共查询到20条相似文献,搜索用时 78 毫秒
1.
V. I. Gushenets N. N. Koval’ V. S. Tolkachev P. M. Shchanin 《Technical Physics》1999,44(11):1318-1321
The emission properties of a plasma cathode based on a nanosecond pulsed glow discharge with currents of up to 200A at a pressure
of 5×10−2 Pa are studied experimentally. Stable ignition and burning of the discharge are ensured if the current in the auxiliary pulsed
discharge is 25–30% of that in the main discharge and its pulse duration exceeds that of the main discharge by more than an
order of magnitude. Emission current pulses from the cathode with amplitudes of up to 140A fully reproduce the discharge current
and are determined by the transparency of the grid anode.
Zh. Tekh. Fiz. 69, 62–65 (November 1999) 相似文献
2.
S. Yu. Bogdanov V. B. Burilina A. G. Frank 《Journal of Experimental and Theoretical Physics》1998,87(4):655-662
The possibilities of current-sheet formation in two-dimensional magnetic fields with a null line as well as the characteristic
features of the plasma dynamics under high initial pressure conditions (helium, P
0≈300 mtorr) are investigated for the first time. It is shown that current-sheet formation and efficient compression of the
plasma into a sheet require that the magnetic field gradient be sufficiently large. A brightly emitting compact region with
electron density N
e∼9×1016 cm−3, an order of magnitude higher than the gas atom density, was observed to form at the center of the layer.
Zh. éksp. Teor. Fiz. 114, 1202–1214 (October 1998) 相似文献
3.
Generation of electromagnetic waves by an annular shell of plasma rotating in crossed radial electrostatic and axial magnetic
fields in a cylindrical resonator is investigated theoretically. Dispersion relations are obtained describing the interaction
of the waves with the plasma. It is shown that generation of waves by a narrow plasma shell is possible due to a cyclotron
resonance, Čerenkov resonance, or plasma resonance. Here we consider a Čerenkov resonance, where the velocities of the plasma
components and the phase velocities of the waves are perpendicular to the constant magnetic field. The frequencies and growth
rates of the waves are found under conditions of the above-mentioned resonances in a uniform and in a nonuniform plasma shell.
Advantages and disadvantages of wave generation under various conditions are noted.
Zh. Tekh. Fiz. 69, 16–21 (February 1999) 相似文献
4.
The neutrino-electron scattering in a dense degenerate magnetized plasma under the conditions μ
2 > 2eB ≫ μE is investigated. The volume density of the neutrino energy and momentum losses due to this process are calculated. The results
we have obtained demonstrate that plasma in the presence of an external magnetic field is more transparent for neutrino than
for non-magnetized plasma. It is shown that neutrino scattering under conditions considered does not lead to the neutrino
force acting on plasma. 相似文献
5.
V. T. Astrelin A. V. Burdakov V. S. Koidan K. I. Mekler P. I. Mel’nikov V. V. Postupaev M. A. Shcheglov 《Journal of Experimental and Theoretical Physics》1998,86(3):489-500
This paper presents the results of experiments on two-stage heating of a dense plasma by a relativistic electron beam in the
GOL-3 facility. A dense plasma with a length of about a meter and a hydrogen density up to 1017 cm−3 was created in the main plasma, whose density was 1015 cm−3. In the process of interacting with the plasma, the electron beam (1 MeV, 40 kA, 4 μs) imparts its energy to the electrons of the main plasma through collective effects. The heated electrons, as they disperse
along the magnetic field lines, in turn reach the region of dense plasma and impart their energy to it by pairwise collisions.
Estimates based on experimental data are given for the parameters of the flux of hot plasma electrons, the energy released
in the dense plasma, and the energy balance of the beam-plasma system. The paper discusses the dynamics of the plasma, which
is inhomogeneous in density and temperature, including the appearance of pressure waves.
Zh. éksp. Teor. Fiz. 113, 897–917 (March 1998) 相似文献
6.
V. M. Astashynski E. A. Kostyukevich A. M. Kuzmitski A. A. Mishchuk P. N. Shoronov 《Journal of Applied Spectroscopy》2012,79(4):610-615
The dynamics of the interaction of two oppositely directed plasma flows generated by miniature gas-discharge magnetoplasma compressors is studied. The maximum plasma electron temperature and density in the region where the plasmas interact are found to be 4.5 eV and 1.4⋅1017 cm–3. Exposure of samples to this kind of plasma near the interaction region leads to an energy flux at the surface of 2–8 J/cm2, which is sufficient for modification of the surface properties of various materials. 相似文献
7.
