Nb3Sn Accelerator Magnets: Designs, Technologies and Performance [1st ed. 2019] 978-3-030-16117-0, 978-3-030-16118-7

Table of contents :
Front Matter ....Pages i-xvii
Front Matter ....Pages 1-1
Superconducting Magnets for Accelerators (Alexander V. Zlobin, Daniel Schoerling)....Pages 3-22
Nb3Sn Wires and Cables for High-Field Accelerator Magnets (Emanuela Barzi, Alexander V. Zlobin)....Pages 23-51
Nb3Sn Accelerator Magnets: The Early Days (1960s–1980s) (Lucio Rossi, Alexander V. Zlobin)....Pages 53-84
Front Matter ....Pages 85-85
CERN–ELIN Nb3Sn Dipole Model (Romeo Perin)....Pages 87-104
The UT-CERN Cos-theta LHC-Type Nb3Sn Dipole Magnet (Herman H. J. ten Kate, Andries den Ouden, Daniel Schoerling)....Pages 105-132
LBNL Cos-theta Nb3Sn Dipole Magnet D20 (Shlomo Caspi)....Pages 133-156
Cos-theta Nb3Sn Dipole for a Very Large Hadron Collider (Alexander V. Zlobin)....Pages 157-192
Nb3Sn 11 T Dipole for the High Luminosity LHC (FNAL) (Alexander V. Zlobin)....Pages 193-222
Nb3Sn 11 T Dipole for the High Luminosity LHC (CERN) (Bernardo Bordini, Luca Bottura, Arnaud Devred, Lucio Fiscarelli, Mikko Karppinen, Gijs de Rijk et al.)....Pages 223-258
Front Matter ....Pages 259-259
Block-Type Nb3Sn Dipole R&D at Texas A&M University (Peter McIntyre, Akhdiyor Sattarov)....Pages 261-284
The HD Block-Coil Dipole Program at LBNL (Gianluca Sabbi)....Pages 285-310
CEA–CERN Block-Type Dipole Magnet for Cable Testing: FRESCA2 (Etienne Rochepault, Paolo Ferracin)....Pages 311-340
Front Matter ....Pages 341-341
The LBNL Racetrack Dipole and Sub-scale Magnet Program (Steve Gourlay)....Pages 343-370
Common-Coil Nb3Sn Dipole Program at BNL (Ramesh Gupta)....Pages 371-394
Common-Coil Dipole for a Very Large Hadron Collider (Alexander V. Zlobin)....Pages 395-423
Front Matter ....Pages 425-425
Nb3Sn Accelerator Dipole Magnet Needs for a Future Circular Collider (Davide Tommasini)....Pages 427-439
Back Matter ....Pages 441-452

Citation preview

Particle Acceleration and Detection

Daniel Schoerling Alexander V. Zlobin Editors

Nb3Sn Accelerator Magnets Designs, Technologies and Performance

Particle Acceleration and Detection Series Editors Alexander Chao, SLAC, Stanford University, Menlo Park, CA, USA Frank Zimmermann, BE Department, ABP Group, CERN, Genève, Switzerland Katsunobu Oide, KEK, High Energy Accelerator Research Organization, Tsukuba, Japan Werner Riegler, Detector group, CERN, Genève, Switzerland Vladimir Shiltsev, Accelerator Physics Center, Fermi National Accelerator Lab, Batavia, IL, USA Kenzo Nakamura, Kavli IPMU, University of Tokyo, Kashiwa, Chiba, Japan

The series Particle Acceleration and Detection is devoted to monograph texts dealing with all aspects of particle acceleration and detection research and advanced teaching. The scope also includes topics such as beam physics and instrumentation as well as applications. Presentations should strongly emphasize the underlying physical and engineering sciences. Of particular interest are • contributions which relate fundamental research to new applications beyond the immeadiate realm of the original field of research • contributions which connect fundamental research in the aforementionned fields to fundamental research in related physical or engineering sciences • concise accounts of newly emerging important topics that are embedded in a broader framework in order to provide quick but readable access of very new material to a larger audience. The books forming this collection will be of importance for graduate students and active researchers alike

