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Solid-density plasmas driven by intense x-ray free-electron laser (XFEL) radiation are seeded by sources of non-thermal photoelectrons and Auger electrons that ionize and heat the target via collisions. Simulation codes that are commonly used to model such plasmas, such as collisional-radiative (CR) codes, typically assume a Maxwellian distribution and thus instantaneous thermalization of the source electrons. In this study, we present a detailed description and initial applications of a collisional particle-in-cell code, PICLS, that has been extended with a self-consistent radiation transport model and Monte-Carlo models for photoionization and KLL Auger ionization, enabling the fully kinetic simulation of XFEL-driven plasmas. The code is used to simulate two experiments previously performed at the Linac Coherent Light Source investigating XFEL-driven solid-density Al plasmas. It is shown that PICLS-simulated pulse transmissions using the Ecker-Kr\"oll continuum-lowering model agree much better with measurements than do simulations using the Stewart-Pyatt model. Good quantitative agreement is also found between the time-dependent PICLS results and those of analogous simulations by the CR code SCFLY, which was used in the analysis of the experiments to accurately reproduce the observed K{\alpha} emissions and pulse transmissions. Finally, it is shown that the effects of the non-thermal electrons are negligible for the conditions of the particular experiments under investigation., Comment: 12 pages, 11 figures

The effect of sheared flows on the m = 0 instability development in a z-pinch is numerically investigated using a 2D magnetohydrodynamic (MHD) code. The behavior of both internal and free-boundary modes is studied by using two types of initial configurations: a diffuse Bennett equilibrium and a free-boundary parabolic equilibrium. It was found that sheared flows change the m = 0 development by reducing the linear growth rates, decreasing the saturation amplitude, and modifying the instability spectrum. Full stability can be obtained for supersonic plasma flows, but a larger shear is needed to obtain stabilization of free-boundary modes.

The synthesis and thermotropic properties are reported for a series of hexaalkoxytriphenylenes that contain an amide, urea or thiourea group in one of their alkoxy tails. The intermolecular hydrogen bonding abilities of these molecules have a disturbing influence on the formation and stability of the columnar liquid crystalline phases. The stronger the hydrogen bonding the more the liquid crystallinity is suppressed, probably due to disturbance of the π–π stacking of the triphenylene discs. As a direct result, urea‐ and amide‐containing triphenylene derivatives are not liquid crystalline, but several thiourea derivatives show hexagonal columnar mesophases. *Present address: Avantium Technologies BV, Zekeringstraat 29, 1014 BV Amsterdam, The Netherlands. **Present address: Delft University of Technology, TUD DelftChemTech, The Netherlands. ***Corresponding author. Email: Ton.Marcelis@wur.nl

A 1,3,5-benzenetrisamide with three pending hexaalkoxytriphenylene groups has been synthesized as an example of an interesting class of intermolecular H-bond-stabilized columnar discotic liquid crystalline materials. The material forms a plastic hexagonal discotic phase that does not crystallize on cooling from the isotropic phase, even after annealing for a few days at room temperature. X-ray and computational studies provide a detailed model for the organization of this material. The charge carrier mobility, 0.12 cm2 V-1 s-1 at 180 °C, is the highest ever reported for liquid crystalline triphenylene systems, and even increases with temperature. The factors responsible for this behavior are discussed.

The dynamics and phase behavior of the discotic liquid crystalline compound hexahexyloxytriphenylene (HAT6) and a derivative were studied by broad-band dielectric spectroscopy, differential scanning calorimetry, X-ray diffraction and optical microscopy. While the pristine compound HAT6 forms both a columnar mesophase (Colh) and a plastic crystal phase, no liquid crystallinity was observed for the highly asymmetric compound HAT6-C10Br. This paper focuses on the dielectric relaxations in the plastic crystal phase. For HAT6-C10Br, a 'high temperature' glass transition, manifested by a Vogel-Fulcher-Tammann (VFT) type α2-process, was found at -31 °C that was assigned to the columnar glass transition in accordance with previous literature. The main result of our study is the observation of a second, low-temperature VFT process (α1) for both compounds, which indicates co-operative liquid dynamics within the framework of the plastic crystal order at temperatures as low as -100 °C. Comparison of these fast dynamics with relaxation data from polyethylene and polymer series with long alkyl groups identifies this process as a 'hindered' polyethylene-like dynamic glass transition that originates from the nanophase-separated, spatially confined fraction of aliphatic tails. © 2005 Elsevier B.V. All rights reserved. ispartof: JOURNAL OF NON-CRYSTALLINE SOLIDS vol:351 issue:33-36 pages:2622-2628 ispartof: location:NETHERLANDS, Delft status: published

