Study of the stability of Z-pinch implosions with different initial density profiles

2014 ◽  
Vol 21 (5) ◽  
pp. 052701 ◽  
Author(s):  
A. G. Rousskikh ◽  
A. S. Zhigalin ◽  
V. I. Oreshkin ◽  
N. A. Labetskaya ◽  
S. A. Chaikovsky ◽  
...  
Keyword(s):  
Initial Density ◽  
Density Profiles ◽  
The Stability ◽  
Z Pinch

Effect of tailored density profiles on the stability of imploding z-pinches at microsecond rise time megaampere currents

2021 ◽  
Author(s):  
Rustam K Cherdizov ◽  
R Baksht ◽  
Vladimir A Kokshenev ◽  
Vladimir Oreshkin ◽  
Alexander Rousskikh ◽  
...  
Keyword(s):  
Rise Time ◽  
Initial Density ◽  
Plasma Jet ◽  
Vacuum Arc ◽  
Radial Density ◽  
Radiation Yield ◽  
High Current Electronics ◽  
Density Profiles ◽  
Z Pinch ◽  
A Current

Abstract To study the effect of the radial density profile of the material of a metal-plasma Z-pinch load on the development of magneto-Rayleigh-Taylor (MRT) instabilities, experiments have been performed at the Institute of High Current Electronics with the GIT-12 generator produced microsecond rise time megaampere currents. The load was an aluminum plasma jet with an outer plasma shell. This configuration provides the formation of a uniform current sheath in a Z-pinch load upon application of a high voltage pulse. It was successfully used in experiments with hybrid deuterium gas-puffs [Klir et al. 2020 New J. Phys. 22 103036]. The initial density profiles of the Z-pinch loads were estimated from the pinch current and voltage waveforms using the zero-dimensional "snowplow" model, and they were verified by simulating the expansion of the plasma jet formed by a vacuum arc using a two-dimensional quasi-neutral hybrid model [Shmelev et al. 2020 Phys. Plasmas 27 092708]. Two Z-pinch load configurations were used in the experiments. The first configuration provided tailored load density profiles, which could be described as ρ(r) ≈ 1/r^s for s > 2. In this case, MRT instabilities were suppressed and thus a K-shell radiation yield of 11 kJ/cm and a peak power of 0.67 TW/cm could be attained at a current of about 3 MA. For the second configuration, the radial density profiles were intentionally changed using a reflector. This led to the appearance of a notch in the density profiles at radii of 1–3 cm from the pinch axis and to magnetohydrodynamic instabilities at the final implosion stage. As a result, the K-shell radiation yield more than halved and the power decreased to 0.15 TW/cm at a current of about 3.5 MA.

scholarly journals Effects of initial density profiles on massive star cluster formation in giant molecular clouds

2021 ◽  
Author(s):  
Yingtian Chen ◽  
Hui Li ◽  
Mark Vogelsberger
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Molecular Clouds ◽  
Globular Clusters ◽  
Cluster Formation ◽  
Initial Density ◽  
Giant Molecular Clouds ◽  
Density Profiles ◽  
Stellar Feedback ◽  
Gas Accretion

Abstract We perform a suite of hydrodynamic simulations to investigate how initial density profiles of giant molecular clouds (GMCs) affect their subsequent evolution. We find that the star formation duration and integrated star formation efficiency of the whole clouds are not sensitive to the choice of different profiles but are mainly controlled by the interplay between gravitational collapse and stellar feedback. Despite this similarity, GMCs with different profiles show dramatically different modes of star formation. For shallower profiles, GMCs first fragment into many self-gravitation cores and form sub-clusters that distributed throughout the entire clouds. These sub-clusters are later assembled ‘hierarchically’ to central clusters. In contrast, for steeper profiles, a massive cluster is quickly formed at the center of the cloud and then gradually grows its mass via gas accretion. Consequently, central clusters that emerged from clouds with shallower profiles are less massive and show less rotation than those with the steeper profiles. This is because 1) a significant fraction of mass and angular momentum in shallower profiles is stored in the orbital motion of the sub-clusters that are not able to merge into the central clusters 2) frequent hierarchical mergers in the shallower profiles lead to further losses of mass and angular momentum via violent relaxation and tidal disruption. Encouragingly, the degree of cluster rotations in steeper profiles is consistent with recent observations of young and intermediate-age clusters. We speculate that rotating globular clusters are likely formed via an ‘accretion’ mode from centrally-concentrated clouds in the early Universe.

