Rayleigh-Taylor instability in quantum magnetized viscous plasma

Quantum effects on Rayleigh-Taylor instability of stratified viscous plasmas layer under the influence of vertical magnetic field are investigated. By linearly solving the viscous QMHD equations into normal mode, a forth-order ordinary differential equation is obtained to describe the velocity perturbation. Then the growth rate is derived for the case where a plasma with exponential density distribution is confined between two rigid planes. The results show that, the presence of vertical magnetic field beside the quantum effect will bring about more stability on the growth rate of unstable configuration for viscous plasma, which is greater than that of inviscous plasma.     

On the excess energy of nonequilibrium plasma

The energy that can be released in plasma due to the onset of instability (the excess plasma energy) is estimated. Three potentially unstable plasma states are considered, namely, plasma with an anisotropic Maxwellian velocity distribution of plasma particles, plasma with a two-beam velocity distribution, and an inhomogeneous plasma in a magnetic field with a local Maxwellian velocity distribution. The excess energy can serve as a measure of the degree to which plasma is nonequilibrium. In particular, this quantity can be used to compare plasmas in different nonequilibrium states.     

Transverse electric conductivity in collisional quantum plasma

Expressions for the transverse electric conductivity and transverse permittivity of collisional quantum plasma for an arbitrary value of the degeneracy factor of the electron gas are derived using the Wigner-Vlasov-Boltzmann kinetic equation with the Bhatnagar-Gross-Krook collision integral. Different particular cases are analyzed. Special attention is paid to the case of completely degenerate quantum plasma. The results obtained are compared with Lindhard??s formula.     

Plasma heating in a variable magnetic field

The problem of particle acceleration in a periodically variable magnetic field that either takes a zero value or passes through zero is considered. It is shown that, each time the field [0]passes through zero, the particle energy increases abruptly. This process can be regarded as heating in the course of which plasma particles acquire significant energy within one field period. This mechanism of plasma heating takes place in the absence of collisions between plasma particles and is analogous to the mechanism of magnetic pumping in collisional plasma considered by Alfvén.     

Transverse permittivity of quantum collisional plasma with an arbitrary collision frequency

Expressions for the transverse permittivity of quantum collisional plasma with an arbitrary collision frequency depending on the momentum (wave vector) of plasma particles are derived in the framework of the Mermin approach by using the kinetic Schröbinger-Boltzmann equation with a collision integral in the relaxation approximation in momentum space. It is shown that, when the collision frequency is constant, the derived expressions take the well-known form. The case of degenerate plasma in which the collision frequency is proportional to the absolute value of the wave vector is analyzed. This case corresponds to the assumption of a constant mean free path of plasma particles. The real and imaginary parts of the plasma permittivity are analyzed graphically.     

Distribution of the absorbed ECRH power among the electrons in a plasma heated by an extraordinary wave

A study is made of the one-dimensional linear problem of the absorption of the energy of an extraordinary wave propagating along a nonuniform magnetic field by a plasma in the ECR region. The plasma electrons are assumed to be nonrelativistic and are described by a collisionless kinetic equation. The distribution of the absorbed power among the electrons and the distribution of the self-consistent field over the confinement system are obtained. The conditions under which the ECRH power is distributed uniformly among the bulk electrons are determined. The limits of applicability of the locally nonuniform magnetic field approximation are established. The solutions derived are compared with the solution to an analogous problem with the collisional absorption mechanism.     

Dielectric permittivity of quantum plasma. Part II

The transverse and longitudinal dielectric permittivities of isotropic quantum plasma are calculated in the quantum plasma models based on the Dirac and Pauli equations. The dispersion relations for transverse-longitudinal waves in quantum particle beams are derived. Relativistic longitudinal and transverse waves in cold isotropic quantum plasma in models based on the Klein-Gordon and Dirac equations, as well as spin waves in the model based on the Pauli equation, are considered. Conditions for wave-particle resonance interactions in relativistic quantum plasma are analyzed.     

Thresholds of bifurcation of the degree of circular polarization of the bremsstrahlung-generated pump field harmonics in plasma

It is established that, for a Maxwellian plasma in a monochromatic pump field, the phenomenon of bifurcation of the degree of circular polarization of the field harmonics is of a universal nature. A general equation determining the thresholds for this phenomenon for arbitrary harmonics is derived, and a set of its solutions is presented for illustrative purposes.     