More information about this series at http://www.springer.com/series/5267

Daniel Schoerling • Alexander V. Zlobin Editors

Nb3Sn Accelerator Magnets Designs, Technologies and Performance

Editors Daniel Schoerling CERN (European Organization for Nuclear Research) Meyrin, Genève, Switzerland

Alexander V. Zlobin Fermi National Accelerator Laboratory (FNAL) Batavia, IL, USA

ISSN 1611-1052 ISSN 2365-0877 (electronic) Particle Acceleration and Detection ISBN 978-3-030-16117-0 ISBN 978-3-030-16118-7 (eBook) https://doi.org/10.1007/978-3-030-16118-7 © The Editor(s) (if applicable) and The Author(s) 2019. This book is an open access publication. Open Access This book is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence and indicate if changes were made. The images or other third party material in this book are included in the book’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the book’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG. The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Foreword

Colliders of highly energetic particle beams are a crucial tool for fundamental research in high-energy physics (HEP), allowing for the investigation of highest mass particles and smallest length scales. Accelerator magnets are essential for steering and focusing such particle beams. The development and the practical implementation of superconducting (SC) accelerator magnets, in particular dipoles and quadrupoles, for the Fermilab Tevatron in the 1970s and 1980s enabled a breakthrough jump in technology and allowed for hitherto unprecedented particlebeam energies and collision rates. The Large Hadron Collider (LHC, in operation since 2008) at the European Organization for Nuclear Research (CERN) represents the current state of the art of large SC colliders. At present, CERN is preparing the high-luminosity LHC (HL-LHC) upgrade to increase the collision rate even further and to fully exploit the LHC potential. For the post-LHC era, various colliders are under study, including linear lepton colliders (Compact Linear Collider (CLIC) and International Linear Collider (ILC)), and circular colliders (for electron–positron and proton–proton collisions). At CERN, the long-term goal of the Future Circular Collider (FCC) Study is to push the energy frontier much beyond other proposed accelerators, so as to increase the discovery reach, in energy, by an order of magnitude with respect to LHC in an affordable and energy-efficient manner. Two FCC options are currently under study, and, depending on the available time span, they can possibly be housed, successively, in the same tunnel, as it had been the case for the Large Electron–Positron Collider (LEP) and LHC at CERN. The FCC hadron collider as second stage would provide a unique opportunity to probe the nature at the smallest distance scales ever explored by mankind; to discover, if existent, new particles with exceedingly tiny Compton wavelengths; to thoroughly examine the dynamics of electroweak symmetry breaking; and to test the fundamental principles that have guided progress for decades. To enable highest energy hadron colliders, new, reliable, and cost-effective magnet technologies are indispensable. Currently, only Nb3Sn SC seem to be technically and commercially mature enough to be considered as candidate material v

vi

Foreword

for the magnets of such a future collider, to be constructed in the coming decades. Although work on Nb3Sn magnets started already in the 1960s, a significant effort is still required to optimize both the SC material and the magnet designs to prepare for mass production. A major milestone will be the first-time implementation of Nb3Sn dipole and quadrupole accelerator magnets in the HL-LHC. In parallel, a worldwide conductor and magnet R&D program has been launched, toward the challenging design goals for the FCC. This global effort is strongly supported by the FCC Study, the EuroCirCol Design Study co-funded by the European Commission, and the U.S. Magnet Development Program (MDP). This book provides a critical review of the existing worldwide experience in the area of Nb3Sn dipole magnets and will play a vital role in supporting this truly global effort toward the next generation of SC high-field accelerator magnets. Genève, Switzerland

Michael Benedikt FCC Study Leader [email protected]

