bluuebunny/crossref_metadata_2025 huggingface dataset:
Equation of state studies at SILP by laser-driven shock waves
Authors: Gu Yuan , Fu Sizu , Wu Jiang , Yu Songyu , Ni Yuanlong , Wang Shiji
Published: March 2009

The experimental progress of laser equation of state (EOS) studies at Shanghai Institute of Laser Plasma (SILP) is discussed in this paper. With a unique focal system, the uniformity of the laser illumination on the target surface is improved and a laser-driven shock wave with good spatial planarity is obtained. With an inclined aluminum target plane, the stability of shock waves are studied, and the corresponding thickness range of the target of laser-driven shock waves propagating steadily are given. The shock adiabats of Cu, Fe, SiO2are experimentally measured. The pressure in the material is heightened remarkably with the flyer increasing pressure, and the effect of the increasing pressure is observed. Also, the high-pressure shock wave is produced and recorded in the experimentation of indirect laser-driven shock waves with the hohlraum target.
Laser produced ion sources: A historical note
Authors: Pease R.S.
Published: March 2009

Research on multiply-ionized atoms was pioneered in the 1930s and 40s, particularly in Sweden by Edlén and his colleagues working first in M. Siegbahn's laboratory in Uppsala, and then at Lund University. The key instrument was the grazing-incidence grating spectrometer which opened to observation the spectral range 500–5Å (Edlén 1963). The source of the multiply-charged ions was the plasma of a vacuum spark, a pulsed (~1 µs) electric discharge of up to 50 kA between electrodes of the desired element, some 3–5 mm apart. When the spark was enclosed in a ceramic tube (with a side opening to let out the radiation), the breakdown voltage was less, the discharge was more controllable. Furthermore, it was found that the range of species produced was a useful function of current.
General features of highly charged ion generation in laser-produced plasmas
Authors: Roudskoy I.V.
Published: March 2009

The simple physical model of highly charged ion generation in plasma produced by laser irradiation with long pulse duration (>1 ns) and moderate intensities (<1015/λ2 W/cm2μm2) is presented. In the frame of a single theory, most of the experimental results on plasma diagnostics are described in total. It is shown that plasma temperatures, ion charge states, and ion velocities as well as angular distributions of highly charged ions can be explained with good accuracy by collisional absorption of laser energy, hydrodynamic acceleration of forming plasma, and three-body recombination through highly exited levels during plasma expansion into vacuum. The general scalings for plasma parameters are derived on the basis of the model proposed.
Slab model for Rayleigh–Taylor instability
Authors: Estévez A.
Published: March 2009

A modelization of the Rayleigh–Taylor instability, in the context of inertial confinement fusion, is made by means of a planar slab model whose main features are a sharp ablation front separating the slab and the expanding corona, absorption of constant intensity laser light at a critical surface, profiles for background flow variables consistent with hydrodynamic equations, and heat conduction present in the expanding corona. A sharp ablation front assumption (density at the critical surface is much less than the slab density, ρc/ρs ≪ 1) supposes that the ablated mass is small, so the model is valid for thick targets. Two main regimes are modelized, subsonic and sonic absorption. The growth rate of the instability is obtained, and its variation with kD and kxc is studied (k = perturbation wavenumber; D = slab thickness; xc = ablation to critical surfaces distance). The model shows
stabilization over the classical Rayleigh–Taylor growth rate (γ = √kg). The stabilization mechanism is based on heat conduction near the ablation front.
New technique for levitating solid particles using a proton beam
Authors: Misconi Nebil Y.
Published: March 2009

A new technique for levitating solid particles inside a vacuum chamber is developed using a proton beam. This new technique differs from the classical laser-levitation technique invented by Ashkin in that it does not heat up light-absorbing levitated particles to vaporization. This unique property of the method will make it possible to levitate real interplanetary dust particles in a vacuum chamber and study their spin-up dynamics in a ground-based laboratory. It is found that a flux of protons from a proton gun of ~1015 cm–2 sec–1 is needed to levitate a 10-mm particle. Confinement of the levitated particle can be achieved by a Z or θ pinch to create a gravity well, or by making the beam profile doughnut in shape.
Multicenter wavefunctions in opacity calculations for dense plasmas
Authors: Foulis D.L. , Beynon T.D. , Rose S.J.
Published: March 2009

We present the results of calculations for the K-edges of representative transient carbon ion clusters in a dense carbon plasma. The calculations use the recently implemented non-“muffin-tin” scattered-wave method previously used in the molecular and solid-state fields. Based on a simple model for the cluster potentials it is shown that, compared with a single ion calculation, the presence of neighboring ions can significantly alter the K-edge photoionization cross sections, and hence the resulting opacities.
Parametric potential for modelling of highly charged heavy ions
Authors: Mabong S. , Maynard G. , Katsonis K.
Published: March 2009

