Solenoid Magnet Research Articles

Paraxial optics of charged particles in solenoids

Paraxial optics of charged particles in solenoid magnets with axisymmetric field is considered. Analytic and symplectic transverse maps for charged particle motion through solenoids with 3D magnetic fields have been derived. The formula for transverse maps contains both linear and nonlinear effects caused by entrance and exit fringe fields of the solenoid. The explicit transfer map can be used for applications of accelerator physics that use solenoid magnets.

Design of Shielded Solenoids for Charged Particle Beam Applications

Focusing solenoids for accelerators and other charged particle beam applications usually have general requirements: focusing strength, stray field, eddy current losses and specific requirements. For industrial applications discussed in the paper, conventional resistive solenoids can be used, which have specific requirements include maximum operation current, minimum inductance or impedance. For high energy applications, superconducting focusing solenoids have been used widely [(T. Yang et al ., 2016), (G. Davis et al. , 2007)], which will have different design requirements. In contrast to a single quadrupole magnet, solenoid magnets can provide simultaneous focusing in both x- and y-directions. However, the focusing strength of solenoids is relatively low compared to quadrupoles due to the second order field effects (E. Muro et al. , 1990). But for low energy industrial application, solenoid magnets will be one of the cost-effective solutions. This paper proposes several design options to improve the performance of conventional resistive focusing solenoids. These design options include adding bucking coils to limit the stray fields, splitting the main coil to reduce the total impedance of the coils and implementing passive shielding layers to minimize the stray field and the effects of external disturbances simultaneously. Simulation results and experimental test data will be presented.

Applying Superconducting Magnet Technology for High-Efficiency Klystrons in Particle Accelerator RF Systems

An MgB2 superconducting solenoid magnet has been developed for electron beam focusing in X-band (12 GHz) klystrons for particle accelerator RF systems, to provide a central field of 0.8 T at 57 A and at ≥20 K. It has successfully realized significant AC-plug power saving in one order of magnitude compared with that for a conventional Cu solenoid magnet. The large-scale application may be expected for the Compact Linear Collider (CLIC) project proposed as a future accelerator candidate at CERN. It requires ~5,000 klystrons, and the MgB2 magnet application will realize significant AC-plug power saving. This paper describes progress in a prototype MgB2 superconducting solenoid magnet development and discusses the future prospect.

Design and fabrication of the Mu2e cryogenic distribution system

The muon-to-electron conversion (Mu2e) experiment at Fermilab will be used to search for the charged lepton flavor-violating conversion of muons to electrons in the field of an atomic nucleus. The Mu2e experiment is currently in the design and construction stage and is expected to begin operations in 2022. The Mu2e experiment uses four large superconducting solenoid magnets including a Production Solenoid (PS), an Upstream and Downstream Transport Solenoid (TSu and TSd) and a Detector Solenoid (DS).This paper will focus on the cryogenic distribution system for these four solenoid magnets. Liquid helium will be supplied from two re-purposed Tevatron satellite refrigerators. A large cryogenic distribution box (DB) is located in the Mu2e building to distribute the required cryogens to each of the four solenoid magnets. Each solenoid magnet will have a dedicated transfer line and cryogenic feed box (FB). The solenoid magnets each require two liquid helium circuits and two liquid nitrogen circuits.The most unique feature about this cryogenic system is that the assemblies for the start of the superconducting portion of the power leads are mounted in feed boxes that are in the range of 23 m to 31 m away from the solenoid magnets. The cryogenic feed boxes are located remotely to provide protection from radiation damage and high magnetic fields. The power leads are NbTi superconducting cable stabilized with high conductivity aluminum. The 6061-T6 aluminum grade was selected for the transfer line piping so that the piping would thermally contract at the same rate as the power lead. A major concern for this transfer line is that a small helium leak could create an electric discharge arc due to the Paschen effect. This paper includes a description of the design features and testing done to ensure that the power leads are protected from the Paschen effect while still being adequately cooled to liquid helium temperatures.

Cryogenic design of FRIB cryomodule and distribution system and the present status

The Michigan State University (MSU) Facility for Rare Isotope Beams (FRIB) accelerator utilizes six types of cryo-modules that are being installed in three Linac segments in the FRIB tunnel. The cryomodules contain both superconducting RF cavities and solenoid magnets with 2 K and 4.5 K refrigeration loads (respectively), magnet lead flow loads and 35-55 K shield loads and power coupler intercept loads. The first Linac segment (LS-1) with fifteen cryomodules was commissioned at 4.5 K and at 2 K. Commissioning experiences and some salient features of the cryogenic design of the cryomodules and the helium distribution systems will be discussed.

