Target utilization of planar magnetron sputtering using a rotating tilted unbalanced yoke magnet

The dependence of the magnetic flux density, erosion uniformity, and target utilization on the yoke magnet tilt angle was investigated in a planar magnetron sputtering system, using a rotating, tilted, unbalanced, asymmetrical magnet. In these experiments, circular and elliptical outer yokes were used as the rotating yoke magnet. The magnetic flux density distributions were measured two-dimensionally on the target surface and compared with the erosion uniformity. As the yoke magnet tilt angle increased, the magnetic flux density distribution expanded and became more uniform, and the eroded areas expanded toward the outside of the target surface. With a circular outer yoke, as the yoke magnet tilt angle increased from 0° to 8°, utilization of a 5-inch target linearly increased from 60 to 80%. On the other hand, with an elliptical outer yoke, the utilization of the target was approximately 70%, regardless of the yoke magnet tilt angle. This is because, as the tilt angle is increased, the inner area of the target eroded more deeply, while the outer area eroded less deeply. The deposition rate when using the elliptical outer yoke was 1.2 times faster than that of when using the circular outer yoke at the same magnet tilt angle. By decreasing the magnetic flux density on the inner area of the target with an elliptical outer yoke magnet, a higher deposition rate may be obtained than is observed with a circular magnet, and target utilization of over 70% can be achieved.     

偏转磁芯中磁滞损耗的估测

通过空间磁场和感应电压的测量,对偏转磁芯中的磁通密度分布进行了计算,并根据磁滞损耗的经验公式对Philips17英寸CMT的磁滞损耗进行了估测。该方法适用于降低能量损耗的偏转系统磁芯结构的优化和磁性材料的选择等。     

Measuring the Magnetic Flux Density in the CMS Steel Yoke

The Compact Muon Solenoid (CMS) is a general purpose detector, designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6-m-diameter by 12.5-m-length free bore, enclosed inside a 10,000-ton return yoke made of construction steel. The return yoke consists of five dodecagonal three-layered barrel wheels and four end-cap disks at each end comprised of steel blocks up to 620 mm thick, which serve as the absorber plates of the muon detection system. Accurate characterization of the magnetic field everywhere in the CMS detector is required. To measure the field in and around the steel, a system of 22 flux loops and 82 3-D Hall sensors is installed on the return yoke blocks. Fast discharges of the solenoid (190 s time-constant) made during the CMS magnet surface commissioning test at the solenoid central fields of 2.64, 3.16, 3.68 and 4.01 T were used to induce voltages in the flux loops. The voltages are measured on-line and integrated off-line to obtain the magnetic flux in the steel yoke close to the muon chambers at full excitations of the solenoid. The 3-D Hall sensors installed on the steel–air interfaces give supplementary information on the components of magnetic field and permit to estimate the remanent field in steel to be added to the magnetic flux density obtained by the voltages integration. A TOSCA 3-D model of the CMS magnet is developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. The results of the measurements and calculations are presented, compared, and discussed.     

偏转磁芯铁氧体材料的磁滞损耗分析

对偏转磁芯所采用的铁氧体材料的磁滞损耗特性进行了分析,得出了磁滞损耗功率与频率、磁通密度和温度的经验公式。对磁滞回线中涡流的影响进行了分析,得出在目前应用的偏转频率下,磁芯损耗中磁滞损耗占主要部分。根据经验公式,对计算磁滞损耗的方法和在计算温度分布中的应用进行了介绍。     

Completely flat erosion magnetron sputtering using a rotating asymmetrical yoke magnet

A completely flat erosion magnetron 5-inch cathode has been developed for planer magnetron sputtering using a rotating asymmetrical yoke magnet. The yoke magnet was composed of an iron yoke base with a 70 mm diameter, an annular outer yoke, a center Fe-Nd-B magnet which was shifted from the yoke base center, and an assisted Fe-Nd-B magnet which was attached to a part of the outer yoke. In order to optimize the magnetic flux density for uniform target erosion from center to outer area, several diameters of the center Fe-Nd-B magnet, from 25 to 36 mm, were tested by the first experiment, and secondly the outer yoke structure was optimized using the first experimental results. The obtained final target utilization was 77% and erosion depth uniformity for the 4-inch diameter was ±6%.     

