Air-core Magnet Research Articles

Design a H-bridge low ripple and high bandwidth air core magnet corrector power supply in NSRRC

This paper is the study of a low-current-ripple and high-bandwidth corrector power supply. The main circuit of this power supply is using a full bridge (H-bridge) structure, and the output current through the high-precision direct current current transducers (DCCT) to transfer the reference voltage to the controller. Previous TPS corrector power supply had a 4.7 kHz current bandwidth, and its output current ripple was 100 μA. Such current ripple and bandwidth do not satisfy the requirements of a rapidly orbiting feedback system of air core loading. Therefore, our research team designed a novel prototype power supply with a high bandwidth (more than 10 kHz) and low output current ripple (less than 10 μA) which was developed via a novel topology circuit. The operation frequency of the main power switch's n-type metal-oxide-semiconductor logic of this novel circuit is increased to 245 kHz. Moreover, the output results of the filter inductor and filter capacitor are modified to 80 μH and 2.46 μF, respectively. The prototype power supply bandwidth reached 10.546 kHz and increase of 124% and its output current ripple was lowered below than 5 μA. The properties of this corrector power supply are very important for the beam correction in storage rings. Finally, A circuit with an input voltage of 48 V, a maximum output current of 10 A, and an output power of 400 W is tested in a laboratory to verify the performance of the developed corrector for the National Synchrotron Radiation Research Center.

Conceptual Design of DUNE Near Detector Superconducting Magnet System

The Deep Underground Neutrino Experiment (DUNE) formed a near detector design group (NDDG) which was tasked with delivering a CDR by the end of 2019. The DUNE Near Detectors will be housed in an underground hall on the Fermilab site. The two main detector systems are a liquid argon detector and a high-pressure gas time projection chamber (HPgTPC). The HPgTPC requires a magnet that generates a 0.5 T solenoidal magnetic field in a large volume of 6 m diameter, and 5 m length. In this paper, we present a superconducting magnet system design. We investigated: an open air core magnet with three coils, and a five-coil s system having two active fringe field shielding coils. Coils positions were optimized to obtain the specified field homogeneity in the magnet good field region, while minimizing the Lorentz forces and the superconductor volume. We discuss the magnetic, mechanical, and thermal conceptual designs.

Measurement of Magnetic Field Properties of a 3.0 T/m Air-Core HTS Quadrupole Magnet and Optimal Shape Design to Increase the Critical Current Reduced by the Incident Magnetic Field

Air-core high-temperature superconducting quadrupole magnets (AHQMs) differ from conventional iron-core quadrupole magnets, in that their iron cores are removed, and instead high-temperature superconductors (HTSs) are applied. The high operating temperature and high thermal stability of HTS magnets can improve their thermodynamic cooling efficiency. Thus, HTS magnets are more suitable than low temperature superconducting magnets for withstanding radiation and high heat loads in the hot cells of accelerators. AHQMs are advantageous because they are compact, light, and free from the hysteresis of ferromagnetic materials, due to the removal of the iron-core. To verify the feasibility of the use of AHQMs, we designed and fabricated a 3.0 T/m AHQM. The magnetic field properties of the fabricated AHQM were evaluated. Additionally, the characteristics of the air-core model and iron-core model of 9.0 T/m were compared in the scale for practical operation. In comparison with the iron-core model, AHQM significantly reduces the critical current (IC) due to the strong magnetic field inside the coil. In this study, a method for the accurate calculation of IC is introduced, and the calculated results are compared with measured results. Furthermore, the optimal shape design of the AHQM to increase the critical current is introduced.

Comparative Study of Magnetic Characteristics of Air-Core and Iron-Core High-Temperature Superconducting Quadrupole Magnets

High-temperature superconductors (HTSs) have a much larger thermal margin than low-temperature superconductors, owing to their high critical temperatures. This characteristic allows HTS magnets to tolerate extremely high heat loads that may arise from radiation. Therefore, research on the development of HTS quadrupole magnets is progressing widely. Quadrupole magnets are commonly used for focusing the transported beams of particles in accelerators. In order to focus the beam, the quadrupole magnet uses an iron yoke with a hyperbolic contour. However, the iron yoke induces nonlinear magnetic characteristics because of saturation. Therefore, an air-core HTS quadrupole magnet is proposed to improve the magnetic characteristics. In this paper, we design air-core and iron-core HTS quadrupole magnet models using a harmonic matching method. The field gradient and effective length of both magnets are 12.1 T/m and 550 mm, respectively. In order to verify the performances of the proposed air-core quadrupole magnet, the magnetic field gradient, field uniformity, and effective length are analyzed for operating currents ranging from 50 to 400 A.

