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1.
Stable ignition and sustention of a pulsed discharge with a current of up to 180 A and duration of 12 μs at a pressure of 10−1–10−2 Pa are achieved in a glow-discharge plasma cathode with the help of an auxiliary initiating discharge. An electron emission current density of up to 100 A/cm2 and accelerating voltageof 15 kV are obtained in a gas-filled diode based on this type of a plasma cathode. An electron beam witha neutralized space charge can be transported almost without losses in a weak axial magnetic field alonga plasma channel formed due to the gas ionization by the accelerated electrons over a distance of up to 30 cm. 相似文献
2.
Generation and transport of high-current electron beams are investigated in gas-filled diodes with plasma emitters based on arc and glow discharges. A space-charge neutralized beam with a current up to 1 kA was produced in a diode with a plasma emitter based on an arc discharge for an accelerating voltage of 15 kV. The beam is constricted from 8 cm down to 1 cm in diameter by a self-magnetic field and is transported through a distance of over 20 cm with an efficiency of 70%. A beam with a current of 80 A and a current density up to 100 A/cm2 was produced in a glow-discharge diode. The beam was transported through a distance of 30 cm in a weak axial magnetic field with induction B = 0.015 T. 相似文献
3.
采用等效媒质处理方法来研究有限引导磁场下沿纵向运动的相对论环形电子注.首先建立运动坐标系以电子注纵向速度匀速运动,在运动坐标系中电子注可以被考虑成静止的磁化等离子体,再通过四维空间的洛伦兹变换得到电子注在静止的实验室坐标系下可以被等效为双各向异性媒质,其不仅具有张量形式的电导率和磁导率,还具有手征特性.在此基础上同时考虑了由于电子注表面波动所引起的表面电流密度.采用该方法研究了有限引导磁场下圆柱波导中沿纵向运动的相对论环形电子注,推导出该模型的色散方程,并进行了数值计算.计算结果表明该研究方法能够得到更准
关键词:
相对论环形电子注
磁化等离子体
色散特性 相似文献
4.
THE PROCESS OF SPACE CURRENT NEUTRALIZATION OF INTENSE RELATIVISTIC ELECTRON BEAM UNDER AN EXTERNALLY APPLIED MAGNETIC GUIDE FIELD
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The process of space current neutralization of intense relativistic electron beam under an externally applied magnetic guide field is discussed in this paper. Ionization by electron avalanching and by beam electrons impact and recombination is included in the calculation of plasma density buildup, with plasma heating by return current and two- stream instability taken into account. A code to evaluate the process of space current neutralization was set up. The calculations demonstrate that the optimum gas pressure increases as peak beam current increases and it decreases as the risetime of beam pulse increases. 相似文献
5.
Yaduvendra Choyal Lalit Gupta Prasad Deshpande Krishna Prasad Maheshwari Kailash Chander Mittal Suresh Chand Bapna 《Pramana》2008,71(6):1301-1310
In this paper, a high power relativistic backward wave oscillator (BWO) experiment is reported. A 230 keV, 2 kA, 150 ns relativistic
electron beam is generated using a Marx generator. The beam is then injected into a hollow rippled wall metallic cylindrical
tube that forms a slow wave structure. The beam is guided using an axial pulsed magnetic field having a peak value 1 T and
duration 1 ms. The field is generated by the discharge of a capacitor bank into a solenoidal coil. A synchronization circuit
ensures the generation of the electron beam at the instant when the axial magnetic field attains its peak value. The beam
interacts with the SWS modes and generates microwaves due to Cherenkov interaction. Estimated power of 2 MW in TM01 mode is observed.
相似文献
6.
