Design and Manufacturing Main Linac Superconducting Quadrupole for ILC at Fermilab

The design and manufacturing of the first model of an International Linear Collider (ILC) Main Linac superconducting quadrupole is in progress at Fermilab. The quadrupole has a 78 mm aperture, a 36 T integrated gradient, and a cold mass length of 700 mm. A superferric magnet configuration with iron poles and four racetrack coils was chosen based on magnet performance, cost, and reliability considerations. Each coil is wound using enamel insulated, 0.5 mm diameter, NbTi superconductor. The quadrupole package also includes shell type dipole steering coils. The results of the quadrupole design, including magnetic and mechanical analyses, are presented. Specific issues related to the quadrupole magnetic center stability, superconductor magnetization and mechanical stability are discussed and analyzed. The magnet quench protection system, current leads, and mounting the quadrupole inside ILC Main Linac cryomodule will also be briefly discussed.     

Dipole and Quadrupole Measurements of an Isolated Turtle Heart

An equivalent cardiac generator, specifically the multipole model, was evaluated for an isolated turtle heart located in a spherical volume conductor. The dipole and quadrupole contributions to the potential field were calculated using weighted integrals of the surface distributions. This procedure has the advantage of eliminating errors due to the truncation of the multipole series. The dipole and quadrupole effects were calculated for the QRS portion of the cardiac waveform. A significant quadrupole contribution was found to exist.     

Fast Nonrecursive Method for Estimating Location and Dipole Moment Components of a Static Magnetic Dipole

This paper presents a method of estimating the position and moment components of a static magnetic dipole based on measurements of the magnetic field component normal to an arbitrary plane in which measurements are obtained. The largest local maximum and smallest local minimum of the field component and the corresponding positions in the plane are all the data necessary to obtain the solution. The solution is accurate, nonrecursive, robust, fast enough to be carried out by a 16-bit microprocessor in a fraction of a second, and makes no assumptions about the orientation of the dipole. The method in most cases gives good results for total field data, too. Results of a computer simulation study, which was performed to evaluate the method using simulated but realistic data, are presented. It is found for both total and vector magnetic field data that accuracy of component estimates are nearly independent of magnetic sensitivity (for S/N ratios greater than 28 dB) and sensor positional errors in the plane of measurement (if less than 5 percent of the dipole depth). Percentage error in estimates of dipole position and moment components is approximately equal to the percentage error in sensor position orthogonal to the plane of measurement (if less than 5 percent of the depth).     

The Interaction Force Between a Permanent Magnet and a Superconducting Ring

The interaction force between a small magnet and a superconducting ring in assumptions of the Meissner state was analyzed using the dipole-dipole interaction model. Two configurations were evaluated: the vertical configuration when the magnetic moment lies parallel to the symmetry axis of the ring and the horizontal when it is perpendicular. The levitation force on the magnet increases by decreasing the distance from the center of the ring up to a maximum value and then decreases down to zero when the magnet is exactly at the center of the ring. The levitation force when the magnet is in the horizontal configuration is mostly higher than that when it is in the vertical configuration. Simulation results were compared with experimental results reported in literature.     

Feasibility Study of a Hybrid Mechanical-Static DC Circuit Breaker for Superconducting Magnet Protection

This paper describes the feasibility studies of a hybrid DC circuit breaker (CB) for quench protection of superconducting magnets rated for current up to some tens of kiloamperes (kA) and voltage of several kilovolts (kV). The proposed scheme is based on a mechanical switch paralleled to a fully controlled static CB; integrated gate commutated thyristors (IGCTs) were selected. In normal operation, the mechanical switch handles the continuous flow of DC current minimizing the on-state losses. When protection against quench is requested, the current is diverted into the static breaker that quickly interrupts the current, withstanding the reapplied voltage of several kV. The reliable turn-ON of several IGCTs in parallel with low voltage applied between anode and cathode is an issue to be assessed to confirm the feasibility of this design solution. The paper highlights that the components commonly used as snubber or protection circuit can guarantee the turn-ON of all the devices in parallel and that the IGCTs can be turned-ON with few volts applied; this latter aspect was proved by means of specific tests. Finally, a comparison between a static only and a hybrid CB is performed, highlighting the benefits introduced by the hybrid solution.     

Fabrication of Liquid Helium-Free Superconducting Magnet for Millimeter Wave Gyrotron

A liquid helium free superconducting magnet was designed and fabricated and for an application to a millimeter wave gyrotron and a peniotron. The magnet generates a magnetic field of 5T in a 100mm room temperature bore and has been continuously working for more than 5,400 hours without troubles. The magnet system was applied to the millimeter wave gyrotron experiments to confirm the stability of the magnet. In the experiments, stable operations of the gyrotron were achieved in the frequency range of 30 - 133GHz.     

