Short Solenoid Research Articles

Пульсации течения жидкого металла, генерируемые переменным магнитным полем

This paper studies numerically a vortex flow of liquid metal driven by an electromagnetic force, which is generated by the interaction of the alternating magnetic field of a short solenoid with the induced electrical current. A short solenoid is placed coaxially to a cylindrical cell at half of its height. The mathematical model used to describe the process is based on the equations of magnetic hydrodynamics in the induction-free approximation. Calculations, which are carried out by the control volume method using the ANSYS Fluent package, show that the average flow has the form of two toroidal vortices. The calculated velocity fields are indicative of the oscillatory behavior of vortices, accompanied by a change in their sizes. In the examined range of the force parameter, the predominant flow pattern is the single-mode oscillatory flow. The dependences of characteristic frequency and Reynolds number on the force parameter, are obtained using spectral analysis. It has been found that the oscillation period is close to the period of rotation of a large-scale vortex. It has been established that the oscillations are of quasi-periodic character, and a distinct oscillation frequency is observed only in the flow region near the solenoid. The effect of velocity fluctuations is strong and can be detected in laboratory conditions when using gallium eutectic. Such experiment is planned for the near future. The flow rate of gallium eutectic will be measured by an ultrasonic Doppler anemometer. The results of numerical modeling and their verifications can be useful in determining the ways of reducing the intensity of vortex flows during the electromagnetic separation of impurities, which is based on the induction mechanism responsible for the generation of electromagnetic force that displaces particles. The data on the oscillation frequency of the unsteady flow can be used in the development of a non-contact technique for estimating the average electrical conductivity of a two-phase medium, such as a liquid metal with undesirable impurities.

Improvement of the uniformity of the magnetic field inside a short solenoid by the end winding system

Improving the level of homogeneity of the magnetic field in the middle of the working volume of a short solenoid makes it possible to improve devices for demagnetizing technical objects and studying the magnetic properties of materials. One of the means of increasing the level of homogeneity of the magnetic field in the middle of the solenoid is to approximate the shape of its winding to the closed surface. The use of a system of a solenoid and two end axisymmetric current windings with a common current source is proposed as such a surface. A mathematical model of the scalar potential of the magnetic field of such a system was built using spherical harmonic analysis, and functional dependences of the current density on each surface were obtained for its first harmonic, which is the dipole component of the magnetic field. Formulas for calculating the number of turns in the end windings and the geometric parameters of their arrangement and the simulated total magnetic field inside the proposed system are obtained. A comparative analysis of the homogeneity of the magnetic field created by a separate solenoid and a solenoid with end windings, depending on the geometry of the system, was conducted. The use of end windings significantly improves the uniformity of the magnetic field near the ends, especially on the axis of the solenoid. Due to this, the efficiency of the end windings significantly depends on the solenoid elongation indicator and allows you to increase the working volume by 5-20%, depending on this indicator. The proposed system makes it possible to obtain a magnetic field with a maximum deviation of 5% from uniformity for a solenoid elongation index of 2. As the elongation increases, the efficiency of the end windings decreases and for systems with an elongation of 10 or more, their use becomes impractical. The results of the analysis testify to the effectiveness of using the proposed system in devices for demagnetizing technical products that differ in a small indicator of the elongation of the working solenoid - primarily devices that create a uniform magnetic field with an amplitude decreasing over time of 240 A/m and are used in particular to remove soft residual magnetization from elements of space vehicles

Magnetised and unmagnetized axisymmetric particle-in-cell simulations of ion energy distributions in cathodic vacuum arcs