scholarly journals Earth-size planet formation in the habitable zone of circumbinary stars

2020 ◽  
Vol 494 (1) ◽  
pp. 1045-1057 ◽  
Author(s):  
G O Barbosa ◽  
O C Winter ◽  
A Amarante ◽  
A Izidoro ◽  
R C Domingos ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Planet Formation ◽  
Terrestrial Planet ◽  
Close Binary ◽  
Habitable Zone ◽  
Density Profiles ◽  
Habitable Planets ◽  
Habitable Zones ◽  
Test Particles ◽  
The Stability

ABSTRACT This work investigates the possibility of close binary (CB) star systems having Earth-size planets within their habitable zones (HZs). First, we selected all known CB systems with confirmed planets (totaling 22 systems) to calculate the boundaries of their respective HZs. However, only eight systems had all the data necessary for the computation of HZ. Then, we numerically explored the stability within HZs for each one of the eight systems using test particles. From the results, we selected five systems that have stable regions inside HZs, namely Kepler-34,35,38,413, and 453. For these five cases of systems with stable regions in HZ, we perform a series of numerical simulations for planet formation considering discs composed of planetary embryos and planetesimals, with two distinct density profiles, in addition to the stars and host planets of each system. We found that in the case of the Kepler-34 and 453 systems, no Earth-size planet is formed within HZs. Although planets with Earth-like masses were formed in Kepler-453, they were outside HZ. In contrast, for the Kepler-35 and 38 systems, the results showed that potentially habitable planets are formed in all simulations. In the case of the Kepler-413system, in just one simulation, a terrestrial planet was formed within HZ.

A study of the stability of the Z pinch under fusion conditions using the Hall fluid model

1984 ◽  
Vol 27 (12) ◽  
pp. 2886 ◽  
Author(s):  
M. Coppins ◽  
D. J. Bond ◽  
M. G. Haines
Keyword(s):  
Fluid Model ◽  
The Stability ◽  
Z Pinch

Stabilized radiative Z-pinch loads with tailored density profiles

1998 ◽  
Vol 5 (9) ◽  
pp. 3377-3388 ◽  
Author(s):  
A. L. Velikovich ◽  
F. L. Cochran ◽  
J. Davis ◽  
Y. K. Chong
Keyword(s):  
Density Profiles ◽  
Z Pinch

scholarly journals Layers from initial Rayleigh density profiles by directed nonlinear force driven plasma blocks for alternative fast ignition

2009 ◽  
Vol 27 (1) ◽  
pp. 149-156 ◽  
Author(s):  
E. Yazdani ◽  
Y. Cang ◽  
R. Sadighi-Bonabi ◽  
H. Hora ◽  
F. Osman
Keyword(s):  
Fluid Model ◽  
Initial Density ◽  
Contrast Ratio ◽  
Laser Pulses ◽  
Fast Ignition ◽  
Single Shot ◽  
Density Profiles ◽  
Nonlinear Force ◽  
Two Fluid Model ◽  
New Phenomena

