diagnostic configurations is necessary to predict the size, velocity, and spatial distribution of shrapnel fragments. The tools we are developing will be used to assure that all NIF experimental campaigns meet the requirements on allowed level of debris and shrapnel generation.

Deposition of maximum laser energy into a small, high-Z enclosure in a short laser pulse creates a hot environment. Such targets were recently included in an experimental campaign using the first four of the 192 beams of the National Ignition Facility [J. A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Technology 26, 755 (1994)], under construction at the University of California Lawrence Livermore National Laboratory. These targets demonstrate good laser coupling, reaching a radiation temperature of 340 eV. In addition, the Raman backscatter spectrum contains features consistent with Brillouin backscatter of Raman forward scatter [A. B. Langdon and D. E. Hinkel, Physical Review Letters 89, 015003 (2002)]. Also, NIF Early Light diagnostics indicate that 20% of the direct backscatter from these reduced-scale targets is in the polarization orthogonal to that of the incident light.

An experimental campaign to maximize radiation drive in small-scale hohlraums has been carried out at the National Ignition Facility (NIF) at the Lawerence Livermore National Laboratory (Livermore, CA, USA) and at the OMEGA laser at the Laboratory for Laser Energetics (Rochester, NY, USA). The small-scale hohlraums, laser energy, laser pulse, and diagnostics were similar at both facilities but the geometries were very different. The NIF experiments used on-axis laser beams whereas the OMEGA experiments used 19 beams in three beam cones. In the cases when the lasers coupled well and produced similar radiation drive, images of x-ray burnthrough and laser deposition indicate the pattern of plasma filling is very different.

The production of supersonic jets of material via the interaction of a strong shock wave with a spatially localized density perturbation is a common feature of inertial confinement fusion and astrophysics. The spatial structure and mass evolution of supersonic jets has previously been investigated in detail [J. M. Foster et. al, Phys. Plasmas 9, 2251 (2002) and B. E. Blue et. al, Phys. Plasmas 12, 056312 (2005)]. In this paper, the results from the first series of hydrodynamic experiments will be presented in which the mass distribution within the jet was quantified. In these experiments, two of the first four beams of NIF are used to drive a 40 Mbar shock wave into millimeter scale aluminum targets backed by 100 mg/cc carbon aerogel foam. The remaining beams are delayed in time and are used to provide a point-projection x-ray backlighter source for diagnosing the structure of the jet. Comparisons between data and simulations using several codes are presented.

We have recently implemented polarization smoothing (PS) on one quad of the NIF laser. Specially cut KDP and DKDP crystals at 420 x 420 mm sizes were used to scramble the incident 351 nm laser polarization over the beam aperture. The intensity contrast deduced from the measured focal spot images for one of the NIF beams is in very good agreement with the expected contrast. KDP and DKDP crystals are known to produce considerable amount of transverse stimulated Raman scattering (SRS) when irradiated with large beams at ∼1-2 GW/cm2. In order to measure the transverse SRS, we attached optical fibers on the side of one of the PS crystals. The KDP PS crystal showed >1 J/cm2side scattered SRS at irradiances of 1.2 GW/cm2. The DKDP (70% deuteration level) PS crystal showed significantly less SRS. Detailed analysis of the SRS scattering in the PS crystal is in progress.

AbstractThe possibility of imploding small capsules to produce mini-fusion explosions was explored soon after the first thermonuclear explosions in the early 1950s. Various technologies have been pursued to achieve the focused power and energy required for laboratory-scale fusion. Each technology has its own challenges. For example, electron and ion beams can deliver the large amounts of energy but must contend with Coulomb repulsion forces that make focusing these beams a daunting challenge. The demonstration of the first laser in 1960 provided a new option. Energy from laser beams can be focused and deposited within a small volume; the challenge became whether a practical laser system can be constructed that delivers the power and energy required while meeting all other demands for achieving a high-density, symmetric implosion. The National Ignition Facility (NIF) is the laser designed and built to meet the challenges for study of high-energy-density physics and inertial confinement fusion (ICF) implosions. This paper describes the architecture, systems, and subsystems of NIF. It describes how they partner with each other to meet these new, complex demands and describes how laser science and technology were woven together to bring NIF into reality.