Cathodic arcs are electrical discharges consisting of a succession of discrete pulses of energetic plasma travelling from the surface of a cathode toward an anode. Currently, there are no vacuum arc simulations where spots are continuously generated with a set frequency, including the far-field plasma jet, with the inclusion of kinetic behaviour for both ions and electrons. The VSim 11 particle-in-cell software was used to simulate specific vacuum arcs as axisymmetric, electrostatic, and fully kinetic, from the initial generation of each cathode spot to the streaming plasma discharge at a far field, validating the predictions against experimental data. The models were configured to match the experimental arc gun of Zohrer et al and the Mevva V experiment with the cathode materials Al and Nb. The ion and electron velocity data were collected at the far edge of the simulation domain, analogous to a physical energy detector. The simulations successfully predicted the evolution of ion charge state energy distributions, showing peak unmagnetized ion energies that agree with prior experimental data, resulting in a mean error of 3% for Al and Nb. A peak in the electrostatic potential is observed above the cathode surface, supporting the potential hump theory as the cause of the higher-than-expected ion energies observed in cathodic arc discharges. Lower than expected relative energies between ion charge states are observed, matching prior experimental results, with this coupling of ion charge states attributed to non-stationary electrostatic wave–particle interactions, as the use of collisionless simulations rules out Coulombic ion friction. Magnetised simulations incorporated a statically powered short solenoid equivalent to the coil used in the Mevva V experiment to create a diverging magnetic nozzle. The magnetised simulation results demonstrate an annular jet of magnetically confined plasma and indicate an increase in nonstationary electrostatic effects including wave–particle interactions.

Theoretical and Experimental Studies of SMES Configurations for Design Optimization

In the current energy scenario, due to the increment in power generation from renewable sources, the importance of electrical storage systems has increased significantly, and as a consequence, the study of the improvement of its efficiency and the design of new storage systems also increased. Superconducting material permits the design of Superconducting Magnetic Energy Storage (SMES). The main problem of SMEs is the low energy density they have, what make the optimization of design to be one of the keys for inclusion of this elements in the power grid and other specific applications as, for instance, flux pumps. As the only basic forms for SMES, and with the objective of its mathematical optimization, this work (i) evaluates the mathematical equations for a real solenoidal winding, and (ii) develops the equivalent equations for a toroidal winding, from the electromagnetic laws. Then, (iii) a practical structure formed by short solenoids connected in series along a circular axis (quasi-toroidal structure) is studied. Due to the large number of equations involved in this case, the finite-element method in used here. Finally (iv), in order to validate the results without building the complete solenoid (impossible at the time), one of the magnetic coupling between two solenoids in the quasi-toroidal winding was developed according with the theoretical method, and experimentally tested. The study was carried out by programming different dimensions in order to make conclusions for a further development of an optimization algorithm. These conclusions are presented. This work is the first stage for the optimized design of a SMES, and presents the complete equations of the real toroidal winding as the base of the outline dimensions of a practical quasi-toroidal SMES.

Modeling of magnetic fields and signals of a ferromagnetic pipe flaw detector induced by a through hole defect

A numerical model has been developed for interaction of the magnetizing field of a short solenoid with a ferromagnetic pipe exhibiting a through hole in the wall, which takes into account nonlinear magnetic properties of the test object. This model was used to calculate spatial distribution of magnetic induction in the pipe wall and spatial distribution of the components of the magnetic induction vector near the pipe surface with a through hole. The validity of the numerical model was confirmed by physical modeling results. The results of theoretical and experimental studies were used to develop a simplified analytical model that describes behavior of the magnetic field of the defect and the electrical signal of the induction transducer of a magnetic flaw detector that implements the method of magnetic flux leakage. It is shown that the dependence of the signal of the induction transducer induced by the through hole on the gap is close to a linear one, and its dependence on the hole diameter is close to a quadratic one. The results obtained in the study can be used for creation, numerical modeling and measurement of magnetic fields.

