Preface

Levitation or suspension is a magical phenomenon that an object occupies a fixed position in a gravitational field without any direct physical contact. Scientists have found and suggested a number of suspension methods, for example, aerodynamic, acoustic, optical, electric, magnetic, and radio-frequency（RF）suspension and so on.The levitation phenomena attracted not only wide attention of the public, but also the interest of scientists and engineers.Magnetic levitation（Maglev）is a promising one in various suspension phenomena, and it is implemented using the principle of independent suspension with magnetic field.

Maglev technologies have a series of potential advantages including high or ultra high speed, low energy consumption, environment friendly, low maintenance, moderate footprint, low operating costs, etc. Maglev is currently attracting world wide interest for both high speed intercity vehicles and low speed urban transit vehicles, especially high or ultra high speed intercity traffic.After nearly a century long development, Maglev finally began to penetrate ground transportation markets and presented the possibility of rapid development.

Traditional and superconducting Maglev have different characteristics.The high-temperature superconducting（HTS）bulk Maglev can realize stable levitation without any active control.The physical characteristics of self-stabilization of HTS bulk Maglev is the unique phenomena in nature.This is especially attractive for practical applications of Maglev transportation.The experts in the world are trying to complete the HTS Maglev vehicle test.This book is devoted to HTS Maglev.

Fundamentals of superconductivity are introduced in Chapter 1. Supercon ductivity is a deep and complex subject.We can only provide a brief overview about basic superconductivity in this book, which is required to understand how HTS Maglev works.

In Chapter 2 we discuss the superconducting materials. After a brief in troduction of superconducting materials, we will focus on the HTS bulk and its thermal, mechanical, and trapped flux properties, all are essential in HTS Maglevapplications.

Magnetic levitation will be discussed in Chapter 3. In order to help the reader understand Maglev transportation, we start with the value of the ground track-based traffic system and the limitations of the traditional railway transport, then move on to levitation phenomena, magnetic levitation concepts, and non-superconducting magnetic levitation applications like the permanent magnet Maglev and normal conductive Maglev.

In addition to the advantages of permanent magnet and normal conduc tive Maglev, superconducting Maglev gains further improvement including more energy-saving, environmental protection, high speed, and most important, the pos sibility of ultra high speed. The superconducting Maglev, LTS and HTS Maglev, will be discussed in Chapter 4.Various types of Maglev have different perfor mance.In the constant pursuit of the"perfect"Maglev transportation, the new HTS Maglev train stands out to be one of the best candidates.

With the previous Maglev testing method, the YBCO bulk is placed in a sim ple liquid nitrogen container which is below the permanent magnet. Other than being highly inaccurate, this simple method is not even close to real conditions of Maglev applications.In order to investigate the levitation forces, guidance forces, as well as their cross stiffness, dynamic rigidity, relaxation time etc.of the HTS Maglev over a PM guideway（PMG），we developed several Maglev measurement systems from 1999 to 2014.The measurement systems are different from the earlier system that the measured HTS bulk is above the PMG.As a result, a cryogenic vessel with a super-thin bottom is needed.In order to investigate HTS Maglev bear ing and flywheel energy storage technology, the HTS Maglev bearing measurement system was designed and successfully developed in 2014.The principles, methods, structure, functions, and specifications of the several HTS Maglev measurement systems are presented in detail in Chapter 5.

The several HTS Maglev measurement systems play an important role in the research and development of the HTS Maglev. Following chapters will present these research results and their applications in developing the prototype of HTS Maglev.The earlier study was carried out in the HTS Maglev measurement system SCML 01，and according to these massive research results the first manned HTS Maglevtest vehicle in the world—"Century"was successfully developed on December 31st，2000.In Chapter 6 the research results and properties of the entire Maglev test vehicle are presented in detail.

After the success of the first manned HTS Maglev vehicle, the theoreti cal and experimental researches of HTS Maglev are carried out by the authors'team unremittingly. The research results of 2D and 3D numerical simulations of HTS Maglev in ASCLab（Applied Superconductivity Laboratory）are presented in Chapter 7.

In Chapter 8 new research progresses about HTS Maglev are presented. These include the new research results on HTS Maglev properties between HTS bulks and PMG, and the ETT HTS Maglev vehicle developed using the new results.