The synthesis and phase behaviour of a new series of unsymmetrically substituted hexaalkoxytriphenylene¿based liquid crystals are reported. One of the hexyloxy chains in hexahexyloxytriphenylene (HAT6) is replaced by either a shorter or a longer chain, HAT¿(OC 6 H 13 ) 5 (OC n H 2 n +1 ). Compounds with chain lengths n of 2¿14, 16 and 18 were prepared and investigated. Compounds with n ¿13 were not liquid crystalline. For all compounds with n ¿12 Col h textures were observed by polarizing microscopy. X¿ray investigations showed that the intercolumnar distance gradually increased with n from n = 2 to n = 12, while the interdisk distance (3.6 Å) remained constant. A small odd¿even effect on the increase of the intercolumn distance with n was observed. This effect was also found in the change of ¿ H of isotropization with n

In this study, the binary phase diagram of two triphenylene derivatives is investigated by using differential scanning calorimetry (DSC), optical polarizing microscopy (OPM), and wide-angle x-ray scattering (WAXS). The triphenylene derivatives studied are based on hexa-alklyoxy-triphenylene. One compound in the binary mixture HAT6 has six symmetrical hexyloxy tails each containing six carbon atoms. The other compound, HAT6-C10UC6, has one asymmetrical tail bearing a urea functionality at a specific distance from the aromatic core. The introduction of this asymmetrical H-bonding unit into the structure results in a complete disruption of liquid crystallinity while a “pseudo re-entrant” phenomenon is observed in the binary mixture phase diagram.

The paper presents the synthesis and thermal behavior of some copolyethers containing a hexamethylenic spacer. The polymers were obtained using a phase transfer catalysis technique, starting from 1,6-dichlorohexane and various bisphenols as follows: 4,4′-dihydroxyazobenzene (DHAB), 4,4′-dihydroxydiphenyl (DHD), bisphenol A (BPA), 2,7-dihydroxynaphtyl (DN) and 4-hydroxydiphenyl sulfide (BPS). The synthesized polyethers have low molecular weights, being situated in the oligomeric domain. The polymers were characterized by 1H-NMR spectroscopy, DSC calorimetry and optical microscopy in polarized light. Only the polyethers containing DHAB, DHD and BPA units exhibited liquid crystalline phase. All liquid crystalline oligomers evidenced enantiotropic behavior.

The thermal behavior of mixtures of bis(4-maleimidophenyl) (A) with bis(4-isomaleimidophenyl)methane (C) and their mixture with 4,4′-diaminodiphenyl methane (D) were investigated by differential scanning calorimetry. The study of the binary system A/C in different proportions led us to determine an eutectic mixture at a molar fraction of C in the range of 0.7–0.9. The ternary ACD mixtures showed themselves able to participate in three principal reactions: polyaddition, ring-opening addition, and homopolymerization. In each mixture studied the addition of diamine changed the melting point and maximum polymerization temperatures in the sense of a general decrease. The properties of the networks were studied by thermal analysis and through evaluation of water absorption. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3547–3556, 2003