AbstractAfter every other failure mode has been considered, in the end, the high-performance limit of all lasers is set by optical damage. The demands of inertial confinement fusion (ICF) pushed lasers designed as ICF drivers into this limit from their very earliest days. The first ICF lasers were small, and their pulses were short. Their goal was to provide as much power to the target as possible. Typically, they faced damage due to high intensity on their optics. As requests for higher laser energy, longer pulse lengths, and better symmetry appeared, new kinds of damage also emerged, some of them anticipated and others unexpected. This paper will discuss the various types of damage to large optics that had to be considered, avoided to the extent possible, or otherwise managed as the National Ignition Facility (NIF) laser was designed, fabricated, and brought into operation. It has been possible for NIF to meet its requirements because of the experience gained in previous ICF systems and because NIF designers have continued to be able to avoid or manage new damage situations as they have appeared.

Time resolved hard x-ray images (hv> 9 keV) and time integrated hard x-ray spectra (hv= 18-150 keV) from vacuum hohlraums irradiated with four 351 nm wavelength NIF laser beams are presented as a function of hohlraum size and laser power and duration. The hard x-ray images and spectra provide insight into the time evolution of the hohlraum plasma filling and the production of hot electrons. The fraction of laser energy detected as hot electrons (f$_{\rm hot})$shows correlation with both laser intensity and with an analytic plasma filling model.

A single beamline of the National Ignition Facility (NIF) has been operated at a wavelength of 526.5 nm (2ω) by frequency converting the fundamental 1053 nm (1ω) wavelength with an 18.2 mm thick type-I potassium dihydrogen phosphate (KDP) second-harmonic generator (SHG) crystal. Second-harmonic energies of up to 17.9 kJ were measured at the final optics focal plane with a conversion efficiency of 82%. For a similarly configured 192-beam NIF, this scales to a total 2ω energy of 3.4 MJ full NIF equivalent (FNE).

The National Ignition Facility (NIF) is the world's largest laser system. It contains a 192 beam neodymium glass laser that is designed to deliver 1.8 MJ at 500 TW at 351 nm in order to achieve energy gain (ignition) in a deuterium-tritium nuclear fusion target. To meet this goal, laser design criteria include the ability to generate pulses of up to 1.8 MJ total energy, with peak power of 500 TW and temporal pulse shapes spanning 2 orders of magnitude at the third harmonic (351 nm or 3ω) of the laser wavelength. The focal-spot fluence distribution of these pulses is carefully controlled, through a combination of special optics in the 1ω (1053 nm) portion of the laser (continuous phase plates), smoothing by spectral dispersion, and the overlapping of multiple beams with orthogonal polarization (polarization smoothing). We report performance qualification tests of the first eight beams of the NIF laser. Measurements are reported at both 1ω and 3ω, both with and without focal-spot conditioning. When scaled to full 192 beam operation, these results demonstrate, to the best of our knowledge for the first time, that the NIF will meet its laser performance design criteria, and that the NIF can simultaneously meet the temporal pulse shaping, focal-spot conditioning, and peak power requirements for two candidate indirect drive ignition designs.

It is shown that the strengths and periodicities of charge and spin density waves in the organic charge-transfer solids depend very strongly on the degree of charge transfer ρ. We thereby explain both the appearance of the 4kF-, charge density wave near ρ = 0.5 and its nonexistence for ρ ≳ 0.6, while for ρ slightly larger (but not smaller) than 0.5 we predict a new kind of Coulomb-induced defect.

We describe an experiment in which the statistical properties of speckle are modified reproducibly through the use of the electro-optic effect in a birefringent liquid crystal. By adjustment of the voltage applied to a specifically designed liquid-crystal cell, the correlation between the ordinary and the extraordinary waves (which are orthogonally polarized) is varied from almost complete correlation to almost complete decorrelation. The correlation’s statistics vary smoothly between the limits of single-speckle-pattern statistics (complete correlation) and the statistics for the intensity addition of two uncorrelated speckle patterns (complete decorrelation). The combined speckle pattern is observed and compared with theory.

