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.     

Quench protection studies of LHC interaction region quadrupoles atFermilab

High gradient quadrupoles are being developed by the US-LHC Accelerator Project for the LHC interaction region inner triplets. Protection strip heaters are the primary means of protecting these magnets against excessively high coil temperatures and coil voltage to ground as a result of a spontaneous quench. The main objective of the quench protection R&D program is to optimize the heater performance within the constraints of the LHC heater power supply and quench detection system. The results of these studies on several two meter long model magnets are presented     

Quench protection of the Fermilab-built LHC inner triplet quadrupole MQXB

High-gradient quadrupoles (MQXB) are being developed at Fermilab within the framework of the US-LHC Accelerator project for the LHC interaction regions. These 5.5-m-long magnets have a single 70-mm aperture and operate in superfluid helium at a peak gradient of 215 T/m. Magnet quench protection is provided by quench heaters installed on the outer surface of the coil. This paper reports the results of quench protection studies on the first full length MQXB prototype (MQXP01). The measurements from these tests as well as results from the 1.9-m-long model magnet program are combined with computer generated quench simulations to predict the MQXB performance under LHC operating conditions.     

Quench performance and field quality of the LHC preseries superconducting dipoles

The preseries production of the LHC main superconducting dipoles is presently being tested at CERN. The foremost features of these magnets are: twin structure, six block two layer coils wound from 15.1 mm wide graded NbTi cables, 56 mm aperture, polyimide insulation and stainless steel collars. The paper reviews the main test results of magnets tested to day in both normal and superfluid helium. The results of training performance, magnet protection, electrical integrity and the field quality are presented in terms of the specifications and expected performance of these magnets in the future accelerator.     

ZnO压敏电阻器在稳态湿热试验中的性能变化与分析

通过对ZnO压敏电阻器试验结果的分析,探讨其在稳态湿热试验中引起性能变化的因素,提出要提高产品的耐湿性能,必须在包封料选择和瓷体制作工艺上加以改进。     

Quench performance and mechanical behavior of the first Fermilab-built prototype high gradient quadrupole for the LHC interaction regions

As part of the US LHC program to provide high gradient superconducting quadrupoles for the LHC interaction regions, a 5.5 meter long prototype magnet has been built and tested horizontally in a production type cryostat at Fermilab. This prototype magnet was used to validate the mechanical and magnetic design, production fabrication and assembly tooling. The first prototype magnet has met the LHC requirements of operating at 215 T/m with excellent magnetic field harmonics. This paper summarizes the test results of this magnet, including quench tests and mechanical behavior over several thermal cycles.     

稳态输入电流试验不确定度评定

对安全稳态输入电流实验方法进行了介绍,探讨使用串联标准电阻测量电流的不确定度评定,根据计算结果对实验过程进行分析。     

Performance Evaluation and Quality Assurance Management During the Series Power Tests of LHC Main Lattice Magnets

Within the LHC project, a series production of superconducting dipoles and quadrupoles has recently been completed in industry and all magnets were cold tested at CERN. The main features of these magnets are: two-in-one structure, 56 mm aperture, two layer coils wound from 15.1 mm wide Nb-Ti cables, and all-polyimide insulation. This paper reviews the process of the power test quality assurance and performance evaluation, which was applied during the LHC magnet series tests. The main test results of magnets tested in both supercritical and superfluid helium, including the quench training, the conductor performance, the magnet protection efficiency and the electrical integrity are presented and discussed in terms of the design parameters and the requirements of the LHC machine.     

Iterative Method for Steady State Reliability Analysis of Complex Markov Systems

An iterative procedure for evaluating steady-state probabilities of complex Markov systems is proposed; it is based upon a generalization of Seidel's method for solving systems of linear algebraic equations. The probabilities are evaluated with desired accuracy by sequentially solving equation sets of much lower order than this of the entire system. For the systems with states transmitting only to states of higher and (or) lower probability magnitude orders, simple, easily composable recurrent formulas for state probabilities are obtained. An illustrative example is included.     

DQDB城域网暂态和稳态公平性分析

本文分析了DQDB城域网在大文件传输时的公平性。通过分析大文件传输时某一节点的性能及网络各节点的关联性,证明了网络经过一个暂态过程后将达到稳态,给出了各节点在稳态及暂态时的吞吐量、暂态过程长度的表达式。     

DC/DC变换器稳态建模的教学方法

本文介绍了一种为DC/DC变换器建立稳态模型,并利用稳态模型分析变换器的稳态工作特性的教学方法和研究思路。本方法所建模型既可以体现变换器的DC/DC变换功能,又可以包含变换器在稳态工作时的主要损耗。模型结构简单,运用简单的电路分析方法,就能够较为简便地得出直流变换器稳态工作时的主要电气特性。本文所介绍的建模方法是研究直流变换器稳态工作特性的有力工具,在教学研究中都具有较高的推广价值。     

