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Iron nanopowders (Fe-NPs) were extracted and downsized by evaporating the iron powders in an atmospheric microwave plasma flame. The microwave plasma, which was generated by a mixture of nitrogen and argon swirl gases, evaporated the iron powders, immediately downsizing them to Fe-NPs. Subsequently, the Fe-NPs samples were collected by using bar magnets inside the collecting chamber. The Fe-NPs were analyzed by X-ray diffraction, Raman spectroscopy, optical emission spectroscopy, and a scanning electron microscopy. The Fe-NPs consisted of only iron phase and no Fe2O3 or Fe3O4 phases were formed during synthesis. The average sizes of the raw iron powders and the Fe-NPs were approximately $20~\mu \text{m}$ and 20 nm, respectively. The proposed method is simple and easily scalable. Thus, it is suitable for the mass production of Fe-NPs, overcoming the limitations of other catalyst-based synthesis methods. This paper provides a potential method for large-scale production of metal nanopowders which have potential applications in various fields owing to their unique properties at the nanoscale. [ABSTRACT FROM AUTHOR]

Tubular-switched reluctance linear launcher (TSRLL) with novel structure is proposed in this paper. The structure of switched reluctance motor is simplified, and the unbalanced force of common types of switched reluctance linear launcher is alleviated in TSRLL. The structure of the single-phase TSRLL with transverse flux is introduced thoroughly. The 3-D finite-element (FE) model of the proposed TSRLL is constructed, and electromagnetic analysis is performed by the FE method (FEM). To improve the electromagnetic force of the proposed launcher, the sensitivity analysis is conducted by means of 3-D FEM. The stator yoke thickness, mover cylinder’s thickness, stator pole arc, and pole width ratio of TSRLL are optimized, and the results of the sensitivity analyses are presented. TSRLL with two different polarity distribution patterns is compared via static FE analysis. The dynamic simulation of TSRLL with optimal specification and polarity distribution is carried out and demonstrated, of which the results agree well with the static analysis by FEM. [ABSTRACT FROM AUTHOR]

This paper proposes some practical methodology and design aids for the linear motion servocontrol systems such as the electromagnetic launchers. Mason’s gain formula was first used in the state space to solve for the transfer function of the complex and multiloop system rapidly and conveniently. The classical feedback control referring to the separation principle, involving a tracking controller and an observer-based compensator, may work well but has limited bandwidth under the constraint of the nominal inertia, and this fact is demonstrated rigorously in this paper and improved by a novel compensation scheme. According to the time-domain performance and Nyquist view, a delicate parameter design of control parameters is made for the tracking controller and the robust observer. The algorithm is verified by use of a rapid control prototype real-time simulation platform. The comparison of the experimental results shows that the proposed control scheme has good properties of trajectory tracking, antidisturbance, and noise suppression. [ABSTRACT FROM AUTHOR]

This paper gives a way to analyze the flux characteristic of a single-phase tubular permanent magnet linear motor (TPMLM) based on the 3-D magnetic equivalent circuit (MEC) method. By studying the flux tubes of this single-phase TPMLM with the finite-element analysis software—FLUX, a 3-D MEC model of this motor can be constructed, and the flux linkage of the single-phase TPMLM can also be calculated. The static and dynamic performances of the single-phase TPMLM calculated with the 3-D MEC model are compared with the 3-D finite-element model and experimental results, which verify the correctness of the proposed 3-D MEC model. [ABSTRACT FROM AUTHOR]

We present a focused review of selected design solutions for the permanent magnet-based magnetic circuitry of Hall-type thrusters, with the emphasis on their relevance to miniaturized devices potentially suitable for application in CubeSats and other types of small satellites. Coaxial, cylindrical, and cusped designs of Hall-type thrusters are considered. The issues related to the influence of magnetic configurations on channel wear are also addressed. This paper also outlines a state of the art in the high-temperature permanent magnets and offers some perspective views onto the further development of miniaturized Hall-type thrusters. Several nontrivial design solutions are considered, and schematics of the potentially promising ones for the reduction of wear and damage were examined. Overall, this paper demonstrates the usability and several significant advantages of Hall thrusters with permanent magnetic system. [ABSTRACT FROM AUTHOR]

A novel augmented railgun using multilayer magnets and sabots is proposed in this paper, in which the rails have dc constant currents. Using dc constant currents for the rails generates the constant acceleration for the projectile. The augmentation with multilayer permanent magnets increases the length of passing current, which improves the railgun efficiency. Furthermore, the proposed railgun does not require the high power supplies because each sabot carries only low current. In addition, the iron structure has been located at the top and bottom of the whole structure to produce a homogeneous magnetic field. Accurate analytical expressions have been derived for the Lorentz force and the velocity of the proposed structure in this paper. The railgun structure has been simulated in Maxwell software for various rail currents, and the analytical results have good agreement with simulation results. The amplitude of the Lorentz force in the z-direction has been calculated for various sabot materials to investigate the effect of the sabot materials on the performance of the railgun. Our results indicate that the velocity of the projectile can achieve to 300 m/s for the projectile mass of 2 kg in our proposed railgun. This makes the railgun a good candidate for the heavy projectiles in the launcher technology. [ABSTRACT FROM AUTHOR]

In previous studies, the field winding of the brushless pulsed alternator (BPA) is embedded in the stator slots, which is supplied by dc power or variable frequency power. The advantage is that the field current can be independently adjusted. It means that the BPA system needs a standalone excitation system, which will increase the volume and cost of the system. If we substitute electric excitation for permanent magnet excitation, not only the volume and cost of the BPA system can be decreased but the efficiency and flexibility can be enhanced. In this paper, the design schemes for electric excitation and permanent magnet excitation BPA are presented. For comparison, the stator and rotor dimensions of the two kinds of BPA are both the same. The characteristics of electric excitation and permanent magnet excitation BPA are analyzed by the finite-element method and field-circuit coupling method. Finally, the BPA systems with a resistive load are established, the performances of both the two excitation modes are compared. According to the simulation results, we conclude their advantages and disadvantages. [ABSTRACT FROM AUTHOR]

In this paper, the stability analysis of a new permanent magnets (PMs) bearings is presented and discussed. The suspension is assured by the repulsive force of properly shaped PMs placed on both the stator and the rotor. Then, exploiting currents induced on a system of null-flux coils attached to the stator, a stabilizing force for the translation of the center of mass of the rotor is obtained. The performance of the proposed bearing is investigated by a research code, previously developed at DESTEC and capable to simulate six degrees of freedom electromechanical devices. [ABSTRACT FROM PUBLISHER]

In this paper, a tubular permanent magnet linear launcher (TPMLL) is proposed. Its basic structure is introduced, and initial dimensions are given. Devoted to improve the performance of TPMLL, an optimization method combined weight determination algorithm based on fuzzy optimization iteration is presented. Based on this, average electromagnetic thrust, electromagnetic force smoothing coefficient, and electromagnetic force copper loss ratio are selected as optimization objectives. The finite-element (FE) models are set up for the sensitivity analysis. The sensitivity analyses of key structural parameters are executed for these three optimization objectives. The final optimization results are obtained by calculation, and the performance of optimized launcher is compared with the initial one. It can be concluded that the proposed algorithm greatly improves the performance of TPMLL. [ABSTRACT FROM AUTHOR]

In order to meet the need of miniaturization and long-term magnetic field stability of a permanent magnet system for the $S$ -band 2.6-MW magnetrons, we propose to replace AlNiCo magnets with samarium cobalt ones as to reduce the volume and to improve the long-term stability of the magnetic system. The simulation design and parameter optimization of the samarium cobalt (Sm2/Co17) permanent magnet system including magnetic pole pieces were carried out, and then the magnetic system was fabricated and tested. The simulation results of radial, angular, and axial magnetic field distributions in the interaction space are found to be in good agreement with those of the test. Both the simulation and testing show that the samarium cobalt magnetic system is able to realize uniform radial, angular, and axial magnetic field distributions to meet the requirements of the magnetron. This paper demonstrates that it is feasible to replace the AlNiCo magnetic system with the samarium cobalt ones to achieve miniaturization and long-term magnetic stability of the magnetic system for the 2.6-MW magnetron. The volume and weight of the magnetic system are reduced by 79% and 64%, respectively, and it has been applied in linear accelerators system. [ABSTRACT FROM AUTHOR]

Linear permanent magnet (PM) brushless dc motor (LPMBDCM) is used for electromagnetic catapult, which may offer significant advantages, in terms of efficiency, high speed and accelerations of heavy payloads, capability of high forces, and so on. In this paper, an LPMBDCM, which is constructed of transverse flux stator and PM mover, is investigated. First, the launch specifications and technical features under the condition of pulse power input are presented. Then, the magnetic circuit parameters including the calculation of the mutual and leakage inductance are derived, and the rated work performances are analyzed. The rated input voltage, current, thrust, and power efficiency are 4000 V, 18041 A, 1.389 MN, and 0.97, respectively, which can meet the requirements of electromagnetic catapult. The availability and reliability are validated as the temperature rise per launch is lower than 1 °C, and the demagnetization of the PM would not happen with high pulse current. Finally, to validate the characteristic of the basic design, the system simulation model including the power supply and power conditioning is built using of Simulink, and the launch trajectory is simulated by the model, which shows the launch can achieve a speed of 99.47 m/s along the distance of 99.47 m within 1.51 s. A small-scale prototype machine is fabricated and the validity of the proposed method has been verified by the experimental results. [ABSTRACT FROM PUBLISHER]

NBImag is a code suitable for the design and optimization of complex magnetic field configurations, such as that of a multiaperture, multistage negative ion source and accelerator. The NBImag code has been developed for the design of the ITER neutral beam injector, whose full-size prototype, MITICA, is presently under construction in Padua, Italy. The ITER injector shall produce a focused beam of neutral particles (H or D) having an energy of about 1 MeV and a total power of 16.5 MW for 3600-s continuous operation. The NBImag code is based on an integral formulation and allows an efficient calculation of any static magnetic field configuration on the basis of the geometry of the magnetic sources, with linear material and permanent magnets. NBImag also includes magnetic force and inductance calculations, based on the same formulation. Thanks to the capability of efficiently describing a large number of permanent magnets with limited computational effort, NBImag has also been integrated with different automatic optimization procedures for the solution of inverse magnetic problems. This paper describes the formulation of the code and optimization algorithms, the validation against analytical models and experimental measurements, and the application to the design of MITICA. [ABSTRACT FROM AUTHOR]

Compensated pulsed alternator (CPA, Compulsator) is a pulsed power supply with high power density and energy density. The principles of electromagnetic shielding and magnetic flux compression are used to provide a huge pulse current to the load. In order to reduce the mass or volume of the alternator and increase the storage density, high-strength composite materials are used in the air-core CPA. They are the preferred sources of modern electromagnetic weapon systems because of their merits. A high-speed air-core permanent magnet CPA (PMCPA) was presented in this paper with Halbach array PM topology of the rotor. The heavy external excitation source was not needed, so the volume and mass of the entire discharge system was reduced. Due to the special topology of air-core PMCPA, the parameters of the PMCPA were designed based on the theory of electromagnetic field analysis, numerical, and analytical methods. The finite element method simulation model is built based on the dimension parameters of CPA. The discharge process is simulated by Ansys Maxwell to optimize the performance of PMCPA. [ABSTRACT FROM PUBLISHER]

This paper presents the methodology for the electromagnetic design and analysis of air-cored pulsed alternators, which is based on a new type counter-rotating dual rotor permanent magnet compensated pulsed alternator (CRDR-PMCPA). The application of the CRDR topology in the field of CPA is used to decrease the large transient torque transmitted to the combat vehicle platform. Based on the air-cored structures and the pulse operation duty, the special design flowchart was presented. Halbach array permanent magnet rotors were designed for using the characteristic of unilateral magnetism gathering in the CRDR-PMCPA. The parameters of the air-cored dual rotors pulsed alternators were calculated and compared by the analytical method and finite-element analysis (FEA) method (FEM). The inductance of the armature winding is important for obtaining the pulsed current waveform accurately. The inductance of the armature winding is calculated by the numerical method and FEM, respectively. The mechanical design of the CRDR-PMCPA was done. The transient discharge process was simulated in detail for evaluating the design performance, and the operation risks of permanent magnets were also evaluated. The special problems for dual rotors rotating were investigated. The electromagnetic design and analysis is the base for accurately calculating the transient thermal rise and mechanical impulse aspects. Thermal and structural analysis was done by the multiphysics coupling analysis. And the results were used to evaluate the demagnetization risk of permanent magnets and evaluate the safety of the whole machine and the discharge system. [ABSTRACT FROM PUBLISHER]

In real power system, when the three-phase short-circuit fault occurs, the vacuum arc in one phase will be influenced by the transverse magnetic field generated by neighbor phases and bus bars. This kind of effect is the main cause of the unstable arc and deflected erosion of contact plates, which leads to the failure of vacuum circuit breakers interruption. The objective of this paper is to get more insight into the influence of external transverse magnetic field (ETMF) on vacuum arc’s behavior. The experiments were conducted in a demountable vacuum chamber with pressure about 10^-4 Pa. The cup-type axial magnetic field contacts were used, whose material was pure copper and the diameter is 35 mm. The uniform ETMF in the arc region was generated by two parallel bulk permanent magnets. The experiments were conducted under different ETMFs (0, 15, and 25 mT) and current levels (1-, 2.5-, and 4-kA rms) with different gap distances (6, 8.5, and 11 mm). The videos of arc column were recorded by a high-speed charge-coupled device camera. Under the action of ETMF, the vacuum arc got deflected. Due to the retrograde motion of cathode spots and Ampere force acting on arc column, the deflection behaviors during three typical periods (that is, initial, peak value, and close-to-current-zero period) were different. Moreover, the deflection level of vacuum arc at current peak value moment was greatly impacted by ETMF and gap distance. Larger the ETMF and gap distance were, higher the deflection level at current peak value moment was. The simulation results of arc deflection based on magnetic-hydrodynamic model were in agreement with experimental results in trends. [ABSTRACT FROM AUTHOR]

Pulsed power technology is widely used in medical treatment, military, and scientific research, such as laser burst and electromagnetic launch. Compensated pulsed alternator (CPA) is a kind of device generating that pulsed power. One of the shortages for the air-core pulsed alternator is the huge excitation loss. In order to solve the problems, a multidisk axial flux CPA (MAFCPA) is proposed, which replaces the excitation windings with permanent magnets, saving the self-excitation process. In addition, multidisks are designed, especially to reduce subtransient reactance when the CPA discharges, which contributes to increasing the discharging current. This paper mainly focuses on researching the feasibility of MAFCPA in aspects of thermal issues, rotor statics, and dynamics problems. First, the topology and principle of MAFCPA are introduced, and the properties of the materials are listed as well. Second, the loss of discharging is calculated and the temperatures of both stator and rotor are solved. Then, the maximum stresses of different materials are obtained. Afterward, the critical speeds are researched in order to avoid resonance. Finally, the conclusion is made that MAFCPA can work safely under a speed of 10000 r/min and supply a pulse of over 50 ms. [ABSTRACT FROM AUTHOR]

The six-phase transverse flux tubular permanent magnet linear motor (PMLM) has many advantages compared with conventional linear motors. However, the reliability of its drive system can still be influenced by power converter or machine faults. This paper presents a fault-tolerant control strategy for six-phase transverse flux tubular PMLM based on synthetic vector method when the machine has a single-phase open-circuit fault. The operation of six-phase transverse flux tubular PMLM is described as well as its basic mathematical model. Then, the principles of synthetic vector method are introduced. Based on these theories, the fault-tolerant control strategy is derived in detail under the single-phase open-fault condition. In addition, a fault-tolerant dual three-phase four-leg inverter’s drive topology that can be applied under this faulted condition is proposed. Moreover, to implement the control algorithms proposed, a modified space vector modulation is presented. Both the finite-element simulation and MATLAB/Simulink simulation results illustrate the validity of the proposed fault-tolerant control as well as the associated control topology and space vector modulation. [ABSTRACT FROM PUBLISHER]

In this paper, a passive permanent-magnet (PM)-based magnetic levitation system is presented and its stability is discussed. The suspension is assured by the repulsive force of properly shaped PMs placed on both the guideway and the vehicle. The interaction between the motional-induced currents on conductors attached to the guideway and the PMs on the armature produces a stabilization force. Two versions of the device are discussed. In the first, the stabilizing currents are the ones induced on a conductive sheet surrounding the guideway. In the second device, the stabilizing currents flow in an array of null-flux coils. Comparison of the performance of the two proposed systems are performed by a research code developed at the Department of Energy, System Territory and Construction Engineering. [ABSTRACT FROM PUBLISHER]

This paper performs the inductance and phase coupling analysis of a tubular permanent magnet machine with transverse flux configuration for electromagnetic launch (EML) applications. Self-inductance and mutual inductance are calculated by employing a frozen permeability finite element technique, and the results are validated by measurement on a prototype machine. The analysis of phase coupling problem is then undertaken, and it has been shown that the tubular transverse flux machine has the merit of magnetic decoupling between phases, and thus shows a brilliant prospect in EML applications. The influence of armature reaction on the inductance is also investigated, and it indicates that at higher current, the inductance fluctuates once instead of twice within one electrical cycle, which is quite different from that in conventional machines. [ABSTRACT FROM PUBLISHER]

In electromagnetic launch (EML) applications, a compensated pulsed alternator is an effective form of pulsed power supply because of its high energy density and power density. The basic advantages of compensated pulsed alternators for EML applications are their higher energy density than capacitors and their export ac output that is suitable for transmission and transformation. In general, external excitation is adopted as a form of self-excitation or pulse excitation in compensated pulsed alternators with an iron core or air core. Using this form not only results in heavy and bulky components but also complicates and reduces the reliability of the system. This paper proposes a novel compensated pulsed alternator that is excited by permanent magnets (PMs) and equipped with an iron core or air-core stator. This system does not require any excitation converter or brush–slip ring, thereby making it more reliable, less massive, and less voluminous than the system with self-excitation or pulse excitation. In addition, analytical models are introduced to simulate the air-gap magnetic distribution, back-electromotive force, pulsed current wave, discharge torque, and energy exchange of this machine. A scale-model prototype of the PM-compensated pulsed alternator is designed, fabricated, and tested. The actual output voltage waveform and pulsed current waveform are sampled and compared with the predicted ones. The results show that the design of the PM compulsator is feasible and reliable. [ABSTRACT FROM PUBLISHER]

Design and development of a high power, widebandwidth W-band travelling wave tube (TWT) is presented in this paper. The design and simulation covers folded waveguide (FWG) circuit, electron gun, periodical permanent magnet system, and coupling window with the emphasis on the FWG optimization and particle-in-cell simulation by Computer Simulation Technology (CST) particle studio. Two TWT prototypes have been developed and tested, which demonstrate over 30-W output power in frequency between 91 and 101 GHz with over 30-dB saturated gain. Maximum power was found to be about 40 W around 95 GHz, while the flat output power curve under same drive level was observed. [ABSTRACT FROM PUBLISHER]

Since permanent magnet linear synchronous motor (PMLSM) has a bright future in electromagnetic launch (EML), moving-magnet PMLSM with multisegment primary is a potential choice. To overcome the end effect in the junctions of armature units, three different ring windings are proposed for the multisegment primary of PMLSM: slotted ring windings, slotless ring windings, and quasi-sinusoidal ring windings. They are designed for various demands of EML, regarding the load levels and force fluctuations. Auxiliary iron yokes are designed to reduce the mover weights, and also help restrain the end effect. PMLSM with slotted ring windings has a higher thrust for heavy load EML. PMLSM with slotless ring windings eliminates the cogging effect, while PMLSM with quasi-sinusoidal ring windings has very low thrust ripple; they aim to launch the light aircraft and run smooth. Structure designs of these motors are introduced; motor models and parameter optimizations are accomplished by finite-element method (FEM). Then, performance advantages of the proposed motors are investigated by comparisons of common PMLSMs. At last, the prototypes are manufactured and tested to validate the feasibilities of ring winding motors with auxiliary iron yokes. The results prove that the proposed motors can effectively satisfy the requirements of EML. [ABSTRACT FROM PUBLISHER]

Compact sources of magnetic field with domains of solenoidlike topology have been proposed to replace electromagnets in plasma devices. A light, nonmagnetic chassis holding an array of neodymium magnets in a honeycomb pattern has been designed, machined, and tested. DC magnetic fields up to 0.5 T have been achieved in extended spatial domains useful for practical applications. Stable operation of RF-driven discharges in air, argon, and nitrogen has been obtained using these regions. Noninvasive fiber-optics and direct in-vacuum spectroscopic measurements have been used for performance analysis. Efficient production of UV light, decomposition of molecules, and ionization of atomic and molecular species have been demonstrated in different configurations. Extreme ultraviolet production and other potential uses, as well as durability, improvements, and limitations are discussed. [ABSTRACT FROM AUTHOR]

DC power relay is a key electromechanical component widely used in electrical vehicles, photovoltaics, as well as more-electric aircrafts for energy managing, power conversion, and distribution. As the voltage and current increase due to relay switches, arc discharge becomes an unavoidable and significant issue during the operation of the dc high-power relay. Bridge-type contact and external permanent magnets are spontaneously employed in its arc chamber to accelerate the quenching of arc. In this paper, the complicated arc discharge plasma in a dc power relay has been investigated by using both experimental and numerical approaches. Initially, arc dwell and arc restriking characteristics during the arc motion phase are presented by analyzing the voltage and current waveforms and arc images acquired in carefully designed breaking experiments. The arc driven by a transverse magnetic field with a variety of flux densities and the influence of flux densities on arc voltage and dwell are preliminarily discussed based on the experimental results. Then, to reveal the arc physics and to determine the influence of transverse magnetic field on arc motion characteristics, a simplified model based on the magnetohydrodynamic (MHD) theory is built and three cases with different magnetic field are calculated. The simulated arc behaviors including distributions of the temperature and current density are presented. The mechanism underlying the influence of transverse magnetic field on the arc motion is analyzed according to arc root transfer and arc voltage variation. In addition, to understand the formation of the arc restriking, the critical breakdown electric-field strength inside the arc gap is also calculated based on streamer breakdown theory. The parameters in the space occupied by earlier arcs, as predicted by the MHD simulations, are used in the breakdown calculation. Results show that the critical breakdown voltage reduces remarkably along with growth of the operating voltage and breaking current, and the arc dwell time can be reduced by strengthening the external magnetic field within a reasonable extent. [ABSTRACT FROM PUBLISHER]

The results of an experimental and a numerical study of a relativistic A6 magnetron with single radial microwave power output slot operating with angular segment (AS) NdFeB permanent magnets placed inside the anode vanes and cylindrical rod magnets inside the cathode are presented. With permanent magnets, ~10−7 s long pulses of tens of megawatts of microwave power with an electronic efficiency of ~7% are generated. The results of experiments and simulations show that electron losses near the poles of the anode magnets where magnetic field lines cross the anode-cathode gap limit the microwave generation efficiency. [ABSTRACT FROM AUTHOR]

In the field of compulsators, hybrid excitation concepts have been verified through the development of several hybrid excitation prototypes. Although there are some advantages associated with the hybrid excitation compulsator in comparison with the traditional electrical excitation topology compulsator, some drawbacks still exist, which may lead to demagnetization of the permanent magnets and therefore affect the performance and operational safety of such compulsators. For practical applications, the risk of demagnetization needs to be assessed, measurements need to be taken, and design parameters need to be refined. The problem is critical during discharge, with many factors associated with dictating the demagnetizing of these compulsators. In particular, the demagnetizing magnetic strength, temperature rise, and stress effects were analyzed. The temperature distribution in the compensation shield caused by eddy-current losses was simulated. During discharge of a permanent magnet, the location of temperature sources is important. The impact stress imposed on the permanent magnets was simulated and safety characteristics were evaluated. [ABSTRACT FROM PUBLISHER]

Pulsed alternators integrate kinetic energy storage, electromechanical energy conversion, and pulse shaping into one unit, and it is the research focused on the field of pulsed power sources. The electrical excitation and the permanent magnet excitation are contained in one hybrid-excitation pulsed generator together in which the advantages of two different excitation types are integrated. The brush slip ring mechanism with low reliability and high maintenance costs can be cancelled. In addition, the electromagnetic field can be adjusted quickly by external electrical excitation source and correspondingly the performance can be quickly adjusted. An all-iron-core hybrid-excitation compulsator prototype was designed, fabricated, and optimized. The hybrid excitation concept was validated in the research of compulsators. Although compulsator research is mainly focused on the all-air-core electrical excitation topology, there exist some bottleneck technologies that restrict the application of compulsators in actual fields. The hybrid-excitation compulsator can decrease the cost, increase the reliability, and widen the application scope of compulsators, especially in the middle–low power range. The Halbach array is a permanent magnet arrangement structure, which is a combination structure of different direction arrays. The Halbach array offers a number of attractive features in comparison with the normal array. The air-gap magnetic flux can be increased and the rotor yoke magnetic flux is decreased. Based on this, the Halbach array can be designed on the composite rotor core. A part-air-core compulsator that includes an air-core rotor and an iron-core stator was designed. For analyzing the electromagnetic design results, the 3-D model was built and finite element analysis method was used. The performance simulation results of the Halbach hybrid-excitation compulsator were presented. [ABSTRACT FROM PUBLISHER]

A small helicon source using a permanent magnet has been tested for possible application as a spacecraft thruster. Ion energy distributions measured with a retarding-field ion analyzer show that ions are ejected with energies of \sim 5~KTe , in agreement with theory. The specific impulse can be increased by applying a positive bias to the endplate of the discharge. [ABSTRACT FROM PUBLISHER]