Cylindrical Beam Research Articles

Time-delayed mass spectrometry of the low-energy electron impact with a liquid beam surface.

We set up an experimental apparatus to investigate the low-energy electron impact with a liquid beam surface, in which a cylindrical liquid beam with a diameter of 25 μm emits as the laminar flow from a microjet and the positively charged ions produced by the electron-impact ionizations are detected with a linear time-of-flight mass spectrometer. We propose a time-delayed mass spectrometry for this apparatus to identify the cationic fragments produced on the liquid surface, in which the application of the ion extracting pulse is delayed with different time intervals after the electron beam pulse. Sensitivity and specificity of the present methodology are demonstrated by the combinational experiments of the gas-phase and liquid ethanol. In comparison with the gas-phase experiments, the ion peaks become much broader in the mass spectra of the liquid beam, primarily due to the molecular evaporation and diffusion. After delaying with about 2 μs, we find that the hydrocarbon ions are ultimately the predominant products in the mass spectra of the liquid ethanol and they are proposed to be produced on the liquid surface. Above observations are in line with the widely accepted picture of the molecular orientation on the liquid surface; namely, the ethanol's CH3-CH2- group on the liquid surface prefers to be oriented outside. Therefore, we demonstrate a new mass spectrometry to explore the molecular structures of the liquid surface.

Structured Light by Linking Diffraction-Resistant Spatially Shaped Beams

In this paper we present a theoretical method, together with its experimental confirmation, to obtain structures of light by connecting diffraction-resistant cylindrical beams of finite lengths and different radii. The resulting "Lego-beams" can assume, on demand, various unprecedented spatial configurations. We also experimentally generate some of them on using a computational holographic technique and a spatial light modulator. Our new, interesting method of linking together various "pieces of light" can find applications in all fields where structured light beams are needed: in particular, such as optical tweezers, e.g. for biological manipulations, optical guiding of atoms, light orbital angular momentum control, holography, lithography, non-linear-optics, interaction of electromagnetic radiation with Bose-Einstein condensates, and so on, besides the field in general of Localized Waves (non-diffracting beams and pulses).

Six-Axis Column-Type Force and Moment Sensor for Robotic Applications

A flexible cylindrical beam is used to design a six-axis column-type force and moment sensor for robotic applications, where accurate small force and moment measurements are required. One of the ends of the beam is fixed, and the other remains free. A rigid cover with a mushroom shape is placed at the free end. This cover is the contact surface between the sensor and the object being touched, and it transmits the contact forces and moments to the flexible beam. The 12 miniature strain gauges are strategically placed on the surface of the beam to measure the contact forces and moments by using a simple model based on the classical theory of elasticity. The calibration method of the sensor is performed by using the least-square fitting method, and the experimental results demonstrate that maximum and mean relative errors are below 9% and 3%, respectively, of fullscale in all measured variables.

Structured spin angular momentum in highly focused cylindrical vector vortex beams for optical manipulation.

We investigate the spin properties of a family of cylindrical vector vortex beams under a focusing condition. The spin-orbit interaction is demonstrated by comparing the energy flow and spin flow density of the focused field to those of the incident field. This spin-orbit interaction is analyzed to construct the desired distribution of spin angular momentum for optical manipulation. The structured spin angular momentum of the focused field can transfer to the optical torque for the non-magnetic absorptive particle. The influences of polarization topological charge, vortex topological charge and wavelength on optical torque in the hot-spot of focused field are summarized for three typical particles. Such results may be exploited in practical optical manipulation, particularly for optically induced rotations.

Label-free high-speed wide-field imaging of single microtubules using interference reflection microscopy.

The cytoskeleton gives a cell its shape and plays a major role in its movement and division. It's also helps organise the content of cells and is the base for intracellular transport. Important components of the cytoskeleton are microtubules, which are hollow cylindrical beams (25 nm in diameter) that assemble from protein building blocks called tubulin. Deficiencies in microtubules are related to many diseases including cancer and Alzheimer. Given their important role, microtubules are heavily investigated in many laboratories. One way to study microtubules is to isolate them from cells and image them using light microscopy. Over the years a number of imaging techniques have been used. These techniques have a number of drawbacks which are addressed by ongoing efforts which this work is a part of. Here, we present a method based on light interference that produce high quality images of microtubules. The technique is cheap and easy to implement making it accessible to a wide base of researchers.