An approach to development of the HTS magnet for SMES at JINR

Particle accelerator complex NICA (Nuclotron-based Ion Collider fAcility) comprises superconducting Booster and Nuclotron synchrotrons which magnets operating at pulse mode in opposite phase with period of about 4 seconds. Summary stored energy of Booster and Nuclotron magnets will vary from 1 to 2.6 MJ during the period. NICA power supply system can be significantly improved by Superconducting Magnetic Energy Storage (SMES) application that will help to move the energy back and force between Booster and Nuclotron. The useful energy at this SMES must be about 1.6 MJ so the maximum total SMES energy should be 3-5 MJ. SMES with this energy should have several Tesla magnetic fields to keep a reasonable size. SMES operating current can be not less than Booster and Nuclotron magnets current so it might be 10-12 kA. It is better to make such a SMES magnet from an HTS (high temperature superconductor) cable for the stability at 6-7 T and 4 s pulse mode. The SMES magnet is planned to be wound as a short solenoid (Brooks coil) of cables optimized for several coaxial sections. HTS cables with helical structure similar to well-known CORC (conductors on round core) cables are under the development at JINR. The HTS cabling technology is based on the same principle as Nuclotron type cable manufacturing technology. HTS tapes, cables and magnets experimental study and testing methods are being developed on the base of an existing test facility at LHEP. First HTS cable short sample with 6 HTS tapes was prepared and tested at 77 K in self-field. Its critical current is about 800 A that will allow achieve required operating currents of SMES magnet with a reasonable amount of HTS tapes in cables. Developments of high field high current fast cycling HTS magnets for accelerators are also being planned at JINR.

Строгие и аппроксимирующие выражения для индуктивностей соленоидов круговой и квадратной формы

Closed expressions for the inductances of circular and square solenoids are presented in a systematic manner. Transformed expressions written in terms of spherical Legendre functions with a semi-integer index are given. Both rigorous estimates of compression forces for circular and square solenoids written through derivatives with respect to generalized coordinates and using well-known approximating expressions are obtained. The new expressions are compared with the previously known ones. An appendix to the article contains derivation of the expression for the self-induction coefficient of a short circular solenoid based on the spherical Legendre functions with semi-integer indexes. The derived expression is compared with the well-known Wheeler’s and Lundin’s formulas.

Status of high intensity proton injector for Facility for Antiproton and Ion Research.

The high intensity proton injector for the international accelerator Facility for Antiproton and Ion Research located at GSI-Darmstadt in Germany consists of a pulsed 2.45 GHz microwave ion source, a Low Energy Beam Transport (LEBT), and an electrostatic chopper matching the proton beam to the radio frequency quadrupole. The ion source is based on electron cyclotron resonance plasma production and it has to provide a proton beam at 95 keV energy and up to 100 mA current. The LEBT system with two short solenoids each including two magnetic steerers will transport the proton beam into the compact proton linac, accelerating it to the energy of 68 MeV and serving as the injector of the upgraded heavy ion synchrotron (SIS18). This paper describes the commissioning of the proton injector including beam characterization measurements that have been done at CEA/Saclay in France and is currently at the final commissioning stage.

Study on a High Sensitive Online Sensor for Wear Particles in Lubricant

On-line condition monitoring reflects the condition of mechanical equipment, which designs to avoid unnecessary detection and discover serious accident timely. This paper proposes a short solenoid inductance sensor for monitoring the metal abrasive particles in lubricant within internal combustion engine. The mathematical model of sensor is established to analyse the influence of different metal abrasive particles on the magnetic field. In the actual tests, when the particle passes through the specific magnetic field, the signal of the induced electromotive force is converted into a signal frequency which is convenient to detect. The results of the experiments show that the sensor could effectively detect iron particles of 50μm in size and copper particles of 100μm in size, which means this short solenoid inductance sensor is effective in monitoring the internal combustion engine online.

Speaking of E&M

This paper describes a new lab experiment where students explore the magnetic force on a permanent magnet placed inside a short solenoid. This lab is the fourth experiment performed in the second semester of the calculus-based introductory physics course at Washington University in St. Louis. The experiment is performed using a speaker (which students themselves have constructed), function generator, multimeter, and Vernier microphone while all analysis is done using Logger Pro. Experiments confirm a functional relationship similar to one that students have seen in class, while showing students the applicability of classroom physics to their world.

The external magnetic field created by the superposition of identical parallel finite solenoids

We use superposition and numerical methods to show that the external magnetic field generated by parallel identical solenoids can be nearly uniform and substantial, even when the solenoids have lengths that are large compared to their radii. We examine both a ring of solenoids and a large hexagonal array of solenoids. In both cases, we discuss how the magnitude and uniformity of the external field depend on the length of and the spacing between the solenoids. We also discuss some novel properties of a single solenoid, e.g., that even for short solenoids the energy stored in the internal magnetic field exceeds the energy stored in the spatially infinite external magnetic field. These results should be broadly interesting to undergraduates learning about electricity and magnetism.

