An ultra-wideband coding polarizer for beam control and RCS reduction

Pancharatnam–Berry(PB)phase metasurface,as a special class of gradient metasurfaces,has been paid much attention owing to the robust performance for phase control of circularly polarized waves.Herein,we present an element-based polarizer for the first step,which enables the incident electromagnetic waves into the cross-polarized waves with the relative bandwidth of 71%,and the polarization conversion ratio exceeds 90%at 6.9–14.5 GHz.Then an eight-elements coding polarizer based on the PB phase is presented for the applications on beam control and radar cross section reduction.The simulated values indicate that the reduction of radar cross section is more than 10 dB at 6–16 GHz.Our work reveals the availability of manipulating the waves,beamforming in communication systems and electromagnetic stealth,and so on.

Coherent beam combination of adaptive fiber laser array with tilt-tip and phase-locking control

We present an experimental study on tilt-tip（TT） and phase-locking（PL） control in a coherent beam combination（CBC） system of adaptive fiber laser array.The TT control is performed using the adaptive fiber-optics collimator（AFOC）,and the PL control is realized by the phase modulator（PM）.Cascaded and simultaneous controls of TT and PL using stochastic parallel gradient descent（SPGD） algorithm are investigated in this paper.Two-fiber-laser-,four-fiber-laser-,and six-fiber-laser-arrays are employed to study the TT and PL control.In the cascaded control system,only one high-speed CMOS camera is used to collect beam data and a computer is used as the controller.In a simultaneous control system one high-speed CMOS camera and one photonic detector（PD） are employed,and a computer and a control circuit based on field programmable gate array（FPGA） are used as the controllers.Experimental results reveal that both cascaded and simultaneous controls of TT using AFOC and PL using PM in fiber laser array are feasible and effective.Cascaded control is more effective in static control situation and simultaneous control can be applied to the dynamic control system directly.The control signals of simultaneous PL and TT disturb each other obviously and TT and PL control may compete with each other,so the control effect is limited.

Data Processing Middleware in a High-Powered Neutral Beam Injection Control System

A set of data-processing middleware for a high-powered neutral beam injection（NBI） control system is presented in this paper.The middleware,based on TCP/IP and multi-threading technologies,focuses mainly on data processing and transmission.It separates the data processing and compression from data acquisition and storage.It provides universal transmitting interfaces for different software circumstances,such as WinCC,LabView and other measurement systems. The experimental data acquired on Windows,QNX and Linux platforms are processed by the middleware and sent to the monitoring applications.There are three middleware deployment models：serial processing,parallel processing and alternate serial processing.By using these models,the middleware solves real-time data-processing problems on heterogeneous environmental acquisition hardware with different operating systems and data applications.

Focusing Properties of Partially Coherent Controllable Dark-Hollow Beams through a Thin Lens

Analytical propagation formulas are derived for partially coherent controllable dark-hollow beams （CDHBs） through a thin lens based on the generalized Huygens-Fresnel integral. The expressions of the position for maximum irradiance on-axis and the relative focal shift are evaluated by the analytical propagation formulas. Our numerical results show that both the relative focal shift and the effective beam width of focused partially coherent CDHBs are mainly determined by the initial transverse coherence width 6g and the Fresnel number Nw, which are also affected by the changes of both the dark-size adjusting parameter p and the order N of CDHBs.

Synchronization and Control of Halo-Chaos in Beam Transport Network with Small World Topology

同步条件二种小世界(SW ) 网络一再学习。小世界拓扑学罐头大部分在横梁运输网络( BTN )的动态行为上影响，如果 BTN 与 SW 拓扑学被构造，全球线性联合和特殊线性反馈能也认识到横梁光圈混乱的同步控制 asper 在有 SW 拓扑学的 BTN 的碘的状态分别地。这重要结果能提供一个有效方法因为试验性的学习和在驱使放射性的 high-currentaccelerator 的 BTN 的设计设计清洗原子力量系统，并且可以为光圈混乱在未来的应用有潜在的使用安全通讯。

