Neutron flux from nondegenerate nonrelativistic neutron gas polarized by a magnetic field

The effect of a strong magnetic field on the average neutron velocity both in an equilibrium neutron system and in a beam of particles flowing from the system is assessed in the context of the statistical thermodynamics of equilibrium systems. The calculations are based on the Maxwell-Boltzmann distribution for a nondegenerate, nonrelativistic, magnetized neutron gas with allowance for Pauli paramagnetism. Byelorussian State University, Brest State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 44–48, April, 2000.     

Influence of the intrinsic magnetic moment of an electron on the filling of energy levels of a nonrelativistic degenerate electron gas in a quantizing magnetic field

The effect of a quantizing magnetic field on the filling of energy subbands of a degenerate nonrelativistic electron gas, whose magnetic moments are parallel and antiparallel to the direction of the field, is studied. Calculations are made under the assumption that the Fermi kinetic energy of the electron system increases as a result of Pauli's paramagnetism as compared to the kinetic energy calculated without taking this effect into account. Numerical values of the electron concentration are calculated as a function of the magnetic moment direction for magnetic fields under which the electrons are in states with given numbers of the Landau quantum level.A. S. Pushkin State Education Institute, Brest. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 9–13, June, 1992.     

Magnetothermal factor of intersubband relaxation of 2D electrons from a highly doped heterotransition in AlGaAs (Si)/GaAs

Characteristics of the Shubnikov-de Haas transverse magnetoresistance oscillations of 2D electrons in highly dopedAlGaAs(Si)/GaAs heterostructures are investigated in the present paper. Anomalies caused by the occupation of two quantization subbands are revealed for samples with 2D-electron density n_s>7·10¹¹ cm⁻² at T=1.7–16 K and magnetic field induction B up to 7.4 T. The dependences of the normalized oscillation amplitude on the magnetic field show bends that typically displace toward weaker magnetic fields with decreasing temperature and electron density n_s. A nonmonotonic (oscillating) dependence of the Dingle temperature on the experimental temperature is found. These anomalies are interpreted for a model of the occupation of two quantization subbands with electrons. They are caused by the competitive character, of intersubband 2D-electron scattering. Small-angle relaxation times are estimated for 2D electrons of the zero and first quantization subbands. S. A. Esenin Ryazan' State Pedagogical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 52–57, January, 2000.     

Ionization equilibrium of atoms in a strong magnetic field (the saha formula)

The effect of an external magnetic field on the ionization equilibrium of atoms in the nondegenerate nonrelativistic plasma is examined. When taken into account that the interaction of the magnetic moments of electrons with the magnetic field immediately changes their kinetic energy, which is incorrect, the degree of ionization of atoms will increase with increase in the magnetic field strength compared to the atomic concentration in the absence of a magnetic field at the same temperature. When taken into account that this energy changes in view of the Pauli principle and spontaneous minimization of the quantum system, the degree of ionization must decrease with increase in the external magnetic field strength, that is, a strong magnetic field suppresses ionization of atoms in the nonrelativistic plasma at a given temperature. Byelorussian State University; Brest State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 36–39, July, 1999.     

Energy of a nondegenerate, nonrelativistic electron gas polarized by a magnetic field. II

The average kinetic energy density of a nondegenerate, nonrelativistic, magnetized electron system of a given densityn _e is determined with allowance for changes in its kinetic energy due to the added energy of interaction of its intrinsic magnetic moment with a magnetic field of a given strength. Brest State University, Brest. Translated from Izvestiya Vysshikh Uchenbnykh Zavedenii, Fizika, Vol. 42, No. 2, pp. 46–50, February, 1999.     

Energy losses of a neutron star due to inverse muon decay in the superstrong magnetic field

The emission of a pair of neutrinos by a charged lepton under the influence of a strong magnetic field is examined. The expression found in general form for the probability of the process l l'vV in the strong magnetic field of a neutron star is used to evaluate the contribution of inverse muon decaye vV to the energy losses of the neutron star. The conditions under which this contribution to the energy losses of a neutron star may compete with that due to neutrino pair emission in the processe evV are discussed.Lomonosov State University, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 39–44, July, 1995.     

Electron polarization in nonrelativistic nondegenerate magnetized electron gas

For a nondegenerate nonrelativistic electron system, taking account of the minimum of its total energy, the population of the Landau electron levels by electrons with intrinsic magnetic moments parallel and antiparallel to the external magnetic field is determined, as a function of the external magnetic field strength H. The results are then compared with analogous data obtained by other authors without taking the minimum of the system’s total energy into account. Brestsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 14–19, February, 1997.     