Since 2011, Romania has faced an HIV outbreak among injecting drug users (IDUs). Our aim was to identify and describe clinical and epidemiological patterns of this outbreak. A cross-sectional study enrolled 138 IDUs diagnosed with HIV infection between 2011 and 2013 with 58 sexually infected individuals included as the control group. The IDUs had a long history of heroin abuse (10 years) and a recent history of new psychostimulant injection (3-4 years). Classical epidemiological data and molecular techniques were used to describe the transmission dynamics. A high prevalence of hepatitis C virus (HCV) coinfection was noted (98.6%) compared to the control group (10.3%) (p

A systematic study of the linear stage of sheared flow stabilization of Z-pinch plasmas based on the Hall fluid model with equilibrium that contains sheared flow and an axial magnetic field is presented. In the study we begin with the derivation of a general set of equations that permits the evaluation of the combined effect of sheared flow and axial magnetic field on the development of the azimuthal mode number m=0 sausage and m=1 kink magnetohydrodynamic (MHD) instabilities, with the Hall term included in the model. The incorporation of sheared flow, axial magnetic field, and the Hall term allows the Z-pinch system to be taken away from the region in parameter space where ideal MHD is applicable to a regime where nonideal effects tend to govern stability. The problem is then treated numerically by following the linear development in time of an initial perturbation. The numerical results for linear growth rates as a function of axial sheared flow, an axial magnetic field, and the Hall term are reported.

The x-ray laser-matter interaction for a low-$Z$ material, carbon, is studied with a particle-in-cell code that solves the photoionization and x-ray transport self-consistently. Photoionization is the dominant absorption mechanism and nonthermal photoelectrons are produced with energy near the x-ray photon energy. The photoelectrons ionize the target rapidly via collisional impact ionization and field ionization, producing a hot plasma column behind the laser pulse. The radial size of the heated region becomes larger than the laser spot size due to the kinetic nature of the photoelectrons. The plasma can have a temperature of more than 10 000 K ($g1\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$), an energy density greater than ${10}^{4}$ $\mathrm{J}/{\mathrm{cm}}^{3}$, an ion-ion Coulomb coupling parameter $\ensuremath{\Gamma}\ensuremath{\ge}1$, and electron degeneracy $\ensuremath{\Theta}\ensuremath{\ge}1$, i.e., strongly coupled warm dense matter. By increasing the laser intensity, the plasma temperature rises nonlinearly from tens of eV to hundreds of eV, bringing it into the high energy density matter regime. The heating depth and temperature are also controllable by changing the photon energy of the incident laser light.

Miscibility in blends of semicrystalline polymers (poly(ethylene) adipate and poly(tetrahydrofuran)) and liquid crystal cholesteryl palmitate was investigated by means of differential scanning calorimetry and polarizing optical microscopy. Some(concentration-dependent) miscibility was found. A more pronounced miscibility exhibits the polyester-based blends probably due to the similar chemical structure of the two components and stronger interactions between the two components.

Mechanically-driven systems often contain both fast and slowrotating parts. The fastest moving parts determine the simulation timestep size of such systems, which often leads to unacceptable simulationtimes. By separating the model in a slow geometrically nonlinear partand a fast geometrical linear part, simulation times become reasonable.The paper describes how the dynamic influence of the fast rotating partson the slowly moving parts can be derived. A special finite element,modeling the interface between the fast and slow moving parts, isdescribed. An application is presented.