Parametric electron-ion potential for fast estimation of atomic data required for “on-line” calculations in inertial confinement fusion (ICF) driven by heavy ions is presented. Comparisons of our results (outer- and inner-shell ionization energies, oscillator strengths, and logarithmic mean excitation energies) with experimental and self-consistent-field (SCF) calculation values are made. Using the wave functions generated by the previously mentioned potential, generalized oscillator strengths and integrated inelastic collision cross sections are computed within the frame of Born approximation.
Conical targets and pinch confinement for inertial fusion
Authors: Velarde P.M. , Martinez-Val J.M. , Eliezer S. , Piera M. , Chacon L.
Published: March 2009

Conical microducts and minithrottles can be used to accelerate micropellets of fusionable fuel up to very high speeds (∼108 cm/s). The central collision of two pellets flying in opposite directions can produce a hot plasma where fusion reactions are triggered. The main drawback of this scheme is the short confinement time provided by the external guide tube (throttle). To obtain high yield, an extra force of confinement is advisable. In this paper, the performance of fuel implosions within conical targets and the effect of ultrashort magnetic fields and pinch forces are analyzed. Although very high currents are needed to stretch the confinement time, modern technologies based on pulse-power machines and fast discharges induced by ultrashort lasers can provide a solution to this problem.
Structure and equation of state of metallic plasmas
Authors: Amato M.A. , March N.H.
Published: March 2009

Evidence will first be presented in favor of the usefulness of coordination number-dependent equations of state of metallic plasmas. After some theoretical discussion of the way such an equation of state may be related to dimer properties, with specific regard to Na and Al, critical point predictions for the alkalis will be brought into contact with experiments. In this context, some results on W will also be surveyed. Structural properties, static and dynamic, will then be considered in relation to transport in both Cu and H plasmas. This will embrace experiments on electrical resistivity in both examples. For H, a simple inference can be extracted about the structure factor, and the discussion will finally be generalized to treat the metalization of solid H.
Charge state and nonlinear stopping power of heavy ions in a fully ionized plasma
Authors: Boine-Frankenheim O. , Stöckl C.
Published: March 2009

Due to the high nonequilibrium charge states specific to heavy ions, the plasma regime with coupling parameters l/ND < 1 and Zp/ND > 1 (ND ∼ number of electrons in a Debye sphere, Zp mean charge state of the projectile) is of interest for the applications. In this regime the stopping power cannot be obtained by a linearization of the Vlasov-Poisson system, but forcing a fully nonlinear treatment. In the present paper the Vlasov-Poisson system is solved numerically by using the capability of the new generation of massively parallel supercomputers. The results are compared with the standard dielectric theory and a binary collision approach. Charge-state calculations are performed, accounting for all relevant features of the atomic processes and the spectra characteristic to heavy ions in dense plasma targets. The results show good agreement with experimental measurement for medium and heavy ions penetrating a Z-pinch device.
LLAMPÜDKEÑ: A high-current, low-impedance pulser employing an auxiliary exponential transmission line
Authors: Chuaqui H. , Wyndham E. , Friedli C. , Favre M.
Published: March 2009

The design and constructional aspects of a novel pulse power generator for use in dense plasma research presently under construction are presented. The generator consists of two Marx capacitor banks, each of 0.25 μF, 480 kV, and 28.8 kJ. Each Marx generator drives a water transmission line, in which the live electrode is the central conductor. The transmission lines consist of a constant impedance section followed by a multielectrode gas linegap followed by an exponential taper to the load section. The novel feature is the use of an auxiliary exponential line coupled at the load. This line controls both the voltage and the effective impedance at the load section. In addition, by leaving this line circuit open, energy not coupled to the plasma in the initial high-impedance phase may be reflected back and deposited into the discharge, increasing the peak current by 50%. Circuit simulations using a real-time-varying load impedance show that the current pulse rises in an approximately linear way to a maximum of 1.2 MA at 250 ns. The current falls to zero in the following 250 ns. The current waveform may be flattened simply by disconnecting the auxiliary line, giving a rectangular pulse of 350 ns with a maximum value of 950 kA. The overall impedance of the entire system may be adjusted by varying the separation between the conductors. The equivalent source impedance at the load is 0.8 Ω. This low value is by virtue of the auxiliary line, which limits the voltage at the load section and reduces the insulator constraints. We present simulations of the generator under real load conditions. The model also is checked against analytical solutions of exponential line behavior and against other published models of pulse power generators.
Evaluation of brightness of an intense pulsed ion beam by Thomson spectrometer
Authors: Masugata K. , Okuda H. , Yatsui K. , Tazima T.
Published: March 2009

A method is proposed to evaluate the power brightness of an intense pulsed ion beam by using a Thomson parabola spectrometer (TPS). In the method, the time-dependent power brightness of each ion species can be determined independently from the density profile of ion tracks. The method is successfully utilized to evaluate the power brightness of ion beams produced in point pinch diode. The brightness of highly ionized carbons of 660 keV and oxygens of 880 keV, and singly ionized molecular ions of 400 keV, are evaluated independently. The total brightness is evaluated to be 3.2 GW/cm2/sr for highly ionized ions, and 1.9 GW/cm2/sr for molecular ions.
Excilamp producing up to 130 W of output power and possibility of its applications
Authors: Lomaev M.I. , Panchenko A.N. , Skakun V.S. , Sosnin E.A. , Tarasenko V.F. , Adamson M.G. , Myers B.R. , Wanga F.T.
Published: March 2009