Mathematical Model of the Processes of Heat and Mass Transfer and Diffusion of the Magnetic Field in an Induction Furnace

We propose a mathematical model describing the motion of a metal melt in a variable inhomogeneous magnetic field of a short solenoid. In formulating the problem, we made estimates and showed the possibility of splitting the complete magnetohydrodynamical problem into two subproblems: a magnetic field diffusion problem where the distributions of the external and induced magnetic fields and currents are determined, and a heat and mass transfer problem with known distributions of volume sources of heat and forces. The dimensionless form of the heat and mass transfer equation was obtained with the use of averaging and multiscale methods, which permitted writing and solving separately the equations for averaged flows and temperature fields and their oscillations. For the heat and mass transfer problem, the boundary conditions for a real technological facility are discussed. The dimensionless form of the magnetic field diffusion equation is presented, and the experimental computational procedure and results of the numerical simulation of the magnetic field structure in the melt for various magnetic Reynolds numbers are described. The extreme dependence of heat release on the magnetic Reynolds number has been interpreted.

Short intense ion pulses for materials and warm dense matter research

We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r<1mm within 2ns FWHM and approximately 1010 ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2MeV Li+ ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Here we describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminum perovskite using the fully integrated accelerator and neutralized drift compression components.

Two examples of in-flight spin flippers

In precise experiments with polarized beam it’s very often appear a necessity to change beam polarization on opposite. If such operation does not change other beam parameters, it helps to avoid or minimize some systematic errors. It is especially important in experiments, where spin dependent effect is small enough. This paper describes two set of equipments, that make spin flip for extracted beams. In both cases, these devices are absolutely distinct, because they are appropriate for different particles and at different energy range. The first of them is intended for future muon (g-2) experiment, which is under preparation now at JPARC. Here, the muon spin flip will be done by chain of electrostatic and magnetic bends at the kinetic energy 340 keV. A beam matching is provided by a number of short solenoids. The other flipper (or Siberian snake) will rotate spin of protons or antiprotons, which come from Λ-meson decay with the energy up to 40 GeV. This experiment (no. 24) is planed at IHEP, Protvino. In this case, two superconducting helical magnets with opposite helicities and magnetic field 4.5 T will be used. To correct beam trajectory, additional dipole correctors are required.

Improvement of extraction system geometry with suppression of possible Penning discharge ignition

During the past two years, a new ECR 2.45 GHz type ion source has been developed especially dedicated to intense light ion injector project like IPHI (Injecteur Proton Haute Intensité), IFMIF (International Fusion Materials Irradiation Facility), to reduce beam emittance at RFQ entrance by shortening the length of the LEBT. This new ALISES concept (Advanced Light Ion Source Extraction System) is based on the use of an additional LEBT short length solenoid very close to the extraction aperture. The fringe field of this new solenoid produces the needed magnetic field to create the ECR resonance in the plasma chamber. Such geometry allows first putting the solenoid at ground potential, while saving space in front of the extraction to move the first LEBT solenoid closer and focus earlier the intense extracted beam. During the commissioning of the source in 2011-2012, ALISES has produced about 20 mA extracted from a 6 mm diameter plasma extraction hole at 23 kV. But the magnetic configuration combined to the new extraction system geometry led to important Penning discharge conditions in the accelerator column. Lots of them have been eliminated by inserting glass pieces between electrodes to modify equipotential lines with unfavorable ExB vacuum zones where particles were produced and trapped. To study Penning discharge location, several 3D calculations have been performed with OPERA-3D/TOSCA code to simulate the possible production and trapping of electrons in the extraction system. The results obtained on different sources already built have shown very good agreement with sparks location observed experimentally on electrodes. The simulations results as well as experimental measurements are presented and solutions to prevent possible Penning discharge in future source geometries are established.