An analysis of stability of rectangular-like galleries or caverns is developed from the point of view of creep, creep failure and short-time failure. The initial stress distribution around the cavern just after excavation is obtained with an exact elastic solution. Further this solution is used in conjunction with an elastic/viscoplastic non-associated constitutive equation to determine first the domains around the excavation where the rock becomes dilatant, where compressible, and where a short-time failure is expected. This constitutive equation is further used to determine the creep of the rock around the opening, and where and when a creep failure is to be expected due to excessive dilatancy. It is shown that the location of the incipient creep failure depends on the stress concentration due to the presence of the ‘corners’, on the possible elongated shape of the cavern, and also to the stress concentration induced by the far field stresses. This location also depends on the internal pressure and on depth, and it can be determined quite accurately. Thus the location of incipient creep damage depends on a variety of parameters and the determination of this exact location is very important, and is described in this paper. It is shown that the evolutive damage is spreading mainly in the direction of minimum far field stresses or in the direction of greater elongation of the cross-section. The same constitutive equation allows us to determine the creep convergence (or divergence) of the walls, where this creep is quite fast and when for the first time the incipient creep failure due to dilatancy is to be expected. This timing depends primarily on the magnitude of octahedral shear stress. The time up to creep failure is shorter if this stress is larger (close to the short-term failure value), but tends towards infinity if the stress is relatively small (close but still above the compressibility/dilatancy boundary). Once the various failure modes are well understood the orientation and magnitude of far field stresses can be determined by this analysis if not known a priori. Also, once the location of losing the stability and that of the volume of rock involved in fast creep and creep failure are determined, one can suggest the optimal design of a support. The way in which the stress variation is influencing the above mentioned problem will be discussed in forthcoming papers. While the authors recognize the importance of the pre-existing rock discontinuities in the overall cavern stability, it was thought that a better understanding of this stability starts from analyzing a rock without such pre-existing discontinuities. The examples are given for rock salt.

The design of large rectangular-like underground caverns in relatively unfractured rock is approached with exact elastic solutions. A study is performed in order to see what would be the optimal shape of the cavern cross section for the purpose of avoiding or reducing the amount of rock subjected to failure and to ensure stability (in the sense that no “fast creep” leading to creep failure is to be expected). In this study, we check how much one has to round off the corners of the cross-section in order to obtain an optimal solution. Three particular cases are examined in some detail: wide rectangular-like caverns, square-like caverns, and tall rectangular-like caverns. Several possible ratios of the far-field stresses and several possible internal applied pressure are considered. The domains around the excavation where the rock becomes dilatant or compressible are very precisely delineated so that one can determine quite accurately where the rock will be damaged by microcracking. Also it is shown where the closure by creep is quite fast and where a “fast creep” failure is to be expected. All these results can be used to estimate the location and amount of the necessary support. Failure on pre-existing discontinuities has not been included in this analysis.

The dynamics of the discotic liquid-crystalline system, hexakis (n-hexyloxy) triphenylene (HAT6), is considered in the frame of the phenomenological model for rate processes proposed by Berlin. It describes the evolution of the system in the presence of the long-time scale correlations in the system, and we compare this with experimental quasielastic neutron scattering of the molecular assembly of HAT6 in the columnar phase. We interpret the parameters of this model in terms of nonextensive thermodynamics in which rare events in the local fast dynamics of some parts of the system control the slower dynamics of the larger molecular entity and lead to a fractional diffusion equation. The importance of these rare local events to the overall dynamics of the system is linked to the entropic index, this being obtained from the data within the model approach. Analysis of the waiting-time dependence from momentum transfer reveals a Levy distribution of jump lengths, which allows us to construct the van Hove correlation function for discotic liquid-crystalline system.

Investigation of the mechanisms of penetration of high-beta plasma flows across the magnetic field is important for numerous applications. These studies are relevant to the physics of z-pinches, space physics (e.g. solar wind), and astrophysics (e.g. supernovae).

Summary form only given. Sheared flows in plasmas can play an important role in reducing the growth of instabilities. Axial sheared flows in cylindrical configurations are especially of interest in studying Z-pinch plasmas with applications to fusion energy and fusion propulsion, as well as in understanding the behavior of astrophysical jets. We use a 2D MHD simulation code (MHRDR) to study the linear and nonlinear development of m=0 modes. In order to allow the modeling of high Mach number plasma flows, the code was modified to include the use of periodic boundary conditions and a Van Leer monotonic advection treatment. The initial equilibrium was initialized either with pure instability modes or with random perturbation modes. The growth, saturation, and mode interaction was studied using FFT analysis. This study extends the linear theory results previously obtained by solving the ideal MHD linearized equations.

