Solid Electron Beam Research Articles

Enhanced electron radiation shielding composite developed by well dispersed fillers in PDMS polymer

This study reports a novel shielding material against high energy electron beam, where bismuth oxide (Bi2O3) and multiwalled carbon nanotube (MWCNT) nanoparticles added in a polymer matrix can solid electron beam radiation several times more efficient than aluminum with the same areal density. The polymer nanocomposites were prepared by dispersing nanoparticles in polydimethylsiloxane (PDMS) with a simple one-step fabrication process, in five areal densities (0.5, 1, 1.5, 3, and 5 g/cm2). All the samples were irradiated by 9, 12, 16, and 20 MeV electron beam. The prepared PDMS/CNT/BiO (CNT and BiO are the shorten name of fillers for coding the samples) showed better electron shielding ability than aluminum (Al) for any areal density. The weight advantageous of nanocomposite over aluminum was calculated up to 36 wt% for same attenuation efficiency. The thermal stability of nanocomposites up to 415 °C, as well as the tensile strength of up to 4.7 MPa, exhibited the high potential of developed samples for high energy electron beam shielding in medical and aerospace applications.

The effects of surface treatments on electron beam melted Ti-6Al-4V disks on osteogenesis of human mesenchymal stromal cells

Additive manufactured (AM) Titanium-6Aluminum-4Vanadium (Ti64) scaffolds display unique mechanical and biological properties for implant devices. The elastic modulus can be tailored by adjusting the porosity, further facilitating bone ingrowth. Although Ti64 implants are biocompatible, the effects of AM surfaces without porous structures, and how the topography and surface chemistry of the respective surfaces affect the osteogenesis of bone marrow-derived mesenchymal stromal cells (BMSCs) has not yet been revealed. In this paper, we cultured BMSCs on solid electron beam melted Ti64 disks subjected to three surface treatments: chemical etching (HF), atomic-layer deposition of TiO2 (TiO2), and polished (POL), or left untreated (AB). The biocompatibility and osteogenic properties of these surfaces were investigated, and the results were compared to cells cultured in regular tissue-culture polystyrene culturing wells (TCPS). The surfaces were hydrophobic, except for the polished surface which was hydrophilic.All surface treatments are biocompatible and allow for osteogenic differentiation, as revealed by viability assays and gene expression analysis. Scanning electron microscopy shows that cells adhere differently depending on the surface properties, with more filopodia on the rougher surfaces, AB and TiO2 disks, and more lamellipodia on the smoother surfaces, HF and POL disks. All groups stimulated with beta glycerophosphate, ascorbic acid, and dexamethasone, have elevated expression of genes related to matrix formation, where the cells cultured on the disks treated with TiO2, HF and POL have the overall highest expression. The AB group appears to be less favorable in regards to matrix formation. Considering the matrix mineralization, the rougher surfaces, AB and TiO2, are able to induce matrix mineralization, with an elevated gene expression of vitamin D receptors and calcium deposition of unstimulated cells. Finally, imaging at day 21 revealed an even amount of cells and matrix, covering most of the partially melted particles. Our results suggests that surface topography is more important to osteogenesis than the wettability of the surface. Overall, the present study contributes to the understanding of using surface modifications to AM Ti64 implant materials and reveals how they affect bone growth.

Nonlinear analysis of the efficiency and saturation length of free electron laser with realistic helical wiggler and ion-channel guiding

A nonlinear study of the efficiency, power, and the saturation length of a free-electron laser with realistic helical wiggler and ion-channel guiding using numerical simulation is presented. A set of coupled nonlinear differential equations is derived using the Lorentz force equation for the ensemble of electrons and Maxwell’s equations for radiation waves. To calculate the efficiency, power, and the saturation length of the amplifier, these equations are solved simultaneously using a code developed in this study. By choosing different values of the plasma frequency of ion-channel guiding, the dominant mode for the group I and group II orbits is found. The effect of ion-channel guiding on efficiency and saturation length was studied, and the results show that ion-channel guiding increases efficiency and reduces saturation length. Moreover, the efficiency increases, and the saturation length decrease when the annular electron beam is substituted for a solid electron beam. Finally, the results show that the efficiency of a realistic wiggler free-electron laser is higher than that of an idealized one, while the saturation length is lower.