Compact cryogenic test stand for superconducting magnets characterization

A new compact experimental facility for testing compact superconducting magnets down to 4.2 K using cryogenic fluids has been developed at CEA Paris-Saclay. This facility has been constructed to test the solenoid magnets for the next Soreq particle accelerator (SARAF) project. The magnets are cooled with liquid helium at 4.2 K and the liquid bath can be pressurized up to 2 bars to regulate the temperature of the magnet during operating conditions. In this facility, it is possible to measure and dissociate the heat loads coming from the magnet and the current leads by flow-metry. The voltage of the solenoids and their current leads are measured using National Instrument devices and monitored with a Labview program to identify and analyze eventual quenchs. The magnetic performance of the magnets are also monitored dynamically with 3D hall probes. Numerous cryogenic temperature sensors are used to characterize the thermal evolution of the magnet and its current leads during the test. In the present paper, the compact facility is described and the first results obtained on the current leads of the magnet prototype are presented.

Design, Manufacturing and Testing of a High-Field 2 + 3 T MgB$_2$ Dry Magnet Demonstrator

This paper presents the design, manufacturing and testing result of a 2 + 3 T high field MgB $_2$ conduction-cooled solenoid magnet demonstrator. The prototype almost reached 2 T at 10 K inside a homogeneous background field of 3 T produced by a NbTimagnet. The demonstrator was wound with 1.6 km of Columbus ex-situ React and Wind (R&W) conductor. The mechanical design of the prototype is presented including the homogenization of the mechanical properties of the composite conductor. The Von Mises equivalent strain calculated after both cooling and energizing conditions is below the conductor strain criteria of 0.4%. In order to obtain the required magnetic field, three length of wires were linked together by two resistive junctions of approximately 150 n $\Omega$ each. The heat generated by the junctions was extracted by several heat sink apparatus. The different apparatus designed for the thermalization of both the junctions and the magnet are presented. Prior to the testing of the demonstrator, the conductor used for the prototype was tested. The results of these tests are compared to the current measurement of the demonstrator and no current degradation of the conductor wound is evidenced, proving the good handling of the wire during all the manufacturing steps and testing phase.

A Transducer for Measuring the Field Quality in Superconducting Solenoids

The critical current of superconducting wires is measured at CERN in four test stations that use high-field superconducting solenoid magnets achieving up to 15 T. The reduction of the uncertainty in the critical-current measurements requires the field mapping of the solenoids in their operating condition. This paper presents the design and application of a solenoidal-field transducer based on a pair of nested induction coils, which are moved along the axis of the magnet. The system allows to extract the longitudinal and transverse field components as a function of the sensor's longitudinal position. The radial dependence of the magnetic flux density can be estimated directly from the nested coils of different diameters validated by applying the theory of pseudo-multipoles in solenoidal magnets. The results and uncertainties of the field mappings are presented.

Development of Prototype MGB 2 Superconducting Solenoid Magnet for High-Efficiency Klystron Applications

A wind-and-react MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> solenoid magnet for klystrons has been developed. While the current normal-conducting (Cu) magnet consumes 20 kW per magnet, this MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> magnet consumes less than 3 kW in refrigerator power. The conduction-cooled half coil of the magnet is 337 mm in inner diameter; the winding pack, 19.4 mm wide × 136.6 mm high, uses 2.7 km of 10 filament circular conductor, which is insulated with glass 0.83 mm in diameter, and is reacted after being wound onto a stainless steel bobbin. The coil has Cu plates of 0.2 mm in thickness between each coil layer and on the inner and outer sides. The magnet has two coils and produces 0.8 T in the center and its stored energy is 11.8 kJ. Together with the above-mentioned coil structure, these coils can consume stored energy in itself at quench without a special quench protection system. A performance test of the magnet was successful.

Analysis of the Mechanical Behavior of the KSTAR CS Magnet During Long-Pulse Plasma Discharges

The KSTAR central solenoid (CS) magnet consists of four pairs of coils stacked vertically and eight preloading structures that compress the coils in the axial direction. The strain and dis-placement of the CS magnet are monitored in real time, limiting the minimum compression as an important parameter of the supervisory interlock system for the safe operation of KSTAR. An equivalent vertical force method for a simplified multi-spring system was developed to analyze the preload and displacement variations of the CS magnet. The equivalent vertical force is based on the plasma and poloidal field (PF) coils currents during plasma discharge. The estimated displacements by the developed method agreed fairly well with the measured displacements of the long-pulse plasma discharges in 2017 (#18437) and 2018 (#21735) campaigns. The analyzed displacement can be used to simply estimate the remaining preload of the CS coils. This approach will contribute to the development of advanced operation scenarios for large plasma current and long-pulse discharges. By applying this algorithm to the plasma control system, the CS magnet can be controlled more safely during KSTAR operation.

