Spinning Beam Research Articles

Modeling and analysis of a flexible spinning Euler-Bernoulli beam with centrifugal stiffening and softening: A linear fractional representation approach with application to spinning spacecraft

The derivation of a linear fractional representation (LFR) model for a flexible, spinning and uniform Euler-Bernoulli beam is accomplished using the Lagrange technique, fully capturing the centrifugal force generated by the spinning motion and accounting for its dependence on the angular velocity. This six degrees of freedom (DOF) model accounts for the behavior of deflection in the moving body frame, encompassing the bending, traction and torsion dynamics. The model is also designed to be compliant with the Two-Input-Two-Output Port (TITOP) approach, which offers the possibility to model complex multibody mechanical systems, while keeping the uncertain nature of the plant and condensing all the possible mechanical configurations in a single LFR. To evaluate the effectiveness of the model, various scenarios are considered and their results are tabulated. These scenarios include uniform beams with fixed root boundary conditions for different values of tip mass, root offset and angular velocity. The results from the analysis of the uniform cantilever beam are compared with solutions found in the literature and obtained from a commercial finite element software. Ultimately, this paper presents a multibody model for a spinning spacecraft mission scenario. A comprehensive analysis of the system dynamics is conducted, providing insights into the behavior of the spacecraft under spinning conditions.

Dynamic characteristics of multi-span spinning beams with elastic constraints under an axial compressive force

Dynamic characteristics of multi-span spinning beams with elastic constraints under an axial compressive force

Broadband large-angle beam scanning with dynamic spin energy distribution based on liquid crystal cascaded bilayer metasurface

Abstract Dynamic manipulation of terahertz (THz) beams plays an important role in THz application systems. The PB metasurface provides an effective scheme for space separation and deflection of the spin beam. However, mirror symmetry locking of the conjugated spin states severely limits the versatility of the device. In this work, we demonstrate a liquid crystal (LC) cascaded bilayer metasurface that includes an LC layer, anisotropic metasurface, and PB metasurface. By controlling anisotropy and polarization conversion effects, dynamic spin asymmetric transmission is realized. Meanwhile, two different dynamic energy distribution processes are realized between the L and R state with the corresponding deflection side. The results show that the device achieves a large angular spatial dispersion within the frequency-angle scanning range of ±35° to ±75° corresponding to the broadband range of 0.6–1.1 THz. Moreover, it achieves a spin beam spatial separation with a maximum proportion of energy distribution greater than 26 dB, and the active modulation rate in the energy distribution process reaches 98 %. This work provides a dynamic THz spin conversion and efficient large-angle beam scanning, with important potentials in wavelength/polarization division multiplexing and frequency-scanning antenna for large-capacity THz wireless communication, radar, and imaging systems.

Terahertz magneto-optical metadevice for active spin-selective beam steering and energy distribution with nonreciprocal isolation

Active beam steering and energy distribution have important applications for terahertz (THz) communication, radar, and imaging. However, the spin-conjugated mirror symmetry of a passive Pancharatnam–Berry (PB) metasurface limits the active energy distribution. Here, we prepared a low dispersion, low loss, and high magneto-optical coefficient La:YIG single crystal, ±45∘ Faraday rotation angle that can be actively tuned by a weak magnetic field in broadband THz range at room temperature. Based on this functional material, a THz magneto-optical (MO) spin-modulated metadevice has been demonstrated, which is integrated with a La:YIG, an anisotropic metasurface, and a PB metasurface layer. The spin-conjugated mirror symmetry is broken by the MO chirality effect and photonic spin Hall effect in this metadevice so that spin-selective beam steering within the range of ±27∘−±41∘ is dynamically manipulated by external magnetic fields and power distribution can be tuned with the max modulation depth of 91.6%. More importantly, the MO crystal introduces nonreciprocal phase shift between two spin states so that the device not only achieves active THz beam steering but also provides isolation for reflected waves with the max isolation of 23 dB. This mechanism of THz nonreciprocal spin beam steering provides multiple functions for THz point-to-point networking communication, anti-shielding, anti-interference, and power distribution.

