Calculation of interstrand coupling losses in superconducting Rutherford cables with a continuum model

Bottura, L.; Breschi, Marco; Musso, Andrea

doi:10.1016/j.cryogenics.2018.10.003

Cited by 8 publications

(11 citation statements)

References 29 publications

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“…The current density is assumed uniformly distributed in each strand cross section. The transport current distribution and redistribution between strands occurs through distributed electrical conductances, and self and mutual inductances, according to the nonlinear electric circuit of a cable element described in [28]. The whole electrical model is obtained assembling a total of N strand strands, conductances and inductances becoming matrices of dimension N strand .…”

Section: A Electrothermal Modelmentioning

confidence: 99%

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Stability modeling of the LHC Nb-Ti Rutherford cables subjected to beam losses

Bottura

Breschi

Felcini

et al. 2019

Phys. Rev. Accel. Beams

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The Large Hadron Collider (LHC) at CERN is being prepared for its full energy exploitation during run III, i.e., an increase of the beam energy beyond the present 6.5 TeV, targeting the maximum discovery potential attainable. This requires an increase of the operating field of the superconducting dipole and quadrupole magnets, which in turn will result in more demanding working conditions due to a reduction of the operating margin while the energy deposited by particle loss will increase. Beam-induced magnet quenches, i.e., the transition to normal conducting state, will become an increasing concern, because they could affect the availability of the LHC. It is hence very important to understand and be able to predict the quench levels of the main LHC magnets for the required values of current and generated magnetic fields. This information will be used to set accurate operating limits of beam loss, with sufficient but not excessive margin, so to achieve maximal beam delivery to the experiments. In this study we used a one-dimensional, multistrand thermal-electric model to analyze the maximum beam losses that can be sustained by the LHC magnets, still remaining superconducting. The heat deposition distribution due to the beam losses is given as an input for the stability analysis. Critical elements of the model are the ability to capture heat and current distribution among strands, and heat transfer to the superfluid helium bath. The computational model has been benchmarked against energy densities reconstructed from beam-induced main dipole quenches during LHC operation at 6.5 TeV. The model was then used to evaluate the stability margin of both main dipole and main quadrupole magnets at different beam energies, up to the expected ultimate operating energy of the LHC, 7.5 TeV. The comparison between the quench levels underlines how the increase of beam energy implies a substantial reduction of magnets stability and will require much stricter setting on the allowable beam losses to avoid resistive transitions during operation.

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Section: A Electrothermal Modelmentioning

confidence: 99%

“…At the extremities of the cable, the voltage difference between all strands is set to zero, thus assuming an equipotential boundary condition. Details on the impact of the boundary conditions on current distribution in the presence of time varying external magnetic fields are reported in [28].…”

Section: A Electrothermal Modelmentioning

confidence: 99%

Stability modeling of the LHC Nb-Ti Rutherford cables subjected to beam losses

Bottura

Breschi

Felcini

et al. 2019

Phys. Rev. Accel. Beams

Self Cite

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show abstract

“…The cable is described through a distributed parameters electric circuit, in which the strands are connected to each other through contact conductances and mutual inductances, taken uniform along the cable length. The electromagnetic model, applied in [31] to compute the long-range coupling currents in Rutherford cables, was recently modified to allow the computation of short-range coupling currents and corresponding losses [32].…”

Section: A Electro-thermal Stability Modelmentioning

confidence: 99%

Modeling of Beam Loss Induced Quenches in the LHC Main Dipole Magnets

Breschi

Felcini

Breccia

et al. 2019

IEEE Trans. Appl. Supercond.

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The full energy exploitation of the Large Hadron Collider, a planned increase of the beam energy beyond the present 6.5 TeV, will result in more demanding working conditions for the superconducting dipoles and quadrupoles operating in the machine. It is hence crucial to analyse, understand and predict the quench levels of these magnets for the required values of current and generated magnetic fields. A one-dimensional multi-strand electro-thermal model has been developed to analyse the effect of beam-losses heat deposition. Critical elements of the model are the ability to capture heat and current distribution among strands, and heat transfer to the superfluid helium bath. The computational model has been benchmarked against experimental values of LHC quench limits measured at 6.5 TeV for the MB (Main Bending) dipole magnets.

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“…Current redistribution plays an important role in what the signatures of many observed quench signals look like. Although we have good understanding of main characteristics of current redistribution it is still unclear what exactly the role of splices is, leading to competitive assumptions (boundary conditions) [4] needed to analyze magnet data or design magnets. One of the problems is that related tests done so far are mostly on cables alone [4], [5], [6], [7], [8] and not on operating magnets and this is especially true for Nb3Sn based data.…”

mentioning

confidence: 99%

“…Although we have good understanding of main characteristics of current redistribution it is still unclear what exactly the role of splices is, leading to competitive assumptions (boundary conditions) [4] needed to analyze magnet data or design magnets. One of the problems is that related tests done so far are mostly on cables alone [4], [5], [6], [7], [8] and not on operating magnets and this is especially true for Nb3Sn based data. Studying all aspects of a quench in real magnets is non-trivial and although analysis tools and simulations are ever improving [4], [9], [10], [11], [12], [13], [14], [15] experiments are still unavoidable in probing fine effects during magnet operation and transients.…”

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confidence: 99%

“Mirror” magnet experiment for quench studies, quench analysis techniques development and in support of superconducting magnet modeling

Stoynev

2020

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In order to progress on various research points related to superconducting magnets, we suggest performing series of tests with induced and natural quenches on a mirror magnet, probably using a "11 T" coil. The "mirror" is to have voltage taps instrumented on half the strands, on both coil ends. It is to be instrumented with multiple spot-heaters, of the order of ten, in designated pole-turn areas. Instrumentation is to include quench antenna array facing the inner coil surface, as well as acoustic sensors on the inner layer pole. Further, acoustic sensors at the magnet ends and an acoustic calibration transducer are to be installed. Thus, we are to test sensitivity and precision of acoustic and quench antenna (QA) array sensors, both at close proximity to the coil, and we are to test and commission acoustic onmagnet real-time "calibration". New or extended DAQ will be tested as well. In addition to diagnostic development, the purpose of the magnet experiment is to investigate current redistribution in the coil, both during quenching and in operating conditions; to assess voltage build up across strands and in the coil segments during quenching, to explore voltage signature differentiation between different type of quenches; to improve modeling of processes during quenching and for magnet design purposes. In this experiment, we expect to be able to characterize the processes during a quench in unprecedented details.

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Calculation of interstrand coupling losses in superconducting Rutherford cables with a continuum model

Cited by 8 publications

References 29 publications

Stability modeling of the LHC Nb-Ti Rutherford cables subjected to beam losses

Stability modeling of the LHC Nb-Ti Rutherford cables subjected to beam losses

Modeling of Beam Loss Induced Quenches in the LHC Main Dipole Magnets

“Mirror” magnet experiment for quench studies, quench analysis techniques development and in support of superconducting magnet modeling

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