Simultaneous magneto-optical Kerr effect and Sixtus-Tonks method for analyzing the shape of propagating domain walls in ultrathin magnetic wires

The controlled nucleation and propagation of magnetic domain walls in ultrathin ferromagnetic wires, such as nanowires and submicrometer wires, is extremely important for the development of new high performance magnetic domain wall logic devices. Therefore, it is equally essential to possess adequate advanced experimental investigation techniques in order to be able to achieve a comprehensive in situ analysis of as many as possible parameters related to the domain wall propagation, e.g., wall shape besides wall velocity and position. In this paper, we report on a method developed specifically for the investigation of the shape of propagating magnetic domain walls in ultrathin magnetic wires, i.e., with the diameter of the magnetic wire in the range 100-950 nm. The newly developed experimental method is based on the simultaneous use of two full-fledged experimental techniques: the magneto-optical Kerr effect for analyzing the surface effects of the passing domain wall and the Sixtus-Tonks method for the investigation of the entire moving wall. The results obtained offer essential information about the shape of the propagating magnetic domain walls, being unique to this new method.     

Note: Investigation of atom transfer using a red-detuned push beam in a double magneto-optical trap setup

We present our results on transfer of cold (87)Rb atoms from a vapor cell magneto-optical trap to ultrahigh vacuum magneto-optical trap (UHV-MOT) using a red-detuned continuous wave push beam in a double-magneto-optical trap setup. We find that use of retro-reflected red-detuned push laser beam results in higher number in UHV-MOT than the number obtained without retro-reflection of push beam.     

Development of an in situ magnetoelastic magneto-optical Kerr effect magnetometer

Reported here is the development and implementation of an integrated in situ magnetoelastic measurement setup with a MOKE magnetometer, repositionable electromagnet, and sample transfer/straining device. The former were used within a molecular beam epitaxial vacuum growth chamber. Consequently the magnetostriction constants for both Cr capped and uncapped Fe/GaAs(100) films were acquired without film oxidization occurring. Samples were bent in a four point bending geometry to produce a quantifiable tensile mechanical strain on the films during magnetoelastic measurements. In addition, a laser measurement system was developed to confirm the induced strain in the samples.     

A combined surface stress and magneto-optical Kerr effect measurement setup for temperatures down to 30 K and in fields of up to 0.7 T

An optical 2-beam surface stress measurement and magneto-optical Kerr-effect has been combined with a liquid helium cooled cryostat. Sample temperatures down to 30?K and magnetic fields up to 0.7?T are achieved under UHV conditions. Low temperatures are exploited to obtain the first experimental data on the surface stress change induced by the adsorption of the noble gas Xe on Pt(111). High magnetic fields and low temperatures are used to characterize the magnetic properties of Co monolayers in longitudinal and polar Kerr geometries. The effective magnetic anisotropy is extracted from hard axis magnetization loops.     

Development of an experimental setup for microflow measurement using interferometry

The precise measurement of micro and nanoflow of incompressible liquids (below 1 μL/h) is a complex task due to several factors involved in, namely, evaporation, adsorption and the existence of air bubbles within the system. Nevertheless, the importance of its measurement is undeniable in equipment such as insulin pumps, or medical drug delivery devices for new-born, microchip flow pumps, to mention few.The work herein presented was developed in a partnership between the Volume and Flow Laboratory (LVC) of the Portuguese Institute of Quality (IPQ) and the Department of Mechanical and Industrial Engineering (DEMI) of The New University of Lisbon under the project MeDD II – Metrology for Drug Delivery. It had the main objective of conceiving a new Portuguese standard for the measurement of ultra-low flow using interferometry, with a target uncertainty of 1% (k = 2). Therefore, the new setup relies on an interferometer made up of a laser unit, two retroreflector cubes, one beam splitter, as well as a flow generator (a Nexus syringe pump) and a computer for data acquisition.Experimental tests on a Flow generator and a Coriolis flow meter were carried out at different flow rates. With the innovative methodology developed during the present research, it was possible to measure flow rates of an incompressible fluid (water) down to 1 μL/h with an uncertainty of 3% (k = 2).     

The measurement of magneto-optical Kerr effect of ultrathin films in a pulsed magnetic field

A Kerr rotation measurement system in a pulsed magnetic field (up to 11 T) was built to study magnetic properties of several ultrathin films. Our result shows that the Kerr rotation angle increases with the increasing wavelength of the incident light, while the difference between the spectras of Fe and CoFeAl is attributed to plasma resonance. We also studied the dynamic properties of the magnetic films: while ferromagnetic materials (Fe, CoFeAl, MnAs and CoMnAl) show quasi-static behavior in the time-scale of a few 100 μs, diamagnetic material GaAs shows time-dependent hysteresis.     