Preface

The goal of this book is to summarize and review the vast experience with Nb3Sn accelerator dipole magnets accumulated in the United States, Europe, and Asia since the discovery and production of Nb3Sn composite conductors. Interest in Nb3Sn accelerator magnets is soaring, and their further development is rapidly gaining momentum worldwide, thanks to the growing maturity of this technology and its great potential for particle accelerators used in high-energy physics. This book is intended to contribute to the transfer of the accumulated experience with the design, technology, and performance of such magnets in view of the challenging requirements set by the needs for ever-higher collision energies in future colliders. Engineers and physicists working in the field of particle accelerators, as well as students studying courses in particle accelerator physics and technologies, may find it an indispensable source of information on Nb3Sn accelerator magnets. Readers with a general interest in the history of science and technology may also find useful information that was obtained over a long period of time, from the late 1960s to the present day. The book contains 16 chapters, structured within 5 sections. The first section includes three introductory chapters. It starts with a brief description of the general problems of accelerator magnet design and operation (Chap. 1), followed by historical overviews of the research and development (R&D) of Nb3Sn wires and cables for accelerator magnets (Chap. 2), and the early period of Nb3Sn magnet R&D—a time during which this technology was competing with Nb-Ti magnets in the same field range (Chap. 3). It took almost 25 years (1965– 1990) to advance the performance of Nb3Sn accelerator magnets to fields above 10 T—a field range beyond the limits of Nb-Ti accelerator magnets. The next three sections describe the period from the early 1990s to the present day. This period is characterized by the appearance of powerful numerical computer programs for the electromagnetic, mechanical, and thermal analysis of superconducting magnets, advanced superconducting and structural materials and fabrication techniques, and significant progress in magnet instrumentation and test methods. The great progress in these areas allowed significant advances in the vii

viii

Preface

magnet design process, improving the magnets’ operating parameters and deepening the understanding of their performance. A key result of this progress is that the maximum field in Nb3Sn accelerator magnets has approached at the present time 15 T. In this period, three main dipole designs (cos-theta, block type, and common coil) were thoroughly explored. Their design features, technologies, and performances are described in detail in Chaps. 4, 5, 6, 7, 8, and 9 (cos-theta), Chaps. 10, 11, and 12 (block type), and Chaps. 13, 14, and 15 (common coil). In each of the three sections, the chapters follow chronological order to demonstrate the progress made within each design approach. The structure of the material presented in the chapters follows the main theme of the book: magnet design, technology, and performance. This approach is used to ease the finding of appropriate information inside each chapter and to simplify the comparison of similar data presented in the various chapters. The last section of the book outlines the future needs and the target parameters of the next generation of Nb3Sn accelerator magnets and briefly summarizes the main open issues for their design and performance (Chap. 16). One of the main challenges in the next decade will be increasing the nominal operation field in accelerator magnets towards 16 T. To provide sufficient operation margin, it will require raising the magnet maximum field above 18 T and approaching the limit of the Nb3Sn accelerator magnet technology. New cost-effective materials and technology affordable for the next generation of particle accelerators have to be also developed. The discussion presented in this session could be considered also as an invitation to the reader to take part in this new, exciting R&D phase of Nb3Sn accelerator magnet technologies. Genève, Switzerland Batavia, IL, USA

