Stability and Protection of Superconducting Magnets—A Discussion

Iwasa, Y.

doi:10.1109/tasc.2005.849207

Cited by 47 publications

(31 citation statements)

References 1 publication

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“…Beam Loss AC Loss Figure 2.2: Expected spectrum of heat sources for superconducting accelerator magnets built with low-T c superconductor [12].…”

Section: Conductor Motion Flux Jumpmentioning

confidence: 99%

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Stability of superconducting Rutherford cables for accelerator magnets

Willering

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f c e e r g s o r a c l r a t o m a n e t Gerard Willering S t a b i l i t y o f S u p e r c o n d u c t i n g r C b l e R u t h e f o r d a s PrefaceThe work described in this thesis results from an extensive collaboration between the special chair for Industrial Application of Superconductors in the Low Temperature Division at the University of Twente and the Magnets, Superconductors and Cryostats group at CERN. The research has been carried out at CERN as well as at the University of Twente and it is funded by both institutes. Part of the cable samples were prepared by GSI in the frame of research collaboration on cable stability.I am very grateful to the members of these groups for giving me the opportunity to perform the research, for their interest and useful discussions.i ContentsPreface i Chapter 1 IntroductionAfter the discovery of superconductivity in the beginning of the 20 th century the understanding of the phenomenon has grown. Practical conductors are produced for various magnet applications. Although the number of superconducting materials is high, only a few can be used in high-field and high-current density applications. This thesis deals with cable stability, with the focus on application in accelerator magnets.In this chapter a brief overview of the existing and near future accelerators and their superconducting magnets is presented. The most recent superconducting accelerator, the lhc and the near future superconducting accelerator sis 300 are described.The phenomenon of superconductivity is shortly discussed and practical superconductors are introduced with an emphasis on strands and cables. Different types of cables are presented and the relevance of this thesis for in particular the Rutherford type of cable is discussed.The terms quench and recovery are introduced. The importance of research on stability is illustrated by the large number of training quenches in the lhc main dipole magnets. Superconducting accelerator magnetsIn High Energy Physics the interaction of elementary particles is being studied. Many particle accelerators have been constructed to accelerate particles and collide them at high energy. Synchrotron accelerators provide a circular track with RFcavities to accelerate bunches of particles each cycle.Synchrotron accelerators require dipole magnets to bend the particle beam and keep it in its circular track. Quadrupole magnets are used to focus and defocus the beam and higher-order magnets correct field distortions and chromaticity. The collision energy depends on the magnetic field in the aperture of the dipole B a (T) and the bending radius of the dipole magnets r d (km) following E ≈ 0.3B a r d (TeV). The limitation in the track circumference is strongly dictated by the amount of material and the costs involved. In normal conducting magnets iron is applied to enhance the electromagnetic field produced with copper windings. The magnetic field in iron saturates at about 2 T, therefore the needed amount of copper windings and the costs involved increase strongly for hig...

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“…Beam Loss AC Loss Figure 2.2: Expected spectrum of heat sources for superconducting accelerator magnets built with low-T c superconductor [12].…”

Section: Conductor Motion Flux Jumpmentioning

confidence: 99%

“…The heat dissipation in a normal conducting wire section with length ∂z is defined by 12) with J m the current density in the matrix, A m the cross-sectional area of the matrix. ρ cu is assumed to be constant below 10 K, where it is only depending on purity and magnetic field.…”

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confidence: 99%

Stability of superconducting Rutherford cables for accelerator magnets

Willering

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“…A quench is a transition that causes an amount of resistive losses, which cannot be absorbed by the cooling system. Quench detection and magnet protection against overheating and voltage peaks during a quench are important issues in the design of superconducting magnets [6]. An incipient quench is detected by the resistive-voltage rise across the normal zone, which must be distinguished from the induced voltage during the ramping of the magnet.…”

Section: A Active and Passive Quench Protectionmentioning

confidence: 99%

“…Passive-protection schemes may include a diode or a resistor connected in parallel to the magnet, but principally, they rely on strong stabilization of the conductor, such that the magnet can withstand the current decay without overheating. A stabilized conductor is a conductor with a copper-tosuperconductor ratio that is large enough so that, in case the superconductor quenches, the copper can take over the current for a long enough time to ramp down the magnet safely [6].…”

Section: A Active and Passive Quench Protectionmentioning

confidence: 99%

Numerical Field Calculation in Support of the Hardware Commissioning of the LHC

Schwerg

Auchmann

Russenschuck

2011

IEEE Trans. Appl. Supercond.

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Abstract-The hardware commissioning of the Large Hadron Collider required the testing and the qualification of the cryogenic and vacuum system, as well as the electrical systems for the powering of more than 10 000 superconducting magnets. Nonconformities had to be resolved within a tight schedule. In this paper, we focus on the role that electromagnetic-field computation has played during hardware commissioning in terms of the analysis of a magnet quench and electromagnetic-force calculations in busbars and splices, as well as field-quality prediction for the optimization of powering cycles.

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“…HTS coils are more vulnerable than low-temperature superconducting (LTS) coils because of their slow normal zone propagation velocities (NZPVs) that limit the dissipation of local heat energy. Therefore, it is important to understand quench initiation and propagation in HTS racetrack coils [6][7][8][9][10]. The quench and recovery characteristics of HTS coils have been widely reported [2,[11][12][13][14][15], though there are insufficient data regarding the thermal/electrical stabilities and normal zone propagation (NZP) characteristics of second-generation (2G) HTS racetrack pancake (RP) coils.…”

Section: Introductionmentioning

confidence: 99%

Quench Initiation and Propagation in GdBCO Racetrack Pancake Coil for Large-Scale Rotating Machines

Yang¹,

Song²,

Kim³

et al. 2011

J Supercond Nov Magn

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Quench tests of a GdBCO racetrack pancake coil were conducted in liquid nitrogen at 77 K. Minimum quench energy and two-dimensional normal zone propagation velocities of the coil are discussed. Longitudinal normal zone propagation velocities in the curved section were almost twice those in the straight portion due to stress effects, showing that protection of the straight portion is of greater importance than protection of the curved portion when using racetrack-type, GdBCO pancake coils in large-scale rotating machines.

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Stability and Protection of Superconducting Magnets—A Discussion

Cited by 47 publications

References 1 publication

Stability of superconducting Rutherford cables for accelerator magnets

Stability of superconducting Rutherford cables for accelerator magnets

Numerical Field Calculation in Support of the Hardware Commissioning of the LHC

Quench Initiation and Propagation in GdBCO Racetrack Pancake Coil for Large-Scale Rotating Machines

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