Comparative Study of Linear Permanent Magnet Generator with Different Shape of Permanent Magnet for Wave Energy Conversion

This paper presents the design of linear permanent magnet generator for wave energy conversion using finite element analysis software. Four designs have been proposed which are simple, lightweight, portable and can produce 100 Watt electric power. Air-cored linear permanent magnet generator have been chosen and their electromagnetic characteristic were analyzed using finite element analysis. The determined electromagnetic analysis reveals that rectangular permanent magnet arrangement (Rect-PM) design gives efficient performance as compared to other designs.

A compact solution for ion beam therapy with laser accelerated protons

The recent advancements in the field of laser-driven particle acceleration have made Laser-driven Ion Beam Therapy (L-IBT) an attractive alternative to the conventional particle therapy facilities. To bring this emerging technology to clinical application, we introduce the broad energy assorted depth dose deposition model which makes efficient use of the large energy spread and high dose-per-pulse of Laser Accelerated Protons (LAP) and is capable of delivering homogeneous doses to tumors. Furthermore, as a key component of L-IBT solution, we present a compact iso-centric gantry design with 360° rotation capability and an integrated shot-to-shot energy selection system for efficient transport of LAP with large energy spread to the patient. We show that gantry size could be reduced by a factor of 2–3 compared to conventional gantry systems by utilizing pulsed air-core magnets.

NESSiE: An experimental search for sterile neutrinos with the CERN-SPS beam

NESSiE (Neutrino Experiment with SpectrometerS in Europe) is an experiment dedicated to the search for sterile neutrinos beyond the Standard Model with the CERN-SPS neutrino beam. The experiment is based on two identical LAr-TPC's followed by magnetized spectrometers, observing the electron and muon neutrino events at the “Near” (600m) and “Far” (1300m) positions from the proton target. The main characteristics of the spectrometers are described here. Spectrometers will exploit a classical dipole magnetic field with iron slabs, and a new concept air-core magnet will perform charge identification and muon momentum measurements in the energy range from ∼100MeV to few GeV over a large transverse area (>50m2).

The magnet system for rapid scan electron paramagnetic resonance imaging and spectroscopy

The magnet and gradient systems suitable for electron paramagnetic res- onance imaging experiments at RF range are presented. The air-core magnet based on the Helmholtz design in the article has a unique conical shape. A comprehensive study regarding the coils adjustment providing for the maximum field homogeneity is given. The z gradient is a four-coil system (seventh order), the transverse gradients are Golay coils (fifth order), and the scan system is the Helmholtz coil (fourth order). The magnet generates continuously a field of 37 mT (370 G), and the orthogonal gradient coils are designed to yield 100 mT/m (10 G/cm). The experimental tests have shown that the field generated is homogeneous to 610 ppm in the 6 3 6 3 3c m 3 region (x/y/z), which is our field of interest, and to 650 ppm in the 8 3 8 3 4c m 3 region (x/y/z). The system has the potential to monitor temporal changes of oxygen concentration in biological samples. 2013 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 43B: 22-31, 2013

Application of Response Surface Methodology and Elitist Multi-objective Hybrid Particle Swarm Algorithm for Optimization Design of an Air-Core Linear Motor

The main purpose of this study was to find out the optimal design variables of an air-core linear brushless permanent magnet motor (LBPMM) by simultaneously considering the maximal thrust, minimal temperature, and minimal volume. Airgap length, magnet dimensions (magnet height and magnet width), and coil winding height were chosen as design variables in this multi-objective optimization problem. Using response surface methodology (RSM), this study developed a mathematical predictive model for each of the objectives. A multi-objective hybrid particle swarm optimization (PSO) with a mutation operator and a dynamic inertia weight factor was used to optimize the model developed by RSM. In addition, an elitist mechanism with crowding distance sorting was used to improve the correctness and diversity of the solutions. The results show that the Pareto-optimal front solutions of the proposed approach, providing the designers with more design plans, are superior to those of non-dominated sorting genetic algorithm ( NSGA II ). Designers can expand the effective method for designing linear motors to successfully solve more complex problems in other designed components.