Elliptical and circular annular solid electron beam for excitation of hybrid modes in the plasma combined circular and elliptical waveguides

For two new configurations presented and by considering annular solid electron beam with background plasma the growth rates of the hybrid modes and the dispersion relation of electromagnetic waves propagating are studied. The interaction of elliptical and circular annular solid electron beams with plasma is investigated that it occurs microwave radiation generation dependent of configuration dimensions. The structures are including metallic elliptical(circular) waveguide with elliptical(circular) dielectric cladding and a core having a circular(elliptical) dielectric rod in center that it is surround by circular(elliptical)annular plasma and a circular(elliptical)annular relativistic electron beam is injected in to plasma. The electromagnetic fields components in each of regions in the considered configurations are calculated. By applying the boundary conditions dispersion relation and operating frequency are obtained. Furthermore for another case that it is applied an infinite magnetic field to considered structures,the problem is investigated. Numerical computations are made and results are graphically presented.

Semianalytical Solution for Determination of Wave Amplification Characteristics in a Complex Elliptical Dielectric Waveguide Including Strongly Magnetized Plasma Circular Column

In this research, the excitation of hybrid electromagnetic waves in a complex dielectric-plasma waveguide is investigated semianalytically using the perturbation method and applying the suitable boundary conditions. Under this study waveguide combines circular and elliptical geometries, eccentrically. This elliptical waveguide has been filled with a dielectric material, whereas two axial hollows with circular section have been created in its focuses. In one of the hollows, there is an axial strongly magnetized plasma and a relativistic solid circular electron beam (RSCEB) is injected inside the other hollow. In addition, the growth rate of slow waves amplified by the electron beam is numerically calculated. The effects of accelerating voltage, current density of RSCEB, and geometrical parameters, such as radii of plasma column and electron beam, on the growth rate, electric field profile, and the frequency spectra are studied. Finally with considering the results, we will propose the optimum configuration to obtain maximum amplification of slow waves.

Limitations on Current of a Solid Axially Symmetric Electron Beam in the Drift Tubes of Millimeter-Wave Vacuum Electronic Devices

Conditions for ensuring the equilibrium stationary state of high-density solid electron beams, transported in cylindrical drift tubes and focused by uniform magnetic field, are investigated. Calculation results are compared to data obtained using the quasi-three-dimensional Arsenal-MSU computer code and analytical formulas proposed by other authors.

Limitations on Currents in Cylindrical Drift Tubes of Millimeter-Wave Vacuum Electronic Devices

The conditions providing the equilibrium stationary state of high-density solid and annular electron beams, transported in cylindrical drift tubes and focused by a homogeneous magnetic field, have been investigated. An efficient numerical model is proposed to determine the distributions of the electrostatic potential, charge density, and electron velocities in the stationary state of these beams, with allowance for the space-charge forces. The results of the numerical calculations for the limiting currents, determined by the longitudinal deceleration (caused by space-charge forces) and conditions for equilibrium transverse magnetic focusing for transported beams of different configurations on the length of a klystrontype vacuum electronic device, are presented. The limitations on the device working length, related to the excitation of diocotron instability, are estimated. The calculation results are compared with the data obtained using the quasi-three-dimensional program “Arsenal-MSU” and analytical formulas suggested by other researchers.

Effect of doping concentration, temperature and magnetic field on magnetic properties of Mn doped ITO nanoparticles and thin films

Manganese substituted indium-tin-oxide (Mn: ITO) nanoparticles (NP) and thin films (TF) were prepared using solid state reaction and electron beam evaporation techniques, respectively and studied the role of doping concentrations, temperature and applied magnetic fields on structural, optical and magnetic properties. The structural, optical and magnetic properties of the prepared NP and TF were studied using X-ray diffractometer, UV–Vis-NIR spectrophotometer and vibrating sample magnetometer, respectively. The Mn: ITO NP and TF exhibited a cubic structure without any secondary phases. The optical band gap of the Mn: ITO NP increased (3.07 eV–3.15 eV) whereas it decreased in Mn: ITO TF (3.9 eV–3.25 eV) with an increase of Mn concentration. The Mn: ITO NP exhibited a clear hysteresis loop at a temperature of 32 K and the strength of magnetization increased with the increase of Mn concentration and it decreased with the increase of temperature. The Mn: ITO NP has shown antiferromagnetic nature at higher applied magnetic fields. The Mn: ITO TF has shown weak ferromagnetic nature at room temperature and the magnetization decreased with the increase of Mn concentration. The magnetic saturation was not observed in these films even at higher applied magnetic fields.

