Effects Of Electron Beam Parameters Research Articles

Suppressing of even harmonics in free electron lasers by modifying the energy spread of the beam

Using an analytical description of the evolution of the power of harmonics in free electron laser (FEL) undulators, we study the effect of electron beam parameters on the main characteristics of FEL radiation: the gain length, spectrum, and harmonic power. The possibility of suppressing even harmonics of the FEL as a light source in the study of materials and surfaces by analyzing the second harmonic nonlinear response (SHG) is being studied. The main factors influencing the radiation of even FEL harmonics are revealed; the influence of the beam cross section and the spread of electron energies on their radiation is analyzed. An example of a LEUTL FEL with visible light emission, which is used in studies of the optical properties of materials and the chemical state of molecules on surfaces and interfaces between media, is considered. In this context, the possibility of suppressing the second FEL harmonic is analyzed.

Specific features of focused electron beam transport through a narrow metal tube at negative potential in the forevacuum pressure range

We describe our investigations on the transport of a focused electron beam through a long and narrow metal tube, held at negative potential with respect to the vacuum chamber walls, in the elevated forevacuum pressure range. We have explored the effect of electron beam parameters and tube potential on beam transport. It is shown that the strength of this effect is connected to the initiation of a non-self-sustained glow discharge within the tube, as well as to the beam magnetic focusing parameters. We also show that increase in the fraction of electrons transported through the tube is conducive to uniformity of the distributions of the non-self-sustained discharge current and the discharge plasma density along the tube length.

Beam Asymmetry, Divergence and Energy Spread Effects on the Radiation from Planar Undulators

The theoretical study of the effect of electron beam parameters, in particular, the emittance and its asymmetry on the radiation from relativistic electrons in undulators is conducted both analytically and numerically. The reasons for the odd and even harmonic generation and radiation are explored. The difference in the underlying physical reasons for the spontaneous and stimulated radiation of harmonics in free electron lasers (FELs) is elucidated. The generalized forms of the special functions of the Bessel and Airy type are employed to account analytically for the off-axis and angular effects together with the effect of the beam energy spread. A comparative analysis of the radiation spectra for undulators with different beams is performed. The examples of the radiation at SPARC and LEUTL are given. The effect of the asymmetry of the beam on the radiation properties is analyzed. The alternative theoretical approaches of other authors are also employed for the analytical calculation of the harmonic powers in FELs. The results are compared with existing experimental data.

Investigation of the effect of electron beam parameters on the characteristics of the steam-gas channel during welding of nickel and titanium alloys

The article presents the developed technique of high-speed video recording of the combined-cycle gas channel and subsequent frame processing to obtain the dimensional characteristics of the combined-cycle gas channel. On the basis of this technique, dependences of the width of the weld at different depths were obtained depending on the current and welding speed. A pattern of dimensional characteristics of the steam-gas channel depending on the running energy and the dependence of the frequency of collapse of the steam-gas channel on the electron beam current at a constant welding speed of 40 m/h by the example of nickel and titanium alloys was revealed.

Electron beam synthesis of silicon-carbon coatings in the forevacuum pressure range

We describe our investigations of the synthesis of silicon-carbon coatings obtained by electron-beam evaporation of silicon carbide at forevacuum background gas pressure. The electron beam was generated by a forevacuum-pressure, plasma-cathode electron source operating at a gas pressure of 5–10 Pa. The effect of electron beam parameters on the morphology and tribology of the deposited coatings was explored, and the results are described here.

Head-on collision of ion-acoustic multi-solitons and study of rogue waves in electron-beam superthermal plasma

In this investigation, head-on collision of ion-acoustic (IA) multi-solitons and study of characteristics of ion acoustic rogue waves in an unmagnetized plasma which includes ion fluid, superthermal hot electrons, and penetrated by electron beam have been presented. The Korteweg-de Vries equation have been derived by employing the extended Poincaré-Lighthill-Kuo (PLK) method. Further, multi-solitons of different KdV equations have also been determined by following the Hirota bilinear method. The combined effects of electron beam parameters and variation of different physical parameters on the characteristics of IA solitons and phase shifts of multi-solitons have been analyzed. It is remarked that electron beam components and other plasma parameters significantly influence the phase shifts and other properties of ion-acoustic solitons (IASs). Furthermore, the nonlinear Schrodinger equation (NLSE) has been derived from the KdV equation by using appropriate transformation. The characteristics of different orders rogue waves have also been studied from the different solutions of NLSE. The results of this study may be of great importance to understand the characteristics properties of various kinds of nonlinear solitary structures in different kinds of plasma systems.