The CLAS12 Spectrometer at Jefferson Laboratory

The CEBAF Large Acceptance Spectrometer for operation at 12 GeV beam energy (CLAS12) in Hall B at Jefferson Laboratory is used to study electro-induced nuclear and hadronic reactions. This spectrometer provides efficient detection of charged and neutral particles over a large fraction of the full solid angle. CLAS12 has been part of the energy-doubling project of Jefferson Lab’s Continuous Electron Beam Accelerator Facility, funded by the United States Department of Energy. An international collaboration of 48 institutions contributed to the design and construction of detector hardware, developed the software packages for the simulation of complex event patterns, and commissioned the detector systems. CLAS12 is based on a dual-magnet system with a superconducting torus magnet that provides a largely azimuthal field distribution that covers the forward polar angle range up to 35∘, and a solenoid magnet and detector covering the polar angles from 35° to 125° with full azimuthal coverage. Trajectory reconstruction in the forward direction using drift chambers and in the central direction using a vertex tracker results in momentum resolutions of <1% and <3%, respectively. Cherenkov counters, time-of-flight scintillators, and electromagnetic calorimeters provide good particle identification. Fast triggering and high data-acquisition rates allow operation at a luminosity of 1035 cm−2s−1. These capabilities are being used in a broad program to study the structure and interactions of nucleons, nuclei, and mesons, using polarized and unpolarized electron beams and targets for beam energies up to 11 GeV. This paper gives a general description of the design, construction, and performance of CLAS12.

AC Loss Measurement of the DEMO TF React&amp;Wind Conductor Prototype No. 2

The EUROfusion DEMO is being designed as the fusion machine to be built after ITER. During the preconceptual phase, several design options are investigated by theoretical analyses as well as tests on newly developed conductor prototypes. One design option for the toroidal field magnet (TF) and central solenoid (CS) is based on flat Nb 3 Sn forced-flow conductors made with react&wind technique. The usage of these conductors simplifies some steps in the conductor and coil manufacturing, and together with graded layer-winding allows approx. 50% reduction of the required amount of Nb 3 Sn compared to ITER-like design based on wind-react-insulate pancake-winding. Two full-size prototype cables for DEMO TF coil were manufactured, jacketed and tested in several test campaigns in SULTAN test facility. The DC results for the second prototype, RW2, rated for 63 kA at 12.3 T, were presented and published in 2018. The AC loss data were collected over several test campaigns performed on various assemblies of RW2 at AC field parallel and perpendicular to the broad cable side. The measurements done at 4.5 K and 20 K allow us to decompose the AC loss contributions originating from the bundle of superconducting strands (hysteresis and coupling loss) and copper-matrix stabilizer located around the cable. The AC loss for sinusoidal and trapezoidal field variations are presented and discussed. The low AC loss of the flat cable makes the cable an attractive choice for the central solenoid operating in a pulse mode.

A Modified Mechanical Model for the Optimization of High Field Solenoid Magnets

A modified mechanical model for the stress analysis of solenoid pulsed magnets is presented, which includes the influence of bending on the plane stress analysis. The bending effect in the axial direction is included by introducing the discrete axial strain with the assumption of the uniform distribution of the axial force load. The modified model improves the accuracy remarkably compared to the classical Generalized Plane Strain (GPS) analysis. The results are verified with the FEA software. The algorithm of identifying the optimum positions of the separations between windings is also proposed. This model achieves both high efficiency and high precision, which are of great significance to optimize high field solenoid pulsed magnets and explore the existing potential for higher magnetic fields.

Electromagnetic Analysis on 2.5MJ High Temperature Superconducting Magnetic Energy Storage (SMES) Coil to be used in Uninterruptible Power Applications

Abstract In recent years, due to the digitization of the electrical devices electric load demand has been increased. Power security and stabilization are the other two challenges which necessitate the need of electrical energy storage. Along with the technological constraints, economical and environmental issues are the other challenges in the development of energy storage technologies. Fast response and high energy density features are the two key points due to which Superconducting Magnetic Energy Storage (SMES) Devices can work efficiently while stabilizing the power grid. Two types of geometrical combinations have been utilized in the expansion of SMES devices till today; solenoidal and toroidal. It has been found that the solenoidal arrangement is easier to fabricate and provides efficient approach to handle stresses produced by Lorentz forces. This work represents the development of 2.5MJ SMES solenoidal Magnet using 2G (SuperPower, YBCO having Tc=90K @ 0T) HTS tape. The effect of the operating current (passing through a single superconducting tape) has been evaluated. A reference magnetic flux of 3.5T has been considered in designing of HTS SMES. It has been found that the parallel fields for solenoidal magnet are large as compared to perpendicular fields which results into large magnitudes of Lorentz forces acting on HTS tape which may leading to structural instabilities and can cause failure. It has been concluded that higher currents can be used in order to lower down the total length of the superconductor as it can reduce the overall cost of the device