Qualitative estimation of kinetic energy components of longitudinal continuous motion of magnetized nonrelativistic electrons within the landau level

In the framework of the quantum statistical physics it was shown that direct subtraction of the electron interaction energy in a magnetic field from the kinetic energy or its addition to the latter in the strength function contradicts to the well-known fact according to which the magnetic field does no positive work over a charged particle. Byelorussian State University, Brest State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 31–35, June, 2000.     

Landau diamagnetism and determination of the longitudinal and transverse kinetic energy components of a degenerate nonrelativistic electron gas

The Fermi energy, average total kinetic energy density, and also average kinetic energy of finite diamagnetic motion of an electron gas of specified concentration are calculated. The kinetic energy of continuous longitudinal motion of the electrons along the direction of an external magnetic field H is determined. It is found that in the quantum limit, when the maximum Landau quantum number N _m =0, the kinetic energy of continuous longitudinal motion tends to zero with increase in the external magnetic field strength. If the maximum Landau quantum number is greater than zero, the longitudinal and transverse kinetic energy components of the degenerate electron gas change only insignificantly. Byelorussian State University; Brest State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 31–35, July, 1999.     

Radiation by relativistic dipoles. III

The classical radiation of a point magnetic moment (a magneton) moving at a constant velocity in an arbitrary direction with respect to the field lines of a uniform magnetic field is analyzed. All characteristics of the radiation agree with the Ternov-Bagrov-Khapaev relativistic quantum thoery of the radiation by a neutron. It is thus demonstrated that the classical model of radiation with spin flip is valid. The correspondence principle in the theory of radiation with spin flip will be discussed in more detail in subsequent papers.V. V. Kuibyshev Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 53–59, January 1994.     

System of quantum wells in a parallel magnetic field

The energy spectrum and quantum states of electrons in a system of quantum wells in a strong magnetic field parallel to the heterogeneous boundaries are studied. The combined effect of the quantizing magnetic field and the potential of the system of quantum wells leads to a radical change in the electron dispersion relation owing to the appearance of one-dimensional Landau bands. The neighborhoods of the anticrossing points of the different bands correspond to an effective redistribution of the electron envelope functions, which becomes stronger as the magnetic field is raised. The character of the electron-state density in the size-quantization subbands is examined qualitatively in connection with the change in the system of isoenergy contours when a magnetic field is applied. Fiz. Tverd. Tela (St. Petersburg) 40, 1719–1723 (September 1998)     

Use of CR-39 solid state nuclear track detector in neutron personnel monitoring

Neutron sources like ²⁴¹Am–Be, ²³⁹Pu–Be, ²⁵²Cf and 14.6 MeV neutron generator are being used in oil exploration industries as well as in research institutions. While handling these neutron sources, personnel may be exposed to neutrons. Also personnel working in reactors, accelerators may receive dose from neutrons. These exposed individuals need to be monitored regularly for measurement of neutron doses. The individual neutron doses can be estimated by using Kodak NTA films and CR-39 Solid State Nuclear Track Detector with a polyethylene radiator to increase sensitivity in front in holder. Nearly 1450 personnel are being monitored regularly throughout the country on a quarterly basis. In India, the monitoring system adopted for individual neutron dose estimation having energy from 100 keV and above is described in this paper. Background counts of 0.20 mSv could be measured with CR-39 SSNTD foil system and it has been successfully introduced for Fast Neutron Personnel Monitoring for the country.     

Oscillator strengths of optical transitions of a cylindrical shell: Crossed static electric and magnetic fields

The single-electron eigenstates of a cylindrical shell are determined as functions of the applied crossed electric and magnetic fields in the effective-mass approximation. The system considered consists of donor charges taken to be uniformly distributed within an inner core of infinitely long length. The core is concentrically enveloped by a semiconducting material of finite thickness; which is essentially the host material. This configuration of the donor charges sets up a spatially varying electric field nonetheless with only the radial component. In addition, a uniform magnetic field is applied parallel to the axis of symmetry of the inner core. As is well known, the axial applied magnetic field lifts the double degeneracies of the electron’s subbands characterized by the same azimuthal quantum numbers which differ only in sign. The main effect of increasing the external electric field is to elevate the various energy subbands, more or less to the same extent, to higher values. Further, evaluations of the oscillator strengths of optical transitions of the cylindrical shell are carried out within the dipole approximation. The radiation field is taken to be that of circularly polarized light incident along the axis of the core. The oscillator strengths of optical transitions are found to increase with an increase of the applied magnetic field, particularly in the regime of small magnetic fields. In contrast, the oscillator strengths of these optical interactions become suppressed as the donor charge density is increased.     