Design and Large-Signal Modeling of a $W$ -Band Dielectric TWT

The performance capabilities of a dielectric traveling-wave tube (TWT), designed for operation near 94 GHz near the 100-W power level, are investigated using large-signal simulations. Key design elements include a dielectric liner with a moderately high dielectric constant of 13.5, consistent with magnesium orthotitanate ceramic, and the use of a solid round electron beam with properties (26-kV, 100-mA, and 0.185-mm beam radius) that are comparable to those employed in W -band coupled-cavity TWTs. The optimal simulated performance, computed assuming a 5-cm beam-wave interaction length, is 115 W of output power at 94 GHz, with 6-GHz half-power bandwidth, 10.3-dB large-signal gain, and 4.4% electronic efficiency. Technical issues, including the existence of a higher linearity Crestatron regime, the mitigation of beam charging, and thermal management, are discussed.

Comparison of the effect of annular and solid electron beams on linear and nonlinear traveling wave tube

Abstract The present paper, compares the effect of the annular and solid electron beam on the efficiency of linear and nonlinear TWTs. To do this, first we introduce four different geometric structure of the beam-helix. Then, we calculate the output power of each structure, in linear and nonlinear modes, at different frequencies using the numerical solution of the mathematical equations of the multi-frequency Eulerian model. Now, plot the output power in terms of distance for each structure at different frequencies and compare them. In a linear tube, the effect of annular beams on the output power is better than the solid beam, while this affects the frequency in nonlinear tubes. It is shown that in linear regime the power increase linearly with frequency but for nonlinear regimes is nonlinear.

Linear theory of beam–wave interaction in double-slot coupled cavity travelling wave tube**Project supported by the National Natural Science Foundation of China (Grant No. 11205162).

A three-dimensional model of the double-slot coupled cavity slow-wave structure (CCSWS) with a solid round electron beam for the beam–wave interaction is presented. Based on the “cold” dispersion, the “hot” dispersion equation is derived with the Maxwell equations by using the variable separation method and the field-matching method. Through numerical calculations, the effects of the electron beam parameters and the staggered angle between adjacent walls on the linear gain are analyzed.

Dielectric-Loaded Plasma Filled Helix Traveling Wave Tube Analysis Based on the Linearized Field Theory

A linear relativistic field theory of a plasma-loaded helix traveling wave tube is presented. The configuration consist of a solid electron beam propagating through a tape helix enclosed within a loss-free wall in which the gap between the helix and the outer wall is filled with a dielectric. The dispersion relation is derived for azimuthally symmetric modes. The effects of dielectric constant, plasma density, axial guide field, and electron beam density on the phase velocity and growth rate were considered numerically. Numerical results indicate that the phase velocity and growth rate increase in the presence of the plasma. Further the growth rate and frequency are maximum at the special value of the dielectric constant. The growth rate increases with axial guide field and remains relatively constant at strong magnetic field, however the growth rate increases considerably by incrementing the electron beam density.

Side-effects of the space charge field introduced by a hollow electron beam in the electron cooler of CSRm**Supported by National Natural Science Foundation of China (11375245)

An electron cooler is used to improve the quality of the ion beam in a synchrotron; however it also introduces a nonlinear electromagnetic field to the accelerator, which causes tune shift, tune spread and may drive resonances leading to ion beam loss. In this paper the tune shift and the tune spread caused by the nonlinear electromagnetic field of a hollow electron beam is investigated, and the resonance driving terms of the nonlinear electromagnetic field are analysed. The differences are presented compared with a solid electron beam. Calculations are performed for 238U32+ ions of energy 1.272 MeV stored in the main Cooler Storage Ring (CSRm) at the Institute of Modern Physics, Lanzhou. It is found that in this situation the nonlinear field caused by the hollow electron beam does not lead to serious resonances.

Theoretical analysis of a thermal plasma-loaded relativistic traveling wave tube having corrugated slow wave structure with solid electron beam

A relativistic traveling wave tube with thermal plasma-filled corrugated waveguide is driven by a finite solid electron beam with the entire system immersed in a strong longitudinal magnetic field that magnetized plasma and electron beam. The dispersion relation for the relativistic traveling wave tube is obtained by linear fluid theory. The numerical results show that the growth rate decreases by increasing plasma temperature, waveguide radius, plasma density and electron beam energy. As show in this paper the effect of electron beam density and corrugation period is to increase growth rate.

