Measurement of laser light thomson-scattered from a cooling electron beam

First results are presented from an experiment scattering laser light from a relativistic electron beam. The 5 cm diameter continuous electron beam of 28 keV kinetic energy and 2.6 A current presents an electron gas of a density of 8×10⁷ cm^–3, from which 20 ns pulses of laser light (490 nm) were scattered at a repetition rate of 15 Hz and an average power of 20 mJ per pulse. The Doppler-shifted wavelength of photons backscattered under 180° was analysed with a Fabry-Perot interferometer. This technique provides, for the first time, a non-destructive measurement of the velocity distribution in an electron beam radially resolved in space. The results presented here comprise the direct measurement of the absolute electron energy and the degree of space-charge compensation in the electron beam. The determination of an upper bound of 10^–2 for the ratio of longitudinal to transverse electron temperature implies the first direct measurement of a flattened velocity distribution.     

Quasiclassical distribution function of electrons in a homogeneous magnetic field

Vlasov's equation is used to find the classical nonrelativistic and relativistic distribution functions that describe an electron beam of bounded radius in a homogeneous magnetic field. In the quasiclassical approximation, by means of the exact wave functions of an electron in a homogeneous magnetic field, the quantum relativistic distribution function with allowance for the electron spin is found. The mean physical quantities that characterize the radially bounded electron beam are found as functions of the temperature and electron spin.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 50–56, July, 1976.It is a pleasant duty to thank Professor V. G. Bagrov for discussing the results.     

Low-frequency longitudinal oscillations in a plasma with a relativistic electron component

Ion-sound oscillations in a three-dimensional plasma with relativistic electron component are studied. It is established that in this case ion-sound oscillations can exist only at electron and ion temperatures much less than the rest mass of the ions. In particular, it is shown that for an electron-positron plasma at relativistic temperatures ion-sound is impossible. The problem of ion-sound excitation by a charged particle beam is considered. Corresponding increments in beam instability are calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 24–27, December, 1985.     

Characteristics of electron beams formed in a diode with magnetic insulation

The problems of the formation of relativistic electron beams in a cylindrical diode with an annular cathode are discussed in the approximation of an infinitely strong guiding magnetic field. The beams are treated as infinitely thin. The following cases are investigated: 1) The formation of an electron beam moving off the cathode with an initial velocity. The case in which the field on the cathode is not equal to zero is investigated. It is shown that the potential of the electron beam can be determined in a nonunique fashion in the drift region. 2) The formation of a two-velocity electron beam. The possibility of controlling the flow of kinetic energy of the beam by varying the fraction of fast electrons in it is shown. 3) The formation of an electron beam in a diode with the help of two opposed cathodes at different potentials. A strong dependence of the current in the diode on the potential difference between the cathodes is obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 36–39, December, 1981.     

Optical Polarization Radiation of Relativistic Electrons in Conducting Targets

A theoretical model and results of experiments on optical polarization radiation of relativistic electrons from conducting targets performed on the synchrotron and microtron of Nuclear Physics Institute at Tomsk Polytechnic University are reported. The measurements of spectral characteristics of resonance polarization radiation in periodic targets over a wide range of electron energies (both in the Smyth–Purcell geometry and for different angles between the targets and the direction of the electron beam) show reasonable agreement with theoretical estimates.     

新型高功率径向强流速调管振荡器

 提出了一种新结构的高功率径向强流速调管振荡器,该器件利用折叠式同轴谐振腔的微波场与接近空间电荷限制电流的径向电子束强烈相互作用产生高功率微波。首先对这种器件的实现机理进行了初步的分析，提出了有间隙电压情况时的径向同轴间隙的空间电荷限制电流1维近似估计模型。分析表明：对于电子束直流接近但小于直流空间限制电流的径向速调管，当有调制间隙电压时，空间限制电流要小于无调制间隙电压情况下的直流空间限制电流，径向强流电子束电流接近和超过空间电荷限制电流时会出现强烈的调制。然后用PIC程序对其特性进行了粒子模拟，在二极管输入电压500 kV、电子束电流为30 kA条件下，最终得到了峰值功率6 GW、频率1.3 GHz的微波输出。     

Principles of the alloying of steel in a beam of relativistic electrons

It is shown that it is possible to significantly strengthen steel by alloying a surface layer melted by the energy from a beam of relativistic electrons. A study was made of the effect of different treatment parameters (accelerating voltage, beam current, specimen velocity and temperature, etc.) on the structure, depth, hardness, and wear resistance of the alloyed layer. Several types of alloying mixtures were developed based on carbides of tungsten, chromium, and boron, and including special additions and modifiers. The proportions of the components was optimized. The technology of alloying in a beam of relativistic electrons is compared with vacuum electron-beam alloying. Heat treatment is used to additionally improve the structure of the layers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 115–125, March, 1996.     

