Superferric Magnet Research Articles

Analysis of the Eddy Current Relaxation Time Effects in the FAIR SIS 100 Main Magnets

The magnetic properties of main accelerator magnets operated in a static mode are dominated by the two-dimensional symmetry. In case of fast-pulsed magnets, the calculation of the electromagnetic dynamic properties becomes a three dimensional problem. Additional conductive design elements, high packing density of the iron yoke, and the ratio of the aperture size to the magnet length increase the complexity of the problem. We analyse the electrodynamic effects for the superferric SIS100 main magnets, with help of finite element methods (ANSYS). Besides a calculation of the characteristic AC loss, special effort is made to define the relaxation, time spectra of the magnetic field and their impact on various operations modes. Typical relaxation time values are found to be in the order of 5 seconds. This time frame is on the order of the required supercycles. Therefore, these effects are significant for the dynamic properties of the full size dipoles and quadrupoles.

The 100000 Amp DC Power Supply for a Staged Hadron Collider Superferric Magnet

A 1.5 volt 100000 A DC switcher power supply was developed for testing a superferric magnet string at Fermi National Accelerator Laboratory, FNAL. This supply was used during testing as both the ramping supply and holding supply powering a single magnet load with a total load resistance of 0.7 muOmega. The supply consists of ten paralleled switcher cells, powered by a 400 V/600 A DC power supply. Each cell consists of an IGBT H-bridge driving a step-down transformer at a switching frequency of 2 kHz. The transformer has an effective turns ratio of 224:1. The secondary consists of 32 parallel single-turn full wave rectifier windings. The rectification is done with 64 Shottky diodes. Each cell is rated at 1.5 V/10000 A. During this test each cell was operated as a constant power source without load current or field feedback. This paper will describe the design of the switcher cell and control system used during testing. We will also describe the next level of improvements to the current feedback system to improve the ramp control

Design of a Superferric Quadrupole Magnet With a High Field Gradient

FAIR, a new international accelerator complex is now being developed by GSI (Darmstadt, Germany). The synchrotron SIS100 is a part of this complex and will be equipped exclusively with fast-cycling superferric magnets. The magnet system of this accelerator includes 168 identical quadrupoles with a maximum gradient of 33.4 T/m in an elliptical useable aperture of 120 mm times 65 mm. An important requirement of the quadrupole design is a field gradient uniformity better than plusmn0.06% for field gradient variation range of 3 T/m-3.3 T/m. This goal is achieved by introducing slots in the central part of the magnet poles, creating the effect of artificial saturation. Simultaneously, these slots reduce the eddy currents in the yoke, induced by the current ramp in the magnet coil. This is important because the whole magnet will be operated near 4.2 K, so the power loss in the yoke should be minimized. Additionally, the shape of the quadrupole pole ends was optimized to provide the necessary integral field quality

3-D Transient Process Calculations For Fast Cycling Superferric Accelerator Magnets

Fast cycling superferric magnets are planned for use in the new International Accelerator Facility for Antiprotons and Ion Research (FAIR) at GSI, Darmstadt. The efficiency of this magnet is basically defined by the AC loss at liquid helium temperatures in the construction elements of the dipoles and quadrupoles (iron yoke, coil, beam pipe restraints and suspension). A detailed knowledge of the 3D magnetic field, the eddy current distributions and their transient behavior is necessary to minimize the hysteresis and the eddy current losses through the use of an appropriate design. Methodical problems are considered for finite element calculations (ANSYS) of eddy currents in a laminated iron yoke. The results for window-frame dipoles and quadrupoles of the Nuclotron type are given. We present the influence of nonlinear and anisotropic magnetic and electrical properties of laminated steel and of bulk restraint elements

Progress in the Design and Study of a Superferric Dipole Magnet for the GSI Fast-Pulsed Synchrotron SIS100

New experimental results from the investigation of a superferric window frame type dipole magnet with the operating parameters: B=2T, dB/dt=4T/s and pulse repetition rate f=1Hz are presented. The magnet SC coil is made from a hollow multifilamentary NbTi cable, cooled with two-phase helium flow. Special attention is devoted to minimization of AC power losses in the magnet to the specified value of 13W/m. The value of 9W/m has been obtained for a model magnet with the yoke at T=50K. Different possibilities were investigated to reduce the losses in the case of a cold iron yoke (T=4.5K). Other problems, connected with the magnetic field quality, mechanical and cryogenic stability of the magnet under SIS100 operating conditions are also discussed.

