By @BP
Magnets are ubiquitous in modern life, used in motors, generators, wind turbines, steel foundries, toys, and all sorts of technological equipment. They are also essential for several distinct classes of device, including particle accelerators.
Particle Accelerator Magnets
Beams from particle accelerators are used to treat cancer patients and to create radioactive isotopes for medical diagnostics, medicine and sterilization of instruments. They are used to make computer chips and to deal with biological waste. Particle accelerators are also used to study proteins and molecules, including viruses such as COVID-19. The most powerful particle accelerators – such as the LHC at CERN (see Figure 1) – are used for particle physics, built by multi-national collaborations seeking to shed light on the basic constituents of the universe.
Figure 1: Superconducting dipole magnets in the LHC tunnel. Maximilien Brice – CC BY-SA 4.0.
Particle accelerators come in several different forms – linear accelerators or linacs, and circular accelerators, with cyclotrons and synchrotrons being the most common. They all use radio frequency electromagnetic waves to accelerate charged particles, and various kinds of magnets – permanent, resistive and superconducting – to bend and focus the beams of particles.
The magnets used to control the beam must be designed accurately if the beams are going to remain focused and reach the target at the desired point. SIMULIA Opera is used to support the design of different types of magnets, with each performing a specific role in these ground-breaking devices. Figure 2 shows a quadrupole magnet modelled with SIMULIA Opera, with the magnetic flux density displayed on the steel poles, and also on a cross-section where the beam would pass.
A 3D dipole model is shown in Figure 4.
Figure 5 shows a quadrupole magnet from the SLAC National Accelerator Laboratory.
Other imperfections in the beam (such as it becoming unstable over time) arise due to magnet imperfections, misalignments or intra-beam effects for instance, can be addressed using higher order multipole magnets, supplementing the dipoles and quadrupoles commonly used for steering and focusing. These types of magnets might be DC, but they could also be pulsed or programmable.
Kicker magnets are pulsed rapidly, redirecting the beam to a new trajectory. A very important design characteristic of a kicker magnet is how quickly it can be turned on and off – after all, the beam in the 27 km circumference LHC goes round about 11,000 times each second!
Charged particle beams can be simulated in Opera, and tracked through the complex fields generated by these magnets. Figure 6 shows charged particles being tracked through a specialized dipole called a fragment separator, used to identify short lived radioactive isotopes.
Opera Electromagnetics SIMULIA-Blog