Vibration and Stability Analysis of a Spinning Hollow Functionally Graded Beam with Exponentially Varying Cross-Section

This paper presents an analytical investigation of the whirl characteristics and flexural instability of a spinning functionally graded (FG) hollow beam with exponentially varying cross-section. Applying Rayleigh beam theory, the governing equation of motion of the spinning beam with eccentricity is formulated via the Hamilton principle. The dimensionless whirl frequency equation is obtained for the FG beam with pinned–pinned end supports. On the basis of the obtained model, the whirl frequency, critical spinning speed, and stability conditions of the system are studied. Also, the effects of the main parameters on the whirl characteristics and stability of the system are evaluated. Results show that the unbalanced mass is the main source of system instability. It is also shown that the whirl frequency, critical spinning speed, and stability boundaries of the system are strongly dependent on the slenderness ratio, taper parameter, gradient index, hollow ratio, and eccentricity effects.

Improved airy function formalism for the study of anti-parallel double δ-magnetic-barrier nanostructure under the modulation of the applied bias

The Goos–Hänchen (GH) shift and the spin polarization are theoretically investigated under the anti-parallel double [Formula: see text]-magnetic-barrier nanostructure model by applying a bias using Airy’s function formalism and transfer-matrix technique, which is an improvement on previous calculation. The results show the magnitude and sign of GH shift and spin polarization can be easily changed by modulating the applied bias. The closer the applied bias to the critical value is, the more intensive GH shift and spin polarization will be. Furthermore, two critical values come through modulating the strength of magnetic fields, and an intensive GH shift and a spin polarization also exist near each critical value. These findings can provide a practical approach to designing and fabricating spin beam filters or splitters modulated by applied bias.

Achieving Photonic Spin Hall Effect, Spin-Selective Absorption, and Beam Deflection with a Vanadium Dioxide Metasurface.

Metasurface-based research with phase-change materials has been a prominent and rapidly developing research field that has drawn considerable attention in recent years. In this paper, we proposed a kind of tunable metasurface based on the simplest metal-insulator-metal structure, which can be realized by the mutual transformation of insulating and metallic states of vanadium dioxide (VO2) and can realize the functional switching of photonic spin Hall effect (PSHE), absorption and beam deflection at the same terahertz frequency. When VO2 is insulating, combined with the geometric phase, the metasurface can realize PSHE. A normal incident linear polarized wave will be split into two spin-polarized reflection beams traveling in two off-normal directions. When VO2 is in the metal state, the designed metasurface can be used as a wave absorber and a deflector, which will completely absorb LCP waves, while the reflected amplitude of RCP waves is 0.828 and deflects. Our design only consists of one layer of artificial structure with two materials and is easy to realize in the experiment compared with the metasurface of a multi-layer structure, which can provide new ideas for the research of tunable multifunctional metasurface.

Static and dynamic analysis of the postbuckling of axially moving spin beams

This paper aims to investigate the static and dynamic behaviors of the postbuckling of axially moving spin beams (bi-gyro system). The Hamilton’s principle is used to derive the nonlinear governing equations of bi-gyro systems, which are based on the Euler-Bernoulli beam model and account for von Karman geometric nonlinearity. After neglecting the time-dependent terms, the static equations are discretized using the differential quadrature method and then solved as a nonlinear algebraic system via the Newton-Raphson iteration method. Subsequently, the linear vibration problem is accurately solved for axially moving spinning beams in their first buckled configuration. Finally, numerical calculations are conducted to investigate the impact of axial and spinning velocities on the steady-state dynamic responses of bi-gyro systems. The findings are as follows: (a) the critical axial velocity where trivial equilibrium is unstable remains unaffected by the presence of spinning velocity; (b) the bifurcation point of the axial velocity corresponding to amplitude is reduced by spinning velocity, resulting from centrifugal force; (c) the vibration amplitude of the bi-gyro system will diverge under a weaker displacement constraint spring; and (d) stable buckled and straight configurations can coexist under certain axial and spinning velocities.