Results of an experimental study of a coaxial exciplex lamp pumped by glow discharge are presented. An average power of radiation in the wavelength region below 250 nm and as high as about 130 W has been achieved. Efficiency of the excilamp operation based on input power of 14% was demonstrated. The possibility of applications of this excilamp is discussed.
Review of theoretical works on X-ray laser research performed at RFNC — VNIITF
Authors: Avrorin E.N. , Lykov V.A. , Loboda P.A. , Politov V.Yu.
Published: March 2009

A review of theoretical works on the laboratory X-ray laser (XRL) research performed at RFNC–VNIITF for the last few yearsis presented. Three potential photopumped XRL schemes with relatively short laser wavelengths (44, 23, and 64 Å) have been investigated. Theoretical studies of lasing plasma parameters for some of the published recombination and resonantly photopumped XRL schemes have been performed using our kinetics and line-profile codes.
Experimental investigation into inertial properties of Rayleigh–Taylor turbulence
Authors: Kucherenko Yu.A. , Balabin S.I. , Cherret R. , Haas J.F.
Published: March 2009

An experimental investigation into inertial properties of the developed Rayleigh–Taylor instability with the different initial values of the kinetic energy of turbulence has been performed. The experiments were performed by using two fluids having different densities with density ration n = 3. Fluids were placed in an ampoule. At the unstable stage of motion, the ampoule was moving under an acceleration. At a certain instant of time the acceleration was removed and the ampoule moved under the force of inertia. By means of pulsed X-ray photography, the mixing region size and the time-space distributionof the average density of matter in the turbulent mixing region have been determined at different instants of time. The time-space distributions are compared with those obtained by semiempirical theories of mixing.
Kinetic processes in the overdense plasma under the action of ultra-intense laser pulses
Authors: Cadjan M.G. , Ivanov M.F. , Ivlev A.V.
Published: March 2009

The results of numerical and analytical investigation of the ultra-intense laser pulse's interaction with overdense plasma are presented. The mechanisms of the wave field energy transformation into the overdense plasma energy are discussed. The effects of radiation propagation deep into plasma as well as long-living vortex formation, plasma boundary instability, and the surface structures formation are obtained. The basic mechanisms for the absorption of incident radiation and the role played by polarization of the radiation are studied. Nonlinear theory of plasma surface instability in the field of the strong electromagnetic wave is developed.
Instabilities of a Hall plasma flowing across a magnetic field
Authors: Alekseeva Liliya M.
Published: March 2009

Under certain restrictions imposed on the plasma parameters, an analytical 2D solution to the magnetohydrodynamic equations, taking into account the Hall effect [of the HMHD (Hall magnetohydrodynamic) equations], is found for the case when plasma flows across a magnetic field. This solution has the form of the sum of a rather arbitrary steady flow and a small time-dependent disturbance. We show that waves of a purely acoustic nature can propagate against the background of the flow. The magnetic field manifests itself in this process only in that it produces an effective gravity force, the “gravitational” acceleration being proportional ωeτe. Like acoustic-gravity waves in the atmosphere, such quasiacoustic-gravity (QAG) waves in a plasma increase greatly in their amplitude as they propagate “upward,” that is, in this case, to the anode of an accelerating plasma channel. The existence of a rather general dimensionless similarity criterion is also shown. It can be found directly from the structure of the HMHD equations without any restrictions as to the plasma parameters.
Investigation of the shock-induced evolution of turbulent zone
Authors: Lazareva E.V. , Aleshin A.N. , Zaytsev S.G.
Published: March 2009

This study was devoted to the investigation of the shock-induced intensification of the turbulent mixing zone. Our data were compared with those reported by the authors from the United States and France. The experiments were performed in a shock tube of square section filled with the two gases, which were separated with a thin lavsan film. The working gases were helium, argon, krypton, xenon, and their combinations. This allowed us to perform the studies for the Atwood numbers ranging from 0.095 to 0.91 in magnitude. The incident shock wave passed from light to heavy gas and vice versa. The initial pressure of 0.5 atm and Mach number of the incident shock wave 3% were chosen as the working parameters because under these conditions the experimental x, t-diagram coincided with the calculated x, t-diagram within the 3% experimental error. The process was visualized by the Schlieren method with the IAB-451 device using continuous recording or recording in frames. We studied the shock-induced intensification of the turbulent zone, the effect of initial conditions on this intensification, and the influence of the turbulent zone on the intensification of the shock passed through the zone.
Studies of Rayleigh–Taylor instability of a thin liquid layer
Authors: Bakhrakh S.M. , Simonov G.P.
Published: March 2009