Development of Distributed Control System for Neutral Beam Injector on EAST

A distributed control system of Neutral Beam Injector （NBI） on the Experimental Advanced Superconducting Tokamak （EAST-NBI） is briefly presented in this paper. The control system is developed in accordance with the experimental operational characteristics of the EAST- NBI. The NBI control system （NBICS）, which is based on the computer network technologies and classified according to the control levels, consists of three levels： a remote monitoring layer, a server control layer, and a field control layer. The 3-layer architecture is capable of extending the system functions and upgrading devices. The timing system provides the reference clock of the synchronization and interlock for the EAST-NBI system. An interlock system ensures the safety of the experiment operators and field devices. Both of the ion sources of the beamline are designed to operate independently. This lays an important foundation for developing a control system for the second beamline on EAST. Experimental results demonstrate that the NBICS meets functional requirements of the EAST-NBI control, and makes experimental operations visual and automatic.

ADAPTIVE CONTROL OF FLEXIBLE BEAM WITH UNKNOWN DEAD-ZONE IN THE DRIVING MOTOR

Adaptive control of a flexible beam system preceded by an unknown dead-zonein the driving motor is investigated in state space form. By introducing an important lemma forsimplifying error equation between the flexible beam model and the matching reference model, arobust adaptive control scheme is developed by involving the dead-zone inverse terms. The newadaptive control law ensures global stability of the entire system and achieves desired trackingprecision even when the slopes of the dead-zone are not equal. Simulations performed on a typicalflexible beam system illustrate and clarify the validity of this approach.

ACTIVE VIBRATION CONTROL OF TWO-BEAM STRUCTURES

The wave propagation approach is presented to research the active vibration control of two-beam structures.Considering the continuity of the generalized displacement and the equilibrium of the generalized force at the discontinuity,the wave reflection and transmission coefficients are calculated.Wave control is applied somewhere upstream or downstream to two-beam structures.Vibrations of two coupled beams per unit disturbance are investigated.The results show that wave control is efficient,and the influence of the thickness ratio of two-beam structures on control location is discussed.

Control on Electron Beam Scanning Track

In order to use electron beam as a movable welding heat source and whose energy distribution along its moving trace can be controlled, a method of electron beam scanning track and scanning mode control was put forward. Based on it, the electron beam scanning track and scanning mode can be edited at will according to actual requirements, and the energy input of each point of the scanning track can be controlled. In addition, the scanning frequency and points control, real time adjusting of the scanning track etc. were explained. This method can be used in electron beam brazing, surface modification, surface heat treatment etc.

Ｎonlinear Control of Beam Halo—Chaos in Accelerator—Driven Clean Nuclear Power System

Beam halo-chaos in high-current accelerators has become a key concerned issue because it can cause excessive radioactivity from the accelerators therefore significantly limits their applications in industry,medicine,and national defense.Some general engineering methods for chaos control have been developed in recent years,but they generally are unsuccessful for beam halo-chaos suppression due to many technical constraints.Beam halo-chaos is essentially a spatiotemporal chaotic motion within a high power proton accelerator.In this paper,some efficient nonlinear control methods,including wavelet function feedback control as a special nonlinear control method,are proposed for controlling beam halo-chaos under five kinds of the initial proton beam distributions (i.e.,Kapchinsky-Vladimirsky,full Gauss,3-sigma Gauss,water-bag,and parabola distributions) respectively.Particles-in-cell simulations show that after control of beam halo-chaos,the beam halo strength factor is reduced to zero,and other statistical physical quantities of beam halo-chaos are doubly reduced.The methods we developed is very effective for suppression of proton beam halo-chaos in a periodic focusing channel of accelerator.Some potential application of the beam halo-chaos control in experiments is finally pointed out.