Free vibration analysis of micro and nano fiber-metal laminates circular cylindrical shells based on modified couple stress theory

ABSTRACTIn this manuscript the frequencies of micro and nano fiber-metal laminate (FML) cylindrical shells based on modified couple stress theory (MCST) have been obtained. Love's first approximation shell theory has been applied to consider the thin cylindrical shell and beam modal function model used to satisfy the governing equations of motion subjected to different boundary conditions. Vibration of micro and nano FML cylindrical shells has been considered for carbon/epoxy, glass/epoxy and aramid/epoxy as composites and for aluminum as metal. Also, the frequencies of the shells have been calculated for different volume fractions of composite section, lay-ups, material length scale parameters, length to radius ratio, axial and circumferential wave numbers. The results have been compared to the other researches and showed excellent agreement with them. Also, the frequencies of aramid reinforced aluminum laminate micro and nano cylinder are more than the other ones.

Deformaciones de haces cilíndricos y cónicos al atravesar una placa plano-paralela de cristal uniaxial

Una de las herramientas más usadas en la óptica es el trazado de rayos ya que es la herramienta fundamental para el diseño de todo instrumento óptico. En este trabajo se analizan las sucesivas deformaciones que un haz cilíndrico (modelo a primer orden de un haz colimado) y un haz cónico (modelo a primer orden de un haz divergente o convergente), que inciden normalmente sobre una placa planoparalela de cristal uniaxial, sufren a medida que van atravesando las distintas interfaces. Esto se hace siguiendo el camino de cada rayo incidente sobre la primera interfaz. El trazado de rayos para los rayos ordinarios es igual al trazado de rayos en medios isótropos. El trazado de rayos extraordinario, en cambio, presenta más dificultad ya que los rayos no están contenidos en el plano de incidencia y no coinciden con las normales a los frentes de onda. Se analizan también la pérdida de simetría de revolución de los haces y la formación de las sucesivas imágenes.

Study of a Dual-Mode <inline-formula> <tex-math notation="LaTeX">${W}$ </tex-math> </inline-formula>-Band Extended Interaction Oscillator

A W-band extended interaction oscillator (EIO) operating at two different types of $2\pi $ modes is presented. The modes and output characteristics were studied, and the circuit was optimized to ensure similar and efficient outputs of two standing-wave modes. For a cylindrical electron beam radius of 0.2 mm, voltage of 14 kV, and current of 0.5 A, particle-in-cell simulation predicts 616 W at 93.76 GHz for the $2\pi $ gap mode and 367 W at 94.22 GHz for the $2\pi $ cavity mode. In this paper, numerical simulations demonstrate the ability of the EIO circuit to be operated with two standing-wave modes in the millimeter-wave range.

Formation and focusing of converging sheet electron beam based on field emission

The development of compact amplifiers with an average power of the frequency range 0.2–0.3 THz is related to the design of electron-optical systems using converging sheet beams that allow obtaining sufficiently high current densities with a lower current load on the cathode and with a lower value of the magnetic field. Based on the theory of synthesis the numerical simulation results for electron-optical systems for the formation of a converging sheet electron beam are presented. Reduction of the current load on the cathode allows the principle of transformation of a cylindrical electron beam into a sheet by employing electrostatic compression of the beam in one plane. A sheet beam electron-optical system with a field emission cathode with convergence of 10, and with the beam of 0.1 × 1.1 mm2 and current density of 45 A/cm2 has been performed. The electron gun employing the cathode–gate structure with diameter of 1 mm has an emitting current up to 10 mA in experiment. The modulation coefficient of the cathode current for a gun with a sheet electron beam has 0.3% of the anode potential.

Theoretical investigation of confocal microscopy using an elliptically polarized cylindrical vector laser beam: Visualization of quantum emitters near interfaces

We theoretically study laser-scanning confocal fluorescence microscopy using elliptically polarized cylindrical vector excitation light as a tool for visualization of arbitrarily oriented single quantum dipole emitters located (1) near planar surfaces enhancing fluorescence, (2) in a thin supported polymer film, (3) in a freestanding polymer film, and (4) in a dielectric planar microcavity. It is shown analytically that by using a tightly focused azimuthally polarized beam, it is possible to exclude completely the orientational dependence of the image intensity maximum of a quantum emitter that absorbs light as a pair of incoherent independent linear dipoles. For linear dipole quantum emitters, the orientational independence degree higher than 0.9 can normally be achieved (this quantity equal to 1 corresponds to completely excluded orientational dependence) if the collection efficiency of the microscope objective and the emitter's total quantum yield are not strongly orientationally dependent. Thus, the visualization of arbitrarily oriented single quantum emitters by means of the studied technique can be performed quite efficiently.