Summary form only given. The growth and saturation of the m=0 magnetohydrodynamic (MHD) instability is numerically studied in a cylindrical Bennett equilibrium in the presence of sheared plasma flows with the aid of a 2D MHD code (MHRDR). Using Fourier analysis the amplitude of different axial modes is followed from the linear to the nonlinear regime. Their linear growth is measured and compared to the results obtained by solving the ideal MHD linearized equations and to the results obtained using a 3D hybrid simulation code

The development of z-pinch instabilities in the presence of the Hall term, finite Larmor radius effects (FLR), and axial magnetic field is being investigated. The linear stage of instability development is studied with linearized magnetohydrodynamic (MHD) equations based on the Hall fluid model. Results for linear growth rates as a function of axial sheared flow, axial magnetic field, and the Hall term, with an emphasis on the sausage and kink instabilities, are reported. We also present simulations performed with the 3D version of the hybrid code based on the CAM-CL algorithm Matthews, AP (1994) These simulations serve the dual purpose of comparing with the linear Hall MHD analysis and of investigating the nonlinear stage of instability development with a kinetic model. The overall aim is to characterize the combined influence of sheared axial flow, the Hall term, axial magnetic field, and finite Larmor radius (FLR) effects on the development of sausage and kink modes. Calculations have been carried out in several regimes with respect to the Hall parameter /spl epsiv/=c//spl omega//sub pi/r/sub 0/ (c is the speed of light, Opi is the ion plasma frequency and r/sub 0/ is the plasma radius), with and without axial magnetic field. The axial magnetic field used in the calculations has been varied from Br/sub 0z/=0 to Br/sub 0z/=0.5, where the amplitude of the axial magnetic field is measured relative to the azimuthal magnetic field created by the axial current in the z-pinch. We have also initiated 3D hybrid simulations to study the time development of density and magnetic field profiles produced in the process of long pulse Z-pinch implosions in Saturn. Apruzese, JP et al. (2001). The 3D hybrid code allows for multiple ion species with multiple charges. This code also contains term with finite resistivity in the magnetic field equation. We can thus model realistic wire array loads with wires composed of different materials, for example Al (95%) and Mg (5%), like in Saturn.

The two-dimensional MHD numerical simulation MHRDR has been applied to develop and investigate a new possible fusion scheme, and design experiments to test it. The confinement of magnetized high-beta plasma directly by material walls holds considerable promise for fusion. An interesting prospective Magnetized Target Fusion (MTF) target plasma is the cylindrical inverse pinch, which is, in theory, an MHD-stable, self-organized plasma. An inverse pinch consists of coaxial, metal, current-carrying cylinders with plasma between them. Important insight into this plasma has been obtained using the MHRDR simulation. First, simulations observe that interchange m=0 modes rearrange the plasma into a pressure profile that is stable to m=0 (the Kadomtsev stable profile). Such plasma self-organization is very encouraging for the development of a robust practical device, since the pressure profile does not have to be created in a very particular manner to satisfy the Kadomtsev criterion. Second, the plasma beta can be adjusted by using an initial bias current on the central conductor to magnetize the gas before it is ionized. In this way, the plasma beta can be kept below 40%, so that, according to theory, the troublesome m=1 mode is also stabilized. (The r-z MHRDR code does not analyze the three-dimensional kink motion.) Although the convection associated with self-organization enhances thermal transport, the kinetic energy of turbulent motion is small compared to the thermal energy, and the energy transport is globally Bohm-like, which is acceptable for MTF. The MHRDR modeling is guiding the design of an experiment on the 2-TW Zebra z-pinch at UNR to test the inverse-pinch concept. For the parameters of the designed experiment, MHRDR simulations predict the 2-MV, 1-MA Marx generator will produce a deuterium plasma with B/spl sim/4T, n/spl sim/10/sup 22/m/sup -3/, T/spl sim/300 eV, and a lifetime of 10-50 microseconds. Understanding of the energy transport in this simple wall-confined plasma will increase confidence in the design of eventual integrated liner-on-plasma experiments.

