共查询到20条相似文献,搜索用时 125 毫秒
1.
E. V. Ilyakov I. S. Kulagin V. N. Manuilov A. S. Shevchenko 《Radiophysics and Quantum Electronics》2007,50(9):713-719
We propose a method of increasing the pitch factor and decreasing the spread of rotational velocities of helical electron
beams (HEBs) formed in nonadiabatic magnetron-injection guns of gyroresonant devices. The method is based on the effect of
a special diaphragm mounted at the starting point of the transport channel on the process of formation of the laminar electron
beam. The diaphragm located at one of the trajectory minima has such a diameter that it cannot be bent around by electrons
with minimum rotational velocities. Such electrons land on it, whereas the remaining electrons pass further, moving in an
increasing magnetic field. Then the electrons with the maximum rotational velocities reflect from the magnetic mirror adiabatically
and land on the other side of the same diaphragm. Thus, the electron beam in the cavity contains electrons with a smaller
resulting spread of rotational velocities. In the region of the HEB formation, the accumulation of the space charge of reflected
electrons is eliminated, and the shielding of the electric field at the cathode is reduced, which eventually leads to an increase
in the HEB pitch factor. Using such a diaphragm in the regime of current limitation by the space charge, the HEB with a high
pitch factor (about 1.4) and a velocity spread acceptable for gyrotron applications (lower than 30%) was formed.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 9, pp. 785–792, September 2007. 相似文献
2.
S. V. Kuznetsov 《Journal of Experimental and Theoretical Physics》2012,115(1):171-183
The trapping and acceleration of nonmonoenergetic electron bunches in a wake field wave excited by a laser pulse in a plasma channel is studied. Electrons are injected into the region of the wake wave potential maximum at a velocity lower than the phase velocity of the wave. The paper analyzes the grouping of bunch electrons in the energy space emerging in the course of acceleration under certain conditions of their injection into the wake wave and minimizing the energy spread for such electrons. The factors determining the minimal energy spread between bunch electrons are analyzed. The possibility of monoenergetic acceleration of electron bunches generated by modern injectors in a wake wave is analyzed. 相似文献
3.
The paper describes the influence of the velocity spread of the electrons on the interaction efficiency and on other operational characteristics in the gyro-peniotron oscillator. Numerical simulation shows a drastic efficiency reduction from more than 45% to less than 30% with an electron velocity spread of 10% for a 35GHz, TE03 mode gyro-peniotron operating at the third harmonic. The operation ranges of the device parameters at a defined efficiency level are also decreased when the velocity spread of the electrons increases. 相似文献
4.
J. Jančařík 《Czechoslovak Journal of Physics》1969,19(8):964-973
The paper describes the operation and construction of an electron gun designed to form beams with variable transverse energy and a variable spread of magnetic moments. Transverse energy is acquired by the electrons as the beam passes through a weakly non-adiabatic magnetic step, and in an adiabatic motion through a growing magnetic field. The small spread of magnetic moments of the beam electrons is achieved by fulfilling the so-called focusing conditions which ensure that the spread of moments resulting from different initial radii of the particles is compensated by their initial radial velocities. 相似文献
5.
根据电子多重散射理论,基于蒙特卡罗方法研究不同能量电子垂直入射不同材料的阳极靶后,电子在阳极靶内的沉积能量分布,及X射线发射位置的能量分布.结果表明:电子在靶内的轨迹扩展和入射电子能量、靶材料有关,99%电子能量沉积在近似圆柱形区域内.且电子在入射方向上的沉积能量分布不是直接递减,而是先递增到一定深度后再递减,符合电子背散射理论.说明X射线产生区域是在距表面一定深度区域内.另外,通过对比分析发现金刚石膜作为电子吸收光栅是不可行的,但作为热沉材料有很大的潜力.这些结论可为微结构X射线源研究及高亮度高相干X射线源设计提供参考. 相似文献
6.
A. S. Dzarakhohova N. P. Zaretskiy A. V. Maksimychev L. I. Menshikov P. L. Menshikov 《Journal of Experimental and Theoretical Physics》2020,130(1):140-147
The conditions of suppressing the collective slowing-down of an ionic beam on electrons, which is caused by the excitation of electron plasma oscillations (beam instability) by ions, are found. In contrast to available explicit and implicit indications, a large spread of the energies only in an ionic beam is insufficient for this suppression. The acceleration of ions is shown to become stable when a sufficiently large spread of the electron velocities is simultaneously present. The beam instability of ions is suppressed by the Landau damping of the ion-excited plasma waves at electrons. The results obtained are used to analyze the possibility of ion acceleration by collapsed cylindrical plasma liners. 相似文献
7.