Criteria for Determining Maximum Theoretical Oscillating Frequency of Extended Interaction Oscillators for Terahertz Applications

Extended interaction oscillators (EIOs) are high-frequency vacuum-electronic sources, capable to generate millimeter-wave to terahertz (THz) radiations. They are considered to be potential sources of high-power submillimeter wavelengths. Different slow-wave structures and beam geometries are used for EIOs. This paper presents a quantitative figure of merit, the critical unloaded oscillating frequency ( ${f}_{\textsf {cr}} $ ) for any specific geometry of EIO. This figure is calculated and tested for $2\pi $ standing-wave modes (a common mode for EIOs) of two different slow-wave structures (SWSs), one double-ridge SWS driven by a sheet electron beam and one ring-loaded waveguide driven by a cylindrical beam. The calculated ${f}_{\textsf {cr}}\text{s}$ are compared with particle-in-cell (PIC) results, showing an acceptable agreement. The derived ${f}_{\textsf {cr}}$ is calculated three to four orders of magnitude faster than the PIC solver. Generality of the method, its clear physical interpretation and computational rapidity, makes it a convenient approach to evaluate the high-frequency behavior of any specified EIO geometry. This allows to investigate the changes in geometry to attain higher frequencies at THz spectrum.

Fast readout algorithm for cylindrical beam position monitors providing good accuracy for particle bunches with large offsets.

A simple, analytically correct algorithm is developed for calculating "pencil" relativistic beam coordinates using the signals from an ideal cylindrical particle beam position monitor (BPM) with four pickup electrodes (PUEs) of infinitesimal widths. The algorithm is then applied to simulations of realistic BPMs with finite width PUEs. Surprisingly small deviations are found. Simple empirically determined correction terms reduce the deviations even further. The algorithm is then tested with simulations for non-relativistic beams. As an example of the data acquisition speed advantage, a Field Programmable Gate Array-based BPM readout implementation of the new algorithm has been developed and characterized. Finally, the algorithm is tested with BPM data from the Cornell Preinjector.

Focusing properties of cylindrical vector vortex beams

In this paper, following Richards and Wolf vectorial diffraction theory, the focusing properties of cylindrical vector vortex beams (CVVB) are investigated, and a diffractive optical element (DOE) is designed to spatially modulate the amplitude of the CVVB. Simulated results show that the CVVB focused by an objective also carry orbital angular momentum (OAM), and the optical fields near the focal region can be modulated by changing the topological charge of the CVVB. We numerically simulate the focus properties of radially and azimuthally polarized beams with topological charge equal to 0, 1, 2 and 10 respectively. As a result, a dark channel with a length about 20 λ can be obtained. These new properties have the potential applications such as particle acceleration, optical trapping and material processing.

Vibration analysis of FG spinning beam using higher-order shear deformation beam theory in thermal environment

By using higher-order shear deformation beam theory (HSDBT), free vibration analysis of functionally graded (FG) spinning cylindrical beam subjected to thermal environment is performed. A new displacement field for hollow circular cylindrical beam is proposed that keeps the shear stress to be free at both inner and outer surfaces of the beam. The present formulation includes all possible terms of linear equations of spinning beam such as centripetal and Coriolis forces. Material properties are assumed temperature dependent and graded in the thickness direction. To discretize the system, the Rayleigh–Ritz method, which is an efficient and accurate approximation method, is used. The convergence of the method is verified, and the results are compared with available solutions in the literature. We investigate the effects of spinning speed, temperature dependence of material properties, and material property graded index on the natural frequency parameter of the FG cylindrical beam with different boundary conditions.

Estimation of Beam and Plasma Parameters for Electron Beam Transport in Ion-Focused Regime

This paper presents the analysis of cylindrical electron beam and beam-impact-generated plasma using particle-in-cell simulation code VSim 6.2 at different operating conditions. The transient plasma parameters, such as, beam density, charge neutralization factor, space charge potential, ionization time, beam compression, and plasma electron temperature, have been estimated and analyzed for a 40-keV, 10–100-A electron beam propagating in argon gas-filled drift space at different operating pressures. These parameters are difficult to be measured experimentally. The evaluated charge-neutralizing factor has been found dynamic in space and time, which is maximum at the beam envelope. The voltage profile of space charge potential required for effective electron beam propagation approaches zero due to formation of the plasma in the order of ionization time. The estimated average plasma electron temperature has been found to be less than ~1 eV, which is less damaging for interaction structure of the plasma-assisted microwave sources. It has been observed that an optimum pressure limit needs to be maintained inside the drift space to prevent the loss of electron beam due to instabilities resulting in excessive collisions with the drift space walls.

Preliminary research on flow rate and free surface of the accelerator driven subcritical system gravity-driven dense granular-flow target.