Research on Axial Magnetic Force and Rotor Mechanical Stress of an Air-Cored Axial-Flux Permanent Magnet Machine Based on 3D FEM

Due to its compact construction and high power density, the axial-flux permanent-magnet (AFPM) machine with coreless stator has obtained more and more attention and interest from researchers. For an AFPM machine with coreless stator, the axial magnetic attraction force may cause the rotors’ deflection and affect the machine’s reliability. In this paper, the magnetic field and the rotor mechanical strength of a coreless stator AFPM machine are studied. Finite-element method and analytic method are both used to calculate the axial attraction magnetic force between the two rotor discs. Structure finite-element analysis is used to simulate the maximum stress and deflection due to the axial magnetic force. The research is very significant to the power density elevation of the AFPM machine.

Jefferson Lab injector development for next generation parity violation experiments

To meet the challenging requirements of next generation parity violation experiments at Jefferson Lab, the Center for Injectors and Sources is working on improving the parity-quality of the electron beam. These improvements include new electron photogun design and fast helicity reversal of the Pockels Cell. We proposed and designed a new scheme for slow helicity reversal using a Wien Filter and two Solenoids. This slow reversal complements the insertable half-wave plate reversal of the laser-light polarization by reversing the electron beam polarization at the injector while maintaining a constant accelerator configuration. For position feedback, fast air-core magnets located in the injector were commissioned and a new scheme for charge feedback is planned.

Upgrade of the ATLAS Muon Trigger for the SLHC

The outer shell of the ATLAS experiment at the LHC consists of a system of toroidal air-core magnets in order to allow for the precise measurement of the transverse momentum (pT) of muons, which in many physics channels are a signature of interesting physics processes [1,2]. For the precise determination of the muon momentum Monitored Drift Tube chambers (MDT) with high position accuracy are used, while for the fast identification of muon tracks chambers with high time resolution are used, able to select muons above a predefined pT threshold for use in the first Level of the ATLAS triggering system (Level-1 trigger). When the LHC peak luminosity of 1034 cm−2s−1 will be increased by a factor of 4–5 in about a decade from now (''SLHC''), an improvement of the selectivity of the ATLAS Level-1 triggering system will be mandatory in order to cope with the maximum allowed trigger rate of 100 kHz. For the Level-1 trigger of the ATLAS muon spectrometer this means an increase of the pT threshold for single muons. Due to the limited spatial resolution of the trigger chambers, however, the selectivity for tracks above ∼ 20 GeV/c is insufficient for an effective reduction of the Level-1 rate. We describe how the track coordinates measured in the MDT precision chambers can be used to decisively improve the selectivity for high momentum tracks. The resulting increase in latency will also be discussed.

Alignment of the ATLAS muon spectrometer with tracks

The muon spectrometer of the ATLAS experiment at the Large Hadron Collider is designed to measure the muon momenta of up to 1 TeV/ c with a resolution of better than 10% in a toroidal magnetic field of superconducting air–core magnets. The muon track sagitta is measured in three layers of pressurized drift-tube chambers. The precision muon chambers have to be aligned with an accuracy of better than 30 μ m in the track bending plane. An optical alignment system monitors movements of the muon chambers with a precision of few microns. In order to determine the chamber positions in the spectrometer, the initial chamber positions have to be measured with 30 μ m accuracy using straight muon tracks from proton–proton collisions in a dedicated run of the ATLAS detector with the toroid magnets turned off. A Least Square algorithm has been developed which determines the misalignment parameters of a complete azimuthal sector of the barrel part of the muon spectrometer. It has been tested with straight cosmic muon tracks during the commissioning of the ATLAS experiment. Simulations show that the required alignment accuracy is reached with 100,000 muons per sector originating from the interaction point with transverse momentum greater than 10 GeV. About half of the barrel chambers have already been aligned with 30 μ m accuracy using cosmic muons.

CONCEPTUAL DESIGN OF A SUPERCONDUCTING QUADRUPOLE WITH ELLIPTICAL ACCEPTANCE AND TUNABLE HIGHER ORDER MULTIPOLES

For charged particle beams that are wider in the dispersive plane compared to the transverse plane it is cost efficient to utilize magnets that accept beams with elliptic cross section. In this paper we presents the conceptual design of a quadrupole magnet with elliptic cross section and with tunable higher order multipoles. The design consists of 18 superconducting race-track coils placed on two hollow concentric rhombic prism support structures. To compute the magnetic field for the proposed design a new method of calculating 2D and 3D fields for the air core magnets based on differential algebra (DA) techniques is developed. We will present the new method and discuss its implementation of new numerical tools based on this method in the code COSY Infinity.