L. Yu. Bogdanov N. V. Dvoretskaya G. G. Sominskii A. Ya. Fabirovskii 《Technical Physics》1997,42(8):930-934
An experimental investigation is made of the influence of local nonuniformities of a mirror-configuration magnetic field on
oscillations of the space charge and the structure of a long-pulse relativistic electron beam. It is found that the outcome
depends on the axial configuration of the nonuniformity. A nonuniformity near the cathode can substantially reduce the amplitude
of the oscillations and improve the beam transport. The creation of a nonuniformity far from the cathode leads to an accelerated
increase in the oscillations and causes spreading of the transverse structure of the beam. A possible explanation is given
for the mechanism responsible for the influence of these local magnetic field nonuniformities assuming reflection of the cathode
plasma and electron flux from the magnetic mirror, and also allowing for a jump in the drift velocity.
Zh. Tekh. Fiz. 67, 83–88 (August 1997) 相似文献
7.
K. V. Afanasyev N. M. Bykov V. P. Gubanov A. A. Elchaninov A. I. Klimov S. D. Korovin V. V. Rostov A. S. Stepchenko 《Radiophysics and Quantum Electronics》2006,49(10):754-759
We study the generation of electromagnetic pulses with a carrier frequency of 3.7 GHz in a relativistic backward-wave oscillator
with a long slow-wave system in the superradiance regime of super-radiation for a magnetic induction of 0.2 T (below the cyclotron
resonance). To decrease transverse velocities of the electrons, we use decompression of a hollow electron beam. Decompression
in combination with a sharp leading edge of the high-voltage pulse (460 kV) applied to the explosive-emission cathode are
used for increasing the cathode lifetime and improving the azimuthal uniformity of the beam. As a result, the achieved peak
power of the microwave radiation amounts to 800 MW for a pulse duration of 2.5 ns and a repetition rate of 100 Hz. The uninterrupted
operation in such a regime determined by the lifetime of the explosive-emission cathode is increased up to 105–106 pulses. The efficiency of conversion of the electron-beam power into the electromagnetic-wave power is increased up to 50%,
The possibility of locking the electromagnetic oscillations phase by a sharp edge of the high-voltage pulse at the cathode
was observed for the first time in such a relativistic generator.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 10, pp. 837–842, October 2006. 相似文献
8.
Yu. V. Kirichenko 《Technical Physics》1999,44(6):709-711
A theoretical analysis is made of the conditions for generation of electromagnetic waves by a thin cylindrical layer of relativistic
electrons rotating in crossed axial magnetic and radial electrostatic fields in a cylindrical cavity. A dispersion equation
is obtained to describe the interaction between waves and electrons under plasma resonance conditions. The dependence of the
growth rates on the relativistic factor and the magnetic field are studied.
Zh. Tekh. Fiz. 69, 112–114 (June 1999) 相似文献
9.
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
10.
R. Illingworth 《Optics Communications》1977,23(1):109-112
The Faraday rotation of the plane of polarisation of a probe beam by azimuthal magnetic fields in the presence of beam deflection caused by refractive index gradients is discussed for a plasma carrying an axial current. A method for calculation of the magnetic field profile from experimental data is described. Bθ can be found by Abel inversion if the electron density is known and if deflected rays can be collected by an optical system and focussed onto a detector. Typical Faraday rotations calculated for the Bennett pinch assuming small beam deflection are found to be proportional to the plasma current and to the angle of deflection. If the probe beam wavelength is chosen to satisfy the approximate relation N0λ2 ≈ 3.5 × 1013 m-1, where N0 is the electron density on the axis, measurement of Bθ with beam deflections less than 2 × 10-2 radians should be possible in cases where small rotations can be detected in the mid-to-far infra-red part of the spectrum. 相似文献
11.
V. V. Skobelev 《Journal of Experimental and Theoretical Physics》2011,113(5):791-797
The Fermi energy, pressure, internal energy, entropy, and heat capacity of completely degenerate relativistic electron gas
are calculated by numerical methods. It is shown that the maximum admissible magnetic field on the order of 109 G in white dwarfs increases the pressure by a factor of 1.06 in the central region, where the electron concentration is ∼1033 cm−3, while the equilibrium radius increases by approximately a factor of 1.03, which obviously cannot be observed experimentally.
