We apply magnetohydrodynamic (MHD) modeling to the radio galaxy Hercules A to investigate the jet-driven shock, jet/lobe transition, wiggling, and magnetic field distribution associated with this ...source. The model consists of magnetic tower jets in a galaxy cluster environment, which has been discussed in a series of our papers. The profile of the underlying ambient gas plays an important role in the jet/lobe morphology. The balance between the magnetic pressure generated by the axial current and the ambient gas pressure can determine the lobe radius. The jet body is confined jointly by the external pressure and gravity inside the cluster core radius image, while outside image it expands radially to form fat lobes in a steeply decreasing ambient thermal pressure gradient. The current-carrying jets are responsible for generating a strong, tightly wound helical magnetic field. This magnetic configuration will be unstable against the current-driven kink mode, which visibly grows beyond image, where a separation between the jet forward and return currents occurs. The reversed pinch profile of the global magnetic field associated with the jet and lobes produces projected image - vector distributions aligned with the jet flow and the lobe edge. An AGN- driven shock powered by the expanding magnetic tower jet surrounds the jet/lobe structure and heats the ambient ICM. The lobes expand subsonically; no obvious hot spots are produced at the heads of lobes. Several key features in our MHD modeling may be qualitatively supported by observations of Hercules A.
We present an extensive synthetic observational analysis of numerically simulated radio galaxies designed to explore the effectiveness of conventional observational analyses at recovering physical ...source properties. These are the first numerical simulations with sufficient physical detail to allow such a study. The present paper focuses on extraction of magnetic field properties from nonthermal intensity information. Synchrotron and inverse Compton intensities were effective in providing meaningful information about distributions and strengths of magnetic fields, although considerable care was called for in quantitative usage of the information. Correlations between radio and X-ray surface brightness correctly revealed useful dynamical relationships between particles and fields, for example. Magnetic field strength estimates derived from the ratio of X-ray to radio intensity were mostly within about a factor of 2 of the rms field strength along a given line of sight. When emissions along a given line of sight were dominated by regions close to the minimum energy/equipartition condition, the field strengths derived from the standard power-law spectrum minimum energy calculation were also reasonably close to actual field strengths, except when spectral aging was evident. Otherwise, biases in the minimum energy magnetic field estimation mirrored actual differences from equipartition. The ratio of the inverse Compton-estimated magnetic field to the minimum energy magnetic field provided a rough measure of the actual total energy in particles and fields in most instances, although this measure was accurate within only about an order of magnitude. This may provide a practical limit to the accuracy with which one may be able to establish the internal energy density or pressure of optically thin synchrotron sources.
Capsules driven with polar drive 1, 2 on the National Ignition Facility 3 are being used 4 to study mix in convergent geometry. In preparation for experiments that will utilize deuterated plastic ...shells with a pure tritium fill, hydrogen-filled capsules with copper- doped deuterated layers have been imploded on NIF to provide spectroscopic and nuclear measurements of capsule performance. Experiments have shown that the mix region, when composed of shell material doped with about 1% copper (by atom), reaches temperatures of about 2 keV, while undoped mixed regions reach about 3 keV. Based on the yield from these implosions, we estimate the thickness of CD that mixed into the gas as between about 0.25 and 0.43 μm of the inner capsule surface, corresponding to about 5 to 9 μg of material. Using 5 atm of tritium as the fill gas should result in over 1013 DT neutrons being produced, which is sufficient for neutron imaging 5.
A 2-D Eulerian code with a turbulent mix model was used for the first time to model a set of plastic (CH) ablator capsules with 15 mu m thick CH shells. Our simulations of these capsules do a ...reasonable job of matching the implosion radius versus time, self-emitting core radius, and have an experiment/simulation yield ratio that is about 0.24.
The Defect Induced Mix Experiment (DIME-II) will measure the implosion and mix characteristics of CH capsules filled with 5 atmospheres of DT by incorporating mid-Z dopant layers of Ge and Ga. This ...polar direct drive (PDD) experiment also will demonstrate the filling of a CH capsule at target chamber center using a fill tube. Diagnostics for these experiments include areal x-ray backlighting to obtain early time images of the implosion trajectory and a multiple-monochromatic imager (MMI) to collect spectrally-resolved images of the capsule dopant line emission near bangtime. The inclusion of two (or more) thin dopant layers at separate depths within the capsule shell facilitates spatial correlation of mix between the layers and the hot gas core on a single shot. The dopant layers are typically 2 mu m thick and contain dopant concentrations of 1.5%. Three dimensional Hydra simulations have been performed to assess the effects of PDD asymmetry on capsule performance.
The effect of small localized perturbations, such as fill tubes and mounting tents, on the NIF ignition capsule and the effect of hemi-joints on high gain double shell capsules are an important issue ...in achieving ignition on NIF. Our codes have difficulty modeling small features and their effect on mix. Because of issues of symmetry, shock timing, high-z shells, mix etc. trying to understand the effect of localized perturbations ("defect") on these high gain NIF capsules will be difficult. To begin the study of defects on DT burn, a direct-drive exploding pusher is used. Experimental results are presented for capsules with and without defects. The unperturbed capsules give reproducible yields while the perturbed capsules show significant drops in yield. Both AMR and Lasnex codes over predict the unperturbed capsule yield
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