Design of a Superferric Dipole Magnet With High Field Quality in the Aperture

A project to design and construct a new international accelerator was proposed by GSI (Darmstadt, Germany). This project includes the design of several new facilities. One of them is a collector ring (CR). The magnets of the CR operate at constant field (DC), but the level of this field varies for different operational tasks. The magnet system of the CR includes 24 deflecting dipole magnets. The maximum operating field in the aperture is 1.6 T, with a deflection angle of 15 degree, and a bending radius of 8.125 m. The most important requirement for this dipole is a high field uniformity (better than /spl plusmn/0.01% over a volume of 380 mm /spl times/ 150 mm). This requirement must be met for all levels of magnetic flux density in the aperture. Several magnet designs have been investigated including window frame and H-type versions with normal and superconducting coils. The best economical and technical parameters were obtained for a superferric H-type magnet with a wide air filter in the pole. The field homogeneity requirements were fulfilled in such a magnet for field range of 0.2-1.63 T. The effects of the field distortion in the end parts of the magnet, as well as influence of the end plates on the field quality, were also investigated.

Hydrogen Cooled Superferric Magnets for Accelerators and Beam Lines

The possibility of superferric accelerator and beam line magnets is described. A cooling system that is not helium and nitrogen based, but one based on hydrogen, is proposed to make full use of the recent MgB/sub 2/ superconductor around 20 K. A hydrogen cooling system is more effective than the nitrogen cooling for usual high T/sub c/ superconductors around 70 K. Liquid hydrogen is also excellent as refrigerant for high T/sub c/ superconducting apparatus to increase the critical current and to provide a self-sustained cooling system by means of a combination of evaporated hydrogen and a fuel cell. This paper also discusses hydrogen safety issues, as compared to that of helium and nitrogen. It is expected that dipole magnets for a synchrotron would be good candidates for a superferric design based on these principles.

Superferric magnets for the proposed international accelerator facility at GSI

The proposed International Accelerator Facility at Gesellschaft fur Schwerionenforschung (GSI) has several new experimental devices that may require superconducting magnets to provide the required magnetic fields. Superferric magnets have been designed that allow the production of the required high gradients in the large aperture quadrupoles and also allow the insertion of sextupole and octupole inserts. Dipoles have been designed that fulfill the field uniformity and radiation resistance requirements. Most of the magnets are static field, but the New Experimental Storage Ring (NESR) needs magnets that ramp at 1 T/s. Solutions are presented that use warm iron to reduce losses.

Superferric model dipole magnet with the yoke at 80 K for the GSI future fast cycling synchrotron

Experimental data of a fast cycling (f=1 Hz) 2T dipole magnet based on a superconducting NbTi multi filament hollow cable cooled with forced two phase helium flow at T=4.5K and iron yoke at T=80 K are presented. A new magnet design is proposed. The magnet yoke made of laminated steel consists of two parts: the internal smaller part has close mechanical and thermal contact with the coil while the outer part is separated from the cold mass with a gap of 1 mm and cooled with liquid nitrogen.

MAGNET R&D FOR A FUTURE VLHC

Superconducting magnets are the underlying technology for all existing and future hadron colliders. A vigorous national R&D effort has been launched to improve magnet performance and reduce costs. Various designs are being considered including a low-field superferric magnet that could be the first step in a staged construction of a Very Large Hadron Collider. High-field magnets are being developed based on cosine-theta, block, and common-coil arrangements using both wind-and-react and react-and-wind fabrication techniques. A review of the different magnet R&D programs and the status of each is presented. An important part of the national effort is an R&D program to improve the performance and lower the cost of Nb3Sn superconducting wire.

Design of a superferric quadrupole magnet for the RIKEN RI-beam factory project

Two superferric quadrupoles with a pole-tip radius of 170 mm and a maximum pole-tip field of 2.4 T are designed for the BigRIPS projectile fragment separator at RIKEN. Taking the feasibility of coil winding into account, the shape of quadrupole coil has been optimized.

Design optimization of a superferric octupole using various evolutionary and deterministic techniques

The paper describes different strategies for the design optimization of electromagnets. In order to compare the efficiency of these procedures, the same objective weighting function was minimized using a deterministic search algorithm, evolution strategy, and genetic algorithms. The objective function is based on minimizing the relative normal multipoles produced by the harmonic analysis of the flux density produced by the pole. The pole shape was treated differently in applying the various techniques to the problem. The optimization techniques were independently applied to optimize the magnet's shape. Results of the numerical solution as well as the harmonic analysis were compared. The methods are tested on an example of a superferric octupole magnet. Good results from the various techniques was achieved. A discussion on the practical aspects of these optimization methods is presented.