Daniel Schoerling Alexander V. Zlobin

Acknowledgments

The editors and authors thank the forefront experts from the research and development (R&D) projects, programs, and fields treated here for openly sharing with us their work and their enthusiastic engagement in the preparation of this book. We also thank the many other colleagues who have helped us in finding material spread over the archives of the laboratories involved in this field over the last six decades and for providing their valuable insights and comments on the book’s content, in particular Daniel Dietderich (LBNL), Michael Fields (B-OST), René Flükiger (University of Genève and CERN), Eugeny Yu. Klimenko (Kurchatov Institute), David C. Larbalestier (ASC-FSU), Peter Lee (ASC-FSU), Clément Lorin (CEA-Saclay), Alfred D. McInturff (LBNL), Jean-Michel Rifflet (CEA-Saclay), Tiina-Maria Salmi (UoT), William B. Sampson (BNL), Ronald M. Scanlan (LBNL), Manfred Thoener (B-EAS), Peter Wanderer (BNL), Akira Yamamoto (KEK), and Franz Zerobin (ELIN-UNION). We would also like to acknowledge the technical staff of BNL, CEA-Saclay, CERN, FNAL, KEK, LBNL, TAMU, and the University of Twente for their contributions to magnet design, fabrication, and testing. Most names are indicated in the corresponding references. Our thanks are also due to the copy editors from Sunrise Setting for editing and proofreading the text, Simon-Niklas Scheuring (Dreamlead Pictures) for image processing and coloring, and Pierre-Jean François and his team (Intitek) for drawing and sketch preparation. We thank Jens Vigen (Head of the CERN library) for his efforts toward publishing this book as an open access publication and Salomé Rohr (CERN library) for her great support in finding and archiving the references. Special thanks also go to Springer Nature and its editorial staff, in particular Hisako Niko, who supported this project from the beginning, and their valuable help in the publication process. Without the large effort and patience of all these people, this book would have not been possible.

ix

Contents

Part I

Introduction

1

Superconducting Magnets for Accelerators . . . . . . . . . . . . . . . . . . . Alexander V. Zlobin and Daniel Schoerling

3

2

Nb3Sn Wires and Cables for High-Field Accelerator Magnets . . . . . Emanuela Barzi and Alexander V. Zlobin

23

3

Nb3Sn Accelerator Magnets: The Early Days (1960s–1980s) . . . . . . Lucio Rossi and Alexander V. Zlobin

53

Part II

Cos-Theta Dipole Magnets

4

CERN–ELIN Nb3Sn Dipole Model . . . . . . . . . . . . . . . . . . . . . . . . . Romeo Perin

87

5

The UT-CERN Cos-theta LHC-Type Nb3Sn Dipole Magnet . . . . . . 105 Herman H. J. ten Kate, Andries den Ouden, and Daniel Schoerling

6

LBNL Cos-theta Nb3Sn Dipole Magnet D20 . . . . . . . . . . . . . . . . . . 133 Shlomo Caspi

7

Cos-theta Nb3Sn Dipole for a Very Large Hadron Collider . . . . . . . 157 Alexander V. Zlobin

8

Nb3Sn 11 T Dipole for the High Luminosity LHC (FNAL) . . . . . . . 193 Alexander V. Zlobin

9

Nb3Sn 11 T Dipole for the High Luminosity LHC (CERN) . . . . . . . 223 Bernardo Bordini, Luca Bottura, Arnaud Devred, Lucio Fiscarelli, Mikko Karppinen, Gijs de Rijk, Lucio Rossi, Frédéric Savary, and Gerard Willering

xi

xii

Contents

Part III

Block-Type Dipole Magnets

10

Block-Type Nb3Sn Dipole R&D at Texas A&M University . . . . . . . 261 Peter McIntyre and Akhdiyor Sattarov

11

The HD Block-Coil Dipole Program at LBNL . . . . . . . . . . . . . . . . . 285 Gianluca Sabbi

12

CEA–CERN Block-Type Dipole Magnet for Cable Testing: FRESCA2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 Etienne Rochepault and Paolo Ferracin

Part IV

Common-Coil Dipole Magnets

13

The LBNL Racetrack Dipole and Sub-scale Magnet Program . . . . . 343 Steve Gourlay

14

Common-Coil Nb3Sn Dipole Program at BNL . . . . . . . . . . . . . . . . 371 Ramesh Gupta

15

Common-Coil Dipole for a Very Large Hadron Collider . . . . . . . . . 395 Alexander V. Zlobin

Part V 16

Future Needs and Requirements

Nb3Sn Accelerator Dipole Magnet Needs for a Future Circular Collider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 Davide Tommasini