Dispersion and Growth-Rate Characteristics of a Sinusoidally Corrugated Slow-Wave Structure in Presence of Cylindrical Electron Beam

A theory of relativistic traveling wave tube (RTWT) with magnetized cold plasma-filled corrugated waveguide with solid electron beam is given. The entire system influenced a strong longitudinal magnetic field that magnetized plasma and electron beam. The characteristic of the dispersion relation is obtained by numerical solutions. The effect of electron beam density, corrugated period, waveguide radius on the dispersion relation and growth rate is analyzed. Some useful results are given.

Plasma Thermal Effect on the Growth Rate of the Helix Traveling Wave Tube

Field theory is applied to analyze the behavior of the thermal plasma-loaded tape helix traveling-wave tube in the presence of a solid electron beam present inside the plasma. The plasma temperature effect on the phase velocity and the growth rate of the system are investigated. It is shown that, if plasma temperature increases in the system, its working frequency and growth rate will increase. The results indicate that the axial electric field and growth rate increase with plasma density.

The effect of beam and plasma parameters on the four modes of plasma-loaded traveling-wave tube with tape helix

Field theory is applied to analyze the behavior of the electromagnetic wave in the presence of a solid electron beam and magnetized plasma-loaded tape helix traveling-wave tube. The obtained dispersion relation implicitly includes azimuthal variations and all spatial harmonics of the tape helix. Results indicate that the frequency and the phase velocity of (X bp − X p ) and (O bp − X p ) modes increase with cyclotron frequency and for (O bp − O p ) and (X bp − O p ) modes decrease. In the strong magnetic field limit, the maximum growth rate and frequency of all modes are constant at different values of cyclotron frequency and beam energy. If the plasma density increases, the frequency and phase velocity of four modes will increase. The maximum growth rates of the four modes in the lower plasma density are equal and for higher values of plasma density the (O bp − X p ) mode has greatest value. The phase velocity and the frequency of (X bp − X p ) with (X bp − O p ) modes and (O bp − O p ) with (O bp − X p ) modes are coinciding with each other and for first case increase with beam density, but for latter decrease. The maximum growth rate of (O bp − O p ) mode and the maximum frequency of (X bp − X p ) mode have highest values as a function of the electron beam density.

Plasma effect in tape helix traveling-wave tube

A linearized relativistic field theory of a plasma-loaded helix traveling-wave tube is presented for a configuration where a solid electron beam propagate through a sheath helix enclosed within a loss-free wall in which the gap between the helix and the outer wall is filled with a dielectric. Numerical study of the effect of plasma density on the phase velocity and growth rate has been done. Numerical results show that the plasma have different behaviors in different density limits.

Nonlinear analysis on electron beam current in cylindrical waveguide

The space-charge-limited currents of both solid electron beam and annular electron beam in cylindrical waveguide are derived from the nonlinear Poisson equation for potential in the region of electron beams. Corrections for the transverse motion of electrons are made to the solution, which bring more consistent with the results from PIC simulations. Though numerical computation, it is showed that electrons located along the axis and by outer radius of solid and annular electron beams respectively and electrons standing near to the outside of the beam has larger axial velocity than these inside. This approach is available for analyzing the characteristics of electron beam transporting in high power microwave generator with other configuration waveguide.

Further theoretical study on laminar-flow equilibria in magnetically focused relativistic electron beams

A numerical solution for the self-consistent differential equations describing the laminar-flow equilibrium in magnetically focused relativistic electron beams is given and proved to be available by comparison with analytical results of solid electron beam in the case of pθ=0 （magnetically shielded sources）. With the numerical method, the space-charge limited current and the externally applied magnetic field of both solid and annular electron beam in three cases of pθ=0,pθ=const and pθ∝r2 （magnetically immerged sources） are presented and compared. It is shown that the conditions at the source with respect to the canonical angular momentum pθ have little effect on the space-charge limited current and the externally applied magnetic field, but more intense annular electron beam generated by the source with pθ=const. can be transported in the same drift tube under lower guided magnetic field than solid ones.