This paper presents the results of experiments on the generation of pulsed γ radiation of average photon energy ∼1.2 MeV and
duration ≤20 ns on the MIG system with a plasma opening switch. Operating modes with a maximum dose downstream of the anode
of (1–2)·1013 and 1012 R/s over an area of 2–3 and 100 cm2 are obtained, respectively.
Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh
Uchebnykh Zavedenii, Fizika, No. 12, pp. 26–30, December, 1999. 相似文献
8.
A. Ya. Faenov S. A. Pikuz A. G. Zidkov I. Yu. Skobelev P. S. Komarov O. V. Chefonov S. V. Gasilov A. V. Ovchinnikov 《JETP Letters》2010,92(6):375-378
The characteristics of X rays of a laser plasma generated in the interaction of a femtosecond pulse with solid targets in
an air atmosphere have been investigated. It has been shown that the mechanism for the generation of X rays in the interaction
of short intense laser pulses with solid targets in a gas atmosphere is attributed to the generation of fast electrons in
the region of the filamentation of a laser pulse. It has been proven experimentally that under such conditions, the solid
target irradiated by laser radiation of even a low density of about 1015 W/cm2 very efficiently emits ∼10-keV photons. It has been shown theoretically that the maximum energy of accelerated electrons
can reach ɛmax ∼ 100–200 keV under these conditions. This means that the proposed method can provide characteristic radiation with the energy
of photons much higher than 10 keV. 相似文献
9.
Pogorelsky I. V. Polyanskiy M. N. Babzien M. Yakimenko V. Dover N. P. Palmer C. A. J. Najmudin Z. Schreiber J. Shkolnikov P. Dudnikova G. 《Laser Physics》2011,21(7):1288-1294
A picosecond CO2 laser was used successfully in a number of experiments exploring advanced methods of particle acceleration [1]. Proton acceleration
from gas-jet plasma exemplifies another advantage of employing the increase in laser wavelength from the optical to the mid-IR
region. Recent theoretical- and experimental-studies of ion acceleration from laser-generated plasma point to better ways
to control the ion beam’s energy when plasma approaches the critical density. Studying this regime with solid-state lasers
is problematic due to the dearth of plasma sources at the critical electron density ∼1021 cm−3, corresponding to laser wavelength λ = 1 μm. CO2 laser offers a solution. The CO2 laser’s 10 μm wavelength shifts the critical plasma density to 1019 cm−3, a value attainable with gas jets. Capitalizing on this approach, we focused a circular polarized 1-TW CO2 laser beam onto a hydrogen gas jet and observed a monoenergetic proton beam in the 1–2 MeV range. Simultaneously, we optically
probed the laser/plasma interaction region with visible light, revealing holes bored by radiation pressure, as well as quasi-stationary
soliton-like plasma formations. Our findings from 2D PIC simulations agree with experimental results and aid in their interpretation. 相似文献
10.
Galina A. Vergunova Sergey Yu. Gus’kov Vladislav B. Rozanov Olga N. Rozmej 《Journal of Russian Laser Research》2010,31(5):509-518
We investigate theoretically the formation of a plasma in a plane layer of polymer foam (density ρ = 0.002 g/cm3 and thickness 800 μm) under the action of an external source of soft X-ray radiation under the conditions of PHELIX experiments. The incident
flux is assumed to have a Planck’s distribution over the spectrum with T
rad = 20–40 eV. In numerical calculations, the flux of incident X-ray radiation and the spectral constants of the target substance
are varied. The action of an external X-ray radiation source on a low-density foam substance with a density of 2 mg/cm3 causes a plasma to be formed with relatively homogeneous profiles of density and temperature T = 15–35 eV. Absorption of externalradiation energy is distributed in the volume. The plasma temperature increases with increase
in the external energy, and the energy passed through the plasma also increases. The results prove to be sensitive to the
values of optical constants used in numeral simulation. The spectral flux of external radiation passed through the plasma
is chosen as a criterion of correctness of the optical constants used in the calculations. In future experiments using the
PHELIX facility, we plan to investigate the slowing-down of an ion beam in a plasma formed as a result of indirect heating
of low-density polymer triacetate cellulose (TAC) foam with densities ρ = 0.001–0.01 g/cm3 under the action of a pulse of X-ray radiation, into which the laser radiation is preliminarily transformed. 相似文献
11.