On the basis of Lagrangian representation for equation of thin-liquid-layer dynamics, analytic solutions of the Rayleigh–Taylor instability problem at the nonlinear stage in the observer's space are found. Evolution of various perturbation types, in the layer shape and in layer velocity components, is considered. It is shown that there are both exponentially growing and limited oscillating solutions. The results of the theoretic considerations are substantiated with numerical calculations that use the complete system of the law of conservation.
Experimental and numerical evolution studies for 2D perturbations of the interface accelerated by shock waves
Authors: Bashurov V.V. , Bondarenko Yu.A. , Gubkov E.V. , Dudin V.I. , Meshkov E.E. , Poduvalov A.N. , Shanin A.A. , Stenin A.M. , Til'kunov V.A. , Tolshmyakov A.I. , Trofimova L.Ya. , Yanilkin Yu.V. , Zmushko V.V.
Published: March 2009

In this article, the results of experimental and numerical studies of the behavior of perturbed interface between air and helium are presented. The interface is initially accelerated by the incident shock wave coming from air to helium and then decelerated by a series of reflected shock waves. Two types of initial interface perturbations like “saw” and “step” are considered.
Computational optimization of indirect-driven targets for ignition and the engineering test facility
Authors: Avrorin E.N. , Lykov V.A. , Chernyakov V.E. , Shushlebin A.N. , Mustafin K.A. , Frolov V.D. , Kozmanov M.Yu. , Kandiev Ya.Z. , Sofronoval A.A.
Published: March 2009

The results of ID-ERA and 2D-TIGR, OMEGA codes calculations of compression and burn of indirect-driven targets for the thermonuclear ignition and Engineering Test Facility are presented. The possibility to obtain high-energy yield of G > 100 with driver energy of Ed = 5−10 MJ by using the heavy-ion one-beam accelerator as the main driver and powerful laser for fast ignition of thermonuclear detonation of cylindrical targets is pointed out.
Simulation of relativistic electron generation in under-dense laser plasma experiments
Authors: Manfredi G. , Bingham R. , Dendy R.O.
Published: March 2009

The generation of relativistic electrons by nonlinear coupling of a laser beam to an under-dense plasma is simulated. An Eulerian Vlasov code is used, which enables direct solution of the fully nonlinear Vlasov-Maxwell system in real space. The impact of stimulated Raman and Compton scattering on the electron velocity distribution is investigated. Simulations show that electrons can be accelerated to energies of several MeV. The role of induced scattering processes is analyzed in detail, using electromagnetic field spectra and electron phase-space information as diagnostics. The effects of density gradients in the back-ground plasma are also quantified.
2D Modeling of Inductively Coupled Helical Flux-compression Generators—FLUXAR Systems
Authors: Novac B.M. , Enache M.C. , Enache M.C. , Smith I.R. , Stewardson H.R.
Published: March 2009

In a number of single-shot applications and experiments at remote locations where flux-compression generators provide the most practicable power source, it may be necessary to use cascaded generators with inductive coupling between them to provide the required power amplification. The complexity of the resulting system appears to have so far inhibited the development of any simple but complete numerical code, and has prevented a full understanding of the complex action of the overall system. The present paper meets these requirements, by extending an existing simple 2D helical generator code, and shows how this can be used to solve problems arising from the design stage of a prototype system.
Space-resolved Spectral Diagnosis of Line-shaped Laser-produced Magnesium Plasmas
Authors: Zhang Ling-Qing , Han Shen-Sheng , Xu Zhizhan , Song Xiang-Yang , Zhang Zheng-Quan
Published: March 2009

Space-resolved spectra of line-shaped laser-produced magnesium plasmas in the normal direction of the target have been obtained using a pinhole crystal spectrograph. These spectra are treated by a spectrum analyzing code for obtaining the true spectra and fine structures of overlapped lines. The spatial distributions of electron temperature and density along the normal direction of the target surface have been obtained with different spectral diagnostic techniques. Especially, the electron density plateaus beyond the critical surface in line-shaped magnesium plasmas have been obtained with a fitting technique applied to the Stark-broadened Ly-α wings of hydrogenic ions. The difference of plasma parameters between those obtained by different diagnostic techniques is discussed. Other phenomena, such as plasma satellites, population inversion, etc., which are observed in magnesium plasmas, are also presented.
Ablative Acceleration of Foils, Their Pulsations, and Interchange Instability
Authors: Inogamov N.A.
Published: March 2009

The problem of hydrodynamic stability is important for inertial confinement fusion (ICF) systems based upon high compression of fuel before its ignition. This problem for the case of complicated multilayer foils has been studied here by a new approach describing the development of Rayleigh-Taylor or interchange instability in compressible media with inhomogeneous distribution of “entropy”s = ρ/ρk, ∂ where K = (∂ In ρ/∂ In ρ)s is an adiabatic derivative taken in the local hydrostatic values of ρ and ρ. Inhomogeneous distribution of s simulates the dynamics of development of perturbations of multilayer flyer foils and shells. Besides instability, the same approach has been used for analysis of ID pulsations of a levitated foil. The problem of pulsations is real in the case of foils. Indeed, (1) an ablative acceleration is equivalent to an effective gravity field, which causes the appearance of an atmospheric-type distribution of thermodynamic functions, (2) the duration of ablative flight of foil is at least several times larger than the time that is necessary for an acoustic wave to travel from one side of the foil to another side, and (3) there is a strong initial impulse that initiates the motion of foil. This impulse together with (1, 2) is a reason for the powerful pulsations of foils. The period of pulsations is defined by the velocity of sound in the foil material, which is dependent on the derivatives of an equation of state (EOS). The check of the derivatives gives us finer information concerning the current state of matter and the EOS than the usual measurements of material velocity and pressure that are rougher measures. Therefore, an analysis of pulsations seems to be a promising tool for tracking the dynamics of flyer foil and for the definition of thermodynamic properties of matter.
Density Expansion of the Equation of State for a Multicomponent Quantum Plasma
Authors: Riemann J. , Schlanges M. , Kraeft W.D.
Published: March 2009