A magnetic field of ∼108 G or lower has no effect on the pressure and other thermodynamic functions. It is also shown that the contribution of degenerate
electron gas to the total pressure in neutron stars is negligible compared to that of neutron gas even in magnetic fields
with a maximum induction ∼1017 G possible in neutron stars. The neutron beta-decay forbiddeness conditions in a superstrong magnetic field are formulated.
It is assumed that small neutron stars have such magnetic fields and that pulsars with small periods are the most probable
objects that can have super-strong magnetic fields. 相似文献
12.
The return current induced in a plasma by a relativisitc electron beam generates a new electron-ion two-stream instability
(return current instability). Although the effect of these currents on the beam-plasma e-e instability is negligible, there
exists a range of wave numbers which is unstable only to return current (RC) instability and not to e-e instability. The electromagnetic
waves propagating along the direction of the external magnetic field, in which the plasma is immersed, are stabilized by these
currents but the e.m. waves with frequencies,ω
2≪Ω
e
2
≪ω
pe
2
(Ω
e andω
pe being cyclotron and plasma frequency for the electrons of the plasma respectively) propagating transverse to the magnetic
field get destabilized. Heuristic estimates of plasma heating, due to RC instability and due to decay of ion-acoustic turbulence
generated by the return current, are made. The fastest time scale on which the return current delivers energy to the plasma
due to the scattering of ion-sound waves by the electrons can be ∼ω
pi
−1
(ω
pi being the plasma frequency for the ions). 相似文献
13.
Millimeter-wave emission from the rippled-field magnetron (cross-field free electron laser (FEL)) is investigated experimentally and theoretically. In this device, electrons move in quasi-circular orbits under the combined action of a radial electric field, a uniform axial magnetic field, and a radial azimuthally periodic wiggler magnetic field. In excess of 300 kW of RF power is observed in two narrow spectral lines whose frequency can be tuned continuously from ~25 to ~50 GHz by variation of the axial magnetic field. The observations are interpreted as a FEL type of instability, associated with a resonance in the particle motion of a layer of electrons embedded in the dense spacecharge cloud. The resonance is shown to occur when 2kw?0 ? (?>0/?0) ?1 -(?p/?0)2, where kw is the wiggler wavenumber, ?0 is the azimuthal electron velocity, ?0 is the relativistic cyclotron frequency in the axial magnetic field, wp is the relativistic plasma frequency, and ?0 = [1 - (?0/c)2]-1/2 of the resonant electron layer. 相似文献
14.
S. I. Nanobashvili Z. R. Beria L. R. Gakheladze G. V. Gelashvili G. E. Gogiashvili M. O. Mdivnishvili I. S. Nanobashvili G. I. Rostomashvili 《Czechoslovak Journal of Physics》1999,49(6):999-1004
The properties of plasma injected into an open magnetic trap of uniform field from an independent UHF source have been investigated.
Plasma is created in the UHF source at the frequency of 2400 MHz (power input 150 W) in the electron cyclotron resonance (ECR)
regime at the pressure of neutral argon (10−5−10−2) torr. It is established that a rather quiescent target plasma with controlled density within the range of (2 × 108−2 × 1012) cm−3 and temperature 2–3eV is accumulated in the trap. It turned out that plasma lifetime in the trap is determined by a classical
mechanism of particle escape at the expense of collisions, at fixed value of magnetic field in the trap it practically is
not changed with the variation of neutral gas pressure and reaches the value ≈ 4×10−3 s at the magnetic field strength in the trap equal 1600 Oe. 相似文献
15.