Dense Plasma Focus (DPF) discharge is a very promising mechanism to achieve high neutron production yield (about 10/sup 11/-10/sup 12/ per pulse) from the D-T reactions. Focus is conjectured to be a finite 2D Z-pinch formation near the end of the coaxial plasma accelerator, typically having the density above the level of 10/sup 19//cm/sup 3/ and temperature of a few keV during 100 to 150 ns. Interest to DPF appeared since the pioneer experiments of Filippov and the first theoretical reviews of Dyachenko and Imshennik and Mather. During the last decades theoretical investigation of DPF lagged behind the experiments, giving scant explanation of the experimental results. At the same time modeling and diagnostic capabilities have been dramatically improved. This presentation shows that the computer simulation by the code MHRDR (Magneto Hydro Radiative Dynamic Research) can help meet the goals and challenges of the LANL-Bechtel Nevada Dense Plasma Focus Accelerator project. Theoretical estimations, made in this report, represent the bounds between the parameters of source generator, geometry of the electrodes and feeding circuit and the initial density of the background gas in the form of the simple scaling laws.

A radiation-magnetohydrodynamic (MHD) model of gas discharges has been developed to accelerate the development of compact, intense sources of EUV radiation for microlithography. The model is an MHD numerical simulation with atomic and radiation physics. The plasma evolution is simulated with the MHRDR (Magneto-Hydro-Radiative-Dynamic-Research) 2D, three-temperature, MHD computer code. The MHD results are postprocessed with a code that calculates the 13.4-nm EUV radiation output from Xe ions, based on a detailed collisional-radiative atomic kinetics model. Modeling of a dense plasma focus discharge, in a Xe-He gas mixture, has been initiated with this new tool.

Summary form only given, as follows. A high-repetition-rate, 2-terawatt Z-pinch (HDZP-II from LANL: 2 MV, 1 Mg 100 ns, 200 kJ, 1.9 ohm) has been reassembled to investigate the early-time evolution of a current-driven wire, the plasma turbulence around and between wires, the acceleration of a plasma current sheet by a magnetic field, and the suppression or reduction of plasma instabilities. The heating, expansion, and dynamics of wires driven by current prepulses similar to those at SNL-Z is being examined first. Optical, laser, and radiographic measurements of prepulse-driven exploding wires will be compared with the modeling results of Reisman et al. (LLNL). SNL-Z wires are exploded by an independent pulse generator (100 kV, 2 kA, 50 ns). Plasma self-emission, laser-schlieren, laser-absorption, and interferometric images (10 micron, 0.1 ns resolution) are obtained with streak cameras (S-l and S-20) and an Nd:glass laser (30 ns, 1064 or 532 nm). Multiframe point-projection radiography (few-micron, sub-ns resolution) is acheived by driving several X-pinch backlighters with HDZP-II. In addition, laser-induced-fluorescence imaging and X-ray absorption spectroscopy are being developed for this prepulse experiment, while laser polarimetry and collective Thomson scattering, and a suite of X-ray diagnostics, are being developed for future high-current experiments.

Summary form only given. A wide variety of advanced extreme ultraviolet (EUV) and X-ray diagnostics are being developed for the Nevada Terawatt Facility (NTF) at the University of Nevada, Reno. Time-resolved short-wavelength imaging, backlighting, imaging spectroscopy, and polarization spectroscopy will be employed to measure profiles of plasma temperature, density, flow, charge state, and magnetic field. The instruments are state-of-the-art applications of glass capillary converters (GCC), multilayer mirrors (MLM), and crystals. The devices include: a prototype of a new glass-capillary-based two-dimensional imaging spectrometer; a pinhole camera with 6 MCP imagers; a 5-channel crystal/MLM spectrometer ("Polychromator") with fast X-ray diodes and an added transmission grating spectrometer; a convex-crystal X-ray survey spectrometer; a prototype of an X-ray polarimeter/spectrometer; and a multiframe X-pinch backlighter yielding point-projection microscopy with few-micron, sub-ns resolution. Spectroscopic data will be interpreted with state-of-the-art spectral calculations that take into account line intensity, plasma broadening, opacity, and polarization effects, for both resonance and satellite lines. Emission spectroscopy will be used to measure plasma density and temperature in the hot plasma around exploding wires, with polarization measurements helping to determine the electron distribution function and the magnetic field in this region. The density and temperature of the high-density, low-temperature plasma inside exploding Al wires will be measured with absorption spectroscopy.