Within the grand canonical ensemble, we use a general quantum statistical formula and the thermodynamic Green's functions to derive a perturbation expansion for the pressure of a multicomponent plasma. Different contributions to the equation of state (EOS) are given analytically and by numerical calculations. Exact results for the EOS are presented in the shape of a low-density expansion up to the order (ne2)5/2, including ladder-type contributions and “beyond Montroll–Ward” terms.
Analysis of the retrograde hydrogen boron fusion gains at inertial confinement fusion with volume ignition
Authors: Scheffel Chr. , Stening R.J. , Hora H. , Höpfl R. , Martinez-Val J.M. , Eliezer S. , Kasotakis G. , Piera M. , Sarris E.
Published: March 2009

The very clean nuclear fusion reaction of hydrogen and boron-11 by inertial confinement arrives at conditions for power stations by volume ignition only at compressions to 100,000 times the solid state. The earlier (numerically) observed anomaly of decreasing gain at increasing density (retrograde behavior) is analyzed and the reason clarified: the strong stopping power mechanism, based on Gabor's collective model, is reaching its limit of too small Debye lengths at the extremely high densities because of the optimum temperature in the range of 30 keV due to the reabsorption of the bremsstrahlung. The relativistic correction of the bremsstrahlung for the always much higher temperatures after volume ignition is included from Maxon's model.
Development of advanced fuel inertial fusion targets
Authors: Tahir N.A. , Hoffmann D.H.H.
Published: March 2009

This paper discusses the implications of using different fuels, including pure deuterium, deuterium–tritium, deuterium–helium3, and proton–boron11, on safety and environmental compatibility of the fusion reactor, as well as on the driver requirements. Due to present-day technology limitations, it seems likely that the first generation of the fusion reactors will be based on a deuterium–tritium cycle. Such a scheme, however, would pose serious problems, including neutron activation and tritium handling. We show that by developing low-level tritium inertial fusion targets, one may substantially reduce the daily use of tritium in the reactor that may ultimately lead to a reduction in the overall tritium inventory in the power plant. Such reduced tritium targets will still generate sufficient energy to run the power plant economically.
Soft X-ray lasing at 519.7 Å in a Recombining Z-pinch Plasma
Authors: Eberl E. , Wagner T. , Jacoby J. , Tauschwitz A. , Hoffmann D.H.H.
Published: March 2009

This paper is reviewing the amplification of XUV radiation at 519.7 and 498.5 Å with a gain-length product of 2.5 and 2.2 for the 4f-3d and 4d-3p transition in an oxygen Z-pinch plasma. Time resolved measurements of the O VI (519.7 Å) transition were performed and the dependence of the line intensity on the discharge current and initial gas pressure is reported.
The evolution of high-energy-density physics: From nuclear testing to the superlasers
Authors: Campbell E. Michael , Holmes Neil C. , Libby Steven B. , Remington Bruce A. , Teller Edward
Published: March 2009

We describe the role for the next-generation “superlasers” in the study of matter under extremely high-energy-density conditions in comparison with previous uses of nuclear explosives for this purpose. As examples, we focus on three important areas of physics that have unresolved issues that must be addressed by experiment: equations of state, hydrodynamic instabilities, and the transport of radiation. We describe some of the advantages the large lasers will have in a comprehensive, laboratory-based experimental program.
Finite-element simulation code for high-power magnetohydrodynamics
Authors: Humphries Stanley , Ekdahl Carl
Published: March 2009

We describe the mathematical basis and organization of Crunch, a ID shock-hydrodynamics code to analyze pulsed-power experiments at Los Alamos National Laboratory. The program uses finite-element methods that preserve stability during material collisions and shock convergence on axis. It handles coupled calculations of nonlinear magnetic diffusion to simulate imploding liners. These calculations may be driven by multiple current waveforms or a selfconsistent current variation derived from a pulsed-power generator model. Crunch incorporates elastic material contributions and calculates element break and melt points. The primary goal in program development was effective use by experimentalists. Crunch is controlled by a streamlined script language and runs on standard personal computers. An interactive graphical postprocessor expedites analysis of results. To support the program we have assembled data resources in machine-independent format including Sesame equation-of-state tables, a material strength library and a library of temperature-dependent conductivities.
Main physical problems of AVLIS technology in producing ytterbium-168 in weighable amounts
Authors: Yakovlenko S. I.
Published: March 2009