Research results and the experimental prototype of HTS Maglev bearing and 5 kWh flywheel energy storage system are presented in Chapter 9.

HTS Maglev launch technology prototype system and HTS linear synchro nous motors are presented in Chapter 10.

The book presents the research findings from our team of the HTS Maglev R&D, and I wish to thank all members of our team very much for their hard work and selfless dedication.

We especially thank our previous graduate students Dr. Xiao-Rong Wang of Lawrence Berkeley National Laboratory, Dr.Hong-Hai Song of Michigan State University, Dr.Zhong-You Ren of Siemens Shenzhen Magnetic Resonance Ltd.，research scientist He Jiang of Aerospace Science Research Institute, Dr.Min Zhu of Institute of Electronics of Chinese Academy of Sciences, Dr.Wei Wang of Cambridge University, Dr.Rong Zeng, Dr.Long-Cai Zhang, Dr.Lu Liu, and Dr.Si-Ting Pan et al.for offering the unpublished papers or summaries of their original research work on HTS Maglev.

The birth of"Century"16 years ago is the reason why we wrote this book. Therefore, we'd like have to thank Zhong-You Ren, He Jiang, Min Zhu, Xiao-Rong Wang, Chang-Yan Deng, You-Wen Zeng, Qi-Xue Tang, Hi-Yu Huang, Xu-Ming Shen et al.for their important and substantive contributions to the development of"Century".We are very grateful to Hong-Tao Ren and his group, the Beijing General Research Institute for Nonferrous Metals, for providing high quality HTSbulk materials, and Li-Ming Pan and his group, the Yuxin Machinery Co.，Ltd.，for providing help for the rectangle-shape thin bottom liquid nitrogen vessel.

This book is based on the research work of the ASCLab group that is com posed of the above-mentioned researchers and ACSLab alumni including Dr. Min Xian Liu, Hua Jing, Qing-Yong He, Yu-Jie Qing, Dong-Hui Jiang, Chang Qing Ye, and Xing-Zhi Wang, whose work we are also thankful for.

We also thank my colleagues and friends outside our team for discussions and exchanges about the HTS Maglev during their visits to our lab：Prof. Y.Iwasa of the Francis Bitter Magnet Laboratory of MIT in USA, Dr.Frank N.Werfel of the Adelwitz Technologiezentrum GmbH（ATZ），Dr.E.H.Brandt of the Institut für Physik, and Dr.Wolfgang Gawalek of the IPHT-Jena in Germany, Prof.M.Izumi of the Tokyo University of Marine Science and Technology, Prof.Masato Murakami of the Shibaura Institute of Technology, Dr.Hiroyuki Fujimoto of the Railway Technical Research Institute in Japan, Prof.Richard M.Stephan of the Federal University of Rio de Janeiro in Brazil, and Prof.Du-Xing Chen of the Universitat Autonoma Barcelona in Spain.

During his visit, Prof. Iwasa presented draft chapters of his book Case Studies in Superconducting Magnets, Second Edition for three lectures.

Not long after his visit to ASCLab, Dr. Brandt got terminally ill.He gave his entire research archive to us before he passed away.We will always remember the important contribution he made to superconductor research and his devotion to scientific research.

The continuous collaboration between Werfel's group and our team has been highly productive.

As part of the project of science and technology cooperation between the government of China and Germany in 2004-2005，extensive and in-depth exchanges between our team and Dr. Ludwig Schultz's group of the IFW was conducted, and this cooperation promoted the HTS Maglev development.Prof.Archie Campbell of the Cambridge University in UK sent the details of his research findings of Maglev in 2001.

We also acknowledge the National High-tech R&D Program（National 863 Program）and the National Natural Science Foundation in China for their long-term research grants for the HTS Maglev project from 1990 to 2010.

Last but not least, we'd like to thank Wei Wang at Cambridge University and Xin-Ju Wang at Intel for proofreading Chapter 1 to 6. We highly appreciate Prof.D.G.Naugle at Texas A&M University for reviewing this book rigorously.

Jia-Su Wang

Su-Yu Wang

Chengdu, P. R.China

January 5，2016