50% ethanolic extract of seeds of forty plant species were tested for their fungitoxicity against Aspergillus niger and Absidia ramosa. Only the seed extract of Pimpinella diversifolia showed absolute toxicity against both the test organisms, inhibiting the mycelial growth completely. The maximum inhibitory dilution (MID) was found to be 1:10and 1:50 (w/v) againstA niger and A. ramosa respectively. The extract showed fungistatic effect against A. niger but fungicidal to A. ramosa at the respective maximum inhibitory dilutions. Further the extract exhibited a broad fungitoxic spectrum. Autoclaving was found to have adverse effect on the fungitoxicity of the extract but temperature (100°C) and storage (12 months) did not affect the toxicity.

On assaying different parts of Iberis amara L. (Cruciferae) for their fungitoxicity against Hel-minthosporium oryzae, flowers and seeds were found to possess strong toxicity. Seed extract was found to be fungicidal at the minimum inhibitory concentration (2%), remained active up to 35 days, and exhibited a broad range of activity and non-phytotoxicity. The fungitoxicity of the seeds was thermostable up to 120°C, remained active up to 9 months at room temperature but declined on autoclaving.

A statistical theory is presented of the dependence of Raman amplification in a dispersive medium on the cross correlation of the pump and the Stokes input. Both forward and backward amplification of broadband Stokes radiation by a broadband pump are considered. It is shown that group-velocity dispersion reduces the gain enhancement that is observed when the pump and the Stokes input are correlated. The curve for the gain enhancement versus the relative time delay (advance) of the two waves becomes asymmetric and broader than it would in the absence of dispersion. For typical parameters the lack of perfect correlation between the Stokes output from a Raman generator and the pump reduces the gain enhancement in a cascaded Raman amplifier by only a few percent.

A microscopic mechanism of optical nonlinearity in π-conjugated polymers is presented. It is shown that the bulk of the nonlinearity is determined by only two well defined channels, even though an infinite number of channels are possible in principle. The above conclusion is true for both short and long range Coulomb interactions. The complete frequency dependence of the third harmonic generation in both trans-polyacetylene and polydiacetylene are explained within the same theoretical picture.

We discuss the design and fabrication of 80-cm-diameter random phase plates for target-plane beam smoothing on the Nova laser. Random phase plates have been used in a variety of inertial confinement fusion target experiments, such as studying direct-drive hydrodynamic stability and producing spatially smooth x-ray backlighting sources. These phase plates were produced by using a novel sol-gel dip-coating technique developed by us. The sol-gel phase plates have a high optical damage threshold at the second- and third-harmonic wavelengths of the Nd:glass laser and have excellent optical performance.

This communication describes the immunochemical and biochemical characterization of three polypeptide chains, alpha 1(IV)130K, alpha 1(IV)110K, and alpha 1(IV)75K belonging to the alpha 1(IV) chain of basement membrane collagen isolated from a pepsin digest of bovine kidney cortices. From the CNBr digests of the mixture of these chain fragments three peptides, a major and two minor peptides with an apparent Mr = 32,000, 24,000 and 13,000, respectively, were purified and characterized. The data presented show that CNBr peptides 24K and 13K are generated from CNBr peptide 32K by pepsin cleavage in the native molecule at the NH2-terminal end. Antisera were raised in rabbits against peptide CB32K. Inhibition assays using enzyme-linked immunoadsorbant assays (ELISA) showed cross-reactivity with alpha 1(IV)130K, alpha 1(IV)110K and alpha 1(IV)75K fragments. Peptides CB24K and 13K also inhibited the antiserum. Antiserum was not active when tested against alpha 1(IV)95K, alpha 1(IV)55K, alpha 2(IV)120K, and alpha 2(IV)95K fragments as inhibitors. These studies provide further evidence that alpha 1(IV)130K, 110K, and 75K are derived from the same parent chain. The pepsin cleavage sites resulting in the formation of these fragments and their internal alignment are described.