Advanced light ion source extraction system for a new electron cyclotron resonance ion source geometry at Saclay

One of the main goal of intense light ion injector projects such as IPHI, IFMIF, or SPIRAL2, is to produce high current beams while keeping transverse emittance as low as possible. To prevent emittance growth induced in a dual solenoid low energy transfer line, its length has to be minimized. This can be performed with the advanced light ion source extraction system concept that we are developing: a new ECR 2.45 GHz type ion source based on the use of an additional low energy beam transport (LEBT) short length solenoid close to the extraction aperture to create the resonance in the plasma chamber. The geometry of the source has been considerably modified to allow easy maintenance of each component and to save space in front of the extraction. The source aims to be very flexible and to be able to extract high current ion beams at energy up to 100 kV. A specific experimental setup for this source is under installation on the BETSI test bench, to compare its performances with sources developed up to now in the laboratory, such as SILHI, IFMIF, or SPIRAL2 ECR sources. This original extraction source concept is presented, as well as electromagnetic simulations with OPERA-2D code. Ion beam extraction in space charge compensation regime with AXCEL, and beam dynamics simulation with SOLMAXP codes show the beam quality improvement at the end of the LEBT.

Estimation of an equivalent short solenoid model using different numerical methods

Estimation of an equivalent short solenoid model using different numerical methodsThis paper deals with an inverse magnetostatic problem related to the reconstruction of a permanent magnet encapsulated inside the cathode of a magnetron sputtering device. The numerical analysis is aimed to obtain the estimation of a short solenoid equivalent to the unknown magnet. Least squares approach has been used to solve the functional defined as squared sum of the residuals. A comparison of the results obtained with Genetic Algorithm approach and nonlinear system of equations is performed. A regularized solution, which is in good agreement with the experimental data, was found by applying a Newton adapted regularization technique.

Quench Protection of Curved Solenoids for High Intensity Muon Beamlines

A quench protection system for superconducting curved segmented solenoids has been experimentally studied. The curved solenoids consist of short straight solenoids aligned along a curved beamline axis. The quench propagation between the short solenoids may not naturally occur because of the separation between the solenoids, and an artificial quench need to be induced by a protection heater for each short solenoid to boost the quench propagation. A protection heater driven by the coil self current was tested with a model coil.

Rapid Detection of Infestation of Apple Fruits by the Peach Fruit Moth, Carposina sasakii Matsumura, Larvae Using a 0.2-T Dedicated Magnetic Resonance Imaging Apparatus.

Infestation of harvested apple fruits by the peach fruit moth (Carposina sasakii Matsumura) was studied using a dedicated magnetic resonance imaging (MRI) apparatus equipped with a 0.2-T permanent magnet. Infested holes on the three-dimensional (3-D) images tracked ecological movements of peach fruit moth larvae within the food fruits, and thus in their natural habitat. Sensitive short solenoid coil and surface coil detectors were devised to shorten measurement times. The short solenoid coil detected infestation holes at a rate of 6.4 s per image by the single-slice 2-D measurement. The multi-slice 2-D measurement provided six slice images of a fruit within 2 min taken by the two detectors. These results indicate that the 0.2-T MRI apparatus allows one to distinguish sound fruits from infested ones, and also as a means for plant protection and the preservation of natural ecological systems in foreign trade.

Wireless Power Transfer in Loosely Coupled Links: Coil Misalignment Model

A novel analytical model of inductively coupled wireless power transfer is presented. For the first time, the effects of coil misalignment and geometry are addressed in a single mathematical expression. In the applications envisaged, such as radio frequency identification (RFID) and biomedical implants, the receiving coil is normally significantly smaller than the transmitting coil. Formulas are derived for the magnetic field at the receiving coil when it is laterally and angularly misaligned from the transmitting coil. Incorporating this magnetic field solution with an equivalent circuit for the inductive link allows us to introduce a power transfer formula that combines coil characteristics and misalignment factors. The coil geometries considered are spiral and short solenoid structures which are currently popular in the RFID and biomedical domains. The novel analytical power transfer efficiency expressions introduced in this study allow the optimization of coil geometry for maximum power transfer and misalignment tolerance. The experimental results show close correlation with the theoretical predictions. This analytic technique can be widely applied to inductive wireless power transfer links without the limitations imposed by numerical methods.