ترغب بنشر مسار تعليمي؟ اضغط هنا

Anti-ExB flow field associated with a vortex formation in a partially ionized plasma

91   0   0.0 ( 0 )
 نشر من قبل Atushi Okamoto
 تاريخ النشر 2004
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

A high-density magnetized plasma has been studied for understanding of plasma dynamics in partially ionized plasmas. Ion flow field has been obtained experimentally, and is shown to be associated with a vortex formation. The most remarkable result is that the direction of rotation is opposite to that of the ExB drift. Measurement of neutral density profile reveals that there is a steep density gradient of the neutrals around the vortex, suggesting that the generation of inward momentum of the neutrals due to the density gradient. The momentum is transfered to ion with charge-exchange collision, and cause effective force on the ion. The present experiment shows that this effective force may dominate the ambipolar-electric field and drive the anti-ExB vortical motion of ions.



قيم البحث

اقرأ أيضاً

The temperature dependence of rates of electron impact ionization and two electrons recombination are calculated using Wannier cross section of electron impact ionization of neutral hydrogen atom. Entropy production and power dissipation are derived for the case when the ionization degree deviates from its equilibrium value. This is the special case of the obtained general formula for entropy production accompanying chemical reactions. Damping rate of the sound waves is calculated and the conditions when ionization processes dominate are considered. A quasi-classical approximation for the heating mechanism of solar chromosphere is proposed. Several analogous phenomena for damping rates in liquids and crystals are shortly discussed, for example, deaf sound of a glass of beer or English salt solution. An explicit expression for the second or bulk (or volume) viscosity of hydrogen plasma is calculated from firsts principles. For the first time some second viscosity is calculated from first principles.
168 - Roberto Soler , Marc Carbonell , 2013
Compressible disturbances propagate in a plasma in the form of magnetoacoustic waves driven by both gas pressure and magnetic forces. In partially ionized plasmas the dynamics of ionized and neutral species are coupled due to ion-neutral collisions. As a consequence, magnetoacoustic waves propagating through a partially ionized medium are affected by the ion-neutral coupling. The degree to which the behavior of the classic waves is modified depends on the physical properties of the various species and on the relative value of the wave frequency compared to the ion-neutral collision frequency. Here, we perform a comprehensive theoretical investigation of magnetoacoustic wave propagation in a partially ionized plasma using the two-fluid formalism. We consider an extensive range of values for the collision frequency, ionization ratio, and plasma $beta$, so that the results are applicable to a wide variety of astrophysical plasmas. We determine the modification of the wave frequencies and study the frictional damping due to ion-neutral collisions. Approximate analytic expressions to the frequencies are given in the limit case of strongly coupled ions and neutrals, while numerically obtained dispersion diagrams are provided for arbitrary collision frequencies. In addition, we discuss the presence of cutoffs in the dispersion diagrams that constrain wave propagation for certain combinations of parameters. A specific application to propagation of compressible waves in the solar chromosphere is given.
High-throughput plasma separation based on atomic mass holds the promise for offering unique solutions to a variety of high-impact societal applications. Through the mass differential effects they exhibit, crossed-field configurations can in principl e be exploited in various ways to separate ions based on atomic mass. Yet, the practicality of these concepts is conditioned upon the ability to drive suitable crossed-field flows for plasma parameters compatible with high-throughput operation. Limited current predictive capabilities have not yet made it possible to confirm this possibility. Yet, past experimental results suggest that end-electrodes biasing may be effective, at least for certain electric field values. A better understanding of cross-field conductivity is needed to confirm these results and confirm the potential of crossed-field configurations for high-throughput separation.
We present experiments and numerical simulations which demonstrate that fully-ionized, low-density plasma channels could be formed by hydrodynamic expansion of plasma columns produced by optical field ionization (OFI). Simulations of the hydrodynamic expansion of plasma columns formed in hydrogen by an axicon lens show the generation of unit[200]{mm} long plasma channels with axial densities of order $n_e(0) = 1 times 10^{17} cm^{-3}$ and lowest-order modes of spot size $W_M approx 40 mu m$. These simulations show that the laser energy required to generate the channels is modest: of order 1 mJ per centimetre of channel. The simulations are confirmed by experiments with a spherical lens which show the formation of short plasma channels with $1.5 times 10^{17}cm^{-3} lesssim n_e(0) lesssim 1 times 10^{18} cm^{-3}$ and $61 mu m gtrsim W_M gtrsim 33 mu m$. Low-density plasma channels of this type would appear to be well-suited as multi-GeV laser-plasma accelerator stages capable of long-term operation at high pulse repetition rates.
We address an experimental observation of shear flow of micron sized dust particles in a strongly coupled complex plasma in presence of a homogeneous magnetic field. Two concentric Aluminum rings of different size are placed on the lower electrode of a radio frequency (rf) parallel plate discharge. The modified local sheath electric field is pointing outward/inward close to the inner/outher ring, respectively. The microparticles, confined by the rings and subject to an ion wind that driven by the local sheath electric field and deflected by an externally applied magnetic field, start flowing in azimuthal direction. Depending upon the rf amplitudes on the electrodes, the dust layers show rotation in opposite direction at the edges of the ring-shaped cloud resulting a strong shear in its center. MD simulations shows a good agreement with the experimental results.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا