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By triggering the switches in sequence and controlling the brick charging voltage independently, a pulsed power system can generate flexible current waveform in the load, which could allow high-accurate magnetic pressure in experimental materials in the study of EOS data and dynamic response of material characterization. Currently, a 1.5-MA driver with 20 independent bricks has been developed, and a programmable 256-brick parallel discharge driver which is able to generate shaped current greater than 6.5 MA is under construction in the China Academy of Engineering Physics. In this paper, for these two multibrick parallel discharge drivers, the method of optimizing the output current waveform of the driver is studied by using the genetic algorithm and the corresponding optimization results of different target current waveforms are obtained. An experimental platform is set up for studying the gas switch breakdown characteristics. The self-breakdown and triggering breakdown experiments of the switch are conducted, and its breakdown characteristics are researched. Meanwhile, the effect of breakdown delay and jitter on the output current waveform is studied by simulation. This paper is of great significance to the actual operation of the multibrick parallel discharge drivers. [ABSTRACT FROM AUTHOR]

This paper at first proposes a method to calculate a trigger strategy before launching in order to control the muzzle velocity of railguns. Five triggering points are set equidistantly and six pulsed forming unit (PFU) groups are triggered in total. First, given a desired muzzle velocity, the expected uniformly accelerated rectilinear motion of the armature is calculated. Second, the module number of each PFU group is obtained according to the principle of minimizing the absolute relative error between the actual and the expected velocity at each triggering point. The results show that, when the desired muzzle velocity is within [1500, 2000] m/s, the absolute muzzle velocity relative error $\delta $ is less than 0.5%. In order to achieve a better control performance, the places of the five triggering points are then optimized by a genetic algorithm (GA). The objective function is the sum of absolute $\delta $ , when the desired muzzle velocities are 1500, 1600, $\ldots $ , 2000 m/s. After the optimization, $\delta $ is reduced to less than 0.05%. At last, based on this velocity control method, the railgun system is optimized to pursue the highest system efficiency $\eta $ by GA. The independent variables are the armature mass, the precharged voltage, and the places of the five triggering points. The constraints are that the desired muzzle velocity is 1800 m/s and the absolute $\delta $ is within 1%. The results show that $\eta $ increases from 6.57% to 25.37%. [ABSTRACT FROM AUTHOR]

The development of pulsed power supplies and switched-mode power supplies raises urgent need for medium-frequency high-power transformers. This paper proposes an optimal design method of medium-frequency Fe-based amorphous transformer based on multiobjective postdecision genetic algorithm. The optimization targets at transformer volume (expressed in terms of area product $A_{p}$) and its loss. Transformer operating frequency $f$ , operating magnetic flux density $B_{m}$ , and current density $J$ are taken as design variables, while temperature rise and efficiency are taken as constraints. This design method helps to solve the traditional transformer’s design problem of repetitive calculation. Moreover, it proposes to the designer a series of optimized transformers, rather than a single solution, so the designer can choose the best transformer according to the application needs. Finally, the simulation and experimental results are presented to validate the effectiveness and feasibility of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Energy efficiency is a critical quantity of interest in the performance of electromagnetic railgun (EMRG). To improve the energy efficiency of EMRG with the presence of uncertainty, a hybrid robust optimization method is proposed. EMRG simulation model is developed to simulate the behavior of exterior ballistics and the corresponding robust optimization issue is formulated. With the help of the impact factor analysis, several significant factors of energy efficiency are selected as the design variables while the insignificant ones are not taken into account. In the robust optimization, the polynomial chaos expansion approach coupled with Latin hypercube design is proposed to propagate the uncertainty for alleviating the computational burden of fitness function (energy efficiency) evaluation. Then, the genetic algorithm is employed to solve the EMRG energy efficiency optimization problem with the constraint of mean miss distance. The optimization results illustrate that the hybrid robust optimization method is an efficient approach to improve the energy efficiency, which can be applied in the practical application of EMRG projectile design. [ABSTRACT FROM AUTHOR]

In order to improve the performance of multipole Galatea traps, this paper proposes an optimized method for the design of coil parameters. Based on an accurate magnetic field model, key parameters describing the multipole Galatea magnetic trap configuration were analyzed to establish an optimization model using the axial electromagnetic force, weak magnetic field area, and average magnetic mirror ratio as the optimization goals with the coil current as the design variable. Applying the improved multiple population genetic algorithm (MPGA), which has a strong searching ability and a fast convergence speed, enables production of optimization results following selection of the appropriate weight coefficients. Results confirm that optimization design results from MPGA are consistent with the design goals for different weight coefficients. In addition, the performance of multipole Galatea magnetic traps with optimization coil parameters was improved. Finally, the results from finite-element simulation software proved the validity and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, based on the comparisons of the stator pole flux density and phase current with corresponding rotary switched reluctance machine, the original design scheme of a 1-kW single-side switched reluctance linear launcher (SRLL) is obtained by a traditional method. To get higher efficiency and smaller force ripple, the genetic algorithm, which is improved to enhance the convergence rate and global accuracy, is applied to optimize the original design scheme. The global optimum values of key dimensions and control parameters are obtained, and the detailed structure of whole SRLL is given as well. Then a detailed equivalent lumped-parameter thermal network (LPTN) model of the considered SRLL is built, and temperature rises of some parts are obtained. To test the feasibility of the LPTN model, a 2-D finite element thermal model of the SRLL is built, and the temperature rises are obtained. The results from LPTN model match those from the finite-element method very well. Finally, the preliminary tests of the prototype of designed SRLL are carried out and the experimental results are presented. [ABSTRACT FROM PUBLISHER]

Helical coil electromagnetic launchers (HEMLs) using motion-induced commutation strategy solve the problem of synchronization control perfectly. HEMLs have the advantages of symmetric structure, high load impedance, and high energy conversion efficiency. If the structural and launch parameters can be designed reasonably and multiobjective optimization of the velocity, efficiency, and power can be achieved, HEMLs can meet the requirements of multimission applications such as the highvelocity coilgun, electromagnetic mortar, and electromagnetic catapult. In this paper, an improved adaptive genetic algorithm (AGA) based on the solution-reservation strategy to solve the multiobjective optimization problem for HEMLs is presented. The circuit model of the HEML is established and the governing equations are derived. The circuit parameters such as projectile mass, resistance, inductance, and inductance gradient are calculated according to the structural parameters of coils. The classical Runge--Kutta method and the trapezoidal quadrature formula are used to solve the governing equations, besides deriving the velocity, efficiency, and power of the launcher. The AGA is developed in MATLAB. The range of the launch voltage U is 500-5000 V and the number of turns N in coils is 1-500. After the evolution of 14 generations, five noninferior solutions subject to the constraints of temperature rise, launch time, and length are obtained. These different HEML structures can satisfy many different launch applications [ABSTRACT FROM AUTHOR]

Under the condition of given charging voltage, by adjusting the timing of the power supply trigger, the electromagnetic emission can produce different discharge current waveforms, and then produce different initial velocity. This paper mainly uses the characteristics of the discharge current in a single power module in electromagnetic launch, by specifying the rising time and the maximum value of the total discharge current; a multipopulation genetic algorithm is used to obtain the optimal trigger timing, and the speed control of electromagnetic launch can be achieved. The specific implementation process of algorithm are as follows: the rising time and the peak value of the expected current are set as the objective function, the timing is set as a variable, and the multiple time series are binary coded to get multiple individuals, and then calculate the degree of survival by crossover, mutation, and heredity among individuals, that is, to judge whether the rising time and the maximum value of the discharge current can reach the expected goal, and to keep the survival of the genes to the next generation and screen repeatedly, and then to select the optimal control timing. The optimal control strategy can be obtained by adjusting the parameters such as genetic algebra and mutation rate. The experimental results show that this method produces the optimal power supply timing, and through the application of digital signal processing control system, the expected discharge current waveform can be obtained in the experiment of electromagnetic launch, which also lay a good foundation for the rate control of electromagnetic launch. [ABSTRACT FROM PUBLISHER]

Armature is very important for a synchronous induction coil launcher which can transform the electric energy to kinetic energy and push the load forward. The structure of the armature will influence the kinetic energy conversion efficiency directly. This paper analyzes the armature structure of a capacitor-driven synchronous induction coil launcher. Length and thickness of the armature are analyzed that how these parameters influence the maximum velocity and system efficiency of the launcher. Current filaments model is used to calculate the motion characteristics of a tubular linear induction motors, which is verified by an experiment and finite-element code. Genetic algorithm optimizer is used to calculate the best trigger times of the coils and the maximum velocity under the conditions of different length and thickness of the armature. It is shown that when the armature mass is fixed, length and thickness of the armature will greatly increase the velocity of the armature. The best length of the armature should be almost 2–2.5 times the length of the coil. The best thickness of the armature could be estimated by skin depth. [ABSTRACT FROM PUBLISHER]

The structure and trigger control strategy have become the most important factors that restrict the performance of the multistage synchronous induction coilgun (MSSICG). However, it is still a difficult task to design MSSICG under overload constraint due to coupling between the multiple parameters. In this paper, the maximization of the emission efficiency and acceleration stationarity is treated as a multiobjective optimization problem. By analyzing the relationship between the number of turns and the other structural parameters of the launch, the multiobjective optimization model of MSSICG is established by the current filament method which was verified by the experimental data and finite-element method. And then the second generation nondominated sorting genetic algorithm (NSGA-II) and multiobjective particle swarm optimization (MOPSO) were employed to optimize the model in order to maximize the energy transfer efficiency while achieving the smooth acceleration of the armature. With the formulated optimization model, a five-stage synchronous induction coilgun is optimized as a special case. A decision-making procedure based on the fuzzy membership function is used for obtaining best compromise solution from the set of Pareto-solutions obtained through NSGA-II and MOPSO. In addition, the optimization performance of the proposed multiobjective optimization model and the single-objective optimization model of the MSSICG was compared. The result of optimization shows that the proposed multiobjective optimization model of MSSICG can effectively improve the performance of the coilgun compared with the single-objective optimization model which takes of the launch velocity and overload acceleration as the combination objective function or only the launch velocity. [ABSTRACT FROM PUBLISHER]

Pulsed-power systems traditionally have been designed to provide a pulse that is nonprogrammable or requires hardware modifications to adjust the output waveform shape. Advancements in pulsed-power technologies are enabling system designs that allow for greater flexibility such as programmable current shaping. Material science, which uses current pulse shaping to obtain data for the equation of state analysis, is driving much of this work. The programming of pulsed-power systems through the use of simulations and manual curve fitting techniques can work well for systems that only have a few controllable parameters and are generating waveforms with simple spectral content. Complex systems with many controllable parameters become unmanageable for manual trial and error to be effective. This paper discusses the characterization and modeling of a scaled down programmable current adder directed at investigating technical issues that will be encountered in full-scale drivers. A discussion of the procedure used to optimize the adder current output, using genetic algorithms, is presented. The approach to system programmability presented in this paper will allow for a more simplified user interface and system control, as the requirements for flexibility and complexity in future systems increase. [ABSTRACT FROM AUTHOR]

This article introduces an optimal design method for a multistage induction coil launcher. Considering the magnetic coupling and the effect of the armature’s resistance, the basic criteria to select the structure of the driving coil and armature are proposed, and the genetic algorithm is introduced to optimize the pending parameters. Based on the principle that the current in the driving coil matches the movement state of the armature, the design method of optimal capacitor parameters is deduced. The results show that the design error is less than 1%. For a multistage induction coil launcher, the optimization is carried out stage by stage. The effect of the stage spacing between driving coils is analyzed, and it is found that changing the direction of the current in driving coils helps to improve the system efficiency. Finally, based on the above optimal design method, a multistage induction coil launcher is designed, and the energy conversion efficiency of the system is close to 40%. [ABSTRACT FROM AUTHOR]

A coilgun is an electromagnetic launcher based on electromagnetic induction. The projectile with a heavy load can be accelerated to a high speed. The currents that flow through the driving coils and the projectile would produce joule losses. All of the properties are drastically determined by the geometry and power of a coilgun. This paper aims to optimize the geometry and power parameters of the coilgun. The muzzle velocity is selected to be the objective when the temperature rise limitations are taken into consideration. To analyze the performance, an equivalent circuit model including the calculation of temperature rises is employed. The performance of a three-stage coilgun is calculated based on this model and then this coilgun is optimized with the utility of adaptive genetic algorithm taking the influence of temperature rise into consideration. The result of optimization shows that the muzzle velocity is improved and the temperature rises are conformed to the design requirements. The optimized coilgun is simulated by the finite-element method to verify the performance. [ABSTRACT FROM PUBLISHER]

In this paper, we discuss a theoretical optimal design of a nonlinear transmission line using a genetic algorithm (GA) to achieve peak pulse power. The technique is based on an integrated optimization approach that uses a GA coded in Matlab and the circuit simulation program LTspice. A bidirectional interface is created that allowed information to be rapidly transferred between the circuit simulator and GA with real-time monitoring of the entire design process, including peak power and elemental values. The designed process shows a peak voltage enhancement of 318% while eliminating the tedious trial and error process usually required. It is important to note that this result is achieved using only six L-C segments and a much greater voltage increase is likely as the number of segments is increased. [ABSTRACT FROM PUBLISHER]

Enabling technologies are being developed at Sandia National Laboratories to improve the performance and flexibility of compact pulsed-power drivers for magnetically driven dynamic materials properties research. We have designed a modular system that is capable of precision current pulse shaping through the selective triggering of pulse-forming components into a disk transmission line feeding a strip line load. The system is composed of 240 200-kV 60-kA modules in a low-inductance configuration that is capable of producing 250–350 kbar of magnetic pressure in a 1.75-nH 20-mm-wide strip line load. The system, called Genesis , measures approximately 5 m in diameter and is capable of producing shaped currents that are greater than 5 MA. This performance is enabled through the use of a serviceable solid-dielectric insulator system which minimizes the system inductance and reduces the stored energy and operating voltage requirements. Genesis can be programmed by the user to generate precision pulse shapes with rise times of 220–500 ns, allowing characterization of a range of materials from tungsten to polypropylene. This paper provides an overview of the Genesis design, including the use of genetic optimization to shape currents through selective module triggering. [ABSTRACT FROM PUBLISHER]

A three-stage depressed collector was previously designed and simulated to recover the kinetic energy of the spent electron beam in an X-band Gyrotron backward wave oscillator (Gyro-BWO) by using the 3-D particle-in-cell code MAGIC. The geometry of the depressed collector was optimized using a genetic algorithm to achieve the optimum overall recovery efficiency for specific parameters of the spent beam. In this paper, secondary electron emissions were simulated, and a few emission models were compared to investigate the effects of the secondary electrons on the overall recovery efficiency and the backstreaming of the electrons from the collector region. The optimization of the shape and dimensions of each stage of the collector using a genetic algorithm achieved an overall recovery efficiency of more than 80% over the entire operating regime of the Gyro-BWO, with a minimized backstreaming of 1.4%. The heat distribution on the collector was calculated, and the maximum heat density on the electrodes was approximately 195 W/cm², hence avoiding the generation of "hot spots." [ABSTRACT FROM AUTHOR]

Capacitor banks are used to provide a high pulsed power in traditional electromagnetic launch systems, but the large volume of these capacitors greatly limits the movability of the system; meanwhile, more and more applications require a system with significantly higher energy storage density. Rotation machines that can quickly convert rotational kinetic energy into high-current electrical energy have been designed and simulated. These generators are referred to as pulsed alternators. The shape of the high current pulse can be controlled by the triggering time of rectifiers. The direct-quadrature, or Park’s, transformation is used to model a generator for simulation. The pulsed alternator consists of four stator phases, a compensated device, and field winding on the rotor all coupled together electromagnetically, and the theory is based on the standard three-phase Park’s transformation and extends to six-phase systems to make analysis of the four-phase air-core alternator that has a compensation device. After modeling the compensator, we obtain the transformed stator-voltage equations and the flux-linkage current relationship. A method is presented in which the pulsed alternator can be accurately modeled and used to numerically analyze the basic principle of a passive compensator. Finally, we optimize the current using the genetic algorithm. It is shown that this method can simplify the calculation, accurately predict the performance of the system, and provide guidance on the design of the prototype. [ABSTRACT FROM PUBLISHER]

This article presents the complete design of a hybrid metal-plasma transmit-array antenna with beam-scanning capabilities. The antenna operates at 1.07 GHz and consists of an active metallic dipole, a metallic ground plane (GP), and a set of cylindrical plasma discharges arranged in a 2-D lattice. The main lobe of the antenna can be tilted toward different directions simply by turning on/off specific subsets of plasma discharges. Toward this aim, a two-step optimization strategy based on the combination of a particle swarm optimization (PSO) and of a genetic algorithm (GA) is adopted. A realistic model of the antenna has been simulated in CST Microwave Studio. To derive plasma parameters, a prototype plasma discharge has been realized and tested. Each plasma bar included in the numerical setup comprises not only the plasma material, but also the glass envelope and the metallic electrodes used to confine and generate the plasma, respectively. An analysis has been carried out to evaluate the effects of adding the electrically long metallic cables to each discharge needed to ignite and sustain the plasma. The radiation properties of the array can be maintained thanks to the insertion of inductances between the electrodes and the cables. Finally, a sensitivity analysis has been conducted to identify intervals of plasma density and neutral gas pressure within which the beam-scanning capabilities of the antenna remain unaffected. [ABSTRACT FROM AUTHOR]

The frequency-tunability for a Smith°Purcell free- electron laser oscillator in the millimeter wave region is enhanced with the aid of a quasi-periodic distributed Bragg reflector (DBR) made of metallic waveguide gratings with rectangular grooves. For a quasi-periodic DBR, the grating parameters are adjusted by means of genetic algorithms to get the desired reflection coefficient, thus compensating for the frequency dependence of the overall output characteristics. For a typical numerical example, flat output characteristics have been obtained over 10% bandwidth around the center frequency 121 GHz. [ABSTRACT FROM AUTHOR]

A lumped parameter model of capacitor-based railgun (CBRG) with arbitrary number of pulse-forming units is created and design of its simulation code is introduced. To show simulation and optimization capabilities of the code, two applications of the code are given. In the first example, a CBRG with topologically created pulse-forming network is simulated and the results are analyzed to show the availability of the code. In the second example, genetic algorithm-based and iteration-based methods on optimizing timing sequence of pulsed-power supply system are introduced and compared, and influence of timing sequence on launching performance is discussed. Finally, it is concluded that the iteration-based method has preferable effects on calculating timing sequence under the constriction of flat-topped rail current. [ABSTRACT FROM PUBLISHER]

To realize the full potential of a gyrotron backward- wave oscillator (gyro-BWO), an energy recovery system was designed using Particle-In-Cell (PlC) simulations and optimized using both a genetic algorithm and PlC simulations. Simulations were carried out to optimize a periodic structure for separation of the spent electron beam and the output radiation produced by a gyro-BWO in the 8.0-9.5 GHz frequency range. The spent electron beam can be collected using a multistage depressed collector. The number and electric potentials of the electrodes were optimized to achieve the best overall recovery efficiency for specific parameters of the spent beam. The 3-D PlC code MAGIC was used to simulate the electrons' trajectories and a genetic algorithm was used to refine the electrode shapes for optimum efficiency. [ABSTRACT FROM AUTHOR]