Anomalous mass transfer and phase and structural changes in α-Fe when acted upon with electron pulses

The phase composition and the defect structure of armco-iron irradiated with a relativistic electron beam is investigated using electron microscopy and x-ray structural analysis. Specimens with a chromium coating and without it were irradiated.Tomsk State University Architecture-Building Academy. Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 95–99, April, 1994.     

Laser-driven electron beam and radiation sources for basic,medical and industrial sciences

To date active research on laser-driven plasma-based accelerators have achieved great progress on production of high-energy, high-quality electron and photon beams in a compact scale. Such laser plasma accelerators have been envisaged bringing a wide range of applications in basic, medical and industrial sciences. Here inheriting the groundbreaker’s review article on “Laser Acceleration and its future” [Toshiki Tajima, (2010)],¹⁾ we would like to review recent progress of producing such electron beams due to relativistic laser-plasma interactions followed by laser wakefield acceleration and lead to the scaling formulas that are useful to design laser plasma accelerators with controllability of beam energy and charge. Lastly specific examples of such laser-driven electron/photon beam sources are illustrated.     

Theory of stimulated nonresonant emission from relativistic beams

A study is made of the radiative Pierce instability of a relativistic electron beam in a waveguide stabilized by an infinitely strong magnetic field. Analytical and computational methods are used to determine the growth rate of the instability, as well as the efficiency for conversion of the beam energy into electromagnetic field energy as a function of the beam current, how relativistic the beam is, and the geometry of the system. The physical nature of the instability is clarified and the mechanisms for its saturation are discussed. Zh. éksp. Teor. Fiz. 115, 2037–2050 (June 1999)     

Interaction of a relativistic electron beam with a spiral waveguide

The nonlinear period in the interaction of a relativistic electron beam (REB) with an electromagnetic wave in a spiral waveguide at the stage of saturation is investigated for a Cherenkov interaction mechanism. On the basis of the kinetic equation and laws of energy and momentum conservation, analytical relations are obtained, allowing the efficiency of excitation and amplification of the electromagnetic wave to be studied using REB in a retarding structure. The results of the analysis are in good agreement with the data of actual and numerical experiments.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 31–36, May, 1988.It remains to thank É. A. Perel'shtein, Yu. I. Aleksakhin, and their colleagues for discussion of the results.     

Attosecond X-ray pulse obtained from linear Thomson scattering

Linear Thomson scattering by a relativistic electron of a short pulse laser has been investigated by computer simulation. Under a laser field with a pulse of 33.3-fs full-width at half-maximum, and the initial energy of an electron of γ₀=10, the motion of the electron is relativistic and generates an ultrashort radiation of 76-as with a photon wave length of 2.5-nm in the backward scattering. The radiation under a high relativistic energy electron has better characteristic than under a low relativistic energy electron in terms of the pulse width and the angular distribution.     

Ultraviolet laser emission at 337 and 358 nm by collisional energy transfer in fast electron-beampumped,high-pressure Ar-N2 mixtures

Successive laser emission at 337.1 nm and 357.7 nm in the second positive band of N₂ have been observed in high-pressure Ar-N₂ gas mixtures excited by a high current (15 kA) and fast rise time (8 ns) relativistic electron beam. Laser action at 357.7 nm was confirmed in the pressure range 450–6000 torr where output intensity was approximately independent of pressure, while strong pressure dependence of the emission at 337.1 nm was observed in a rather limited pressure range of 760–3000 torr. From the results of spectrally resolved pressure dependences of the laser lines, the processes of successive laser oscillation at these two wavelengths are discussed.     