A review of the AVLIS (atomic vapor laser isotope separation) development performed by GPI and LAD Ltd. (Moscow, Russia) during the last 4–5 years is presented. The processes of laser isotope separation of ytterbium (Yb) have been studied analytically, with numerical simulations, and experimentally. The basic attention is given to the following topics: the selectivity of ionization; the laser beams arrangement in a cavity; the forming of a vapor flux; and the extraction of ions from plasma. Installations to produce highly enriched 168Yb in industrial scales were created. The content of 168Yb in the laser-produced plasma reached 90–95%, in the material deposited on the ion collector up to 62%, and in the washing liquid up to 45%. The rate of the enriched Yb production was up to 5–10 mg/h. For the first time a profitable commodity was produced by the AVLIS method.
An investigation into the use of a non-metallic deodorant during radiotherapy treatment: a randomised controlled trial
Authors: Bennett Claire
Published: March 2009

Introduction: Many patients in the United Kingdom having radiotherapy for breast cancer are recommended not to use a deodorant during treatment. The advice is not evidence based, it is solely thought as deodorants contained metals, which would react with radiation and cause an increased skin reaction. Hence this research was undertaken to establish whether patients having a course of radiotherapy for breast cancer could use a deodorant as part of their daily routine.

Method: The research took place between May 2004 and February 2005. A total of 192 breast cancer patients were recruited. This included breast or chest-wall patients with or without axilla involvement. The study was designed with two groups. Group 1 used no deodorant and Group 2 a specific deodorant. The researcher reviewed patients weekly, assessing skin reactions and recording the researcher and patient's observations.

Results: Most patients experienced no reaction or mild erythema and dry desquamation in the axilla. This was observed in both groups. Therefore, findings of this study indicate that future breast cancer patients should be given the choice of using this deodorant.

Further recommendations: Test the reliability of the skin assessment form, extend the research to include other patient groups who have their axilla treated, test different deodorants.
Addressing the information needs of patients with prostate cancer: A literature review
Authors: Mc Parland Neil A.
Published: March 2009

Psychosocial support is a cornerstone in the holistic care of cancer patients. The provision of information is a key tool in the psychosocial management of the cancer patient, and it is important that the therapy radiographer is cognizant of the patient's need for information.

This article reviews the importance of information to the psychosocial well-being of cancer patients in general, with specific emphasis on patients with prostate cancer. The information services at a large Canadian cancer facility are also reviewed to gain some insight into how the needs of patients with prostate cancer are addressed at the author's workplace.

Most patients with prostate cancer have an expressed need for considerable amounts of information at various stages of their cancer journey. The provision of information has a range of benefits to the prostate patient such as helping the patient deal with their diagnosis, assisting with the decision-making process and reducing anxiety.

Interpersonal sources of information such as face-to-face communication with the oncologist or radiation therapist are preferred by many patients, including patients with prostate cancer. Other sources that include the internet and written hospital material are also used with varying degrees of effectiveness to deliver information.

The provision of quality information in a timely and effective manner cannot be taken for granted. Access to appropriate information resources can be impeded because of poorly designed information material, inadequate communication, ineffective signposting, resource constraints and lack of knowledge/comprehension on the part of frontline health-care workers dealing with the patient. Radiation therapists are encouraged to be advocates for their patients’ information needs and to be involved in initiatives that will improve the quality, dissemination and efficacy of information.
Determination of target volumes in radiotherapy and the implications of technological advances: a literature review
Authors: Mzenda Bongile , Hosseini-Ashrafi M.E. , Palmer A. , Hodgson D.F. , Liu H. , Brown D.J.
Published: March 2009

This study assesses the influence of new techniques and technologies in radiotherapy on the derivation and applicability of the margins currently used for treatment planning. The validity of the continued use of the recommendations of International Commission on Radiation Units and Measurements (ICRU) and other recommendations as a result of the additional information derived from these emerging techniques is also reviewed. The ICRU formulations still remain fundamental in the derivation of target volumes in radiotherapy; however, revisions to these have been recommended through various experimental and modelling techniques leading to the publication of various margin recipes. These recipes are used for margin definitions in new radiotherapy techniques including intensity-modulated radiotherapy (IMRT). The use of image-guided radiotherapy (IGRT) techniques leads to the reduction in organ motion uncertainties and setup errors, allowing for the adjustment of margins and treatment plans as well as dose escalation. Clinical trials are still needed to validate most of the new techniques in radiotherapy, particularly in IGRT techniques leading to adaptive radiotherapy. It is recommended that well devised clinical trials should be conducted to investigate fully the efficacy of these new techniques, particularly in radiotherapy image guidance and adaptive radiotherapy. Such trials would validate any recommendations regarding the current clinical margins and impact on their continued clinical use.
Activity-dependent neuron–glial signaling by ATP and leukemia-inhibitory factor promotes hippocampal glial cell development
Authors: Cohen Jonathan E. , Fields R. Douglas
Published: March 2009