A spallation target is one of the three core parts of the accelerator driven subcritical system (ADS), which has already been investigated for decades. Recently, a gravity-driven Dense Granular-flow Target (DGT) is proposed, which consists of a cylindrical hopper and an internal coaxial cylindrical beam pipe. The research on the flow rate and free surface are important for the design of the target whether in Heavy Liquid Metal (HLM) targets or the DGT. In this paper, the relations of flow rate and the geometry of the DGT are investigated. Simulations based on the discrete element method (DEM) implementing on Graphics Processing Units (GPUs) and experiments are both performed. It is found that the existence of an internal pipe doesn’t influence the flow rate when the distance from the bottom of the pipe to orifice is large enough even in a larger system. Meanwhile, snapshots of the free surface formed just below the beam pipe are given. It is observed that the free surface is stable over time. The entire research is meaningful for the design of DGT.

Investigation of heat and mass transfer processes by the method of structured laser radiation caustics

This paper is devoted to investigation of possibilities of using the caustic method for determination of optical inhomogeneities parameters, which arise by heat and mass transfer processes. Conditions of the caustics appearance are considered for longitudinal probing of the diffusion layer of liquid by plane and cylindrical laser beams. Experimental visualization of dynamics of change in the caustics position is presented for various parameters of inhomogeneous media. New method for determination of surface temperature of a cooled body placed in transparent liquid is described.

Order-Controllable Cylindrical Vector Vortex Beam Generation by Using Spatial Light Modulator and Cascaded Metasurfaces

Cylindrical vector vortex (CVV) beam, which possesses both helical phase front and spatially inhomogeneous polarization, is a promising structured light for its various applications ranging from optical communication to optical field manipulation and optical microscopy. However, approaches to generate CVV beams with switchable and tunable polarization order and topological charge are still immature, which hinders the wide application of CVV beams. In this paper, we have experimentally demonstrated that order-controllable CVV beams can be produced by using spatial light modulator (SLM) and equivalent <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -plate system at wavelength of 1550.8 nm. It is shown that the topological charge of the CVV beam can be switched by directly programming the SLM. We have also demonstrated that the polarization order of the CVV beam can be tuned to as high as eight by employing an equivalent <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -plate system, which consists of two cascaded metasurfaces and a half-wave plate. To further verify the helical phase of the CVV beam, we have proposed a novel measurement method based on first removing the vector property and then interfering the remaining helical phase with plane wave or spherical wave.

Dosimetric optimization of a truncated conical-shaped transmission target for electronic brachytherapy X-ray source: A Monte Carlo study

The purpose of this study is to determine the optimal target configurations to improve the uniformity of dose distribution for the electronic brachytherapy source. A truncated conical-shaped transmission type was designed. Monte Carlo simulation technique was used to investigate the target thickness, geometry of electron beam, and target angle of a truncated conical-shaped target for the electronic brachytherapy X-ray source. Dosimetric parameters recommended by TG-43U1 protocol were used to determine the optimal target design of electronic brachytherapy source. The target thicknesses for maximizing the transmitted X-ray intensity were approximately 1.2 to 1.5 μm for 0° and 90°. In a range of optimal thickness, transmitted X-ray intensity at 90° was approximately 92% of maximum photon intensity. The effects of electron beam shapes on 2D anisotropy functions were investigated at radial distances of 0.5, 1.0, 2.0, 3.0, and 5.0 cm. Minimum variations for all radiation distances and angular ranges were observed for uniform cylindrical electron beam with a radius of 2.0 mm. Anisotropy functions at 0°, F(r, 0° ), were close to unity and slightly more than unity for non-uniform cylindrical (R = 1.0 - 2.0 mm) electron beam and uniform cylindrical electron beam with a radius of 2.0 mm. The angles of target anode between 45° and 50° show minimum fluctuations in the anisotropy functions and are close to unity for F(r, 0° ). The optimal target configurations are a truncated conical-shaped target having an angle between 45° and 50°. It is concluded that tungsten target having the thickness of 1.2 to 1.5 μm and uniform circular with a radius of 2.0 mm as electron beam produces optimal dosimetric characteristics for electronic brachytherapy X-ray source.

Switchable phase and polarization singular beams generation using dielectric metasurfaces

Singular beams which possess helical phase wavefront or spatially inhomogeneous polarization provide new freedom for optical field manipulation. However, conventional schemes to produce the singular beams have difficulty in realizing the flexible switch between different singular beams. In this work, we have experimentally demonstrated the capability of dielectric metasurfaces to generate three types of singular beams and switch between them at working wavelength of 1550 nm. We have shown vortex beam and cylindrical vector beam generation with single metasurface and cylindrical vector vortex beam generation with two cascaded metasurfaces. Moreover, experimental demonstration on switching cylindrical vector beam into vortex beam has also been done by combining one quarter-wave plate and a Glan laser polarizer. The experimental results match well with the analysis from the Jones matrix calculations. The average conversion efficiency of cylindrical vector beam to vortex beam was estimated to be 47.7%, which was about 2.3% lower than the theoretical prediction.