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441

Glossary of Terms

Accelerator magnet Accelerator magnets are a component of particle accelerators used to act on the beam properties. They typically have to meet stringent requirements in terms of design, technologies, and performance to allow a reliable operation of the accelerator Arc Portion of a ring accelerator occupied by a regular structure of dipole, quadrupole, sextupole and octupole magnets ARL Accelerator Research Laboratory (ARL) at the Texas Agricultural and Mechanical (A&M) University ASC-FSU Applied Superconductivity Center at the joint college of engineering of Florida A&M University (FAMU) and Florida State University (FSU) Beam pipe Ultrahigh vacuum chamber in which the beam is being transported Bi-2212 Bismuth strontium calcium copper oxide (Bi2Sr2CaCu2O8), a hightemperature superconductor BICC Boundary-induced coupling currents Block type Dipole magnet type based on racetrack coils with flared ends BNL Brookhaven National Laboratory in Upton, Brookhaven, NY BSCCO Bismuth strontium calcium copper oxide, a family of high-temperature superconductors of which Bi-2212 is one variant CCT Canted-cosine-theta, a magnet type based on pairs of conductor layers wound and powered such that their transverse field components sum and axial (solenoidal) field components cancel. For dipoles, the single layers resemble tilted solenoids. CEA Saclay Commissariat à l’énergie atomique et aux énergies alternatives (CEA) de Saclay (English: French Alternative Energies and Atomic Energy Commission at Saclay) xiii

xiv

Glossary of Terms

CERN European Organization for Nuclear Research CLIC The Compact Linear Collider (CLIC) study is an international collaboration working on a concept for a machine to collide electrons and positrons (antielectrons) head on at energies up to several teraelectronvolts (TeV). CLIQ Coupling Loss Induced Quench (CLIQ), a system allowing to bring a superconducting magnet rapidly to the normal-conducting state Coldmass Assembly of superconducting magnet coils, a mechanical structure and a helium vessel Collider Particle accelerator for acceleration of charged particles which are brought to collision Common-Coil Dipole magnet type based primarily on flat racetrack coils which are common to both apertures (twin-aperture magnets only) Copper-to-non-copper ratio Area ratio of the copper stabilizer to the non-copper in superconducting strands Cos-theta A magnet type with a winding scheme following a cosine current distribution: for a current distribution following cos θ, where θ is the angle around the aperture, a dipolar field is generated; for a current distribution following cos 2θ, a quadrupolar field is generated and so on. Critical surface Graph of the critical current density Jc as a function of the modulus of the magnetic flux density B and the operation temperature T Curing Process during coil production which is performed after winding to glue together the windings of a coil D20 Cos-theta Nb3Sn dipole magnet designed, manufactured, and tested at LBNL DESY Deutsches Synchrotron)

Elektronen-Synchrotron

(English:

German

Electron

ELIN ELIN-UNION at Weiz, Austria, was an Austrian electric company FCC The Future Circular Collider (FCC) study develops options for potential highenergy frontier circular colliders at CERN for the post-LHC era FEM The finite element method (FEM) is a numerical method for approximating the solution of differential equations describing problems of engineering and mathematical physics. FNAL Fermi National Accelerator Laboratory FRESCA2 Upgrade of the Facility for the Reception of Superconducting Cables (FRESCA2)