AbstractMeasurement of extremely new phenomena during the interaction of laser pulses with terawatt and higher power and picoseconds with plasmas arrived at drastically different anomalies in contrast to the usual observations if the laser pulses were very clean with a contrast ratio higher than 108. This was guaranteed by the suppression of prepulses during less than dozens of ps before the arrival of the main pulse resulting in the suppression of relativistic self-focusing. This anomaly was confirmed in many experimental details, and explained and numerically reproduced as a nonlinear force acceleration of skin layers generating quasi-neutral plasma blocks with ion current densities above 1011A/cm2. This may support the requirement to produce a fast ignition deuterium tritium fusion at densities not much higher than the solid state by a single shot PW-ps laser pulse. With the aim to achieve separately studied ignition conditions, we are studying numerically how the necessary nonlinear force accelerated plasma blocks may reach the highest possible thickness by using optimized dielectric properties of the irradiated plasma. The use of double Rayleigh initial density profiles results in many wavelength thick low reflectivity directed plasma blocks of modest temperatures. Results of computations with the genuine two-fluid model are presented.

scholarly journals A medieval multiverse?: Mathematical modelling of the thirteenth century universe of Robert Grosseteste

2014 ◽  
Vol 470 (2167) ◽  
pp. 20140025 ◽  
Author(s):  
Richard G. Bower ◽  
Tom C. B. McLeish ◽  
Brian K. Tanner ◽  
Hannah E. Smithson ◽  
Cecilia Panti ◽  
...  
Keyword(s):  
Initial Conditions ◽  
Initial Density ◽  
Outer Region ◽  
Big Bang ◽  
Small Range ◽  
Density Profiles ◽  
Material Body ◽  
Fundamental Parameters ◽  
Entire Cosmos ◽  
Text Formation

In his treatise on light, written about 1225, Robert Grosseteste describes a cosmological model in which the universe is created in a big-bang-like explosion and subsequent condensation. He postulates that the fundamental coupling of light and matter gives rises to the material body of the entire cosmos. Expansion is arrested when matter reaches a minimum density and subsequent emission of light from the outer region leads to compression and rarefaction of the inner bodily mass so as to create nine celestial spheres, with an imperfect residual core. In this paper, we reformulate the Latin description in terms of a modern mathematical model, teasing out consequences implicit in the text, but which the author would not have had the tools to explore. The equations which describe the coupling of light and matter are solved numerically, subjected to initial conditions and critical criteria consistent with the text. Formation of a universe with a non-infinite number of perfected spheres is extremely sensitive to the initial conditions, the intensity of the light and the transparency of these spheres. In this ‘medieval multiverse’, only a small range of opacity and initial density profiles leads to a stable universe with nine perfected spheres. As in current cosmological thinking, the existence of Grosseteste’s universe relies on a very special combination of fundamental parameters.

scholarly journals Upper limit on the central density of dark matter in the Eddington-inspired Born–Infeld (EiBI) gravity

2015 ◽  
Vol 30 (11) ◽  
pp. 1550056 ◽  
Author(s):  
Ramil Izmailov ◽  
Alexander A. Potapov ◽  
Alexander I. Filippov ◽  
Mithun Ghosh ◽  
Kamal K. Nandi
Keyword(s):  
Dark Matter ◽  
Alternative Model ◽  
Milky Way ◽  
Viable Alternative ◽  
Central Density ◽  
Density Profiles ◽  
Milky Way Galaxy ◽  
Upper Limit ◽  
The Stability ◽  
Individual Galaxy

We investigate the stability of circular material orbits in the analytic galactic metric recently derived by Harko et al., Mod. Phys. Lett. A29, 1450049 (2014). It turns out that stability depends more strongly on the dark matter central density ρ0 than on other parameters of the solution. This property then yields an upper limit on ρ0 for each individual galaxy, which we call here [Formula: see text], such that stable circular orbits are possible only when the constraint [Formula: see text] is satisfied. This is our new result. To approximately quantify the upper limit, we consider as a familiar example our Milky Way galaxy that has a projected dark matter radius R DM ~180 kpc and find that [Formula: see text]. This limit turns out to be about four orders of magnitude larger than the latest data on central density ρ0 arising from the fit to the Navarro–Frenk–White (NFW) and Burkert density profiles. Such consistency indicates that the Eddington-inspired Born–Infeld (EiBI) solution could qualify as yet another viable alternative model for dark matter.

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