Dielectric permittivity of quantum plasma. Part I

Collisionless quantum plasma models based on the Schröbinger, Klein-Gordon, Dirac, and Pauli equations are considered. The transverse and longitudinal dielectric permittivities of isotropic quantum plasma are calculated in the frameworks of the models based on the Schröbinger and Klein-Gordon equations without allowance for the particle spin. Dispersion relations for transverse-longitudinal waves in beams of spinless quantum particles are derived, and the simplest quantum waves are analyzed.     

Broadband Wide-Angle Second Harmonic Generation in Magnetized Plasma: Double Resonant Effect

Conditions for the phase synchronism between high-frequency electromagnetic waves with frequencies ω and 2ω propagating in magnetized plasma are investigated. The variety of the values of the plasma density and magnetic field, as well as of wave polarizations, obeying the synchronism conditions are shown to provide resonant broadband wide-angle nonlinear generation of the second harmonic of the pumping wave. Special attention is given to oblique propagation of interacting waves. The coupling strengths for the resonant mode conversion in magnetized collisional plasma are obtained. The double resonance ensuring efficient nonlinear generation of extraordinary mode in the vicinity of the electron cyclotron resonance (ω(2k) = ω _ce ) is considered. Examples illustrating these nonlinear phenomena for some plasma and radiation parameters are presented.     

Optical properties of a plasma produced by the tunneling ionization of atoms of a matter in the field of a circularly polarized wave

General features of the absorption and reflection of a test wave by a nonequilibrium plasma produced in the tunneling ionization of atoms of a matter by a circularly polarized laser pulse are described. Because of the highly anisotropic distribution of photoelectrons, the optical properties of a nonequilibrium plasma differ considerably from those of a plasma with a Maxwellian electron velocity distribution. Physically, an anomalous behavior of the absorption coefficient and of the phase shift stems from the fact that electron kinetics in the skin layer is modified by the alternating magnetic field of the test wave.     

Operator of pair electron-ion collisions in alternating electromagnetic fields

Collisions of electrons with ions in the presence of an alternating electromagnetic field are considered. Based on the first principles (the Liouville equations for N particles), a general expression for the collisional operator in the approximation of pair collisions at an arbitrary scattering potential, including that depending periodically on time, is derived. The problem of collisions in plasma in the presence of an electromagnetic field can be reduced to this case by introducing drift coordinates. It is shown that the method of test particles can be applied to the problem of particle collisions in an alternating electromagnetic field.     

Taking into account electron-electron collisions in classical absorption of short laser pulses

The previously derived universal expression for the plasma permittivity is used to solve the problem of absorption of a short laser pulse incident on a semibounded solid-dense plasma. It is shown that the results of the exact theory may differ significantly from those obtained with the generally accepted models, especially in a weakly collisional regime corresponding to temperatures in the range 0.5–1 keV.     

Configuration of an inviscid plasma in the field of a rotating magnetized central body

The problem is considered of configurations of a strongly magnetized inviscid plasma around a rotating magnetized central body. Strong plasma magnetization implies that the Hall conductivity is much lower than the transverse conductivity, which in turn is much lower than the longitudinal conductivity. For such conditions, a self-consistent set of equations is derived that describes the conduction current density, the magnetic and electric fields, and the angular frequency of the plasma rotation under the assumptions that the components of the dielectric tensor of the plasma envelope are known functions of height and that the plasma mass velocity has only the azimuthal component. Under the assumption that the transverse conductivity is constant over a magnetic surface, the nonlinear equations derived are solved in quadratures within the class of angular frequency distributions that are symmetric about the equatorial plane. A particular solution for the plasma configurations in a dipole magnetic field is considered that corresponds to a model exponential dependence of the transverse conductivity on the number of the L-envelope (or, equivalently, on the number of the unperturbed magnetic surface).     