Effect of ion-beam assisted deposition on the film stresses of TiO_2 and SiO_2 and stress control

Based on Hartmann-Shack sensor technique, an online thin film stress measuring system was introduced to measure the film stresses of TiO2 and SiO2, and comparison was made between the film stresses prepared respectively by the conventional process and the ion-beam assisted deposition. The effect of ion-beam assisted deposition on the film stresses of TiO2 and SiO2 was investigated in details, and the stress control methodologies using on-line adjustment and film doping were put forward. The results show that the film stress value of TiO2 prepared by ion-beam assisted deposition is 40 MPa lower than that prepared by conventional process, and the stress of TiO2 film changes gradually from tensile stress into compressive stress with increasing ion energy; while the film stress of SiO2 is a tensile stress under ion-beam assisted deposition because of the ion-beam sputtering effect, and the film refractive index decreases with increasing ion energy. A dynamic film stress control can be achieved through in-situ adjustment of the processing parameters based on the online film stress measuring technique, and the intrinsic stress of film can be effectively changed through film doping.

STABILIZATION OF VIBRATING BEAM BY VELOCITY FEEDBACK CONTROL

A flexible structure consisting of a Euler-Bernoulli beam with co-located sensors and actuators is considered. The control is a shear force in proportion to velocity. It is known that uniform exponential stability can be achieved with velocity feedback. A sensitivity asymptotic analysis of the system's eigenvalues and eigenfunctions is set up. The authors prove that, for K-1 epsilon (0, + infinity), all of the generalized eigenvectors of A form a Riesz basis of H. It is also proved that the optimal exponential decay rate can be obtained from the spectrum of the system for 0 < K-1 < + infinity.

Optimal Matching Control of a Low Energy Charged Particle Beam in Particle Accelerators

Particle accelerators are devices used for research in scientific problems such as high energy and nuclear physics.In a particle accelerator, the shape of particle beam envelope is changed dynamically along the forward direction. Thus, this reference direction can be considered as an auxiliary "time" beam axis. In this paper, the optimal beam matching control problem for a low energy transport system in a charged particle accelerator is considered. The beam matching procedure is formulated as a finite "time" dynamic optimization problem, in which the Kapchinsky-Vladimirsky(K-V) coupled envelope equations model beam dynamics. The aim is to drive any arbitrary initial beam state to a prescribed target state, as well as to track reference trajectory as closely as possible, through the control of the lens focusing strengths in the beam matching channel. We first apply the control parameterization method to optimize lens focusing strengths, and then combine this with the time-scaling transformation technique to further optimize the drift and lens length in the beam matching channel. The exact gradients of the cost function with respect to the decision parameters are computed explicitly through the state sensitivity-based analysis method. Finally, numerical simulations are illustrated to verify the effectiveness of the proposed approach.

Inverse Optimal Control of Evolution Systems and Its Application to Extensible and Shearable Slender Beams

An optimal(practical) stabilization problem is formulated in an inverse approach and solved for nonlinear evolution systems in Hilbert spaces. The optimal control design ensures global well-posedness and global practical K∞-exponential stability of the closed-loop system, minimizes a cost functional,which appropriately penalizes both state and control in the sense that it is positive definite(and radially unbounded) in the state and control, without having to solve a Hamilton-Jacobi-Belman equation(HJBE). The Lyapunov functional used in the control design explicitly solves a family of HJBEs. The results are applied to design inverse optimal boundary stabilization control laws for extensible and shearable slender beams governed by fully nonlinear partial differential equations.

Controlling beam halo-chaos via backstepping design

A backstepping control method is proposed for controlling beam halo-chaos in the periodic focusing channels （PFCs） of high-current ion accelerator. The analysis and numerical results show that the method, via adjusting an exterior magnetic field, is effective to control beam halo chaos with five types of initial distribution ion beams, all statistical quantities of the beam halo-chaos are largely reduced, and the uniformity of ion beam is improved. This control method has an important value of application, for the exterior magnetic field can be easily adjusted in the periodical magnetic focusing channels in experiment.

Vibration analysis and active control of nearly periodic two-span beams with piezoelectric actuator/sensor pairs

The piezoelectric materials are used to investigate the active vibration control of ordered/disordered periodic two-span beams. The equation of motion of each sub-beam with piezoelectric patches is established based on Hamilton＇s principle with an assumed mode method. The velocity feedback control algorithm is used to design the controller. The free and forced vibration behaviors of the two-span beams with the piezoelectric actuators and sensors are analyzed. The vibration properties of the disordered two-span beams caused by misplacing the middle support are also researched. In addition, the effects of the length disorder degree on the vibration performances of the disordered beams are investigated. From the numerical results, it can be concluded that the disorder in the length of the periodic two-span beams will cause vibration localizations of the free and forced vibrations of the structure, and the vibration localization phenomenon will be more and more obvious when the length difference between the two sub-beams increases. Moreover, when the velocity feedback control is used, both the forced and the free vibrations will be suppressed. Meanwhile, the vibration behaviors of the two-span beam are tuned.