Completely flat erosion magnetron sputtering using a rotating asymmetrical yoke magnet

A completely flat erosion magnetron 5-inch cathode has been developed for planer magnetron sputtering using a rotating asymmetrical yoke magnet. The yoke magnet was composed of an iron yoke base with a 70 mm diameter, an annular outer yoke, a center Fe-Nd-B magnet which was shifted from the yoke base center, and an assisted Fe-Nd-B magnet which was attached to a part of the outer yoke. In order to optimize the magnetic flux density for uniform target erosion from center to outer area, several diameters of the center Fe-Nd-B magnet, from 25 to 36 mm, were tested by the first experiment, and secondly the outer yoke structure was optimized using the first experimental results. The obtained final target utilization was 77% and erosion depth uniformity for the 4-inch diameter was ±6%.     

Effects of a high-gradient magnetic field on the migratory behavior of primary crystal silicon in hypereutectic Al–Si alloy

The migration of primary Si grains during the solidification of Al–18 wt%Si alloy under a high-gradient magnetic field has been investigated experimentally. It was found that under a gradient magnetic field, the primary Si grains migrated toward one end of the specimen, forming a Si-rich layer, and the thickness of the Si-rich layer increased with increasing magnetic flux density. No movement of Si grains was apparent under a magnetic field below 2.3 T. For magnetic fields above 6.6 T, however, the thickness of the Si-rich layer was almost constant. It was shown that the static field also played a role in impeding the movement of the grains. The primary Si grains were refined in the Si layer, even though the primary silicon grains were very dense. The effect of the magnetic flux density on the migratory behavior is discussed.     

Power loss and flux density distributions in the T-joint of a three phase transformer core

A three phase transformer test facility has been used for measuring the localized power loss and flux distribution within the core. The flux and loss distributions in the T-joint of a core with simple double overlap joints have been investigated. The flux density distribution was measured by an array of search coils wound on individual laminations, and the localized power loss was found by measuring the initial rate of temperature rise using miniature thermocouples. For measurements made in the range of flux densities from 1.1 to 1.6 T, the inner edges of the yoke and limb laminations were the highest loss areas, up to 30% higher than the mean core loss. These regions of high power loss were found to be due to a high third harmonic flux density component being present. The fundamental component of flux density tended to follow the rolling direction of both yoke and limb laminations; however, some deviation from the rolling direction was present in the case of other harmonics.     

Effects of a high-gradient magnetic field on the migratory behavior of primary crystal silicon in hypereutectic Al–Si alloy

Abstract

The migration of primary Si grains during the solidification of Al–18 wt%Si alloy under a high-gradient magnetic field has been investigated experimentally. It was found that under a gradient magnetic field, the primary Si grains migrated toward one end of the specimen, forming a Si-rich layer, and the thickness of the Si-rich layer increased with increasing magnetic flux density. No movement of Si grains was apparent under a magnetic field below 2.3 T. For magnetic fields above 6.6 T, however, the thickness of the Si-rich layer was almost constant. It was shown that the static field also played a role in impeding the movement of the grains. The primary Si grains were refined in the Si layer, even though the primary silicon grains were very dense. The effect of the magnetic flux density on the migratory behavior is discussed.     

3-dimensional computation of the effect of the horizontal magnetic shunt on transformer leakage fields

By using a magnetic scalar potential function, leakage fields in a power transformer are calculated in three dimensions. The effects of the horizontal magnetic shunt are investigated with particular attention to the position of the shunt with respect to yoke. The calculations show how the leakage fields change with respect to the length of a small gap between shunt and yoke.     