Generation of low-frequency radiation by a nonequilibrium plasma of an RF discharge in a linear mirror magnetic confinement system

The generation of ion-cyclotron radiation in a plasma resonator formed by an RF discharge in a linear mirror magnetic confinement system is revealed and investigated. It is shown that the experimental setup makes it possible to study the composition of a multicomponent discharge plasma and to detect multiply charged ions. Collisional losses in such a resonator are estimated, and the pressure range within which the growth rate of the ion-cyclotron instability substantially exceeds the collisional damping rate is determined.     

Langmuir probe study of an inductively coupled magnetic-pole-enhanced helium plasma

This study reports the effects of RF power and filling gas pressure variation on the plasma parameters, including the electron number density n _e , electron temperature T _e , plasma potential V _p , skin depth δ, and electron energy probability functions (EEPFs) in a low-pressure inductively coupled helium plasma source with magnetic pole enhancement. An RF compensated Langmuir probe is used to measure these plasma parameters. It is observed that the electron number density increases with both the RF power and the filling gas pressure. Conversely, the electron temperature decreases with increasing RF power and gas pressure. It is also noted that, at low RF powers and gas pressures, the EEPFs are non-Maxwellian, while at RF powers of ≥50 W, they evolve into a Maxwellian distribution. The dependences of the skin depth and plasma potential on the RF power are also studied and show a decreasing trend.     

A method for calculating the effective charge of ions decelerated in a hot dense plasma

A method for calculating the effective charge of fast ions decelerated in a hot dense plasma is proposed. The method is based on the known experimental dependence of the effective charge of an ion decelerated in cold matter on its velocity. The ion velocity in this dependence is replaced with the velocity of an ion relative to plasma electrons, averaged over the Fermi-Dirac distribution. Using results of numerical calculations performed in a wide range of plasma parameters (from a Maxwellian plasma to a fully degenerate one), a scale-invariant representation of the effective charge of a decelerating ion as a function of its initial velocity and the plasma temperature and density is obtained. An analytical formula fitting the calculated results to within 5% is derived. The obtained dependences of the effective charge are incorporated in the model describing deceleration of fast ions in plasma. Using this model, the stopping powers of krypton and lead ions in a relatively cold rarefied gas-discharge plasma and hot ICF plasma are calculated. The results of calculations are shown to agree satisfactorily with available experimental data.     

Some properties of the angular power distribution of electromagnetic waves multiply scattered in a collisional magnetized turbulent plasma

A study is made of oblique incidence of a small-amplitude plane electromagnetic wave on a semi-infinite slab of a collisional turbulent plasma in an external uniform magnetic field. In the small-angle scattering approximation, the condition for neutralizing the effects of oblique incidence and plasma anisotropy on the statistical properties of radiation multiply scattered in the absorbing plasma medium is determined by using the methods of geometrical optics. The validity of this condition was confirmed by numerical calculations based on the statistical modeling technique. The effect of the shape of the spectrum of the electron density fluctuations on the shape of the angular power distribution of a multiply scattered radiation is investigated.     

Development of a collisional radiative model for interpreting the spectroscopic measurements of ArII line emission

A collisional radiative model for an ArII ion is constructed. The populations of the excited states of ArII ions in a plasma of a magnetic confinement system are calculated. It is shown that, in such a plasma, the populations of metastable states are independent of the electron density but, at the same time, are fairly sensitive to the electron temperature. These results allow one to estimate the electron temperature from the measurements of the Doppler profiles of the spectral lines by the laser fluorescence diagnostics. The populations of nonmetastable states calculated as functions of the plasma parameters also make it possible to estimate the electron temperature from passive spectroscopy measurements.     

A precise error bound for quantum phase estimation

Quantum phase estimation is one of the key algorithms in the field of quantum computing, but up until now, only approximate expressions have been derived for the probability of error. We revisit these derivations, and find that by ensuring symmetry in the error definitions, an exact formula can be found. This new approach may also have value in solving other related problems in quantum computing, where an expected error is calculated. Expressions for two special cases of the formula are also developed, in the limit as the number of qubits in the quantum computer approaches infinity and in the limit as the extra added qubits to improve reliability goes to infinity. It is found that this formula is useful in validating computer simulations of the phase estimation procedure and in avoiding the overestimation of the number of qubits required in order to achieve a given reliability. This formula thus brings improved precision in the design of quantum computers.