Method for modifying the structure and elemental composition of the solid surface during a high-voltage vacuum discharge

A new method for modifying the surface of a solid, which makes it possible to change effectively the structure and elemental composition of the surface with a high precision, is developed and tested experimentally. The method is based on the action of the plasma of a pulsed high-voltage vacuum discharge, the ion beam from the plasma, and the electron beam on a solid target. The emission and plasma parameters are observed in a pulsed electric field produced in the diode system to which a pulsed voltage with an amplitude of ～10³–10⁵ V and a duration from 10^?9 to 10^?5 s is applied.     

Investigation of layers' sheet resistance using the spread of mobile charge carriers

In this work, the insulating layer with a weakly conductive layer on its surface is charged with a needle electrode. The quantities that are measured and calculated are the transients of charging current and transferred charge. In addition, we calculate charge distribution in the weakly conductive layer at various moments of time, and potential kinetics. By comparing the calculation results with measurement data, it is possible to determine sheet resistance of the investigated weakly conductive layer. This sheet resistance can be also determined experimentally: during charging of the weakly conductive layer (deposited onto the insulating layer), the charging current and the deposited charge increase with decreasing sheet resistance of the weakly conductive material, hence its sheet resistance can be related to the measured charging current or to the deposited charge. The proposed method can be applied for measuring sheet resistances from 10⁺⁸ Ω/sq to 10⁺¹² Ω/sq, and those measurements can be done in a second. It is also possible to use the contact-free method proposed in this work to measure various properties of the medium related to the material sheet resistance, e. g. relative air humidity, illumination, sample thickness, intensity of ionizing radiation, etc. This method is also suitable for measuring sheet resistance of island-type (discontinuous) layers, which is difficult to measure using usual methods. Results of this work make it possible to determine potential of a two-layer system consisting of a charged low-conductance layer and an insulator, as well as the radius of an electrographically developed area, which is important, for example, when the image is created using a needle electrode.     

Satellite phenomena in the X-ray photoelectron spectra of lanthanide trihydroxides

Using the direct CI method perturbation corrections to the Koopmans ionization energies have been obtained up to order 10 for the molecules CN^? and H₂O. The results are compared with those from the fully converged CI and B_k-type calculations. The convergence of the perturbation series is found to be quite slow although substantial improvement is possible using a variation-perturbation method.     

New method for determining energies of cosmic-ray nuclei

A new procedure for determining the energies of particles of primary cosmic radiation is described. The procedure is based on measuring the spatial density of the flux of secondary particles originating from the first event of nuclear interaction that have traversed a thin-converter layer. The use of the proposed method makes it possible to create equipment of comparatively small mass and high sensitivity. The procedure can be applied in balloon-and satellite-borne cosmic-ray experiments with cosmic nuclei for all types of nuclei over a wide energy range between 10¹¹ and 10¹⁶ eV per particle. Physical foundations of the method, results of a simulation, and the applicability range are described.     

Effect of prepulses with various durations on the neutron yield in laser picosecond plasma

Experimental results on the effect of picosecond and nanosecond prepulses on the neutron yield in laser picosecond plasma on the surface of solid (CD₂)_n targets at a laser intensity of 10¹⁸ W/cm² are presented. It is demonstrated that the picosecond (nanosecond) prepulse decreases the neutron yield at a laser prepulse intensity of higher than 10¹³ (10¹²) W/cm². The estimates indicate three possible mechanisms for the realization of the observed effect: stimulated Mandelstam-Brillouin scattering of the main pulse by the preplasma, channels of the generation of fast ions, and their possible deceleration in the preplasma. The results of calculations are compared with the experimental data.     

Measuring the gravitational acceleration of antimatter with an antihydrogen interferometer

The gravitational force on antimatter has never been directly measured. A method is suggested for making this measurement by directing a low-energy beam of neutral antihydrogen atoms through a transmission-grating interferometer and measuring the gravitationally-induced phase shift in the interference pattern. A 1% measurement of the acceleration due to the Earth's gravitational field (¯ g) should be possible from a beam of about 10⁵ or 10⁶ atoms. If more antihydrogen can be made, a much more precise measurement of¯ g would be possible. A method is suggested for producing an antihydrogen beam appropriate for this experiment.     