电偶极子和磁偶极子场分布相似性的一种解释

电偶极子电场与磁偶极子磁场具有相似的空间分布。然而,这种相似性并非显而易见：电偶极子由一对等量异号电荷组成,而磁偶极子则是一个电流回路。本文从矢量场边值问题的唯一性定理出发,得出了面散度源和面旋度源产生的矢量场分布的一种等价关系,进而对电偶极子电场与磁偶极子磁场空间分布的相似性进行了解释。     

Magnetic Field Measurement System in Superconducting Combined Function Magnets for the J-PARC Neutrino Beam Line

Magnetic field measurements have been performed for the first full-scale magnet system assembled with the cryostat for the J-PARC proton beam line of neutrino experiment. In the measurement system, the probe position with respect to magnet central axis is measured by a Helium Neon laser and a position sensitive detector, PSD, in order to obtain an exact dipole field strength. Errors associated with the PSD misalignment and influences on the PSD signals by the magnetic field were evaluated. The measured dipole components approached to the design values by compensating those with the probe position. The latest beam simulation indicated that the measured values of magnetic field were good enough for the primary proton beam transport.     

Field Quality and Losses for the 4.5 T Superconducting Pulsed Dipole of SIS300

This paper presents the 2D design of the SIS300 synchrotron dipole of the FAIR facility at GSI. The dipole has a length of 7.8 m, a field of 4.5 T, in a 100 mm bore, and is ramped at 1 T/s. The studies are performed by INFN (Frascati, Genova and Milano-LASA) in a R&D collaboration with GSI. The program started in 2006 (DISCORAP) and has as a final goal the construction and test of a prototype. Particular emphasis is given to the study of the field quality and of the losses during the ramping of the magnet. Some calculation methods and different codes for magnet design are evaluated and compared.     

Magnetic Fields of a Dipole in Special Volume Conductor Shapes

Expressions are presented for the magnetic fields produced by current dipoles in four basic volume conductor shapes. These shapes are the semi-infinite volume, the sphere, the prolate spheroid (egg-shape), and the oblate spheroid (discus-shape). The latter three shapes approximate the shape of the human head and can serve as a basis for understanding the measurements of the brain's magnetic fields. The semi-infinite volume is included in order to investigate the effect of the simplest boundary between a conductor and nonconductor. The expressions for the fields are presented in a form which separates the total field into two parts. One part is due to the dipole alone (the dipole field); the other is due to the current generated in the volume conductor by the dipole (the volume current field). Representative plots of the total field and the volume current field are presented for each shape. The results show that for these shapes the component of the total field normal to the surface of the volume conductor is produced completely or in large part by the dipole alone. Therefore, measurement and use of this component will greatly reduce the complexity of determining the sources of electrical activity inside a body from measurements outside the body by removing the necessity of dealing with the volume current field.     

Magnetic Performance of the Main Superconducting Magnets for the LHC

The field strength and homogeneity of all the LHC superconducting magnets were measured as a part of the production control and qualification process that has taken place during the past four years. In addition to field measurements at room temperature performed on the integral of the production, a significant part of the magnets has been subjected to extensive magnetic measurements at cold. The measurements at cryogenic temperatures, generally performed up to excitation currents of 12 kA corresponding to the ultimate LHC energy of 7.6 TeV, were mainly based on static and dynamic field integral and harmonic measurements. This allowed us to study in detail the DC effects from persistent current magnetization and long-term decay during constant current excitation. These effects are all expected to be of relevance for the field setting and error compensation in the LHC. This paper reports the main results obtained during these tests executed at operating conditions. The integrated field quality is discussed in terms of distribution (average and spread) of the field strength and low-order harmonics as obtained for all the main ring magnet families (dipoles, main and matching quadrupoles). The dependence of field quality on coil geometry, magnet and cable manufacturer is analyzed. A projection of the field quality expected for the critical components in the machine is presented.     