Design of graphene spin beam splitter based on Brewster’s law

Spin beam splitter is one of the building blocks of graphene spintronics. Here, we adopt the concept of electron optics and design a new type of spin beam splitter by analogy with Brewster’s law. The device is a pristine/ferromagnetic/pristine (P/M/P) graphene junction, where the M region is formed by a proximity effect of ferromagnetic insulators, such as EuO, and acts as an “optically thinner medium” relative to the P region. It is found that, when standing waves are formed in the M region with a length of integral multiple of the half longitudinal wavelength of electrons, electrons with the corresponding spin can pass completely through the junction and only electrons with the other spin are reflected by the P/M interface. This manifests Brewster’s law and a spin beam splitter. It is also demonstrated that, due to the strong electric field effect of graphene, the Brewster angles for both spins can be monotonically modulated by a gate voltage in the M region in the whole range of − π / 2 to π / 2. Thus, our proposed spin beam splitter is not only an easily implemented and widely tunable build block for spintronics but also an interesting demonstration of electron optics.

Modified Fourier Approach for Vibration Analysis of Spinning Beam with Elastic Restraints

This paper presents a unified method for analyzing the dynamic behavior of spinning beams under elastic constraints. Based on the Timoshenko beam theory, a dynamic model of a spinning beam with elastic constraints is established. The displacement and bending angle are represented by a modified Fourier series. Compared with the traditional Fourier series, the improved Fourier series eliminates the discontinuity of the derivative at the boundary by introducing auxiliary polynomials, making it more suitable for elastic constraints. The governing equations and boundary conditions are coupled together using the energy method to form a set of standard linear equations. By solving this equation, the modes of the spinning beam structure under elastic constraints can be concisely and quickly obtained. Finally, by comparing with other methods, it is proved that the method has good convergence and practicability. Then, the effects of spinning speed, boundary stiffness and slenderness ratio on the whirling characteristics are analyzed. The results show that the linear spring has a more pronounced effect on the whirl frequency than the torsion spring. Different boundary constraints produce different elastic intervals. Mode exchange was found with increasing spinning speed. In the case of elastic constraints, the mode exchange occurs at lower spinning speed. This method has a certain universal applicability to the dynamic analysis of spinning beams under elastic constraints, and the research results can provide theoretical reference for subsequent research.

Chiral enantiomer recognition of amino acids enhanced by terahertz spin beam separation based on a Pancharatnam-Berry metasurface.

The highly sensitive detection and identification of chiral biochemical substances have attracted extensive attention. Terahertz (THz) spectroscopy and sensing technology have obvious advantages in non-contact and label-free biochemical detection, but the THz chiral spectral response of chiral biochemical substances is too weak to realize highly sensitive chiral enantiomer recognition. Herein, we propose a method of spin beam deflection and separation by using a Pancharatnam-Berry (PB) metasurface to enhance the THz chirality response of chiral amino acids, realizing the identification of chiral enantiomers of the same kind of amino acid. The conjugate spin transmittances and circular dichroism (CD) spectra of d- and l-tyrosine samples on the PB metasurface were measured by an angle-resolved THz time-domain polarization spectroscopy system, and their CD values reached 16.4° and -11.6° at a deflection angle of ±33°, respectively, which were enhanced by about 9.3 and 11.9 times compared with the maximum CD values of the sample without the metasurface. Therefore, this THz chiral sensing method based on a PB metasurface has great potential in highly sensitive chirality identification and enhancement for chiral substances.

Effects of beam spinning on the fourth-order particle resonance of 3D bunched beams in high-intensity linear accelerators

The aim of this study is to make the parameter space of zero-current phase advance greater than 90\ifmmode^\circ\else\textdegree\fi{} available to the high-intensity linear accelerator (linac) design and operation, which has been excluded to avoid the envelope instabilities and particle resonances. The earlier study of Cheon et al. [Nucl. Instrum. Methods Phys. Res., Sect. A 1013, 165647 (2021)] reported that the spinning of ion beams can mitigate the fourth-order particle resonance and the associated envelope instability in high-intensity linacs. In the present work, we further investigate the effects of beam spinning on the fourth-order particle resonance in the case of 3D bunched beams with fast acceleration. We also explore the space-charge-driven resonance in the longitudinal plane and confirm that the fourth-order particle resonance can be manifested when the longitudinal zero-current phase advance ${\ensuremath{\sigma}}_{z0}$ is larger than 90\ifmmode^\circ\else\textdegree\fi{} and the depressed phase advance ${\ensuremath{\sigma}}_{z}$ is less than 90\ifmmode^\circ\else\textdegree\fi{}, similar to the transverse case. The beam spinning effects are examined in both transverse and longitudinal planes during beam acceleration through periodic solenoid and quadrupole-doublet focusing channels.