Guide lines for the design of very large aperture quadrupole magnets

Very large aperture quadrupole magnets have been recently considered as possible spectrometers on high energy colliders. The interesting characteristics are zero field on beam axis, low fields at small angles, transverse field at large angles. Dimension range is 1 m to 5 m for clear bore and 2 m to 8 m for length; typical maximum field is 2.5 T. Superconducting magnets with cosine 2/spl theta/ structure, coils with one or two layers and iron yoke have been modelised. Use of two types of conductors have been investigated: Rutherford cable and aluminium stabilized composite. The paper describes the optimization procedure and gives diagrams of feasibility. Two alternative structures are mentioned: superferric and active shield magnets.

Superferric magnets for fast levitated trains

A new technology for high-speed magnetically levitated train (MAGLEV) transportation is being developed. The technology is based on self-shielded superferric magnets which provide guidance and levitation at above 50 mph'. A linear motor is used for propulsion. The levitation and guidance superconducting magnets are distributed along the entire length of the cars. The superferric magnet shields the fringe field within the car to less than 5 G. Magnetic details and initial calculations of dynamics are presented.

Superferric correction magnets for the SSC

Four models of a superferric correction quadrupole magnet were constructed for possible use in the SSC (Superconducting Super Collider); one of them was tested. The design incorporates a coil winding process. This process uses ultrasonic energy to accurately adhere a Kapton-wrapped superconducting wire in a racetrack configuration onto a substrate material 0.010 cm thick. The substrate is subsequently rolled around a frame in much the same way that a jelly roll is made. The use of iron to shape the field improves efficiency and provides a coil package preload. Design parameters and performance data are provided for the quadrupole magnet.

The high field superferric magnet: Design and test of a new dipole magnet for future hadron colliders

The Texas Accelerator Center has successfully tested a 6 T superferric dipole magnet of a design appropriate for future hadron colliders. The magnet surpassed the design field (90% of the short sample limit) on its first quench without training. The measured field quality is in excellent agreement with design calculations and meets collider requirements. The magnetic field design was developed at Rice University and is the subject of a Master's thesis. The features of the design include simple construction, efficient use of superconductor, and adequate containment of magnetic forces. A straightforward extension of the design to an 8 T dipole is under development. The high-field superferric magnet constitutes a significant improvement in magnet performance and cost for future accelerators.

Ultraprecise superferric storage ring magnet for the Muon G-2 experiment

A new measurement of the anomalous magnetic moment (G-2 factor) of the muon to a precision of 0.35 p.p.m. is being undertaken with the AGS at Brookhaven National Laboratory. It will involve a precision superferric storage ring with a magnetic field of 1.5 T and a radius of 7 m for 3.1 GeV/c muons. The magnetic field in the storage region must be homogeneous to one part in 10/sup 6/ and the effective field averaged around the ring must be known to 1 part in 10/sup 7/. The design status of the superferric storage ring and of the techniques planned for magnetic-field control and measurement are presented. Perturbation field calculations for the iron and coil configuration, considerations on the superconducting coil, shimming and measurement techniques, and plans for a test magnet program are discussed. >

Design and testing of superferric magnets for accelerators

The Texas Accelerator Center has designed, constructed and tested 26 accelerator magnets. The magnets are 3 tesla superferric magnets. Three currents are used to fix the dipole field and zero the sextupole and decapole. High quality magnets, which are simple and inexpensive, are obtained. Three 28 meter magnets have been constructed in industry as well as five 1 meter magnets.

Monitoring the magnetic properties of iron for large scale production of superferric magnets

An automated system for measuring critical ferromagnetic properties of iron sections of superferric magnets from low to high magnetic intensities has been developed and used at the Texas Accelerator Center in conjunction with the construction of the superferric SSC magnet prototypes. The system is readily adaptable to production line measurements and would be an indispensable quality control tool in the construction of production steel lamination cores for superferric systems, such as particle accelerators.

A high field two mode superferric magnet

We have designed and are building a high field Two-Mode (TM) superferric dipole magnet for particle accelerators. At low field it behaves as a ferric magnet while at high field as a \cos\theta magnet. While the magnet can go up to any field as can a \cos\theta magnet (limited by superconductor performance), the use of iron and rectangular rather than radial geometry retains the advantages of low field ferric magnets: substantial superconductor saving, more reliable operation, and easy fabrication.