Study of the beam-wave interaction of a 0.34-THz confocal waveguide gyro-TWT with confocal beam

In this paper, in order to enhance the efficiency of the confocal gyrotron travelling wave tube (confocal gyro-TWT), the confocal beam is first introduced based on the field distribution of the operating mode in the confocal waveguide. Besides, a confocal gyro-TWT with a confocal beam operating at 0.34 THz is simulated and designed based on linear and nonlinear theories. It is verified that the confocal beam can enhance the interaction efficiency and output power significantly through simulation. In addition, the effects of electron beam parameters on output power are also analyzed in this paper. The simulation results indicate that the confocal gyro-TWT can operate at TE06 stably with an output power of 17.3 kW when the beam voltage is 60 kV, beam current is 2 A, input power is 40 mW, and transverse velocity spread is 5%. The corresponding frequency and interaction efficiency are 0.34 THz and 14.4%, respectively.

Application of a forevacuum plasma source of a focused electron beam for cutting quartz glass

The paper presents the results of studies of the effect of electron beam parameters on the geometric dimensions of the hole created in quartz glass by an electron beam with the power density of up to 106 W·cm−2 generated by a forevacuum plasma source. It is shown that the electron beam with such specific power is capable of creating holes up to several centimeters deep. At the same time with the passage of time the hole acquires an established form. The dependences of the geometrical dimensions of the steady-state form of the hole depending on the parameters of the electron beam are presented.

Effects of electron beam parameters and velocity spread on radio frequency output of a photonic band gap cavity gyrotron oscillator

In this paper, the effects of electron beam parameters and velocity spread on the RF behavior of a metallic photonic band gap (PBG) cavity gyrotron operating at 35 GHz with TE041–like mode have been theoretically demonstrated. PBG cavity is used here to achieve a single mode operation of the overmoded cavity. The nonlinear time-dependent multimode analysis has been used to observe the beam-wave interaction behavior of the PBG cavity gyrotron, and a commercially available PIC code “CST Particle Studio” has been reconfigured to obtain 3D simulation results in order to validate the analytical values. The output power for this typical PBG gyrotron has been obtained ∼108 kW with ∼15.5% efficiency in a well confined TE041–like mode, while all other competing modes have significantly low values of power output. The output power and efficiency of a gyrotron depend highly on the electron beam parameters and velocity spread. The influence of several electron beam parameters, e.g., beam voltage, beam current, beam velocity pitch factor, and DC magnetic field, on the PBG gyrotron operations has been investigated. This study would be helpful in optimising the electron beam parameters and estimating accurate RF output power of the high frequency PBG cavity based gyrotron oscillators.

Ferroelectric lithography

The fact that domain polarization affects the surface properties suggests a method to direct chemical reactions on ferroelectric substrates. In combination with domain manipulation at small scales, a new lithography process is developed to assemble several classes of nanostructures. Three domain patterning techniques, which employ contact electrodes, SPM and e-beam are introduced, with focus on the physical interactions between electrons and ferroelectrics. The effects of electron beam parameters on polarization reorientation are quantified and it is shown that both positive and negative polarization can be achieved depending on conditions. Potential applications of ferroelectric lithography on fabrication of complex structures are illustrated.

Effect of electron beam parameters on simulated CBED patterns from edge-on grain boundaries.

Convergent beam electron diffraction (CBED) at vertical grain boundaries (parallel to the electron beam) can be applied to determine the symmetry of bicrystals. It can also be used to investigate the structure of the boundary region itself when subnanometre probe sizes are employed. In this paper it is shown that (sub)nanometre-probe CBED patterns are largely influenced by the electron-beam geometry. In particular, simulations of coherent CBED patterns based on the multislice algorithm show that the CBED pattern of an edge-on interface depends on the defocus distance between the probe position and the specimen midplane, the probe size and the beam-convergence angle. The pattern symmetry may be lower than the theoretically predicted symmetry in case of large spherical aberration. This effect increases with smaller accelerating voltages. An increase in the beam-convergence angle also increases the possibility of a non-optimum symmetry due to spherical aberration of a coherent probe. Thus, for the determination of an interface structure using subnanometre (coherent) probes, the imaging conditions play an important role.