Active terahertz beam deflection and nonreciprocal spin chirality selection based on magneto-optical P-B metasurface with stacked-graphene layers.

Multifunctional, high-efficiency, and active manipulation devices are significant for terahertz (THz) technology and application. In this Letter, a stacked-graphene meta-atom (SGM) structure is investigated, which is composed of periodically patterned graphene in the 2D plane and stacked graphene-dielectric layers perpendicularly to the plane. This structure not only has strong THz artificial anisotropy but also enhances the cyclotron resonance response of graphene to a THz wave under an external magnetic field (EMF). Based on these two characteristics, the SGM can realize dynamic conversion between two functions for the manipulation of THz spin chiral states under different EMFs: from the reciprocal spin-flip without EMF to nonreciprocal spin-selection with EMF. Furthermore, a Pancharatnam-Berry (P-B) metasurface composed of the SGMs with different discrete orientation angles has been designed, which achieves active conversion between THz spin chiral beam deflection and the nonreciprocal one-way transmission for two conjugated spin beams, dynamically manipulated by both the biased voltage and EMF. The spin-select isolation is 42.3 dB with a transmission efficiency of over 70% at 1.38 THz. This manipulation mechanism of the spin beam and related devices has great potential in future THz communication, dynamical imaging, and radar scanning systems.

Polarization control in spin-transparent hadron colliders by weak-field navigators involving lattice enhancement effect

Hadron polarization control schemes for Spin Transparent (ST) synchrotrons are analyzed. The spin dynamics and beam polarization in such synchrotrons are controlled by spin navigators (SN) which are special small insertions of weak magnetic fields. An SN stabilizes the beam polarization and allows for setting any desirable spin orientation at an interaction point in the operational regime, including a frequent spin flip. We present a general approach to design of SNs. We distinguish different types of SNs, namely, those not causing closed orbit perturbation as well as those producing local and global orbit distortions. In the second case, the concept of the spin response function in an ST synchrotron is applied and expanded to reveal the effect of the SN strength enhancement by magnetic lattice of the synchrotron. We provide conceptual schemes for SN designs using longitudinal and transverse magnetic fields allowing for polarization control at low as well as high energies. We also develop the ST concept for ultra-high energies. This development may enable and stimulate interest in polarized beam experiments in possible polarized collider projects such as Large Hadron Collider (LHC), Future Circular Collider (FCC) and Super Proton Proton Collider (SPPC).

Mitigation of space-charge-driven resonance and instability in high-intensity linear accelerators via beam spinning

For modern high-intensity linear accelerators, the well-known envelope instability and recently reported fourth-order particle resonance impose a fundamental operational limit (i.e., zero-current phase advance should be less than 90°). Motivated by the stability of spinning flying objects, we propose a novel approach of using spinning beams to surpass this limit. We discovered that spinning beams have an intrinsic characteristic that can suppress the impact of the fourth-order resonance on emittance growth and the associated envelope instability.

Tunable lateral spin polarization and spin-dependent collimation in velocity-modulated ferromagnetic-gate graphene structures

The influence of spatial variation of Fermi velocity on the spin-polarized transport properties of massless Dirac fermions in proximity-induced ferromagnetic graphene junction was investigated. We found that the velocity ratio ξ causing the width of the spin conductance dip near the Dirac point is broadened as the Fermi velocity ratio increases. In contrast, the effect of the Fermi velocity mismatch does not affect the shifting of the Dirac point. It leads to the indirect measurement of the Fermi velocity ratio that can be tuned by the spin-dependent conductance. In addition to the presence of both the exchange field and the Fermi velocity modulation, we found high spin filtering occurs when the Fermi velocity ratio ξ ≥ 1. Due to the transmission probability of electron with spin down, T↓ is blocked by the effect of Fermi velocity modulation similar to waves travelling through a different media. Moreover, we also found that the resonant transmission of the electron with spin up can be perfectly transmitted through the Fermi velocity barrier at the limit injected angle θ → π/2 for H/EF ≈ 1. The spin transport properties can be controlled by suitably modifying the strength of the ferromagnetic insulator and varying the Fermi velocity modulation, which leads to the highest spin polarization. By manipulating the behavior of spin-dependent collimation and spin beam splitting in this structure, we proposed a spin transport device for making lateral spin polarization. These interesting features will help make the development of spintronic devices in the graphene-based nanostructure.