The C-terminal peptic fragment P1 (about 518 amino acid residues) of bovine lens-capsule collagen alpha 1(IV) chain was cleaved with CNBr and trypsin. The peptides were purified and characterized, allowing their ordering within the P1 fragment by comparison with a corresponding section of mouse collagen alpha 1(IV) chain [Schuppan, Glanville & Timpl (1982) Eur. J. Biochem. 123, 505-512]. About 67% of the sequence of bovine collagen fragment P1 was determined by Edman degradation. Comparison with the sequence of the corresponding mouse collagen fragment P1 showed 76% identity for positions Xaa and Yaa of the triplet structures Gly-Xaa-Yaa. Invariance was found for the positions of two non-triplet interruptions and of 3-hydroxyproline residues, pointing to the functional importance of these structures.

A versatile, rapidly convergent, iterative algorithm is presented for the construction of kinoform phase plates for tailoring the far-field intensity distribution of laser beams. The method consists of repeated Fourier transforming between the near-field and the far-field planes with constraints imposed in each plane. For application to inertial confinement fusion, the converged far-field pattern contains more than 95% of the incident energy inside a desired region and is relatively insensitive to beam aberrations.

An iterative algorithm for constructing fully continuous phase screens for tailoring far-field intensity profiles is presented. The algorithm is robust, stable, and, if run properly, maintains the continuous nature of the phase throughout the iterative process. The iterative procedure is applied to generate continuous phase screens to produce a 12th-power super-Gaussian far-field intensity profile.

While screening 45 samples of pollen suspension for their antifungal activity against Helminthosporium oryzae and Alternaria alternata, only that of Lycopersicon lycopersicum exhibited absolute toxicity against both the pathogens. The maximum inhibitory dilutions were found to be 1: 200 and 1: 500 (w/v) against A. alternata and H. oryzae respectively. The other pollen suspensions exhibited varying degrees of mycotoxicity. The temperature and autoclaving had no adverse effect on the mycotoxicity of the pollen suspension.

During screening of pollen suspensions of 20 species of higher plants against Colletotrichum capsici, Curvularia lunata and Helminthosporium oryzae, only grains of Xanthium strumarium L. inhibited their spore germination completely. Its toxicity did not alter at high temperatures and during autoclaving. However, toxicity was increased when the suspensions stored for 48 h were used. It inhibited 3 out of 11 additional fungi tested at 1: 200 (w/v) dilution during its fungitoxic spectrum.

During a systematic survey of higher plants for their fungitoxicity, the flowers of Rosa chinensis Jacq. were found to exhibit strong antifungal properties. On chemical investigation the antifungal principle was isolated as a shining, needle-shaped crystalline substance. It was identified as gallic acid. It exhibited fungistatic action against as many as 17 fungi at 3% concentration.

During antifungal screening of higher plants, the leaves ofLawsonia inermiswere found to exhibit strong fungitoxicity. On chemical investigation, the antifungal factor was found to be 2-hydroxy-1,4-naphthoquinone (Lawsone). The minimum effective dose against test organism was found to be 1000 ppm. Lawsone was found to exhibit fungicidal activity, wide fungitoxic spectrum and nonphytotoxicity.

Studies on various antifungal properties of the leaf extract ofRanunculus sceleratusL. showed that it was thermostable up to 100°C, retained activity on autoclaving, and remained active up to 15 days at room temperature. It possessed quick fungicidal action, tolerance against heavy fungal inoculum, activity on broad pH range, broad fungicidal spectrum, non-phytotoxicity and non-systemic activity. The extract was lethal at 1∶40 dilution and its volatile vapours were also fungitoxic.

The mechanism of antifungal action of 2-hydroxy-1,4-naphthoquinone (lawsone) isolated from leaves ofLawsonia inermiswas studied. It was found to inhibit nitrate reductase activity in vivo and in vitro. The concentration which inhibited in vivo enzyme activity also reduced ethanol-soluble and ethanol-insoluble nitrogen (protein nitrogen) content in the test organism,Helminthosporium oryzae.