超导磁体失超检测中电压隔离校正电路的设计

采用有源功率检测法,设计和制作了超导混合储能磁体能量储存系统的失超检测中的电压隔离校正装置。该装置用于隔离超导线圈的干扰信号,以及消除串联线圈电感分量,是混合磁体失超检测中的重要环节。通过搭建高温超导线圈的实验装置,在高温超导储能磁体上进行失超检测的实验研究,得出了电压矫正前后的线圈电压波形,验证了本实验装置可行性与合理性。     

A Conceptual Design of Model Coil for the 40-T Hybrid Magnet Superconducting Outsert

The High Magnetic Field Laboratory of the Chinese Academy of Sciences will develop a 40-T hybrid magnet. The superconducting outsert, which consists of a NbTi coil and a $hbox{Nb}_{3} hbox{Sn}$ coil, will provide more than 11 T of central field in a 580-mm bore. The superconducting coils will be wound of cable-in-conduit conductor (CICC) and cooled by flowing 4.5-K supercritical helium. A model coil of the $hbox{Nb}_{3}hbox{Sn}$ coil has been designed and will be manufactured to develop the technology of cabling, jacketing, winding, heat treatment, etc., and the model coil can also simulate the performance of the $hbox{Nb}_{3}hbox{Sn}$ superconducting coil under its operating conditions. This paper gives an overview of the conceptual design for the model coil and predicts its current-sharing temperature (Tcs).      

Construction and Testing of the Final Focus Quadrupole R&D Magnet for the Super-KEKB Interaction Region

Super-KEKB is designed to be a next generation particle accelerator with a target luminosity of 4 times 10³⁵ cm^-2s^-1. For the interaction region, a final focus quadrupole R&D magnet was designed and constructed. The design field gradient and effective magnetic length were 40.12 T/m and 0.299 m, respectively. The magnet consists of 6 layer coils. After construction, the magnet was tested at 4.2 K and a preliminary field measurement was performed. The magnet was energized to a current of 1800 A, which corresponds to 95.8% of the conductor limit, and the quadrupole component error was 0.23 % of the design value.     

一种915MHz印刷偶极子标签天线的分析与设计

射频识别技术由于具有体积小、容量大等优良性能而被广泛应用于很多领域.针对反射调制式RFID系统,介绍了一种基于ISO/IEC18000-6标准应用的RFID印刷偶极子标签天线及其优化设计方案.首先进行了915MHz印刷偶极子天线的结构设计,给出了等效电路模型和具体的设计尺寸和仿真结果;然后使用分支线结构加载的方法进行小型化设计,设计结果为在中心工作频率915MHz处,增益为2.15dBi,电压驻波比小于1.5的工作带宽为78MHz,尺寸减缩幅度达48%以上;最后,在一定的柱面共形半径条件下,对上述印刷偶极子天线进行仿真,结果表明该天线仍能保持较好的工作性能,可以广泛应用于弹体共形等情况.     

导电媒质平面上方垂直磁偶极源赫兹位函数的球面波展开式

精确有效地计算索末菲尔德型积分是分析导电媒质半空间电磁波辐射和散射问题的关键.本文给出求解有限导电媒质平面上方垂直磁偶极源赫兹位函数的解析方法.利用圆柱波函数的球面波函数展开式和超几何函数理论,位函数中的索末菲尔德积分被表示成快速、绝对收敛的球面波展开式;展开系数是以物性参数为复宗量的勒让德多项式.该展开式易于电磁场的计算和分析,并且不受场点和源点的位置、媒质的物性参数和频率等条件的限制.     

Electromagnetic Field Due to a Magnetic Dipole in a Medium Containing Both Planar and Cylindrical Boundaries

An approximate method based on perturbation theory is used to calculate electromagnetic fields due to a vertical magnetic dipole in an Earth formation having both horizontal and cylindrical boundaries. The medium is first assumed to have a constant background permittivity. Any deviation from the background permittivity is treated as a perturbation. Correction terms are then found and expressed in multiple integrals. The first and the second correction terms involve threefold and sixfold integrations, respectively. An efficient integration technique is used to compute these multiple integrals. As an example, this method is used to calculate the field due to a vertical magnetic dipole over a layered Earth containing a cylindrical cavity. In another example, the response of a two-coil induction tool is calculated when it is located in a rugose borehole.     

Optical Methods for the Measurement of Complex Dielectric and Magnetic Constants at Centimeter and Millimeter Wavelengths

A method is described which permits the determination of the complex dielectric constant, epsilon* = epsilon/sub o/k/sub e/(l-j tan delta/sub e/), and the complex permeability, µ* = µ/sub o/k/sub m/ (l-j tan delta/sub m/), using free space transmission and reflection from a plane sheet of the sample dielectric. The procedure represents an extension of that used at optical frequencies. Differences arise however, due to the fact that the assumptions of k/sub m/ = 1 and tan delta/sub m/ = 0, which are made in the optical theory, are not always valid at millimeter wavelengths.