Dipole magnet | EPFL Graph Search

A dipole magnet is the simplest type of magnet. It has two poles, one north and one south. Its magnetic field lines form simple closed loops which emerge from the north pole, re-enter at the south pole, then pass through the body of the magnet. The simplest example of a dipole magnet is a bar magnet. Dipole magnets in accelerators In particle accelerators, a dipole magnet is the electromagnet used to create a homogeneous magnetic field over some distance. Particle motion in that field will be circular in a plane that is perpendicular to the field and collinear to the direction of particle motion, and free in the direction orthogonal to it. Thus, a particle injected into a dipole magnet will travel on a circular or helical trajectory. By adding several dipole sections on the same plane, the bending radial effect of the beam increases. In accelerator physics, dipole magnets are used to realize bends in the design trajectory (or 'orbit') of the particles, as in circular acc

Analysis of Quench Detection and Protection of a Nb3Sn CCT Technology Demonstrator Dipole for FCC

Jiani Gao

From 2016, Paul Scherrer Institut (PSI) started an activity related to developing design, construction and testing of the superconducting magnets. My thesis work is part of this activity and mainly concerns the design and construction of an innovative high-field superconducting magnet of the Canted-Cosine-Theta (CCT) type - a possible candidate for the Future Circular Collider (FCC) 16 T dipole magnet design. The unique mechanical structure intercepts the accumulated forces lowering the stress on the windings, constituting intrinsic stress management in the high-field Nb3Sn accelerator magnets. However, this structure also constitutes a barrier for heat to quickly propagate in case of a quench. To succeed in the CCT-type magnet design and construction, quench protection is a challenging task that requires a detailed investigation of the electrothermal behavior of this magnet. In this thesis, the potential detection and protection concepts are studied by the multiphysics simulations on a two-layer short model built at PSI and also in a subscale experiment. The 2D User-Defined Elements (UDEs) developed at Lawrence Berkeley National Laboratory (LBNL) in ANSYS Mechanical APDL, which support multi-dependence material properties and include the effect of inter-filament coupling currents, are adapted and used in the coupled electrothermal, electrodynamic, and electrical-circuits calculations for a two-layer CCT-type magnet with different protection methods, such as Coupling-Loss Induced Quench (CLIQ) and Energy-Extraction (EE) system. A first-of-a-kind CCT-type magnet protection study using UDEs is presented. The generic model method is validated through the test data of CCT4, a model magnet constructed at LBNL, protected by an energy-extraction system. The simulation predictions are the first steps of the conceptual design and feasibility validation of the construction of a fast and efficient quench protection system for CCT-type magnets to be operated in an accelerator. These calculations are to be compared to the experimental data in the near future on the PSI's first 1-m long two-layer CCT-type model magnet, CD1. Furthermore, these studies lay the ground for the four-layer CCT protection concepts for FCC.

EPFL2020

Modeling of Quench Protection Concepts for Canted-Cosine-Theta Type High-Field Magnets

Bernhard Auchmann, Jiani Gao, Andreas Pautz

An innovative high-field superconducting magnet of Canted-Cosine-Theta (CCT) type has been proposed for Future Circular Collider 16 T dipole magnet design. The unique mechanical structure intercepts the accumulated forces lowering the stress on the windings, constituting intrinsic stress management in high-field Nb3Sn accelerator magnets. However, this structure also constitutes a barrier for heat to quickly propagate in case of a quench. To succeed in the CCT-type magnet design and construction, quench protection is a challenging task that requires a detailed investigation of the electrothermal behavior of the magnet. In this paper, the protectability of a two-layer short model CD1 (Canted Dipole) built at PSI is studied using multiphysics simulations. Two protection methods are considered: energy extraction and coupling-loss induced quench. The 2D User-Defined Elements (UDEs) developed at Lawrence Berkeley National Laboratory in ANSYS Parametric Design Language, which support the multi-dependence material properties and include the effect of inter-filament coupling currents, are adapted and used in the coupled electrothermal, electrodynamic and electrical circuits calculations. A first-of-a-kind CCT-type magnet protection study using UDEs is presented. The generic model method will be validated through CD1 cold tests. Furthermore, these studies will prepare the ground for four-layer CCT protection concepts for FCC.

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2020

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

Luca Bottura, Enrico Felcini, Pier Paolo Granieri

The full energy exploitation of the Large Hadron Collider (LHC), 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 analyze, 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 analyze 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 Main Bending dipole magnets.

2019

Analysis of Quench Detection and Protection of a Nb3Sn CCT Technology Demonstrator Dipole for FCC

Jiani Gao

EPFL2020