用于偏转线圈三维磁场计算的谐波表面磁荷法

将三维磁场计算的表面磁荷法和空间谐波展开技术相结合 ,提出了一种用于偏转线圈磁场计算的谐波表面磁荷法。利用空间谐波的正交性 ,导出了与铁芯表面感应的磁荷各次谐波一一对应的磁场谐波。根据铁芯表面的法向磁场关系 ,建立各次磁荷谐波的积分方程 ,并进行了离散化。此方法将三维问题简化为一维积分方程问题 ,可以处理铁芯磁导率为有限值及铁芯与线匝间具有任意间隙的情况 ,具有较大的普遍适用性。用此方法计算了一个偏转线圈的例子 ,取得了较好的结果。     

Non-destructive Evaluation and Development of a New Wire Rope Tester Using Parallely Magnetized NdFeB Magnet Segments

A new wire rope tester based on principle of magnetic flux leakage is constructed. Two rings of NdFeB are cut in axial direction into 32 equal arc segments such that each arc segment subtends an angle of 22.5° at the centre. These arc segments are then parallely magnetized in magnetizer. A ferromagnetic cylinderical yoke is constructed by hinging two ferromagnetic half cylinders along one axial edge. A fixture consisting of a wooden square base, wooden mandrel, stepped and slotted Aluminium cylinder and Aluminium fillers is made to assemble the NdFeB magnets in a ring on both the ends of the ferromagnetic yoke. A Hall effect sensor is instrumented inside the yoke in the middle at radial distance of 34 mm from the axis of the yoke. A ferromagnetic wire rope with a defect is inserted in the novel wire rope tester. It has been successfully shown by performing Non-destructive testing that whenever a defect in a wire rope passes below the Hall-effect sensor instrumented in the wire rope tester developed in this work, a signal is generated indicating the defect.     

Diffusion positive column of electric discharge in transverse magnetic field

The effect of a transverse magnetic field on the characteristics of planar diffusion positive column of electric discharge has been studied. It is shown that, as the magnetic induction increases, the distributions of plasma density and particle fluxes to walls become asymmetric; the density maximum shifts in the direction of Ampere’s force action, and the ion flux in this force direction can significantly exceed the reverse flux. It is established that there is a maximum value of magnetic induction, which bounds from above the region of magnetic fields in which a stationary state of the positive column is possible. In the region where a stationary state of the positive column is possible, each value of the magnetic induction corresponds to two positive-column regimes with different values of the electron energy, drift velocity, and electric field strength.     

Diffusion layer growth at Zn/Cu interface under uniform and gradient high magnetic fields

As a common phenomenon occurring in many material processes, diffusion may induce significant changes in composition and microstructure near the interface. In the present study, liquid/solid (Zn/Cu) interface diffusion experiments in high magnetic fields (up to 12 T) were conducted and the thickness changes of diffusion layer under different magnetic field conditions were examined. It was found that there were no noticeable effects of high magnetic fields on the formation of intermetallic phases at the interface. However, the magnetic flux density exerted a non-linear influence on the diffusion layer thickness. This phenomenon should be attributed to the effect of magnetic fields suppressing natural convection and inducing thermo-electromagnetic convection. In addition, the diffusion of Zn into Cu could be retarded by a magnetic field gradient. These results indicate that both the strength and the gradient of high magnetic fields can be used to control the diffusion behavior.     

Test Coils Made of Tl-1223 Tapes

Silver sheathed Tl-1223 tapes were prepared by a powder-in-tube process. The critical current density of short samples was 18 kA/cm² at 77 K. Longer tapes up to 1.2 m, prepared by sequential pressing, had a critical current density of 12 kA/cm². From these tapes we have wound two coils. A solenoid coil with 5 windings was made of 8 tapes with a total length of 4.5 m. At 77 K the critical current of the coil was 23 A in the self generated magnetic field (18 Gauss at the centre of the coil). Using an iron yoke the critical current remained at 22 A while the generated magnetic field increased to 120 Gauss. A pancake coil with 15 windings, made of 5 tapes with a total length of 5 m, generated a magnetic field of 149 Gauss at the critical current of 12 A. From measurements of the critical current density of our tapes in applied magnetic fields, we conclude that coils made of Tl-1223 tapes can be used to generate higher magnetic fields at 77 K.     

