C-shaped Magnet Research Articles

Magnetic Form applying a C-Shaped Magnet for Hybrid Electric Vehicles

Magnetic Form applying a C-Shaped Magnet for Hybrid Electric Vehicles

Heating Characteristics of a HTS DC Induction Heater for Aluminum Billets

The heating process of aluminum billets requires controllable temperature distributions and high efficiency. Comparedwith conventional ac induction heaters, the high temperature superconductor (HTS) dc induction heater has advantages ofenergy saving and better heating quality. In this paper, a HTS magnet is designed to achieve controllable temperaturedistribution for dc induction heater. A C-shaped iron yoke is used to separate HTS coils and billets. An aluminum billetis rotated in the air gap of the C-shaped magnet. Magnetic field distribution can be changed through adjusting width ofthe air gap. Therefore, the temperature gradient in axial direction is controllable. A dc induction heater prototypeusing this design is fabricated and its heating characteristics are tested. A numerical model is built to simulateheating process and temperature distributions of aluminum billet. Various uniform and gradient temperature distributionsof a billet are measured and compared with numerical results.

In vivo high‐resolution 3D Overhauser‐enhanced MRI in mice at 0.2 T

Overhauser-enhanced MRI (OMRI) offers the potentiality of detecting low-concentrated species generated by specific biological processes. However molecular imaging applications of OMRI need significant improvement in spatial localization. Here it is shown that 3D-OMRI of a free radical injected in tumor-bearing mice can be performed at high anatomical resolution at a constant field. A 30 mm cavity operating at 5.43 GHz was inserted in a C-shaped magnet for proton MRI at 0.194 T. Nude mice with or without brain-implanted C6 rat glioma were positioned in the cavity and injected with TOPCA (1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole-3-carboxylic acid). OMRI was performed in 3D within several minutes in the brain region without high overheating of the animals. Voxel size was 0.5 × 0.5 × 1 mm³ , providing good delineation of brain regions. Signal amplifications ranged from 2 in tumors to 10 in vessels several minutes after TOPCA injection. Time-course of signal enhancement could be measured by 2D OMRI at 15 s time intervals in a localized thin slice. The method opens the way for molecular imaging of biological activities able to generate OMRI-visible free radicals.

Direct Lorentz force measurement for YBa 2Cu 3O 7–δ superconductor

This study introduced a novel method using a modified helium gas closed cycle cryogenic system to measure the force acting on a C-shaped magnet by a YBCO superconductor with bias current as a function of temperature. The results showed that the measured force agrees with Lorentz force due to the bias current for normal conductor at temperature higher than the superconducting transition temperature, as expected. However, under a temperature at the beginning of the superconducting transition region, the measured force became larger than the expected Lorentz force. As temperature further decreased, the measured force gradually dropped to zero. A qualitative argument based on the Bean’s model was given to explain the peak in the measured force at the beginning of the transition temperature.

An integrated head-holder/coil for intraoperative MRI in open neurosurgery.

With the invention of "open" magnetic resonance imaging (MRI) systems, access to the patient is possible during the imaging procedure. An important application of these systems is intraoperative MRI to control the extent of resection during tumor surgery. Up to now flexible surface coils wrapped around, or placed at each side of the head, were used for imaging. These flexible coils have several disadvantages such as unreliability, interindividual problems, difficult handling, poor hygienic properties, and often unsatisfactory or inhomogeneous image quality. To solve most of these problems, an MR-compatible head-holder in combination with an integrated surface coil for use in a 0.2 T C-shaped magnet was developed. Forty-eight patients with known cranial tumors underwent MRI intraoperatively. In 32 patients (67%), residual tumor was found, and additional surgical resection was performed. The integrated head-holder/coil is a safe and practical tool for intraoperative MRI, providing efficient and reliable resection control during neurosurgical procedures.

Compact storage rings Siberia-AS and Siberia-SM synchrotron radiation sources for lithography

The paper deals with two projects of compact superconducting storage rings for industrial production of integrated circuits (IC) using x-ray lithography within the 8- to 20-Å wavelengths range. The azimuthally symmetric superconducting storage ring Siberia-AS at an energy of 600 MeV is a superconducting analog of VEP-1, one of the earliest storage rings in the world intended for the purposes of high-energy physics. Unlike the conventional design, no iron yoke is used in the storage ring under consideration to form the magnetic field at the equilibrium orbit and to close the return magnetic flux—this is performed by some inner and outer superconducting windings. Such a scheme enables the size of the storage ring to be substantially reduced (a cylinder of 2 m in diameter and 2 m long), and as a result, its weight decreases, too (about 10 tons). The eight-magnet storage ring Siberia-SM is of four-order symmetry so that the periodicity element comprises two rectangular magnets and three lenses. Its basic component is a superconducting bending rectangular magnet at a 6-T magnetic field. Two variants of such magnets have been proposed: in the first, the iron yoke is utilized to form the magnetic field and to close the return flux, while the second is an ironless C-shaped magnet manufactured on the basis of original wedgelike coils.

Three-dimensional magnetostatic field calculation using boundary element method

The boundary-element calculation of three-dimensional magnetostatic field problems using the reduced and total magnetic scalar potential formulation is described. The method is based on a boundary integral equation that can be derived from Green's theorem. Two regions, a current-free iron region and an air region including the source domains, are considered. The material properties of the iron are assumed to be linear and either isotropic or anisotropic (orthotropic). Two examples are investigated: a C-shaped magnet and an iron cylinder of finite length immersed in the magnetic field of a cylinder coil.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Magnetic Analyzer for Nuclear Reaction Products

A magnetic analyzer for nuclear reaction products has been built which employs a sector-shaped uniform magnetic field. The shaped sectors are inserted in the 8.5-in. gap of a C-shaped magnet with a 12×12 in. cross section. The iron core is 54×33 in., and 69 360 ampere-turns give 13 500 gauss across a total air gap of 1⅝ in. In the notation of W. G. Cross, [Rev. Sci. Instr. 22, 717, (1951)], the parameters were: ρ=15 in., φ=60°, useful gap=1.5 in., l′=22.5 in., l″=45 in., ε1=+46°38′, ε2=−18°21′, max usable α=±3°, max usable ω=±1.6°. The entrance boundary was straight, and the exit boundary had a convex curvature of 123.7 in. The boundaries of the sector and the locations of the object and image positions were corrected for the effect of the fringing field. The observed l″ was 46.5 in. Fringing field focusing in the direction perpendicular to the plane of deflection was not as strong as calculated; the maximum image height was 2 in. The magnet is capable of bending 12-Mev protons and has an energy resolution of 300 for the maximum useful solid angle of 1/2000 of 4π steradians. The observed maximum energy resolution was 400. The advantages of this magnet are simplicity of construction and ease of adaptation to other sector parameters.