Design Concepts of Optimized MRI Magnet

This paper describes a simple technique to design compact air core magnets for magnetic resonance imaging (MRI). The optimum geometry is obtained by a combination of analytical and numerical methods. The technique emphasizes achieving the required field homogeneity with a shorter magnet having a minimum amount of ampere turns. The code calculates the total inductance of the set of coils, total conductor length, force, and maximum field on each coil. The code also calculates the allowable geometrical tolerance to achieve the field uniformity. The code is flexible and can be used for various geometries. Here, we present three different cases to demonstrate the efficiency of the code. First, we present the design details of a 1.5 m long 1.5 T actively shielded magnet, where the stray field is reduced to less than 4 gauss outside the sphere of radius 3.65 m using a pair of shielded coils. A total of four pairs of coils provide a field uniform to within 5.2 parts per million (ppm) within a sphere of 50 cm diameter. Calculated values of all the higher order moments lie within a few ppm. Second, we describe optimized geometry of unshielded 1.5 T symmetric magnets having three pairs of coils. Third, we optimize the geometry of a 1.2 m long 1 T asymmetric magnet having five coils. Here, the good field region starts at 20 cm from one of the edges of the magnet, providing the attending physician better accessibility to the patient. But the ampere turns and computation time required are quite large compared to a symmetric magnet.

First experience with the ATLAS muon spectrometer

The ATLAS experiment at the Large Hadron Collider (LHC) at CERN is currently being assembled to be ready to take first data in fall 2007. Its muon spectrometer is designed to achieve a momentum resolution of better than 10% up to transverse muon momenta of 1 TeV. The spectrometer consists of one barrel and two endcap superconducting air-core toroid magnets instrumented with three layers of precision drift chambers as tracking detectors and with a dedicated trigger system. We report on our experience with the commissioning and installation of the precision and trigger chambers. First results of the cosmic ray test of the barrel muon spectrometer with magnetic field are presented, including results of the calibration of the drift chambers and of the spectrometer alignment.

Integration, commissioning and installation of monitored drift tube chambers for the ATLAS barrel muon spectrometer

The ATLAS experiment at the Large Hadron Collider (LHC) at CERN is currently being assembled to be ready to take data in 2007. Its muon spectrometer is designed to achieve a momentum resolution better than 10% at 1 TeV. In the barrel part, a toroidal air-core magnet is instrumented with three layers of Monitored Drift Tube (MDT) chambers for precision tracking. The Max-Planck-Institut für Physik and the Ludwig-Maximilians-University in Munich have built 88 MDT chambers for the outermost barrel layer. We report on our experience with the tests of the MDT chambers, their integration with the Resistive Plate trigger chambers and the installation of the muon stations in the experiment. First results of their commissioning in the ATLAS detector will be presented.

Completion of the Manufacturing of the ATLAS Barrel Toroid Magnet at CERN

The last two years have seen the completion of the integration and the cryostating of 8 superconducting coil windings for the ATLAS Barrel Toroid air-core magnet (BT). The Barrel Toroid is a 20 m in diameter, 25 m long and 5 m wide superconducting magnet for ATLAS, one of the two experiments dedicated to the search of the Higgs boson, which will be installed on the LHC ring at CERN in 2006. The paper presents the last steps of this integration progress which ends with the cold acceptance tests. A special emphasis is put on the integration of the cold mass into the vacuum vessel. The integration of the windings in their coil casings has been completed in October 2003 and the last coil cryostating was performed in June 2005. The BT coils are now being installed in the ATLAS cavern at CERN

Improvement of Open Boundary Magnetic Field Analysis of Air-Core Magnet Using High Order Boundary Sensitivity

This paper presents a new approach to the finite element open boundary problems using high order boundary sensitivity. The finite element method (FEM) gives the solution with boundary truncation error in the open boundary problems like air-core magnet. And it doesn't inform us of the precision of solution. In order to overcome the weakness of FEM, the high-order energy sensitivity method is proposed. It is based on the sensitivity analysis technique. It can be used for the check on the precision of solution and suggest the proper boundary. It was applied to the finite element analysis of air-core magnet to validate the proposed method.

ATLAS End Cap Toroid Magnets Cryostat Design, Manufacture and Integration at CERN

The ATLAS experiment at LHC, CERN will utilize a large, superconducting, air-cored toroid magnet system, with a long barrel and two end cap toroids. Each end cap toroid will contain eight racetrack coils mounted as a single cold mass in a cryostat vessel of approximately 10 m diameter. This paper presents the engineering design of the cryostat: vacuum vessel, thermal radiation shields and superinsulation. The manufacture of the major components is described with reference to the key factors for operation. The delivery to CERN and integration of the main components to form the cryostat assembly is described.