Advanced Multipoles For Accelerator Magnets

This monograph presents research on the transversal beam dynamics of accelerators and evaluates and describes the respective magnetic field homogeneity. The widely used cylindrical circular multipoles have disadvantages for elliptical apertures or curved trajectories, and the book also introduces new types of advanced multipole magnets, detailing their application, as well as the numerical data and measurements obtained. The research presented here provides more precise descriptions of the field and better estimates of the beam dynamics. Moreover, the effects of field inhomogeneity can be estimated with higher precision than before. These findings are further elaborated to demonstrate their usefulness for real magnets and accelerator set ups, showing their advantages over cylindrical circular multipoles. The research findings are complemented with data obtained from the new superconducting beam guiding magnet models (SIS100) for the FAIR (Facility for Antiproton and Ion Research) project. Lastly, the book offers a comprehensive survey of error propagation in multipole measurements and an appendix with Mathematica scripts to calculate advanced magnetic coil designs.

The main topic of the book are the superconducting dipole and quadrupole magnets needed in high-energy accelerators and storage rings for protons, antiprotons or heavy ions. The basic principles of low-temperature superconductivity are outlined with special emphasis on the effects which are relevant for accelerator magnets. Properties and fabrication methods of practical superconductors are described. Analytical methods for field calculation and multipole expansion are presented for coils without and with iron yoke. The effect of yoke saturation and geometric distortions on field quality is studied. Persistent magnetization currents in the superconductor and eddy currents the copper part of the cable are analyzed in detail and their influence on field quality and magnet performance is investigated. Superconductor stability, quench origins and propagation and magnet protection are addressed. Some important concepts of accelerator physics are introduced which are needed to appreciate the demanding requirements on field quality in large storage rings. The operational experience with the superconducting HERA collider serves as an illustration. Finally superconducting correction coils and practical construction and fabrication methods of accelerator magnets are discussed. The physical and technical principles described in the book are substantiated with a wealth of experimental data on multipoles, persistent- and eddy-current effects, quench performance and much more. Contents:IntroductionBasics of SuperconductivityPractical Superconductors for Accelerator MagnetsField CalculationsMechanical Accuracies and Magnetic ForcesPersistent CurrentsEddy Current Effects in Superconducting MagnetsQuenches and Magnet ProtectionImpact of Field Errors on Accelerator Performance and Correction SchemesConstruction Methods of Superconducting Accelerator MagnetsA Techniques of Multipole MeasurementsStretched-Wire System for Quadrupole MeasurementsPassive Superconductor Magnetization in Beam-Pipe CoilsApproximate Relations for NbTi Critical ParametersHelium PropertiesMaterial Properties of KaptonCollar and Yoke Material Properties Readership: Engineers, research scientists and applied physicists. keywords:

Advanced high intensity accelerators have important applications in pulsed spallation neutron sources, synchrotron radiation light sources, radioactive ion beam facilities, etc. In contrast to traditional high energy physics accelerators, these high intensity accelerators require very high beam currents with relatively low particle energy. A common practice in the design of high intensity machines is to employ large aperture and short length magnets packed densely along beam lines in limited spaces. As a result, magnetic fringe fields become more profound, and the interference among adjacent magnets often causes problems for machine operation. This has become a new challenge for the design of high-intensity accelerators.This book describes how to solve the problems of magnetic fringe fields and interference, and how to correctly compute particle optics in advanced high intensity accelerators. The book has evolved from the author's research on the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The author has developed the theory and technique of 3D-field multipole expansion, assisted by advanced 3D-magnet modeling codes and Mathematica scripts. Advanced 3D-magnet modeling produces accurate, discrete magnetic field data on selected boundaries in magnets. With these simulation data, the 3D-field multipole expansion will produce quasi-analytic field distributions within the boundaries. Furthermore, with mathematical tools, particle optics in magnets can be accurately computed with the fringe fields and interference effects taken into account automatically.The author applied the new theory and technique to the SNS quadrupoles, dipoles, other magnets, and beam transport lines. His new approach also helped to discover and to solve the design problems of the SNS ring injection and extraction during the SNS ring commissioning. These practices are described in great detail in this book, and can be followed by the design of any other accelerator project. In addition, based on the comments and feedback from students and readers, the book also includes many important command input files and Mathematica scripts, which should be very useful and can be directly employed by readers to compute particle optics in their own machines.

