An investigation of electron-photon fluxes after two-layer barriers irradiated by a beam of fast monoenergetic electrons

The dependences of the electron and photon fluxes on the thickness of two-layer barriers irradiated with fast electrons were compared. The results were examined as a source of information about the composition of the absorber, which led to a new method of measuring the thickness of two-layer objects and of determining definitely the layer in which a change of thickness occurs.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 131–135, February, 1978.     

Field emission of monoenergetic spin-polarized electrons

Field emission from a tungsten tip, covered by a layer of crystallized ferromagnetic europium sulfide, leads to an electron beam with a current of 10⁻⁸ A, an energy width of less than 100 meV, and a spin polarization of about 0.85 at a tip temperature of 9 K. Proper annealing of the EuS layer is crucial.     

X-ray radiation toward relativistic electrons incident on a flat target

Features of X-ray radiation emitted toward the velocity vector of relativistic electrons incident on a flat target are discussed. The contribution of polarization bremsstrahlung (PB) considered as scattering of the intrinsic field of a fast charge by electrons of the medium is estimated taking into account its dispersion properties. Spectral-angular characteristics of coherent and incoherent PB are analyzed for unstructured and structured targets. Such PB feature not only different intensities, but also different angular dependences reaching a maximum near the velocity direction of a fast charge. It is shown that coherent PB emitted from the target surface layer is characterized by an extraordinary, i.e., inversely proportional to the squared frequency, intensity dependence.     

Tomography of injection and acceleration of monoenergetic electrons in a laser-wakefield accelerator

A tomographic diagnosis method was developed to systematically resolve the injection and acceleration processes of a monoenergetic electron beam in a laser-wakefield accelerator. It was found that all the monoenergetic electrons are injected at the same location in the plasma column and accelerated from 5 to 55 MeV energy in 200 microm distance. This is a direct measurement of the real acceleration gradient in a laser-wakefield accelerator, and the experimental data are consistent with the model of transverse wave breaking and beam loading for monoenergetic electron injection.     

Level inversion by excitation with a monoenergetic electron beam

The efficiency of level excitation with a monoenergetic electronic beam has been studied and compared with plasma excitation. The ratio of the 3s₂ and 2p₄ level populations of neon excited by a monokinetic beam was found to be three times higher than for plasma excitation. This result is in satisfactory agreement with theory.     

脉冲离子束作用下靶面次级电子的抑制

论述了离子束作用下固体表面次级电子产生的机制,介绍了特种真空器件中次级电子抑制的各种方法及其优缺点,提出了脉冲离子束作用下靶面次级电子抑制的自偏势法和曲面靶法等设计思路,并在实验上进行了初步验证。实验结果表明,自偏势电压大于80 V后,次级电子得到很好的抑制。在相同束流情况下,曲面靶较平面靶的次级电子产额少。利用实验结果进行估算得到了近似的次级电子产额约为0.67,比文献中的结果(0.58)偏大。对实验中自偏势法抑制反峰电子电流的效果进行了分析和讨论,结果表明：自偏势法不但能够有效抑制离子打靶产生的次级电子,还能抑制由功率源不稳定带来的入射反峰电子流。     

脉冲离子束作用下靶面次级电子的抑制

论述了离子束作用下固体表面次级电子产生的机制,介绍了特种真空器件中次级电子抑制的各种方法及其优缺点,提出了脉冲离子束作用下靶面次级电子抑制的自偏势法和曲面靶法等设计思路,并在实验上进行了初步验证。实验结果表明,自偏势电压大于80 V后,次级电子得到很好的抑制。在相同束流情况下,曲面靶较平面靶的次级电子产额少。利用实验结果进行估算得到了近似的次级电子产额约为0.67,比文献中的结果(0.58)偏大。对实验中自偏势法抑制反峰电子电流的效果进行了分析和讨论,结果表明:自偏势法不但能够有效抑制离子打靶产生的次级电子,还能抑制由功率源不稳定带来的入射反峰电子流。     

Deflection profiles of a monoenergetic atomic beam crossing a standing light wave

We calculate the shape of the deflection profile of a monoenergetic atomic beam crossing a laser standing wave, in a situation where many spontaneous emission processes occur during the interaction time. We predict that double peaked structures appear when the laser is detuned from resonance.     

Attenuation length of monoenergetic electrons photoinjected into the NaCl layer

A new, precise photoelectric method of electron attenuation length measurement in alkali halides is proposed and experimentally verified. The obtained results confirm the Llacer-Garwin theory of electron-phonon interactions in these substances.     