Glossary of Terms

xv

G-10 Grade G-10 is constructed from a continuous filament woven glass fabric with an epoxy resin binder. The epoxy resin is made from an epichlorohydrin/bisphenol A epoxy resin and contains no other halogenated compounds, except residuals from the manufacture of the base resin. This grade is not manufactured from a brominated epoxy resin and is not flame-retardant (NEMA Standards Publication LI 1-1998 (R2011), Specification Sheet – 21, NEMA Grade G-10) HD Helmholtz dipole series built at LBNL Heat treatment Process in which the precursors of Nb3Sn are reacted and the Nb3Sn phase forms HEP High Energy Physics HERA Hadron-Elektron-Ring-Anlage (HERA) (English: Hadron Electron Ring Facility) was a particle accelerator colliding leptons and protons at DESY, Germany. It was operated from 3 July 1983 until 29 September 2011 HFDA Series of cos-theta dipole magnets which were fabricated and tested at FNAL HL-LHC The High-Luminosity LHC (HL-LHC) is an upgrade of the LHC to achieve instantaneous luminosities, a factor of five larger than the LHC nominal value Hot spot temperature Hottest spot after a quench in a superconducting coil IGC Intermagnetics General Corporation (IGC), a US company ILC The International Linear Collider is an international endeavor aiming at building a machine to collide electrons and positrons (antielectrons) head on at energies of up to 500 gigaelectronvolts (GeV) ISCC Interstrand Coupling Currents ITER ITER (“the way” in Latin) is a project aiming to produce energy with fusion. KEK Kō-enerugī kasokuki kenkyū kikō (English: The High Energy Accelerator Research Organization) LBNL Lawrence Berkeley National Laboratory LEP The Large Electron-Positron Collider was operated from 14 July 1989 until 2 November 2000 at CERN LHC The Large Hadron Collider (LHC) is housed in the former LEP tunnel at CERN. It first started up on 10 September 2008 LHe Liquid helium Magnet training Typical process in which superconducting magnets reach at an initial powering campaign after each quench a slightly higher current and magnetic field

xvi

Glossary of Terms

Magnetic aperture Magnetic aperture of the magnet, contrary to the mechanical aperture, which is the minimum aperture of the storage ring MBH Abbreviation nominating the 11 T dipole magnets used for replacing a regular Nb-Ti bending magnet in a dispersion suppressor region of LHC MDP US Magnet Development Program, a US program to develop high-field magnets for future circular colliders Mica tape Inorganic electric insulation material based on sheets of silicate minerals MIIT Heat load of the normal zone of a quenching magnet. MIIT
106 A2 s Mirror coil Coil tested in a structure of iron which “mirrors” the missing coils to resemble the field distribution in the magnet MJR Modified jelly-roll (MJR) process, a fabrication process of Nb3Sn multifilamentary wires MSUT Model Single of the University of Twente (MSUT) dipole n-Value of a superconductor Exponent obtained in a specific range of electric field or resistivity when the voltage/current curve is approximated by U ¼ In OST Oxford Superconductor Technologies, a former US company which is now part of Bruker Corporation Persistent currents Induced eddy currents in the superconductors which are persistent, due to the fact that there is no resistivity PIT Powder-in-tube process, a fabrication process of Nb3Sn multifilamentary wires PMF Pressure Measurement Film Quench Transition from the superconducting to the normal-conducting state Quench heaters Heaters which are fired to bring a superconducting magnet rapidly to the normal-conducting state RD Series of racetrack dipoles (RD) built at LBNL REBCO REBa2Cu3O7 (REBCO), where RE stands for rare earth element, a group of high-temperature superconductors RHIC The Relativistic Heavy Ion Collider (RHIC) is a heavy-ion collider at BNL, USA. It first started up in 2000 RRR Residual resistivity ratio: the ratio of the electrical resistivity at 273 K to that at 4.2 K Rutherford cable Multistrand flat or slightly keystoned (trapezoidal) two-layer cable being identical to the Roebel bar