A high-repetition-rate, 2-TW Z-pinch (Zebra or HDZP-II from LANL: 2 MV, 1.2 MA, 100 ns, 200 kJ, 1.9 ohm) has been assembled to investigate the early-time evolution of a current-driven wire, the plasma turbulence around and between wires, the acceleration of a plasma current sheet by a magnetic field, and the suppression or reduction of plasma instabilities, and to generate radiation for applications. The heating, expansion, and dynamics of wires driven by current prepulses similar to those at SNL-Z is being examined in isolated wires and soon in SNL-Z wire arrays. 290 trillion watts of X-rays can now be generated by a few cubic millimeters of plasma. The source of this plasma is the Z-pinch. This plasma confinement device drives a giant current through a tiny load, compressing and heating it with extreme current-produced magnetic fields. The Z-pinch suffers from plasma instabilities that limit its performance. The ultimate performance limit of the Z-pinch is unknown: another order of magnitude increase in X-ray power levels may be possible. Such an improvement would open up new applications. Understanding the dense Z-pinch is vital to the search to ameliorate it. This article describes the activation of the 2-TW Zebra Z-pinch, the development of diagnostics, and an initial single-wire experiment.

Summary form only given, as follows. The correlation between the onset times of the X-ray emissions in three energy ranges has been studied on a plasma focus device (11 kJ at 16 kV) with various gas fillings. Soft X-ray line emission at about 1 keV photon energy (H- and He-like neon ion resonance lines) was detected by means of a crystal spectrometer. Medium energy X-ray emission (5-30 keV) was measured by filtered PIN diodes. Hard X-rays (energy above 100 keV) were detected by scintillator-photomultiplier detectors. In most of the measurements all detection devices were placed in a plane perpendicular to the electrode axis viewing a region at about 1 cm in front of the central electrode. The visible light emission from the collapsing plasma sheath was taken as the time reference in the correlation studies. It was found that the onset times of the plasma focus X-ray emission in the energy ranges specified above were highly correlated (correlation coefficients close to unity were found). This was not the case for the duration and intensity of the same emissions.

Summary form only given, as follows. 1D modeling of the initial state of wire explosions ("cold start" with updated SESAME tables) was examined using a 1D version of the Eulerian magnetohydrodynamic radiative code (MHRDR). Simulations were carried out for two regimes: with (black body radiative model) and without radiative losses. The results of the simulations revealed strong dependence of the time of explosion and expansion speed of the wire on the implemented radiative model. This shows that it is necessary to accurately include radiative losses to model "cold start" wire explosions. Comparison with the Imperial College (UK) computational results are also presented. 2D modeling of the m=0 sausage instability with sheared axial flow are given. The MHRDR simulations were used to obtain the growth rate of the m=0 sausage instability in a plasma column with an initial Bennett equilibrium profile with and without shear flow. These growth rates appeared to be in good agreement with growth rates calculated from the linearized MHD equations 2D modeling of single wire z-pinches with a "warm start". MHRDR simulation results are being compared with X-ray measurements of Ti, Fe, and other single wire z-pinches.

Summary form only given, as follows. A systematic study of the linear stage of shear flow stabilization of z-pinches, based on a Hall MHD model with an equilibrium containing shear flow and axial magnetic field, is being performed. Shear flow and axial magnetic field can strongly influence the development of the instabilities. A general set of equations permitting evaluation of the combined effect of shear flow and axial magnetic field on the development of the m=0 sausage and m=1 kink instabilities is being investigated. The development in time of an initial density perturbation is followed numerically until it converges to the fastest growing eigenfunction. Linear growth rates as a function of axial wavenumber (k) are obtained for a wide range of parameters. The Hall term plays a destabilizing role and its inclusion into the model leads to the increase of the instability growth rate. The linear theory results were found to be in agreement with the instability growth observed in MHRDR computer simulations.