A field of free electrons formed as a result of pulsed gamma radiation passing through a liquid medium

A method for describing the change in an electromagnetic field created by electrons generated by a narrow beam of gamma rays passing through a liquid medium is proposed. Results from calculations using this procedure can be employed in designing detectors for experiments in high-energy physics.     

Excitation of resonance lines of the cadmium ion by monoenergetic electrons

The excitation of resonance lines at 226.5 and 214.4 nm, corresponding to the transitions 226.5 (5p ² P ₁ ^2/0 →5s ² S _1/2) and 5p ² P ₃ ^2/0 → 5s ² S _1/2, respectively, in the Cd⁺ ion upon collisions with monoenergetic electrons with an energy in the range of 4–130 eV is studied with high precision by a spectroscopic method in crossing beams. It is found that the dependence of the effective excitation cross sections of the resonance doublet components on the energy of the electrons has a distinct resonance structure. It is shown that the dominant mechanism responsible for this structure is the capture of an incident electron by a Cd⁺ ion with the simultaneous excitation of an electron from the subvalence 4d ¹⁰ shell to the autoionizing states of the Cd atom with their subsequent decay (directly or via cascade transitions) to resonance levels of the ion. The results obtained are compared with data from other experiments and with the results of the R-matrix strong-coupling calculation of 15 states and of semiempirical calculation using the Van Regemorter formula.     

Diffraction radiation interference pattern obtained upon electron beam propagation through a slit target

The interference pattern of coherent diffraction radiation (CDR) from a silt target is measured using the extracted beam of the microtron at Tomsk Polytechnic University. A theoretical interference pattern is calculated based on a model developed earlier for calculating the CDR characteristics in the far and near zones with allowance for the detector-sensitivity function. Comparison of the theoretical and experimental interference patterns makes it possible to obtain information about the longitudinal size of the bunch. The results obtained by the proposed and earlier methods agree well with each other.     

等离子体中相对论电子的同步曲率辐射特性研究

根据同步曲率辐射理论推导了在等离子体环境中,不同磁场条件下的相对论性电子的吸收系数和发射系数表达式，计算了电子的发射强度，并且在此基础上研究了同步曲率辐射机制的脉泽效应.研究了两种磁场位型，第一种是强度均匀但弯曲的磁场，第二种是偶极磁场，结果发现了一些偶极磁场下特有的辐射特性.考虑到在天体的环境下电子具有的不同的能谱分布，分别选用了三种典型的能谱分布(幂率分布，高斯分布，热分布)进行了研究，通过计算负吸收和脉泽放大效应在发射强度上的表现后， 发现在某些天体物理环境中，同步曲率辐射在等离子体中的确存在脉泽放大效应.这些研究结果对太阳系中行星外层辐射的研究和宇宙中的射电高亮温度等问题的研究可能提供有益的帮助. 关键词： 同步曲率辐射 负吸收 脉泽效应     

Second harmonic generation in scattering of intense beam of radiation by bound electrons near-resonance

Second harmonic generation in near-resonance scattering of intense beams of radiation by bound electrons is investigated by solving the equations of motion exactly to all orders in the intensity of the incident radiation. A two-level model for the atom and a one-mode classical field for the incident radiation is assumed and the rotating wave approximation is taken. It is shown that (i) the second harmonic radiation is an equally spaced triplet, (ii) the middle frequency in these is exactly two times the incident frequency and (iii) the splitting depends on the difference of incident frequency and resonance frequency and on the incident intensity. The counting rates for the three frequencies have been studied in the weak and the high intensity limits.     

Coherent X-ray radiation generated by a beam of relativistic electrons in a single crystal under conditions of multiple scattering

The dynamic theory of the coherent X-ray radiation of a divergent beam of relativistic electrons generated in a single-crystal wafer under conditions of the multiple scattering of incident particles is developed. Radiation cross sections are averaged over the divergent beam of rectilinear trajectories of electrons. Expressions describing the spectral-angular characteristics of parametric X-ray radiation and diffracted transition radiation under conditions of multiple scattering are obtained. Conditions under which the contribution of diffracted brehmsstrahlung can be disregarded are shown, and the spectral-angular characteristics of parametric X-ray radiation and diffracted transition radiation are calculated numerically for such conditions.     

Investigation of the spectral and angular distribution of gamma radiation of ultrarelativistic electrons in crystals

A technique and experimental apparatus are described for measuring the properties of radiation from relativistic electrons in crystals as a function of frequency and angle. The results of these measurements are compared with calculations and with the results obtained by other workers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 54–62, June, 1991.