Pollock BB Clayton CE Ralph JE Albert F Davidson A Divol L Filip C Glenzer SH Herpoldt K Lu W Marsh KA Meinecke J Mori WB Pak A Rensink TC Ross JS Shaw J Tynan GR Joshi C Froula DH 《Physical review letters》2011,107(4):045001
Laser wakefield acceleration of electrons holds great promise for producing ultracompact stages of GeV scale, high-quality electron beams for applications such as x-ray free electron lasers and high-energy colliders. Ultrahigh intensity laser pulses can be self-guided by relativistic plasma waves (the wake) over tens of vacuum diffraction lengths, to give >1 GeV energy in centimeter-scale low density plasmas using ionization-induced injection to inject charge into the wake even at low densities. By restricting electron injection to a distinct short region, the injector stage, energetic electron beams (of the order of 100 MeV) with a relatively large energy spread are generated. Some of these electrons are then further accelerated by a second, longer accelerator stage, which increases their energy to ~0.5 GeV while reducing the relative energy spread to <5% FWHM. 相似文献
8.
The effect of the anode-current magnetic field on the electron motion in a triode with a virtual cathode is considered. It is shown that the anode-current magnetic field influences the oscillation period and trajectories of electrons. The condition of self-isolation of the electron beam is investigated as a function of the diode parameter. It is shown that the displacement of the beam electrons under the action of the anode-current magnetic field leads to a decrease in the electron phase modulation and an increase in the spread in the electron oscillation amplitude; as a result, the generation efficiency of microwave radiation decreases. 相似文献
9.
N. A. Koshev N. A. Orlikovskii E. I. Rau A. G. Yagola 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(9):959-964
The inverse problem of reconstructing the true spectrum of electrons backscattered from massive and layered targets with allowance for the spread function of the toroidal sector energy analyzer and for the response function of the spectrometer??s electron detector is solved. We present the results from studying the energy spectra of a number of homogeneous samples and film-on-substrate systems obtained at different energies of the irradiating electron beam at normal incidence of the electrons on the surface, and at a 45° angle of backscattered electron detection. 相似文献
10.
根据拉格朗日方程对电子在平滑会切磁场中的径向波动与速度零散的关系进行讨论。运用Matlab,Magic软件相互结合的方法设计电子枪结构和磁场。用Matlab程序模拟单电子在给定电场、磁场中的运动,分析了单电子径向速度对零散的影响,并优化磁场分布。设计的磁场可以有效地减小单电子束径向速度,降低电子束速度零散。用Magic软件对电流为1 A、能量为30 keV的电子束在优化磁场中的运动进行仿真,得到的电子束速度比约为2,速度零散小于2.5%,轴向速度零散小于8.5%。 相似文献
11.
The formation of an electron beam in a magnetron-injector gun of a gyrotron is investigated in the case when it is affected by the negative-mass instability due to the Coulomb repulsion and nonisochronous cyclotron rotation of particles. A technique is proposed for calculating the spread of the initial energy of electrons caused by the instability, which develops as the electron beam moves in the presence of a nonuniform magnetostatic field of the magnetron-injector gun. It is demonstrated that this instability can be one of the main factors providing the energy spread in electron guns of gyrotrons. 相似文献
12.
Using single electron capacitance spectroscopy, we study electron additions in quantum dots containing two potential minima separated by a shallow barrier. Analysis of the addition spectra in the magnetic field allows us to distinguish between electrons delocalized over the entire dot and those localized in either of the potential minima. We demonstrate that a high magnetic field abruptly splits up a low-density droplet into two smaller fragments, each residing in a potential minimum. An unexplained cancellation of electron repulsion between electrons in these fragments gives rise to paired electron additions. 相似文献
13.