This paper presents an analytical and numerical investigation of an intense circularly polarized wave propagating along the static magnetic field parallel to oscillating magnetic field in magnetoactive plasma. In the relativistic regime such a magnetic field is created by pulse itself. The authors have studied different regimes of propagation with relativistic electron mass effect for magnetized plasma. An appropriate expression for dielectric tensor in relativistic magnetoactive plasma has been evaluated under paraxial theory. Two modes of propagation as extraordinary and ordinary exist; because of the relativistic effect, ultra-strong magnetic fields are generated which significantly influence the propagation of laser beam in plasma. The nature of propagation is characterized through the critical-divider curves in the normalized beam width with power plane For given values of normalized density (ωp/ω) and magnetic field (ωc/ω) the regions are namely steady divergence (SD), oscillatory divergence (OD) and self-focusing (SF). Numerical computations are performed for typical parameters of relativistic laser-plasma interaction: magnetic field B = 10-100 MG; intensity I = 1016 to 1020 W/cm2; laser frequency ω = 1.1 × 1015 s−1; cyclotron frequency ωc = 1.7 × 1013 s−1; electron density ne = 2.18 × 1020 cm−3. From the calculations, we confirm that a circularly polarized wave can propagate in different regimes for both the modes, and explicitly indicating enhancement in wave propagation, beam focusing/self-guiding and penetration of E-mode in presence of magnetic field. 相似文献
16.
An electron-emitting source generating a low-energy beam measuring 1–3 cm in diameter, with current up to 300 A, pulse duration
within 50–200 μs, and pulse repetition frequency up to 10 Hz is investigated in a gas-filled diode with a mesh plasma cathode
at the accelerating voltage up to 25 kV. The beam is transported in a longitudinal pulsed magnetic field to a distance of
up to 30 cm towards the region of its interaction with a solid. For the current densities up to 100 A/cm2, it provides the power density as high as 10–100 J/cm2 sufficient to melt surfaces of metals, alloys, and composite (metalloceramic) materials within one or a few pulses. This
makes this beam useful for modification of material surfaces and articles made thereof. Using the methods of optical, scanning
and diffraction electron microscopy, by building micro-and nanohardness profiles, and via identification of the treated surface
roughness, the phase composition and the substructure state of the materials subjected to pulsed low-energy e-beam of sub-millimeter
durations are investigated. Formation of submicro-and nanocrystalline multi-phase structure is observed, which ensures a multiple
increase in physico-mechanical and tribological characteristics of the treated material.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 60–70, May, 2008. 相似文献
17.
对全腔输出半透明阴极相对论磁控管做了进一步的改进,并对其进行了物理分析和三维全电磁粒子模拟研究。通过半透明阴极结构的改进,即改变阴极角向方位和阴极发射面高度参差设计以及局部参数优化,使得在较宽的工作参数范围内,器件起振初期可能出现的模式竞争得到抑制,起振时间进一步缩短,同时输出效率得到较大提高。在注入电子束电压和电流分别约为518 kV和4.1 kA、外加磁场为0.575 T时,模拟在S波段获得了效率大于66%、功率约1.42 GW的微波输出。同时还给出了电子束电压和外加磁场等参数在一定范围内变化时对输出性能的影响规律。研究结果可应用于高效紧凑型相对论磁控管的实验研究。 相似文献
18.
A. A. Plyutto 《Technical Physics》2005,50(9):1145-1149
It is shown that, while suppressing transverse electron motion, the axial magnetic field with an induction of up to 6.8 ×
10−2 T in the gap of a plasma diode has no significant effect on the current instability and on the acceleration of ions at electron
beam currents of ≤40 A. The increase in both the critical current and the period of current oscillations is related to an
increase in the plasma density after applying the magnetic field. The maximum energy of the accelerated magnesium ions decreases
by ≈25% at an induction of 1.7 × 10−2 T and does not depend on the magnetic field in the range (1.7–6.8) × 10−2 T. 相似文献
19.
20.
We describe mechanisms of microwave pulse shortening in radiation sources with the power of about 108 W based on interaction between relativistic electron beams of nanosecond duration and preformed plasma. The shortening is mainly due to the electron return flow through the plasma, which leads to a multiple decrease in the linear gain of the microwave by the relativistic electron beam and in the reflection coefficient of the plasma wave that provides the generator feedback. The ways to eliminate the effect of microwave pulse shortening are proposed. 相似文献