Investigation of the electromagnetic wave scattering dynamics during microwave streamer evolution

A self-consistent electrodynamic model based on analytic relations, which makes it possible to describe the electromagnetic wave scattering from a thin (compared to the wavelength) plasma channel, is proposed. The results of experimental investigation of the dynamics of the signal scattered by a single channel in air in the pressure range P ₀ = 10⁴−1.4 × 10⁴ Pa are presented. The results are analyzed in terms of the electrodynamic model.     

Hydrogen in the near-surface of crystalline silicon

Abstract

Real-time electric field drift experiments, in-situ capacitance-voltage profiling, deep-level transient spectroscopy and nuclear reaction analysis have been used to monitor hydrogen motion and passivation processes in silicon. Spontaneous hydrogen injection and very fast migration has been detected in the near-surface region of various Schottky barriers and p-n junctions. The effective hydrogen diffusivity is about 10^?8 cm²/s at 400 K in agreement with the estimated value obtained by extrapolation from the high-temperature diffusivity data. The results of real-time in-situ measurements clearly demonstrate that the fast diffusing protons are involved in the hydrogenation processes of both shallow and deep levels. The possible physicochemical mechanisms for the observed spontaneous hydrogen injection which results in unintentional hydrogenation of the subsurface of silicon, and probably other semiconductors, are discussed.     

Viscous flow of magnetic vortices and rapid relaxation of magnetization in YBaCuO ceramics

The viscous flow of magnetic vortices in granular YBaCuO ceramics of various granule sizes is investigated using the microwave absorption method (f=80 MHz) in the range of varying magnetic fields H=±1500 Oe and of temperatures T=77 to 95 K. The conditions for the formation and melting of the vortex lattice, as well as the transition of the high-temperature superconductor (HTSC) state from the irreversibility region to the region of the viscous flow of magnetic vortices, are considered. The rapid magnetic relaxation times in the range τ=72 to 111 ms are determined from the magnetization relaxation in the HTSC materials under investigation depending on the granule size d, which varies from 1 to 30 μm. The experimental results on the variation of the relaxation time τ from 77 to 120 ms in a ceramic exposed to fast neutrons with various fluences (Φ=10¹⁶ to 10¹⁹ cm⁻²) are considered. The depinning process is analyzed; it occurs in the form of a thermally assisted flux flow in the range of low activation energies. __________ Translated from Fizika Tverdogo Tela, Vol. 43, No. 6, 2001, pp. 968–973. Original Russian Text Copyright ? 2001 by Chashchin.     

Investigations of the Current Density in the Cathode Spot of a Vacuum Arc

A short review is given on the problem of the current density in the cathode spot of a vacuum arc, theoretical models and experimental results are discussed. A new measuring method is presented which is directly related to the current carrying area of the spot. It leads to current densities of 10¹² A/m² at clean surfaces (comparable with results obtained from crater measurements) and 10⁹?10¹⁰ A/m² with contaminated surfaces.     

On the analytic extrapolation of scattering amplitudes in L2 norm

The problem of the analytic extrapolation of scattering amplitudes to interior points from a least-squares error channel is studied and found to be stable if some L² norm of the amplitude on the remainder of the cuts obeys a certain bound. The minimal possible value of this bound is of relevance to a model-independent location of the various singularities of scattering amplitudes. A simple and rigorous method is given for its construction and the numerical results of a singularity search are presented. The method is shown to be capable of accomodating unequal errors on the real and imaginary parts of the amplitude and is applicable to both simply and doubly connected domains (energy and cosine extrapolations).     

Estimation of the PCR mass composition in the energy range 1017–1019 eV on the basis of multicomponent analysis of the characteristics of EASs detected at the Yakutsk array

The characteristics of longitudinal and radial extensive air shower development derived from the results of detection of the charged particle flux and Cherenkov light in extensive air showers at the Yakutsk array. To estimate the primary cosmic ray composition, a combination of the parameters X_max and ρ₆₀₀ and the database simulated using the CORSIKA code (QGSJET model) for showers generated by five types of nuclei (p, He, C, Si, Fe) in the energy range 10¹⁷–10¹⁹ eV were used. Application of the multicomponent method made it possible to divide the showers into three groups (p + He), C, and (Si + Fe) and estimate their percentage. The error in identifying nuclei in the energy range 10¹⁷–10¹⁸ eV does not exceed 30%.     