Method of kinematic projecting of pulsar-emission profiles

A method for constructing profiles of incoherent pulsar emission based on the instantaneous angular phase distribution function of radiant power emitted by a relativistic source that moves in the magnetosphere of a neutron star is suggested. In general, this phase function depends on the kinematic parameters of the radiation source (its velocity and acceleration) and on the direction of radiation emission with respect to the rotating neutron star (the observation direction). The method is illustrated by the example of calculated profiles of fan pulsar radiation with the use of the phase function of synchrotron radiation. It is stated that his method can easily be generalized for other types of relativistic radiation. Tomsk State University; Tomsk State Pedagogical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 26–31, January, 2000.     

Neutron diffraction study on the hyperfine-enhanced nuclear spin order of HoVO4

A neutron diffraction experiment on the hyperfine enhanced nuclear spin system of HoVO₄ has been carried out following adiabatic demagnetization cooling. Below 4.5 mK we observed magnetic diffraction peaks due to antiferromagnetic order of the hyperfine enhanced nuclear spin system. A spin-flop transition in an applied magnetic field of about 80 Oe was also observed. The neutron diffraction results are consistent with the magnetic structural model proposed by Bleaney on the basis of dipolar energy considerations.     

Spin depolarization and a metal-insulator transition in a two-dimensional system in zero magnetic field

The conditions for spontaneous spin polarization in a two-dimensional system in a zero magnetic field are considered in the case of a partial filling of the lower quantum-well subbands when the energy of exchange interaction of charge carriers exceeds their kinetic energy. The critical density above which the two-dimensional gas of charge carriers undergoes complete spin depolarization is determined in the Hartree-Fock approximation. It is assumed that this process can be due to a transition of the two-dimensional gas to a metallic state.     

Thermodynamic functions of a nonrelativistic degenerate neutron gas in a magnetic field

The Fermi energy, partial concentrations of polarized neutrons, pressure, and volume energy density of a degenerate nonrelativistic neutron gas in a magnetic field are calculated using numerical methods taking into account the anomalous magnetic moment of a neutron. The results of calculations are a generalization of relations underlying the Oppenheimer-Volkov model of a neutron star to the case of an applied magnetic field. An ultrastrong (up to 10¹⁷ G) magnetic field changes the pressure and internal energy of the star and affects it static configuration and evolution. It is shown that a degenerate neutron gas in ultrastrong and weak magnetic fields is paramagnetic; the corresponding values of magnetic susceptibility differ by a factor on the order of unity. The possibility of experimentally verifying the results from analysis of pulsar-emitted radiation is discussed.     

Suppression of magnetic subbands in semiconductor superlattices driven by a laser field

The effect of strong laser radiation on magnetic subbands in semiconductor superlattices is investigated. Due to the presence of a magnetic field perpendicular to the growth direction, nonlinear effects such as band suppression and electron localization become relevant at relatively lower intensities and for any polarization perpendicular to the magnetic field. Electron quasienergies and density of states are calculated in the Kramers–Henneberger approximation, whose validity is discussed. The conditions under which collapse of magnetic subbands and quenching of N -photon emission or absorption processes occur are discussed. We conclude that at laser frequencies close to cyclotronic frequency and intensities typical of c.w. lasers, magnetic subbands become flat, magnetotunneling is inhibited and multiphotonic processes dominate optical absorption.     

Investigation of the reaction D(γ, <Emphasis Type="Italic">n</Emphasis>)H near the threshold by means of powerful femtosecond laser radiation

The possibility of studying photonuclear reactions near the threshold by means of powerful femtosecond lasers is explored by considering the example of deuteron photodisintegration. The respective experiment was performed by employing the terawatt femtosecond laser facility of the International Laser Center at Moscow State University. The radiation from this facility is characterized by a pulse energy of up to 50 mJ, a duration of 50 fs, a repetition rate of 10 Hz, and a wavelength of 805 nm. This provides a power above 10¹⁸ W/cm². Intense relativistic-electron and photon beams of energy up to 10 MeV were obtained after the optimization of relevant experimental parameters, including the focus of the laser beam, its time structure, and the choice of target. The use of these beams made it possible to study neutron generation in heavy water, to measure the time of neutron moderation, and to determine the detection efficiency. The experimental data obtained in this way are in qualitative agreement with the results of simulations based on the GEANT-4 and LOENТ code packages and indicate that it is possible to create a neutron source on the basis of the aforementioned laser. The cross section measured for deuteron photodisintegration complies with theoretical estimates available in the literature.     

Effect of a magnetic field on the microhardness of ferromagnetic fields

The microhardness of ferromagnets is studied as a function of an external magnetic field. The maximum values of the relative change in microhardness during measurement without a field and in a magnetic saturation field for low-carbon iron, Kh16 steel, and the powder alloys Fe-TiC (ferroTiC) and PG-KhN80SR-4 are 20–34%. The effect of various processes of change in the magnetic structure on the measured microhardness of the ferromagnet is examined. A relation is established between the effect and the change in magnetic energy due to external stresses.Tula State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 30–33, September, 1994.