Logical and Timing Control for Diagnostic Neutral Beam Injection on HT-7

The timing and master control logic （MCL） units are the most important function units of the diagnostic neutral beam （DNB） power supply control system. The units control the operation of nine power supply subsystems of the DNB system, and provide protection for the DNB system from faults such as beam source arc down. Based on the characteristics of the DNB power supply system, the timing and MCL units have been designed, fabricated and tested. Experiments prove that the timing unit is convenient, flexible and reliable, and the MCL is functional.

Designing of an Automatic Paraffin Controlling Device for a Beam Well

Aiming at the paraffin-deposition problem of a beam well, the automatic paraffin-controlling device is designed by making use of ratchet-pallet mechanism, cam mechanism and modern designing method. The device has four main functions： paraffin-controlling, paraffin removal, centralizing the pumping rod, and improving the safety of well tubing. This device integrates the advantages of the paraffin control, such as strong magnetic paraffin controlling and mechanical paraffin-cutting. Theoretical analysis shows that this device has fine working reliability. It turns out to be a new device which can solve the paraffin-deposition problem of a beam well economically and efficiently.

Control System of Neutral Beam Injection on HT-7

Neutral Beam Injection control system (NBICS) is constructed to measure the plasma current, Magnet current, vacuum pressure, cryopump temperature, control water cooling, filament voltage, and power supply, etc. The NBICS, consisting mainly of a Programmable Logic Controller (PLC) subsystem, data acquisition and processing subsystem and cryopump and vacuum pressure monitoring subsystem, has successfully been used on a NBI device. In this article, the design of NBICS on HT-7 is discussed and each subsystem is described in particular. In addition, some experimental results are reported which are very important data for further research related to the HT-7 tokamak.

An Overview of the Control System for Dose Delivery at the UCSF Dedicated Ocular Proton Beam

Since 1978, the University of California San Francisco (UCSF) Ocular Tumor Program has been using particle therapy for treating ocular patients with malignant as well as benign eye disease. Helium ion beams were used initially and were produced by two synchrotron-based systems: first by the 184-inch synchro-cyclotron and later by the Bevalac, at the Lawrence Berkeley National Laboratory (LBNL). Since 1994, protons, produced by a cyclotron-based system at the Crocker Nuclear Laboratory (CNL) Eye Treatment Facility (ETF), have been used for this purpose. The CNL cyclotron produces a 67.5 MeV beam, allowing for a uniquely homogeneous beam for eye treatment, without degradation of the beam or manipulation of the beam line. This paper describes, in detail, the control system for beam delivery, as implemented for measuring and delivering the radiation to ocular tumors at CNL. The control system allows for optimal delivery and rapid termination of the irradiation after the desired dose is achieved. In addition, several safeguard systems are discussed, as these are essential for such a system in the event of failure of software, electronics, or other hardware. The QA analysis shows that the total range of the proton beam is 30.7 ± 1.0 mm in water at iso-center. The beam distal penumbra (80% - 20%) is 1.1 mm for a range-modulated beam at a collimator to iso-center distance of 50 mm. Daily QA checks confirm that the range and modulation is within 0.1 mm. The beam flatness and symmetry in a 25 mm diameter beam are ±1% - 2%. Variation in the daily dosimetry system, as compared to standard dosimetry, is within ±3.5%, with a mean variation of 0.72(±1.9)% and 0.85(±2.3)% for segmented transmission ionization chambers IC1 (upstream) and IC2 (downstream), respectively. From May 1994 to the end of 2015, UCSF has treated 1838 proton ocular patients at the Davis ETF. During this period, no treatments were missed due to any cyclotron or control system failures. The overall performance, maintenance, and quality assurance of the cyclotron and the ocular control system have been excellent.