اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدGeneration of Ultrafast Jets through the Implosion of a Nested Conical Wire Array
48
0
0.0
(
0
)
تأليف
Friedwardt Winterberg
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
It is shown that in contrast to the electric pulse power driven implosion of a single conical wire array, the implosion of a nested conical wire array with opposite alternate opening angles can lead to the generation of fast jets, with velocities of the order 108 cm/s. This technique can be applied for the supersonic shear flow stabilization of a dense z-pinch, but possibly also for the fast ignition of a pre-compressed dense deuterium-tritium target.
قيم البحث
اقرأ أيضاً
The aim of this work is to model the jets produced by conical wire arrays on the MAGPIE generator, and to design and test new setups to strengthen the link between laboratory and astrophysical jets. We performed the modelling with direct three-dimens
ional magneto-hydro-dynamic numerical simulations using the code GORGON. We applied our code to the typical MAGPIE setup and we successfully reproduced the experiments. We found that a minimum resolution of approximately 100 is required to retrieve the unstable character of the jet. We investigated the effect of changing the number of wires and found that arrays with less wires produce more unstable jets, and that this effect has magnetic origin. Finally, we studied the behaviour of the conical array together with a conical shield on top of it to reduce the presence of unwanted low density plasma flows. The resulting jet is shorter and less dense.
Ongoing developments in ultrafast X-ray sources offer powerful new means of probing the com- plex non-adiabatically coupled structural and electronic dynamics of photoexcited molecules. These non-Born-Oppenheimer effects are governed by general elect
ronic degeneracies termed conical in- tersections which play a key role, analogous to that of a transition state, in the electronic-nuclear dynamics of excited molecules. Using high level ab initio quantum dynamics simulations, we studied time-resolved X-ray absorption and photoelectron spectroscopy (TRXAS and TRXPS, respectively) of the prototypical unsaturated organic chromophore, ethylene, following excitation to its S2 state. The TRXAS in particular is highly sensitive to all aspects of the ensuing dynamics. These X-ray spectroscopies provide a clear signature of the wavepacket dynamics near conical intersections, related to charge localization effects driven by the nuclear dynamics. Given the ubiquity of charge localization in excited state dynamics, we believe that ultrafast X-ray spectroscopies offer a unique and powerful route to the direct observation of dynamics around conical intersections.
Intense electric currents called electrojets occur in weakly ionized magnetized plasmas. An example occurs in the Earths ionosphere near the magnetic equator where neutral winds drive the plasma across the geomagnetic field. Similar processes take pl
ace in the Solar chromosphere and MHD generators. This letter argues that not all convective neutral flows generate electrojets and it introduces the corresponding universal criterion for electrojet formation, $ ablatimes (vec{U}timesvec{B}) eqpartialvec{B}/partial t$, where $vec{U}$ is the neutral flow velocity, $vec{B}$ is the magnetic field, and $t$ is time. This criterion does not depend on the conductivity tensor, $hat{sigma}$. For many systems, the displacement current, $partialvec{B}/partial t$, is negligible, making the criterion even simpler. This theory also shows that the neutral-dynamo driver that generates electrojets plays the same role as the DC electric current plays for the generation of the magnetic field in the Biot-Savart law.
Radiation generated by a charge moving through a vacuum channel in a dielectric cone is analyzed. It is assumed that the charge moves through the cone from the apex side to the base side (the case of inverted cone). The cone size is supposed to be mu
ch larger than the wavelengths under consideration. We calculate the wave field outside the target using the aperture method developed in our previous papers. Contrary to the problems considered earlier, here the wave which incidences directly on the aperture is not the main wave, while the wave once reflected from the lateral surface is much more important. The general formulas for the radiation field are obtained, and the particular cases of the ray optics area and the Fraunhofer area are analyzed. Significant physical effects including the phenomenon of Cherenkov spotlight are discussed. In particular it is shown that this phenomenon allows reaching essential enhancement of the radiation intensity in the far-field region at certain selection of the problem parameters. Owing to the inverted cone geometry, this effect can be realized for arbitrary charge velocity, including the ultra relativistic case, by proper selection of the cone material and the apex angle. Typical radiation patterns in the far-field area are demonstrated.
In inertial confinement fusion the target implosion non-uniformity is introduced by a driver beams illumination non-uniformity, a fuel target alignment error in a fusion reactor, the target fabrication defect, et al. For a steady operation of a fusio
n power plant the target implosion should be robust against the implosion non-uniformities. In this paper the requirement for the implosion uniformity is first discussed. The implosion uniformity should be less than a few percent. A study on the fuel hotspot dynamics is also presented and shows that the stagnating plasma fluid provides a significant enhancement of vorticity at the final stage of the fuel stagnation. Then non-uniformity mitigation mechanisms of the heavy ion beam (HIB) illumination are also briefly discussed in heavy ion inertial fusion (HIF). A density valley appears in the energy absorber, and the large-scale density valley also works as a radiation energy confinement layer, which contributes to a radiation energy smoothing. In HIF a wobbling heavy ion beam illumination was also introduced to realize a uniform implosion. In the wobbling HIBs illumination, the illumination non-uniformity oscillates in time and space on a HIF target. The oscillating-HIB energy deposition may contribute to the reduction of the HIBs illumination non-uniformity by its smoothing effect on the HIB illumination non-uniformity and also by a growth mitigation effect on the Rayleigh-Taylor instability.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