12.
We demonstrate the generation of high harmonics (up to the 65th order, λ=12.24 nm) of a Ti:sapphire laser radiation after
the propagation of femtosecond laser pulses through the low-excited plasma produced by a picosecond prepulse radiation on
the surface of different targets. High-order harmonics generated from the surface plasma of most targets showed a plateau
pattern. It is assumed that the harmonic generation in these conditions occurs due to the interaction of the femtosecond pulses
with the ions. The conversion efficiencies at the plateau region were varied between 1×10-7 to 8×10-6, depending on the target. The main contribution to the limitation of harmonic generation efficiency and cutoff energy was
attributed to the self-defocusing of main pulse. A considerable restriction of the 27th harmonic generation was observed at
different focusing conditions in the case of chromium plasma. Our observation of the resonance-induced enhancement of a single
harmonic (λ=61.2 nm) at a plateau region with the efficiency of 8×10-5 in the case of In plasma can offer some expectation that analogous processes can be realized in other plasma samples in the
shorter wavelength range where the highest harmonics were achieved.
PACS 42.65.Ky; 52.35.Mw; 52.38.-r 相似文献
13.
Yu. V. Kovtun E. I. Skibenko A. I. Skibenko Yu. V. Larin V. B. Yuferov 《Technical Physics》2011,56(5):623-627
A proprietary way of introducing a working substance to be separated into a reflective-discharge magnetoplasma separator is
experimentally verified. The efficiency of working substance delivery using this sputtering mechanism providing a plasma density
on the order of 1014 cm−3 is demonstrated. The sputtering yield of the substance being separated achieves (2.6–2.8) × 10−2 atoms/ion depending on the amount of particles in the discharge. Simultaneously, the minimal separation coefficient for light
and heavy particles in a rotating plasma subjected to E × H crossed fields is estimated. 相似文献
14.
Summary A microwave coherent backscattering experiment has been carried out on Mirabelle, a weakly ionised plasma device, with the
objective of measuring the electron density fluctuation level. The experiment is a preliminary step in order to prepare the
detection system for a microwave stimulated backscattering experiment. The incident electromagnetic wave is focused in front
of a plane grid which excites ion acoustic or electron Bernstein waves inducing fluctuations in the plasma. The backscattering
signal is collected by the launching circuit and detected by homodyne mixing. The typical ratio of the scattered power to
the incident power is about 10−12 and the relative density fluctuations are of the order of δn
e/n
e=10−3 against a background electron density ofn
e=1–5·109 cm−3. The backscattering measurement is compared with Langmuir probe measurements. The spectral width of the backscattered signal
has also been studied, by taking into account effects due to the incident wave focusing and plasma wave damping.
The authors of this paper have agreed to not receive the proofs for correction 相似文献
15.
V. E. Fortov V. Ya. Ternovoi S. V. Kvitov V. B. Mintsev D. N. Nikolaev A. A. Pyalling A. S. Filimonov 《JETP Letters》1999,69(12):926-931
The electrical conductivity of a nonideal hydrogen plasma is measured under shock-wave compression to pressures ∼1.5 Mbar.
It is found that the conductivity increases sharply (by five orders of magnitude) at a density ρ∼0.3−0.4 g/cm3, reaching close to liquid-metal values ∼103 S/cm. The data obtained can be described by a nonideal-plasma model taking into account the increase in the number of conduction
electrons as a result of “ionization by pressure.”
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 12, 874–878 (25 June 1999) 相似文献
16.
