748 research outputs found
Magnetised Thermal Self-focusing and Filamentation of Long-Pulse Lasers in Plasmas Relevant to Magnetised ICF Experiments
In this paper we study the influence of the magnetised thermal conductivity
on the propagation of a nanosecond laser in an
underdense plasma by performing simulations of a paraxial model laser in a
plasma with the full Braginskii magnetised transport coefficients. Analytic
theory and simulations show the shortening of the self-focal length of a laser
beam in a plasma as a result of the reduction of the plasma thermal
conductivity in a magnetic field. Furthermore the filamentation of a laser via
the thermal mechanism is found to have an increased spatial growth rate in a
magnetised plasma. We discuss the effect of these results on recent magnetised
inertial fusion experiments where filamentation can be detrimental to laser
propagation and uniform laser heating. We conclude the application of external
magnetic fields to laser-plasma experiments requires the inclusion of the
extended electron transport terms in simulations of laser propagation.Comment: 10 pages, 9 figure
Twisted plasma waves driven by twisted ponderomotive force
We present results of twisted plasma waves driven by twisted ponderomotive
force. With beating of two, co-propagating, Laguerre-Gaussian (LG) orbital
angular momentum (OAM) laser pulses with different frequencies and also
different twist indices, we can get twisted ponderomotive force.
Three-dimensional particle-in-cell simulations are used to demonstrate the
twisted plasma waves driven by lasers. The twisted plasma waves have an
electron density perturbation with a helical rotating structure. Different from
the predictions of the linear fluid theory, the simulation results show a
nonlinear rotating current and a static axial magnetic field. Along with the
rotating current is the axial OAM carried by particles in the twisted plasma
waves. Detailed theoretical analysis of twisted plasma waves is given too
Kinetic modeling of Nernst effect in magnetized hohlraums
We present nanosecond time-scale Vlasov-Fokker-Planck-Maxwell modeling of magnetized plasma transport and dynamics in a hohlraum with an applied external magnetic field, under conditions similar to recent experiments. Self-consistent modeling of the kinetic electron momentum equation allows for a complete treatment of the heat flow equation and Ohm's law, including Nernst advection of magnetic fields. In addition to showing the prevalence of nonlocal behavior, we demonstrate that effects such as anomalous heat flow are induced by inverse bremsstrahlung heating. We show magnetic field amplification up to a factor of 3 from Nernst compression into the hohlraum wall. The magnetic field is also expelled towards the hohlraum axis due to Nernst advection faster than frozen-in flux would suggest. Nonlocality contributes to the heat flow towards the hohlraum axis and results in an augmented Nernst advection mechanism that is included self-consistently through kinetic modeling
Increased Dust Deposition in New Zealand Related to Twentieth Century Australian Land Use
Mineral aerosols (dust) generated in the dryland regions of Australia have the potential to reach New Zealand through atmospheric transport. Although a large portion of dust in New Zealand originates in Australia, little is known about how dust deposition has varied over time in New Zealand or what may have caused this variation. We used geochemical dust proxies to examine the recent history of dust deposition to two alpine lakes in Kahurangi National Park, South Island, New Zealand. Geochemical indicators suggest that dust deposition began to increase around 1900, with the greatest deposition rates occurring from ~1920 to ~1990. In subsequent decades, dust deposition rates to New Zealand lakes appear to have declined. This rise and fall of dust deposition recorded in New Zealand lakes is consistent with dust records from the Antarctic Ice Sheet, Eastern Australia, and incidents of low visibility due to dust events recorded at Australian climate stations. The dust deposition rate over time also follows the temporal pattern of land use in south and central Australia over the time scale of the twentieth century suggesting a causal linkage. It is possible, and perhaps likely, that drought cycles also affected both emissions and transport pathways but over shorter time periods this was difficult to discern at the temporal resolution of these lake sediment cores. The increase in dust deposition to the high‐elevation regions of New Zealand likely has implications for the biogeochemistry of alpine lakes in the Tasman Mountains
Three Dimensional Secondary Ion Mass Spectrometry Imaging and Retrospective Depth Profiling
Secondary Ion Mass Spectrometry (SIMS) for three dimensional analysis of materials is an exciting and rapidly developing technique. We describe a framestore datasystem for ion microprobe instruments and present images and three dimensional SIMS data acquired and processed with this system. The concept of retrospective depth profiling is introduced, particularly as a means to optimise concentration detection limits. We examine the dependence of concentration detection limits on spatial resolution
Маркшейдерська школа Національного гірничого університету
Викладена історія створення та розвитку маркшейдерської школи в НГУ протягом 110 років.Изложена история создания и развития маркшейдерской школы в НГУ в течение 110 лет.History of creation and development ofsurveyor school is expounded in NMU during 110 years
In vitro experiments to inform cell seeding strategies and parameterize a mathematical model for peripheral nerve repair
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