Glossary of Terms

xvii

S2 glass S2 glass is a special glass used for insulation consisting out of 65 wt% SiO2, 25 wt% Al2O3, and 10 wt% MgO Short sample limit The short sample limit is the theoretical current and field limit a superconducting magnet can reach, calculated based on test results in solenoidal background fields of short samples wound around normalized barrels which are heat treated together with the superconducting coils SSC Superconducting Super Collider was a particle accelerator complex under construction in the vicinity of Waxahachie, Texas, aiming at reaching a collision energy of 40 TeV. The project was cancelled in 1993 Strand Composite wire containing superconducting filaments dispersed in a matrix with suitably small electrical resistivity properties Synchrotron A synchrotron is a type of particle accelerators in which the magnetic field is synchronized to the beam energy, so that the particles travel on the same path while being accelerated TAMU Series of block type magnets being developed at the Accelerator Research Laboratory (ARL) at the Texas Agricultural and Mechanical (A&M) University (TAMU) Tevatron The Tevatron is a particle accelerator colliding protons and antiprotons at FNAL. It was operated from 3 July 1983 until 29 September 2011 Thermal cycle Cool down from room temperature (293 K) to cryogenic temperature (4.2 K or 1.9 K), heat back to room temperature (293 K), and cool down again to cryogenic temperature (4.2 K or 1.9 K) of a superconducting magnet Transfer function Current-to-field correspondence in accelerator magnets TWCA Teledyne Wah Chang Albany, a US company Twin-aperture magnet A magnet housing two apertures in the same yoke UNK Uskoritel’no Nakopitel’nyj Kompleks (UNK) (English: Accelerator and Storage Complex) was a particle accelerator complex under construction in Protvino, near Moscow, Russia, at the Institute for High Energy Physics, aiming at reaching a collision energy of 3 TeV. The project was cancelled VLHC Very Large Hadron Collider (VLHC) study

Part I

Introduction

Chapter 1

Superconducting Magnets for Accelerators Alexander V. Zlobin and Daniel Schoerling

Abstract Superconducting magnets have enabled great progress and multiple fundamental discoveries in the field of high-energy physics. This chapter reviews the use of superconducting magnets in particle accelerators, introduces Nb3Sn superconducting accelerator magnets, and describes their main challenges.

1.1

Circular Accelerators and Superconducting Magnets

Circular accelerators are the most important tool of modern high-energy physics (HEP) for investigating the largest mass and the smallest space scales. A key element of a circular accelerator is its magnet system (Wolski 2014). The magnet system is composed of large number of various magnets, mainly dipoles and quadrupoles, to guide and steer the particle beams. The main function of the majority of the magnets (the so-called arc magnets, which are periodically placed along a ring) is to keep the beam on a quasi-circular orbit and confine them in a relatively small and welldefined volume inside a vacuum pipe. Magnets are also used to transfer beams between accelerator rings in so-called transfer lines, to match beam parameters from the transfer line into the injection insertions or into extraction lines and beam dumps, to direct or separate beams for the accelerating radio frequency cavities, and to focus beams for collision at the interaction points where the experiments reside. One of the most important parameters of colliders is the beam energy, as it determines the physics discovery potential. The energy E in GeV of relativistic particles with a charge q in units of the electron charge in a circular accelerator is limited by the strength of the bending dipole magnets B in Tesla and the machine radius r in meters A. V. Zlobin (*) Fermi National Accelerator Laboratory (FNAL), Batavia, IL, USA e-mail: [email protected] D. Schoerling CERN (European Organization for Nuclear Research), Meyrin, Genève, Switzerland e-mail: [email protected] © The Author(s) 2019 D. Schoerling, A. V. Zlobin (eds.), Nb3Sn Accelerator Magnets, Particle Acceleration and Detection, https://doi.org/10.1007/978-3-030-16118-7_1

3

4

A. V. Zlobin and D. Schoerling

E
0:3qBr: Thus, high magnetic fields are an efficient way towards higher energy machines for hadron and ion collisions. The value of the magnetic field in a circular accelerator needs to be synchronized with the beam energy. It is achieved by using electromagnets that allow the field strength to be varied by changing the electric current in the coil. The maximum field of traditional electromagnets with copper or aluminum coils is limited, however, by Joule heating, which limits the current density in a magnet coil typically to ~10 A/mm2. In 1911, the Dutch physicist H. Kamerlingh-Onnes discovered the phenomenon of superconductivity—the vanishing of electrical resistance in some metals at very low (