A. E. Bugrov S. Yu. Gus’kov V. B. Rozanov I. N. Burdonskii V. V. Gavrilov A. Yu. Gol’tsov E. V. Zhuzhukalo N. G. Koval’skii M. I. Pergament V. M. Petryakov 《Journal of Experimental and Theoretical Physics》1997,84(3):497-505
We have experimentally investigated the processes of laser light absorption and energy transfer in porous targets made of
“agar-agar” (C14H18O7) with an average density of 1–4 mg/cm3 illuminated by the focused beam of a neodymium laser with an intensity of 1014 W/cm2 within a pulse of duration 2.5 ns. Many important scientific and technical problems, e.g., inertial-confinement thermonuclear
fusion, the creation of lasers in the x-ray regime, and the modeling of astrophysical phenomena under laboratory conditions,
can be successfully addressed by using low-density porous media as components of such targets. In our experiments with porous
targets of variable density and thickness we used optical and x-ray diagnostic methods, which ensured that our measurements
were made with high temporal and spatial resolution. We show that a region forms within the porous target consisting of a
dense high-temperature plasma which effectively absorbs the laser radiation. Energy is transferred from the absorption region
to the surrounding layer of porous material at up to 2×107 cm/s. Experimental data are in good agreement with the predictions of our theoretical model, which takes into account the
specific features of absorption of laser radiation in a porous material and is based on representing the energy transfer within
the material as a hydrothermal wave.
Zh. éksp. Teor. Fiz. 111, 903–918 (March 1997) 相似文献
17.
The generation of a 250-μs-wide electron beam in a plasma-emitter diode is studied experimentally. A plasma was produced by a pulsed arc discharge in hydrogen. The electron beam is extracted from a circular emission hole 3.8 mm in diameter under open plasma boundary conditions. The beam accelerated in the diode gap enters into a drift space in the absence of an external magnetic field through a hole 4.1 mm in diameter made in the anode. The influence of electron current deposition at the edge of the anode hole on the beam’s maximum attainable current, above which the diode gap breaks down, is studied for different accelerating voltages and diode gaps. The role of processes occurring on the surface of the electrodes is shown. For an accelerating voltage of 32 kV, a mean emission current density of 130 A/cm2 is achieved. The respective mean strength of the electric field in the acceleration gap is 140 kV/cm. Using the POISSON-2 software package, the numerical simulation of the diode performance is carried out and the shape of steady plasma emission boundaries in the cathode and anode holes is calculated. The influence of the density of the ion current from the anode plasma surface on the maximum attainable current of the electron beam is demonstrated. 相似文献
18.
This paper reports the experimental investigation of the anode region of a free-burning inert-gas arc at atmospheric pressure
in the current range from a few amperes to hundreds of amperes. The tungsten thermionic-emission cathode and the large-diameter
water-cooled copper anode that were used permitted the anode arc root to assume its natural form. The general characteristics
of the discharge are given and results are presented from investigations of the anode region at low currents, where the anode
arc root is single and constricted, but erosion-free. Measurements of the plasma parameters as well as the current density
in the arc root are reported, and a comparison is made between the values obtained and those characteristic of the region
of the cathode arc root.
Zh. Tekh. Fiz. 67, 35–40 (January 1997) 相似文献
19.
An attempt is made to create an electric-discharge source for pumping argon, krypton, and xenon dimer lasers. The device is
based on a method proposed previously by the authors, wherein confinement of the discharge is achieved by removing the cathode
spot from the main discharge region and closing the discharge to the spot along a narrow extended auxiliary plasma channel.
The conditions for the formation of such a discharge are investigated. The high stability of the sparkless stage of the discharge
permits the first-ever attainment of energy depositions at the level of 100 J/cm2 at pressures ∼10 atm, a level several orders of magnitude higher than is attainable by conventional methods. A discharge
cell and power supply system are designed for a multisectional discharge with an active length of 200 mm, and the reliability
of the entire apparatus is demonstrated in long-term use.
Zh. Tekh. Fiz. 67, 10–14 (November 1997) 相似文献
20.
A study is made of the electron kinetics in a discharge plasma produced by a high-power beam of electromagnetic radiation
in the centimeter-wave region under conditions approaching free space, when the dimensions of the chamber are much greater
than the wavelength of the microwave radiation. Two regimes of discharge production are investigated: the regime of short
microsecond pulses at a repetition rate of 200 Hz, and a single millisecond pulse regime. It is shown that at threshold values
of the microwave energy flux density the electron density in the initial stages of discharge formation reaches the critical
value, and that the average energy of the electrons is of the order of 1.5–3 eV.
Zh. Tekh. Fiz. 67, 10–14 (June 1997) 相似文献