Estimation of the energy of the electron-photon component of cosmic rays on the basis of data for Cherenkov light from ultrahigh-energy extensive air showers

The energy fraction E _em/E ₀ dissipated to the electron-photon component of extensive air showers (EASs) for E ₀=10¹⁵?10¹⁹ eV is estimated using data on Cherenkov radiation and charged particles from the Yakutsk EAS array. The results are compared with models with different dissipations to the electron-photon component and with calculations for various primary nuclei. In the energy range 10¹⁵?10¹⁶ eV and 10¹⁸?10¹⁹ eV, the ratio E _em/E ₀ is equal to 77 ± 2 and 88 ± 2, respectively, in agreement with the mixed and proton contents of primary cosmic rays in the former and latter energy ranges, respectively.     

A New Model for The Formation of Mini Black Holes

A new model different from the Hawking model is suggested to describe the formation of mini (primordial) black holes. It is based on an idea that the fluids, which fill in the universe at the beginning just after the big bang, are separated into mini clusters, moving with supersonic velocities and colliding with each other under the forces of gravitational attractions. We show that between the time era from 10^–43 to 10^–8 sec. about 36 various generations of mini black holes with masses ranging in the interval 10^–5—10^–30 gm are possible.     

Charge distributions of the isobar pair 40Ar-40Ca from a phenomenological and a model-independent analysis of elastic electron scattering

Cross sections for elastic electron scattering from ⁴⁰Ar have been measured for the momentum transfer range from 0.8 to 1.8 fm^?. The data were analysed by various phenomenological models as well as by a model-independent method. Using the results of Stanford measurements on ⁴⁰Ca analysed in a similar manner, the difference of the charge distributions of ⁴⁰Ar and of ⁴⁰Ca has been calculated. The combined results of the phenomenological analysis are compared with the results of the model-independent analysis.     

Estimates of electron-positron pair production in the interaction of high-power laser radiation with high-Z targets

Electron-positron production processes occurring in the interaction of 10¹⁸–10²⁰ W/cm² laser radiation with high-Z targets are examined. Computational results are presented for the pair production and the positron yield from the target with allowance for the contribution of pair production processes due to electrons and bremsstrahlung photons. Monte Carlo simulations using the PRIZMA code confirm the estimates obtained. The possible positron yield from high-Z targets irradiated with 10²–10³ TW laser radiation is estimated to be 10⁹–10¹¹. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 4, 239–244 (25 February 1998)     

Formation of positive and negative ions of thymine molecules under the action of slow electrons

The formation of positive and negative molecules of thymine—a base of nucleic acids—under the action of slow electrons is investigated by the method of crossed electron and molecular beams. The method developed makes it possible to measure the molecular beam intensity and determine the energy dependences and absolute values of total cross sections for the formation of positive and negative ions of thymine molecules. It is found that the maximal cross section for the formation of positive ions is reached at an energy of 95 eV and its absolute value is, accordingly, 1.4 × 10^?15 cm². The total cross section for the formation of negative ions is 8.2 × 10^–18 cm² at an energy of 1.1 eV. The mass spectra of thymine molecules are measured and the cross sections of dissociative ionization are determined.     

Status of the polarized ions source for the JINR accelerator complex

The project assumes the design and construction of a universal high-intensity source of polarized deuterons (protons) using a charge-exchange plasma ionizer. The output D ⁺↑ (H ⁺↑) current of the source is expected to be at a level of 10 mA. The polarization will be up to 90% of the maximal vector (±1) for D ⁺↑ (H ⁺↑) and tensor (+1, ?2) for D ⁺↑ polarization. Realization of the project is carried out in close cooperation with INR of the RAS (Moscow). The equipment available from the CIPIOS ion source (IUCF, Bloomington, USA) is partially used for the Dubna setup. The new source at the JINR Nuclotron accelerator facility will make it possible to increase the polarized deuteron beam intensity up to the level of 10¹⁰ d/pulse. The first results of the source of polarized atoms testing are presented.     

Frequency dispersion of the dielectric characteristics in polymer films based on the [NiSalen] complex

The results of the measurements of the dielectric properties exhibited by metal-containing polymer structures based on Ni(II) complexes in the frequency range f = 10²–10⁵ Hz are reported. It is established that, in the range of acoustic frequencies, the permittivity ε decreases with increasing frequency, whereas the dielectric loss tangent tan δ increases. At frequencies f > 10⁴ Hz, the dependence tan δ(f) is characterized by a relaxation maximum. The possible mechanisms of dielectric polarization and charge transfer in an alternating-current electric field are considered.