Advances in Superconducting Detector Solenoid Magnets and the Future Prospect

Advances in Superconducting Detector Solenoid Magnets and the Future Prospect

Superconducting Solenoid Magnets for Muon Source

Superconducting Solenoid Magnets for Muon Source

A new design of divided solenoid with high homogeneity based on linear programming

A novel divided solenoid with high homogeneity is designed through linear programming (LP) for actual guiding magnet application in high power microwave devices. During the LP process, current density, magnetic field homogeneity, and total volume of coils are set as variable, constraint condition, and objective function, respectively. The divided solenoid is designed after calculating current density in the available zone where the coil current exists. After comparing the electrical parameters and magnetic field distribution of the conventional and the new solenoid, it is concluded that the inhomogeneity of the new design is reduced from 10% to 0.7%, the central magnetic field is equal, and other factors are in the same range. The divided solenoid magnet designed by LP is able to achieve high uniformity by improving the winding process and mechanical structure, which also has strong generalization.

Effect of Substrate Layer Thickness on the AC Losses in Stacked Superconducting Pancake Coils using Direct H-formulations

Advanced electric aircrafts are in their design phase and superconducting machines are going to be the part of such fascinating technology. In order to diminish the losses involved due to conventional copper conductors, superconductors are proposed for the electric aircraft applications by the American research agencies like NASA and AFRL. Usually, Pancake coils are frequently used in various electric aircraft power applications including high speed motors, generators, transformers and solenoid magnets. Coils are generally bound with high temperature superconducting (HTS) tapes like BSCCO and YBCO. Mostly, 2nd generation coated conductors (YBCO) are employed in power applications due to their merits over BSCCO (1st generation tapes). A superconducting tape manufactured by SuperPower through iBAD manufacturing technique generally consist copper stabilizer, silver over-layer, YBCO layer, buffer layer, substrate material followed by copper stabilizer. The volume fraction of the substrate material and copper stabilizer is more than 90% in the proposed tape. In the present work, the thickness of the substrate material has been varied to evaluate the AC losses involved in the above mentioned applications due to time-varying magnetic fields. A current of 270 A (Ic=330 A) is flowing through a coil of 108 turns. AC loss has been evaluated for various thicknesses 30 μm to 90 μm at a frequency of 50 Hz. The simulations are done using COMSOL MultiPhysics® commercial software package.

A Comparative Study on the Performance of Marine Magnetohydrodynamic Motors With Helical and Linear Channels

A magnetohydrodynamic (MHD) thruster is a type of electric motors which moves electrically conductive fluids without any mechanical moving parts. In this study, a linear-type MHD thruster is compared with a helical-type MHD thruster that has the same channel length and volume. For this purpose, two analytical models are used to predict the behaviors of these two types of marine MHD thrusters. The analytical model used for the helical thruster is validated by comparison to the experimental data obtained by other researchers. To validate the analytical model used for the linear thruster, a thruster prototype is manufactured and tested. The results show that although the solenoid magnet of the helical-type thruster is much easier to get a higher magnetic flux density than the saddle-shaped magnet of the linear-type thruster, the efficiency and propulsion force density of the linear-type thruster are much better than those of the helical-type one. Therefore, the linear-type thrusters cannot be ignored simply because of the complexity of their coils.

Influence of Axial Pressure on Parameters of Single Pancake HTS Coil

The single pancake HTS coil (inner diameter (ID) 85 mm, outer diameter (OD) 96.5 mm, 35 turns) was investigated under axial pressure up to 12 tons in liquid nitrogen to test the influence of axial pressure on critical properties in a central plane of designed HTS double pancake–based 3 T solenoid magnet for magnetic refrigeration machine. It was shown that 15-μm thick Al2O3 oxidized coating of the aluminum disk (which was used as a heat-conducting structure) is stable (in terms of breakdown voltage and mechanical strength) with such a loading. Critical current of pancake coil does not change with axial compression up to 30 MPa pressure and starts to decrease irreversibly if P > 30 MPa. Designed axial pressure level in 3 T magnet does not exceed this permissible boundary.