An Improved Magnetic Equivalent Circuit Model for Iron-Core Linear Permanent-Magnet Synchronous Motors

The aim of this work is to establish an accurate yet simple method for predicting flux density distribution and iron losses in linear permanent-magnet synchronous motors (LPMSMs) for iterative design procedures. For this purpose, an improved magnetic equivalent circuit for calculation of the teeth and yoke flux densities in the LPMSMs is presented. The magnetic saturation of iron core is considered by nonlinear elements and an iterative procedure is used to update these elements. The armature reaction is also taken into account in the modeling by flux sources located on the teeth of motors. These sources are time dependent and can model every winding configuration. The relative motion between the motor primary and secondary is considered by wisely designing air gap elements simplifying the permeance network construction and preventing permeance matrix distortion during primary motion. Flux densities in different load conditions are calculated by means of the proposed model. The effects of saturation and armature reaction on the flux density distribution are shown in detail. Using these flux densities, iron losses in the motor are examined and its variations versus motor parameters are then studied. All results obtained by proposed model are verified by finite-element method based on an extensive analysis.     

Writer pole tip remanence in perpendicular recording

We studied the remanent field from perpendicular writer pole tips by micromagnetic modeling. The pole tip remanence has two causes: 1) the residual flux from the yoke due to undesirable material properties and/or yoke design and 2) the geometry of the pole tip. An optimal yoke design for low remanence includes a wide and short yoke with relatively shallow yoke flare angle around 30/spl deg/ that favors transverse major domains. Horizontal anisotropy in the yoke and the pole tip also helps suppress the vertical magnetization, mainly in the yoke, which yields less residual flux into the pole tip, hence lower remanence. The remanent field is also a strong function of the throat height, i.e., the pole tip length, due to the shape anisotropy effect. Micromagnetic modeling shows that multilayer lamination, both in the yoke and in the pole tip, is an effective way to achieve low remanence. It also eliminates the sensitivity of remanence to the throat height. To improve the robustness of the remanence against the stray field, an antiferromagnetic coupling (AFC) between the lamination layers may also be necessary. Our results apply to both single pole heads and shielded pole heads.     

小型磁偏转质谱计磁场的分析计算

磁偏转质谱计是根据离子在磁分析器中运动时,不同质荷比的离子有不同的偏转半径原理来实现质量分离的。磁场大小和分布对质谱计的性能影响较大,因而设计时需要对质谱计磁场分布进行精确计算。应用有限元法建立了计算质谱计磁分析器磁场的物理模型,并利用这一模型计算了磁分析器磁感应强度在空间的分布情况。结果表明,在半径分别为20 mm和50 mm的1/4圆弧轨道上,其磁场分布规律类似。由于边缘磁场效应,在磁铁边界区域约3 mm范围内,磁感应强度基本呈直线下降,这一结果为磁分析器的结构优化和边缘场补偿提供了理论依据。     

Coil Probe Dimension and Uncertainties During Measurements of Nonuniform ELF Magnetic Fields

Comparisons are made between the calculated average magnetic flux density for single-axis and three-axis circular coil probes and the calculated magnetic flux density at the center of the probes. The results, which are determined as suming a dipole magnetic field, provide information on the uncertainty associated with measurements of nonuniform extremely low frequency (ELF) magnetic fields produced by some electrical appliances and other electrical equipment.     

Plasma parameter analysis of Ag sputter deposition using cathodes with different magnetic flux densities

The effects of the magnetic flux density of the Ag sputter target surface on plasma parameters were investigated using the Langmuir probe system in this work. It was found that the electron energy and electron density near the substrate clearly decreased at a high magnetic flux density. In addition, the difference between plasma potential and floating potential (V_p−V_f) decreased at the high magnetic flux density relative to the potentials at the low magnetic flux density. The changes in plasma parameters could be interpreted as the result of many electrons being trapped in the neighborhood of the target surface (cathode sheath) at the high magnetic flux density; hence, the number of electrons in the space near the substrate is reduced. The Ag thin films exhibited low resistivity at a high magnetic flux density. The reduction in resistivity was attributed to the following factors: the low electron energy and electron density near the substrate; the low kinetic energy of positive argon ions; the low kinetic energy of argon atoms backscattered onto the target surface.