The effect of a strong radiation field on an electron moving in a plane electromagnetic wave

The paper considers the action of an external radiation field with arbitrary spectral composition on an electron moving in the field of a monochromatic plane electromagnetic wave (the first wave). The problem is studied of the change in the average energy of a relativistic electron as a result of its interaction with the radiation field. Conditions are found under which the acceleration of the electron by the external field is compensated by the energy loss due to natural radiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 7–16, January, 1973.     

Generation of coherent X-rays from a relativistic electron beam backscattered by a CO2 laser

On the basis of Palmer's criterion for the self-bunching effect of a relativistic electron beam in a helical magnetic field, it is shown that coherent X-rays can be generated from relativistic electron beams backscattered by laser beams without the need of any resonant cavity.     

激光驱动强流电子束产生和控制

在惯性约束聚变(ICF)电子束快点火物理方案中,需要超强拍瓦激光脉冲驱动MeV能量的强流电子束,并沉积数十kJ能量到压缩氘氚芯区。强流电子束的束流品质是影响点火成功的关键因素之一,为深入了解强流电子束产生物理过程,研制成了三维高性能、适应上万CPU核规模的并行粒子模拟程序,并开展了大规模数值模拟研究,探索了强流电子束的产生机制和输运规律。回顾了近几年来快点火研究团队围绕强流电子束产生和控制开展的研究,介绍了导致束流品质差的两大物理原因:预等离子体效应和束流不稳定性磁场的随机散射。针对这两个物理原因,提出了四种提高强流电子束品质的方法:(1)双层金锥靶减弱预等离子体的负面效应;(2)输运丝产生环向磁场准直强流电子束;(3)外加磁场导引强流电子束提高耦合效率;(4)抑制束流不稳定性以降低随机磁场对电子束流的散射。     

Nonlinear stage of development of resistive hose instability of a high-current relativistic electron beam in a plasma

The nonlinear stage in the development of a resistive hose instability of a highcurrent relativistic electron beam in a finite-conductivity plasma has been studied in the rigid-beam model. The attenuation of the force of the interaction of the beam with the magnetic field of the total current for large beam displacements is shown to result in the stabilization of the instability. The stabilization time and the amplitudes of the oscillations in the saturation regime are determined as functions of the parameters of the beam in the plasma.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fiz., No. 10, pp. 78–81, October, 1987.     

Experimental study of the possibility to increase the pitch factor of an intense relativistic helical electron beam

We present the results of experiments on the formation of a high-quality relativistic helical electron beam (HEB) in a magnetron-injection gun. It is shown that suppression of parasitic excitation of microwaves in the input part of the transportation channel allows eliminating high-voltage breakdowns in the gun and achieving greater beam compression. A modulation of the electron beam current at the frequency of longitudinal electron oscillations between the cathode and the magnetic mirror in the trap, which is related to the instability of the helical electron beam, has been observed for the first time. The modulation depth can reach tens percent. Pickup of reflected electrons by a special diaphragm makes it possible to increase the achievable pitch factor, eliminate the beam-current modulation and, as a result, form although with a current loss on the diaphragm, an HEB with record-breaking values of the pitch factor, which exceed 2. For a moderate HEB compression, when the portion of reflected electrons is relatively low, their pickup by the diaphragm allows one to form a beam in which the total energy of the transverse motion of electrons conserves despite the loss of part of the current. After the optimization, a beam with an electron energy of 300 keV, a current of 100 A, a pitch factor of 1.5, and a velocity spread of 20% is obtained for a 15% loss of the current on the diaphragm. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 10, pp. 855–863, October 2008.     

Population of Landau energy levels by charged particles of degenerate magnetized Fermi gases

The population of the Landau energy levels (from the zero level to the maximum level) is determined as a function of the quantizing magnetic field strength and the charged-particle concentration, for nonrelativistic proton and electron gases and relativistic electron gases.Brest State Pedagogical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 21–27, January, 1994.     

Generation of gravitational radiation during channeling

The channeling effect of relativistic charged particles in crystals enables us to obtain a directed flow of monoenergetic short-wave gravitons. For existing accelerator beam currents it is possible to obtain several hundred graviton radiation events with an energy of several megaelectron volts.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 21–24, March, 1985.