Activity-dependent signaling between neurons and astrocytes contributes to experience-dependent plasticity and development of the nervous system. However, mechanisms responsible for neuron–glial interactions and the releasable factors that underlie these processes are not well understood. The pro-inflammatory cytokine, leukemia-inhibitory factor (LIF), is transiently expressed postnatally by glial cells in the hippocampus and rapidly up-regulated by enhanced neural activity following seizures. To test the hypothesis that spontaneous neural activity regulates glial development in hippocampus via LIF signaling, we blocked spontaneous activity with the sodium channel blocker tetrodotoxin (TTX) in mixed hippocampal cell cultures in combination with blockers of LIF and purinergic signaling. TTX decreased the number of GFAP-expressing astrocytes in hippocampal cell culture. Furthermore, blocking purinergic signaling by P2Y receptors contributed to reduced numbers of astrocytes. Blocking activity or purinergic signaling in the presence of function-blocking antibodies to LIF did not further decrease the number of astrocytes. Moreover, hippocampal cell cultures prepared from LIF −/− mice had reduced numbers of astrocytes and activity-dependent neuron–glial signaling promoting differentiation of astrocytes was absent. The results show that endogenous LIF is required for normal development of hippocampal astrocytes, and this process is regulated by spontaneous neural impulse activity through the release of ATP.
Slow subduction of a thick ultrahigh‐pressure terrane
Authors: Kylander‐Clark Andrew R. C. , Hacker Bradley R. , Johnson Clark M. , Beard Brian L. , Mahlen Nancy J.
Published: March 2009

High‐precision Lu‐Hf and Sm‐Nd ages reported here cover a large portion of the Western Gneiss Region (WGR) ultrahigh‐pressure (UHP) terrane, Norway, and range from 413.9 ± 3.7 to 397.1 ± 4.8 Ma. Collectively, new and existing geochronologic data for eclogites demonstrate that eclogite facies metamorphism occurred over a large area (60,000 km2) for an unexpectedly long period of >20 Ma. A thermal model using slow subduction (2–4 mm a−1) of a relatively warm and thick slab can reproduce the observed P‐T‐t history of the WGR UHP terrane, indicating that large UHP terranes with protracted peak or near‐peak histories probably reflect slow subduction of relatively thick crustal sections.
Confirmation of quasi‐perpendicular shock reformation in two‐dimensional hybrid simulations
Authors: Yuan Xingqiu , Cairns Iver H. , Trichtchenko Larisa , Rankin Robert , Danskin Donald W.
Published: March 2009

Shock reformation involves regions of a shock undergoing periodic collapse and redevelopment on a time scale close to the ion cyclotron period. Reformation is often observed in one‐dimensional (1‐D) hybrid and particle in cell (PIC) simulations of quasi‐perpendicular collisionless shocks provided the Alfvén Mach number MA and ion plasma beta βi are sufficiently high and low, respectively. Initial 2‐D PIC simulations showed some evidence for shock reformation, with ion reflection providing the main energy dissipation mechanism, while recent spacecraft observations showed a reforming shock with large amplitude whistler waves in the foot region. While recent spacecraft observations showed an case with reforming shock crossing with whistler waves dominated in the foot region. However, recent 2‐D hybrid and PIC simulations suggest that reformation does not occur in exactly perpendicular 2‐D shocks. This paper re‐examines shock reformation in quasi‐perpendicular shocks using 1‐D and 2‐D hybrid simulations. We find that 2‐D quasi‐perpendicular shocks (θbn = 85°) indeed undergo cyclic reformation providing MA and βi are high and low enough, respectively. For low MA ≤ 4, 2‐D quasi‐perpendicular shocks are found to be quasi‐stationary, despite 1‐D simulations predicting reformation, confirming and extending recent work for perpendicular 2‐D shocks. The dynamics of reformation are quite different in 2‐D than in 1‐D: in 2‐D large amplitude whistler waves grow in the shock foot, have amplitudes of order the downstream magnetic field, and affect the reformation. The whistlers have almost zero phase speeds in the shock frame and oblique wave vectors with respect to the upstream magnetic field. The predicted reformation period increases in 2‐D compared with 1‐D and increases nonlinearly as MA decreases towards the reformation threshold.
Constraints on thermal state and composition of the Earth's lower mantle from electromagnetic impedances and seismic data
Authors: Verhoeven O. , Mocquet A. , Vacher P. , Rivoldini A. , Menvielle M. , Arrial P.‐A. , Choblet G. , Tarits P. , Dehant V. , Van Hoolst T.
Published: March 2009