A possibility of precise measurement of the electron beam energy using absorption of radiation by electrons in a homogeneous magnetic field for electrons of high energy in the range up to a few hundred GeV, was considered earlier. In this paper, with the purpose of experimental checking of this method in the range of several tens MeV of electrons energies, a possibility of measurement of absolute energy of the electron beam with a relative accuracy up to 10?4, is considered. We take into account influence of the laser beam diffraction, of the spread of electrons over energies, and of the length of formation of radiation absorption in the process of electron beam energy measurement. The laser wavelength and the length of the magnet are chosen depending on the length of photon absorption formation. It is found that the kinematical restrictions on the photon absorption process lead to the selection in angles of propagation of photons, which can be absorbed by the beam electrons. It is shown that parameters of the electron beam will noticeably not vary during the measurement of the energy. 相似文献
14.
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16.
V. V. Ognivenko 《Journal of Experimental and Theoretical Physics》2012,115(5):938-946
The motion of the relativistic electron beam in the spatially periodic magnetic field of an undulator has been considered taking into account the effect of the incoherent field of the spontaneous undulator radiation on the motion of the electrons. An expression for the rms momentum of the electrons has been obtained. It has been shown that the momentum spread in the ultrarelativistic electron beam increases in the spontaneous incoherent emission mode. Conditions for the self-amplification of the spontaneous undulator radiation in ultrashort-wavelength free-electron lasers have been discussed. 相似文献
17.
The floating sheath potential in a plasma having a Maxwellian electron distribution function is e?>s = -kTe 1n (a/b)/2 where Te is the electron temperature, a is the ratio of electron temperature to ion temperature, and b is the ratio of electron mass to ion mass. This expression is derived by equating the flux of electrons and ions to a surface in the plasma. Only electrons initially having an energy greater than -e?s flow to the surface. These electrons are in the tail of the distribution, a region that differs significantly from a Maxwellian in many plasmas. An analysis is performed where the sheath potential is solved for using a two-temperature model for the electron distribution function. The two-temperature model accurately describes the distortion from a Maxwellian in the tail of the distribution function. The magnitude of the sheath potential calculated with the two-temperature distribution is significantly smaller than that obtained using a Maxwellian distribution, a result of the reduction in the relative abundance of energetic electrons in the tail of the distribution. 相似文献
18.
Dipole-allowed optical absorption in a parabolic quantum dot with two electrons are studied by using the exact diagonalization techniques and the compact density-matrix approach. Numerical results are presented for typical GaAs parabolic quantum dots. The results show that the total optical absorption coefficient of two electrons in quantum dot is about five times smaller than that of one electron in quantum dot. 相似文献
19.
E. H. Baksht A. G. Burachenko A. V. Kozyrev I. D. Kostyrya M. I. Lomaev V. K. Petin D. V. Rybka V. F. Tarasenko S. V. Shljakhtun 《Technical Physics》2009,54(1):47-55
The spectra of electrons and X-ray photons generated in nanosecond discharges in air under atmospheric pressure are investigated
theoretically and experimentally. Data for the discharge formation dynamics in a nonuniform electric field are gathered. It
is confirmed that voltage pulses with an amplitude of more than 100 kV and a rise time of 1 ns or less causing breakdown of
an electrode gap with a small-radius cathode generate runaway electrons, which can be divided into three groups in energy
(their energy varies from several kiloelectronvolts to several hundreds of kiloelectronvolts). It is also borne out that the
formation of the space charge is due to electrons appearing in the gap at the cathode and a major contribution to the electron
beam behind the foil comes from electrons of the second group, the maximal energy of which roughly corresponds to the voltage
across the gap during electron beam generation. X-ray radiation from the gas-filled diode results from beam electron slowdown
both in the anode and in the gap. It is shown that the amount of group-3 electrons with an energy above the energy gained
by runaway electrons (in the absence of losses) at a maximal voltage across the gap is much smaller than the amount of group-2
electrons. 相似文献
20.
R. P. Fischer W. M. Manheimer A. W. Fliflet 《International Journal of Infrared and Millimeter Waves》1997,18(4):759-778
The linear theory used to design a two-resonator 85 GHz quasioptical gyroklystron with a nonuniform magnetic field is presented.
It is shown that a tapered magnetic field in the prebunching resonator has a relatively small effect on the electron bunching
parameter. The effect of velocity spread of the electron beam can be minimized by adjusting the magnetic field strength in
the two resonators. Measured amplifier performance is in good agreement with calculations from the nonlinear multimode simulation
code. Gyrophase bunching of the electrons is preserved over the long drift region (30 radiation wavelengths) even though no
attempt has been made to minimize the velocity spread of the beam. 相似文献