Summary form only given, as follows. A 2-TW z-pinch (Zebra from LANL: 2 MV, 1.2 MA, 100 ns, 200 kJ, 1.9 ohm) and a 200-MW z-pinch (100 kV, 2 kA, 50 ns) are used to investigate the early-time evolution of a current-driven load. We studied the heating, expansion, and dynamics of wires driven by current prepulses similar to those at SNL-Z in isolated-wire and SNL-Z wire-array geometries. Diagnostics in the X-ray domain include time-resolved imaging, imaging spectroscopy, and X-pinch backlighting. Laser and optical diagnostics include imaging, schlieren, laser-absorption, interferometry, and imaging spectroscopy, obtained with streak cameras and a Nd:glass laser. Other diagnostics X-ray interferometry, polarization X-ray imaging spectroscopy, laser-induced fluorescence, laser polarimetry, and collective Thomson scattering are coming online. 2D and 3D MHD and PIC modelling of Z-pinches has been initiated, initial instability development will be compared with the linear growth rates of m=0 sausage modes, with and without axial sheared flow, axial magnetic field, and the Hall term.

The presence of plasma turbulence can strongly influence propagation properties of electromagnetic signals used for surveillance and communication. In particular, we are interested in the generation of low frequency plasma density irregularities in the form of coherent vortex structures. Interchange or flute type density irregularities in magnetized plasma are associated with Rayleigh-Taylor type instability. These types of density irregularities play an important role in refraction and scattering of high frequency electromagnetic signals propagating in the earth ionosphere, in high energy density physics, and in many other applications. We will discuss scattering of high frequency electromagnetic waves on low frequency density irregularities due to the presence of vortex density structures associated with interchange instability. We will also present particle-in-cell simulation results of electromagnetic scattering on vortex type density structures using the large scale plasma code LSP and compare them with analytical results.

The results of the study and application of the prototype of the novel imaging spectrometer with a glass-capillary multiplexer of a 2D x-ray image of Z-pinch plasma are presented. Output channels are used to obtain an array of time-resolved spectra, which covers the full plasma evolution. A spatial resolution of the spectrometer is about 100-250 micrometers for plasma size up to 5 by 20 mm. A spectral resolution is 700-1000. A time-gated resolution is 1-2 ns.

The effect of sheared axial flow on the Z-pinch sausage instability has been examined with two-dimensional magnetohydrodynamic simulations. Diffuse Bennett equilibria in the presence of axial flows with parabolic and linear radial profiles have been considered, and a detailed study of the linear and nonlinear development of small perturbations from these equilibria has been performed. The consequences of both single-wavelength and random-seed perturbations were calculated. It was found that sheared flows changed the internal m=0 mode development by reducing the linear growth rates, decreasing the saturation amplitude, and modifying the instability spectrum. High spatial frequency modes were stabilized to small amplitudes and only long wavelengths continued to grow. Full stability was obtained for supersonic plasma flows.

A series of 1,3,5-benzenetrisamide derivatives with three hexaalkoxytriphenylene pendant groups were prepared, in which the triphenylene groups are connected to the central 1,3,5-benzenetrisamide core through a flexible spacer. The length of this spacer, as well as the size of the ortho-substituent at the triphenylene core, influences the columnar packing of these molecules. All compounds show liquid crystalline behavior with high isotropization temperatures. Different columnar hexagonal phases (Colh, Colhp, Colobl and Colr) have been identified using optical polarization microscopy, differential scanning calorimetry and X-ray diffraction. A chiral 1,3,5-benzenetrisamide derivative forms columnar stacks with a single helical sense, both in an apolar solvent and in a film, as observed by circular dichroism studies. Pulse radiolysis time-resolved microwave conductivity (PR-TRMC) studies show that the high ordering in a Colhp phase results in high charge carrier mobilities. On the other hand, the highest mobility was observed for the chiral compound, which has a Colr ordering.