Despite the tight constraints put by seismology on the elastic properties of the Earth's lower mantle, its mineralogical composition and thermal state remain poorly known because the interpretation of seismic measurements suffers from the trade‐off between temperature, iron content, and mineralogical composition. In order to overcome this difficulty, we complement seismic data with electromagnetic induction data. The latter data are mostly sensitive to temperature and iron content, while densities and acoustic speeds mostly constrain the mineralogy. A 0.5 log unit increase in electrical conductivity can be caused either by a 400 K increase of the temperature or by an increase of iron content from 10% to 12.5%. Acoustic velocity is only marginally sensitive to temperature but it increases by 0.8 km s−1 on average as the perovskite fraction increases from 50% to 100%. Olsen's (1999) apparent resistivities in the period range [15 days, 11 years], and Preliminary reference Earth model (PREM) densities and acoustic speeds are jointly inverted in the depth range [800 km, 2600 km] by using a Monte Carlo Markov Chain method. Given the uncertainties on these data, estimates of perovskite fraction are well constrained over the whole depth range, but information on temperature and iron content is only obtained for depths less than 2000 km, corresponding to the penetration depth of the long‐period electromagnetic field. All parameter values are determined with an uncertainty better than 15–20% at the 1σ confidence level. The temperature in the uppermost lower mantle (i.e., down to 1300 km depth) is close to a value of 2200 K and increases along a superadiabatic gradient of 0.4 K km−1 between 1300 and 2000 km depth. Extrapolation of this gradient at greater depth leads to a temperature close to 2800 K at 2600 km depth. The iron content of the lower mantle is found to be almost constant and equal to 10–11% whatever the depth, while a significant linear decrease of the perovskite content is observed throughout the whole depth range, from 80% at 800 km depth down to ∼65% at 2600 km depth.
Turbidity current with a roof: Direct numerical simulation of self‐stratified turbulent channel flow driven by suspended sediment
Authors: Cantero Mariano I. , Balachandar S. , Cantelli Alessandro , Pirmez Carlos , Parker Gary
Published: March 2009

In this work we present direct numerical simulations (DNS) of sediment‐laden channel flows. In contrast to previous studies, where the flow has been driven by a constant, uniform pressure gradient, our flows are driven by the excess density imposed by suspended sediment. This configuration provides a simplified model of a turbidity current and is thus called the turbidity current with a roof configuration. Our calculations elucidate with DNS for the first time several fascinating features of sediment‐laden flows, which may be summarized as follows. First, the presence of sediment breaks the symmetry of the flow because of a tendency to self‐stratify. More specifically, this self‐stratification is manifested in terms of a Reynolds‐averaged suspended sediment concentration that declines in the upward normal direction and a Reynolds‐averaged velocity profile with a maximum that is below the channel centerline. Second, this self‐stratification damps the turbulence, particularly near the bottom wall. Two regimes are observed, one in which the flow remains turbulent but the level of turbulence is reduced and another in which the flow relaminarizes in a region near the bottom wall, i.e., bed. Third, the analysis allows the determination of a criterion for the break between these two regimes in terms of an appropriately defined dimensionless settling velocity. The results provide guidance for the improvement of Reynolds‐averaged closures for turbulent flow in regard to stratification effects. Although the analysis reported here is not performed at the scale of large oceanic turbidity currents, which have sufficiently large Reynolds numbers to be inaccessible via DNS at this time, the implication of flow relaminarization is of considerable importance. Even a swift oceanic turbidity current which at some point crosses the threshold into the regime of relaminarization may lose the capacity to reentrain sediment that settles on the bed and thus may quickly die as it loses its driving force.
On the dependence of boundary layer ventilation on frontal type
Authors: Agustí‐Panareda A. , Gray S. L. , Belcher S. E.
Published: March 2009

Case study simulations with idealized tracers have been used to determine the relationship between the dynamics and conceptual representations of different midlatitude frontal systems and the amount, distribution, and time scale of boundary layer ventilation by these systems. The key features of ventilation by a kata– and ana–cold frontal system are found to be quantitatively and also often qualitatively similar to the main ventilation pathways, which are the conveyor belts, cloud head, and other convection. The conveyor belts and cloud head occur within cloud, implying that they can be identified using satellite imagery. Differences in the transport by the two systems can be related to their conceptual representations and include a sensitive dependence on the diurnal cycle for the kata‐ but not the ana‐cold frontal case.
Postprocessing of L1 GPS radio occultation signals recorded in open‐loop mode
Authors: Sokolovskiy S. , Rocken C. , Schreiner W. , Hunt D. , Johnson J.
Published: March 2009

GPS Radio Occultation (RO) profiling from low‐Earth orbiting satellites is operationally used for numerical weather forecasting and is starting to be used for climate studies. Obtaining high‐quality observations near the surface requires recording of RO signals in model‐aided open loop (OL) mode by the GPS receiver. Postprocessing of the OL RO signals is different from that of the signals recorded in traditional phase‐locked loop (PLL) mode. It requires modeling of the signal frequency for connection of the phase between samples and removal of the GPS navigation data modulation (NDM). It is important that the postprocessing does not introduce errors (biases) in the connected phase. This paper describes the postprocessing of the OL RO signals which does not depend on the receiver model. The postprocessing includes: modeling of the RO signal frequency from refractivity climatology and the subsequent adjustment of this model by use of feedback which makes the postprocessing model‐independent; internal (as in PLL) removal of NDM and the use of externally recorded NDM bit sequence. Statistical comparison of the refractivity inversion results demonstrates that external demodulation of RO signals reduces the inversion bias in the tropical lower troposphere by about 0.5%.