This unique book, written by one of the world's foremost specialists in the field, is devoted to the design of low and medium field electromagnets whose field level and quality (uniformity) are dominated by the pole shape and saturation characteristics of the iron yoke. The wide scope covers material ranging from the physical requirements for typical high performance accelerators, through the mathematical relationships which describe the shape of two-dimensional magnetic fields, to the mechanical fabrication, assembly, installation, and alignment of magnets in a typical accelerator lattice. In addition, stored energy concepts are used to develop magnetic force relationships and expressions for magnets with time varying fields. The material in the book is derived from lecture notes used in a course at the Lawrence Livermore National Laboratory and subsequently expanded for the U.S. Particle Accelerator School, making this text an invaluable reference for students planning to enter the field of high energy physics. Mathematical relationships tying together magnet design and measurement theory are derived from first principles, and chapters are included that describe mechanical design, fabrication, installation, and alignment. Some fabrication and assembly practices are reviewed to ensure personnel and equipment safety and operational reliability of electromagnets and their power supply systems. This additional coverage makes the book an important resource for those already in the particle accelerator business as well as those requiring the design and fabrication of low and medium field level magnets for charged particle beam transport in ion implantation and medical applications.

Advanced high intensity accelerators have important applications in pulsed spallation neutron sources, synchrotron radiation light sources, radioactive ion beam facilities, etc. In contrast to traditional high energy physics accelerators, these high intensity accelerators require very high beam currents with relatively low particle energy. A common practice in the design of high intensity machines is to employ large aperture and short length magnets packed densely along beam lines in limited spaces. As a result, magnetic fringe fields become more profound, and the interference among adjacent magnets often causes problems for machine operation. This has become a new challenge for the design of high-intensity accelerators.This book describes how to solve the problems of magnetic fringe fields and interference, and how to correctly compute particle optics in advanced high intensity accelerators. The book has evolved from the authors research on the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The author has developed the theory and technique of 3D-field multipole expansion, assisted by advanced 3D-magnet modeling codes and Mathematica scripts. Advanced 3D-magnet modeling produces accurate, discrete magnetic field data on selected boundaries in magnets. With these simulation data, the 3D-field multipole expansion will produce quasi-analytic field distributions within the boundaries. Furthermore, with mathematical tools, particle optics in magnets can be accurately computed with the fringe fields and interference effects taken into account automatically.The author applied the new theory and technique to the SNS quadrupoles, dipoles, other magnets, and beam transport lines. His new approach also helped to discover and to solve the design problems of the SNS ring injection and extraction during the SNS ring commissioning. These practices are described in great detail in this book, and can be followed by the design of any other accelerator project. In addition, based on the comments and feedback from students and readers, the book also includes many important command input files and Mathematica scripts, which should be very useful and can be directly employed by readers to compute particle optics in their own machines.

A fundamental step towards gaining a deeper understanding of our world is to increase the resolution of the investigative instruments we use; i.e. to increase the energy, and hence to decrease the wavelength, of the particles which constitute our probes. Almost any substantial progress in our understanding of the fundamental laws of Nature has been obtained when a new generation of accelerators has allowed us to achieve a new energy range. The new results have generated new questions, thus encouraging us to construct new machines to reach even higher energy levels. The relative energy gain from one generation of accelerators to the next is progressively increasing. The energy ga in suggested by the theoretical predictions at the time has usually been much greater than the value allowed by our technical capabilities. But this smaller energy gain permitted by accelerator technology improvement has generally been sufficient up until now to bring about a substantial increase in our knowledge. Hence a large increase in accelerator energy is very important, and we know that this result can essentially be obtained by developing some new device or some new approach.

Written by a leading expert on the electromagnetic design and engineering of superconducting accelerator magnets, this book offers the most comprehensive treatment of the subject to date. In concise and easy-to-read style, the author lays out both the mathematical basis for analytical and numerical field computation and their application to magnet design and manufacture. Of special interest is the presentation of a software-based design process that has been applied to the entire production cycle of accelerator magnets from the concept phase to field optimization, production follow-up, and hardware commissioning. Included topics: Technological challenges for the Large Hadron Collider at CERN Algebraic structures and vector fields Classical vector analysis Foundations of analytical field computation Fields and Potentials of line currents Harmonic fields The conceptual design of iron- and coil-dominated magnets Solenoids Complex analysis methods for magnet design Elementary beam optics and magnet polarities Numerical field calculation using finite- and boundary-elements Mesh generation Time transient effects in superconducting magnets, including superconductor magnetization and cable eddy-currents Quench simulation and magnet protection Mathematical optimization techniques using genetic and deterministic algorithms Practical experience from the electromagnetic design of the LHC magnets illustrates the analytical and numerical concepts, emphasizing the relevance of the presented methods to a great many applications in electrical engineering. The result is an indispensable guide for high-energy physicists, electrical engineers, materials scientists, applied mathematicians, and systems engineers.

This two-volume book serves as a thorough introduction to the field of high-energy particle accelerator physics and beam dynamics. Volume 1 provides a general understanding of the field and a firm basis for the study of the more elaborate topic, mainly nonlinear and higher-order beam dynamics, which is the subject of Volume 2.