Steady State Responses of NRD-Guide Crossbar Balanced Mixer in MM-Wave Band

The periodic and quasi-periodic steady states of the nonradiative dielectric waveguide (NRD-guide) crossbar single-balanced mixer excited by single tone or dual tones in mm-wave band are deeply researched in the paper. Based on the wideband dispersion characteristics, the mode self-contained property and the modes orthogonality and a series of modes excitation criterions of the NRD-guide, a novel mixer is designed and analyzed. Two important parameters, the local oscillator and incident wave inductive electromotive forces corresponding to the LSE/LSM mode-converter and LSM-mode probe respectively, are calculated firstly by using the wire-antenna theory and the moment method. According to the theorem of band-pass signal sampling, a kind of integrated and general quasi-periodical steady-state responses algorithm for the nonlinear microwave/mm-wave circuits excited by multiple tones, the inter-modulation balance method based on the multi-dimension discrete Fourier transformation (MDFT-IMB), is designed and then successfully applied to calculate the performances of the above NRD-guide mixer.     

正弦稳态电路功率问题

正弦稳态电路功率的分析比较复杂,本文介绍了求解这些电路时遇到的问题,强调了表示电压相量的电流相量数学关系式的应用。     

美研制出67kW固体热容激光器

利弗莫尔实验室在美国能源部的支持下继续从事固体热容激光器的研究,在2006年取得了突破性进展,输出能量达到67kW,光束质量优于2倍衍射极限,并已开始着手研制100kW级移动演示系统.     

基于傅立叶级数法的稳态二次电子倍增放电求解

建立一个简单的电路模型，分析二次电子倍增放电与RF腔之间的相互作用。引入适当假设，采用傅立叶级数法，求出二次电子倍增方程的稳态解。稳态二次电子倍增电流可在相当低的水平上达到饱和，主要是通过对腔的装载来完成，而空间电荷相对来说作用不大。     

基于FWCM的非线性动态电路时域稳态模拟

本文提出一种基于快速小波配置法（ＦＷＣＭ）的非线笥动态电路时域稳态模拟方法。该方法可以对电路瞬态响应过程用大步长（低阶小波）模拟,而对稳态响应过程用小步长（高阶小波）模拟,从而避免了为得到电路稳态响应而在瞬态响应时期花费的大量的模拟时间。并且,该方法具有较低的计算复杂度。一些模拟结果证明,本文的方法是一种十分有效的方法。     

Modeling of Cylindrical Pin-Fin Heat Sinks for Electronic Packaging

Analytical models are developed for determining heat transfer from in-line and staggered pin-fin heat sinks used in electronic packaging applications. The heat transfer coefficient for the heat sink and the average temperature of the fluid inside the heat sink are obtained from an energy balance over a control volume. In addition, friction coefficient models for both arrangements are developed from published data. The effects of thermal conductivity on the thermal performance are also examined. All models can be applied over a wide range of heat sink parameters and are suitable for use in the design of pin-fin heat sinks. The present models are in good agreement for high Reynolds numbers with existing experimental/numerical data.      

Numerical Study of Heat Transfer From Pin-Fin Heat Sink Using Steady and Pulsated Impinging Jets

This paper investigates numerically the heat transfer characteristics of confined slot jet impingement on a pin-fin heat sink. A variety of pin-fin heat sinks is investigated, and the resulting enhancement of heat transfer studied. The distribution of heat transfer coefficient on the top surface of the base plate and that along the fin height are examined. Both steady and pulsated jets are studied. It is observed that for a steady jet impingement on a pin-fin heat sink, the effective heat transfer coefficient increases with fin height, leading to a corresponding decrease in base plate temperature for the same heat flux. In the case of pulsated jets, the influence of pulse frequency and the Reynolds number is examined, and their effect on the effective heat transfer coefficient is studied.      

三维集成电路稳态解和瞬态解的建模与热分析

针对三维集成电路(3D IC)热效应问题,提供了三维集成电路热模型的稳态解析解和瞬态解析解,这些解适用于N层(N≥2)模型;热源可以非均匀分布,瞬态时热源的大小可随时间变化。求解的过程使用了分离变量法、格林函数法和本征函数正交性。通过瞬态解可以获得任意时刻模型的温度场,稳态解是与时间无关的函数,通过它可以直接计算出稳态热传导的温度场。使用所获得的解析解在MATLAB中计算得到的温度场和COMSOL仿真温度场进行比较,结果表明,稳态解计算3层和5层3D IC模型得到的结果和COMSOL仿真结果最大误差在1%左右;使用所获得的瞬态解计算3层和5层3D IC模型得到的结果和COMSOL仿真结果最大误差不超过3%。