A magneto-optical setup for studying the time evolution of nanoscale domain-wall displacements under pulsed magnetization

A magneto-optical setup for studying the time evolution of nanoscale domain-wall displacements of domain walls in magnetic films with a regular domain structure is described. Methods for spatial filtering of the output optical flux using the Fourier image of the domain structure and the impulse transient response in the real-time mode are applied in the setup. This allowed an increase in the sensitivity to domain-wall displacements of up to 5 nm and registration of their evolution with a temporal resolution of 1 ns.     

An experimental setup for high resolution 10.5 eV laser-based angle-resolved photoelectron spectroscopy using a time-of-flight electron analyzer

We present an experimental setup for laser-based angle-resolved time-of-flight photoemission. Using a picosecond pulsed laser, photons of energy 10.5 eV are generated through higher harmonic generation in xenon. The high repetition rate of the light source, variable between 0.2 and 8 MHz, enables high photoelectron count rates and short acquisition times. By using a time-of-flight analyzer with angle-resolving capabilities, electrons emitted from the sample within a circular cone of up to ±15° can be collected. Hence, simultaneous acquisition of photoemission data for a complete area of the Brillouin zone is possible. The current photon energy enables bulk sensitive measurements, high angular resolution, and the resulting covered momentum space is large enough to enclose the entire Brillouin zone in cuprate high-T(c) superconductors. Fermi edge measurements on polycrystalline Au shows an energy resolution better than 5 meV. Data from a test measurement of the Au(111) surface state are presented along with measurements of the Fermi surface of the high-T(c) superconductor Bi(2)Sr(2)CaCu(2)O(8 + δ) (Bi2212).     

Application of a NDI method using magneto-optical film for micro-cracks

Leakage magnetic flux is occurred in the cracked area of magnetized specimens, and also it changes the magnetic domain area of the magneto-optical film positioned on the specimen. It causes the change of the optical permeability of the magnetic domain on the crack area. So crack images can be obtained easily using this principle. On the other hand, utilizing a laser in this method makes possible to perform a remote sensing by detecting the light intensity contrast between cracked area and normal area. This paper shows the application of non-destructive inspection system taking advantage of magneto-optical method for micro-cracks and presents examples applied to the several types of specimens having fatigue cracks and fabricated cracks using this method. Also the authors prove the possibility of this method as a remote sensing system under the oscillation load considering application to real fields.     

A simple and effective setup for in situ investigations of the surface magnetooptic Kerr effect in ultrahigh vacuum

A simple and inexpensive device rather sensitive to studies of magnetic properties of very thin (0.5–0.6 nm) ferromagnetic films by the surface magnetooptic Kerr effect (SMOKE) method in ultrahigh vacuum (UHV) conditions is described. The system is intended for measuring both longitudinal and transversal Kerr effects. The special vacuum-tight electromagnet system of the SMOKE device is quite compatible with other surface-sensitive methods. When an additional external magnet system is used, the same optical and electronic system can be also employed for ex situ investigations. Examples demonstrating the high sensitivity of this setup and its efficiency during studies of the magnetic anisotropy are given.     

An experimental study of pressure drop correlations for wire-wrapped fuel assemblies

The main objective of the present study is to perform an experimental evaluation of five existing correlations for the subchannel pressure drop analysis of a wire-wrapped fuel assembly. For this purpose, a series of water experiments have been performed using a helical wire-wrapped 19-pin fuel assembly for various test parameters. For different test sections with different pitch to rod diameter ratios (P/D) and wire lead length to rod diameter ratios (H/D) have been fabricated. A series of pressure drop measurements were made to obtain friction factors for these four test sections. The new data along with existing data are used to evaluate existing correlations. Both the original and the simplified Cheng and Todreas correlations give the best agreement with experimental data for all flow regions.     

Detection of micro gap weld using magneto-optical imaging during laser welding

Accurate seam tracking plays a critical role in acquisition of good weld. During laser butt joint welding, the laser beam focus must be controlled to follow the weld trajectory. The key problem to be solved is the automatic identification of weld position. An approach to detect the micro gap weld (gap width is less than 0.05 mm) based on magneto-optical imaging (MOI) is proposed. The laser butt joint welding of carbon steel was carried out. A magnetic excitation device was used to magnetize the weldment, and it was found that magnetic field distribution at the weld was different from other regions. The magnetized weldment was detected by using a magneto-optical sensor, and magneto-optical images of the weld were captured. By analyzing and processing weld MO images with low contrast and strong magnetic field noises, the weld center position could be detected accurately. Weld MO images at different laser welding speeds were investigated to analyze the varieties of image characteristics. Experimental results indicated that the magneto-optical imaging technique could be applied to detect the micro gap weld accurately, which provides a novel approach for automatic identification and tracking of micro gap weld during laser welding.     