Conservation of angular momentum in second harmonic generation from under-dense plasmas

Spin and orbital angular momentum of an optical beam are two independent parameters that exhibit distinct effects on mechanical objects. However, when laser beams with angular momentum interact with plasmas, one can observe the interplay between the spin and the orbital angular momentum. Here, by measuring the helical phase of the second harmonic 2ω radiation generated in an underdense plasma using a known spin and orbital angular momentum pump beam, we verify that the total angular momentum of photons is conserved and observe the conversion of spin to orbital angular momentum. We further determine the source of the 2ω photons by analyzing near field intensity distributions of the 2ω light. The 2ω images are consistent with these photons being generated near the largest intensity gradients of the pump beam in the plasma as predicted by the combined effect of spin and orbital angular momentum when Laguerre-Gaussian beams are used.

Topology-transport correspondence in silicene under the modulation of electric and antiferromagnetic fields

The low-buckled material silicene undergoes abundant topological phase transitions under external fields. The applications in transport related to the topological properties remain the focus of attention. Utilizing the Berry curvature formula and Boltzmann transport equation, we investigate the spin- and valley-dependent anomalous Nernst effect in silicene, which is subjected to the antiferromagnetic field and perpendicular electric field. The results reveal that the antiferromagnetic field can be used to modulate the pure spin Nernst current; the pure valley Nernst current appears only when electric field exists; the charge Nernst current needs both fields. It is found that the inflection points on the Nernst conductivity correspond exactly to the phase transformation boundary. In the quantum spin Hall (QSH) phase, the spin beam splitting can be realized, in the quantum valley Hall (QVH) phase, the valley beam is split, and in the spin-polarized quantum anomalous Hall (SQAH) phase, the single spin and valley beam can be collected. These findings related to topology are expected to facilitate some applications in spin and valley caloritronics and thermal logical devices.

Analysis and optimization of the spin beam in the CCA-5000 Cuban sugarcane harvester

A linear dynamic study of the tensional status of the unloading conveyor´s spin beam in the new model CCA-5000 Cuban sugarcane harvester is carried out. The dynamic coefficients were determined using a strain gauge experimental evaluation of the KTP-23 harvester, which is a similar model in structure to the CCA-5000. A finite elements analysis is used to obtain the safety distribution factor and the tensions in the beam for different load combinations linked to a dynamic variation curve of the loads. Aiming to verify the presence or not of large amplitudes on the system oscillations caused by the resonance phenomenon, an analysis of the frequency modes for each load status is conducted, and the results are compared with the terrain irregularities frequencies on which the harvester moves. Finally, taking into account the previous results, the shape of the beam is optimized in order to decrease its steevolume.

Real-time sextupole tuning for a long in-plane polarization at storage rings

A long in-plane beam polarization can be a desired feature for spin measurement experiments in storage rings. The spin precession of the particles within a beam can be controlled by means of the frozen spin method and beam bunching via RF cavities, eventually yielding a polarization lifetime of 10–100 s. Previous studies have shown that it can be further improved by sextupoles, which correct the second order effects related to the chromaticity of the beam. However, sextupoles can require readjustment after slight changes in ring parameters. This work presents a real-time sextupole tuning method that relies on a feedback algorithm. It adjusts the sextupole strength during storage, targeting a zero average radial spin component. Satisfying this condition results in a longer polarization lifetime. Simulation studies show that roughly determined feedback coefficients in this method work effectively for a wide range of ring parameters, with practical field imperfections and measurement errors taken into account. Alternatively, this technique can be used to optimize sextupole strengths in a test run without intervening the measurement.