空间滤波器阵列结构优化设计

给出了新型大型激光装置阵列化空间滤波器结构优化设计。对大口径阵列化光束超长程传输、光路控制、光束质量控制,以及支撑稳定性、震动隔离、离轴调节等关键技术进行了分析研究,对物理方案和参数进行分解。运用Pro/E软件建立阵列化空间滤波器三维实体模型,给出了阵列化空间滤波器的总体结构解决方案。对关键部件和技术指标进行了详细分析,采取了新颖的结构和相应的技术措施;运用ANSYS分析软件对结构刚性、强度、振型等指标进行分析,通过有限元仿真与CAD环境的双向嵌入优化结构;为给装置结构的适应性找到可靠的评估依据,对影响稳定性较大的器件和单元进行了微振动测试和分析。理论分析和测试结果表明,该方案达到了优化设计,是可行的。     

A study of Xe 2β decay using the DEVIS tracking setup at the institute for theoretical and experimental physics

The DEVIS experiment aimed at searching for 2ν2β decay of ¹³⁶Xe isotope has been conducted for several years at the Institute for Theoretical and Experimental Physics. The DEVIS (DEtector for VISu-alization) tracking setup is a time projection chamber placed in a magnetic field. Xenon samples with a mass of 4 kg and different isotopic compositions have been sequentially exposed in it. An excess of events has been observed in the run with the sample enriched in ¹³⁶Xe. The stages of the experiment are described, and the background processes capable of simulating events of 2ν2β decay are analyzed. The limit on the half-life of ¹³⁶Xe 2ν2β decay is shown to be T _1/2 (2ν2β) > 2.1 × 10²⁰ years.     

Maximization of process tolerances using an analysis of setup capability

This paper presents a method for tolerance balancing in machining process planning. The surface position tolerance (SPT) method offers several advantages in comparison with the tolerance charting technique. These advantages arise from the separate consideration of the datum and machining surface position capabilities. To solve the problem of tolerance balancing, the mathematical model used in the literature is adapted to the SPT method. When solving the problem, the objective of maximizing process tolerances was chosen. The proposal was applied to a problem that has been used by many authors in the literature and so a wide comparison can be made of the results. The solution enables the tolerances in the process to be improved and the solution can also be optimized with respect to the capability of the fixture.     

Note: An adhesion measurement setup for bioinspired fibrillar surfaces using flat probes

Current adhesion measurement setups designed for experiments on bioinspired fibrillar surfaces, either commercial or constructed in-house, do not allow adhesion measurements with in situ visualization, high resolution, high force range, and controlled alignment at the same time. In this paper a new adhesion tester is presented, which enables contact experiments with controlled tilt angle (accuracy of ±0.02°). This allows the use of flat probes and thus greatly simplifies the determination of experimental parameters such as pull-off strength or Young's modulus. The deflection of a double-clamped glass beam is measured by laser interferometry with an accuracy of ±60 nm, which yields a precise force measurement over three orders of magnitude force range without changing the glass beam. Contact formation and detachment events can be visualized in situ. The current adhesion tester is designed for force measurements in the range of 1 μN to 1 N and fills the gap between macroscopic tests and atomic force microscopy measurements.     

基于设计结构矩阵的耦合任务迭代重叠建模和分析

为优化产品开发过程,把重叠引入耦合过程的研究中。以高斯消去算法为基础,给出了在两任务耦合情况下,确定耦合任务上、下游关系的方法。在建立信息修改比率参数数学描述的基础上,充分考虑到过程重叠时分别由任务返工和并行通讯所产生的时间消耗,结合高斯消去法和耦合任务的迭代特性,给出了两耦合任务迭代情况下开发时间的数学模型。最后,用工程实例验证了该数学模型,并分析了模型中部分参数的特性。     

An experimental setup for simulation of two-phase hydrocarbon mixture flow in porous stratums

A procedure for simulating the two-phase flow of three-component hydrocarbon gas mixtures (for example, of the methane-propane-butane mixture gas condensate) in a porous stratum with the use of strain-gauge pressure sensors is proposed. Results are presented of experimental studies of two-phase hydrocarbon methane-propane-butane mixture filtration through a porous medium on the PLAST setup of the Joint Institute for High Temperatures under conditions close to reality. It is shown that the coordinate of the gas condensate plug formation region in the experimental section of a pipe can be determined with an accuracy up to 10% of its length.     

An experimental setup for obtaining metallic multilayer coatings with layers of nanometer thickness

An automated PC-controlled electrochemical setup for deposition of a specified number of different metal nanodimensional layers onto conducting substrates is described. Metallic layers are deposited in galvanic cells from solutions of corresponding electrolytes on a sample that serves as a cathode, while the anode is a plate of an inert material or a material dissolved during electrolysis. The electroplating is conducted by passing rectangular current pulses through the electrolyte solution between the sample and the anode. The amplitude (1 mA–1 A) and duration (1 ms–1 s) of the current pulses are set by a program. Samples are treated in the galvanic cells and rinsing baths according to a programmed route. In combination with efficient electrolytes for electrodeposition, the setup enables one to obtain multilayer structures of specified configuration with alternation of nanometer layers of different metals: normal metals, ferromagnets, paramagnetics, antiferromagnets, or superconductors. The characteristics of a normal metal (copper)-ferromagnet (palladium-nickel alloy) multilayer coating are presented.