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Slice of the Large Hadron Collider (LHC) prototype beam tubes in dipole magnet The LHC is the world’s largest and most powerful particle accelerator that accelerates and collides two beams of protons or ions to near the speed of light in opposite directions. It first started up in 2008, and is the latest addition to CERN’s accelerator complex (2025). The LHC consists of a 27-km ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way. Thousands of magnets of different varieties and sizes are used to direct the beams around the accelerator. The high bending and accelerating fields needed can only be reached using superconductor magnets at very low temperature (‑271.3°C). There are 1232 dipole magnets like this prototype in the LHC, used to guide the particles around the 27 km ring. Dipole magnets must have an extremely uniform field, which means the current flowing in the coils that produce the magnetic field has to be very precisely controlled. Nowhere before has such precision been achieved at such high currents. The temperature is measured to five thousandths of a degree, the current to one part in a million. The current creating the magnetic field pass through superconducting wires at up to 12 500 amps, about 30 000 times the current flowing in a 100 W light bulb. Since the LHC accelerate two particle beams moving in opposite directions, it is really two accelerators in one. To keep the machine as compact and economical as possible, two dipole magnets are built into a single housing.

When you look through the glass at a picture behind, the picture appears raised up because light is slowed down in the dense glass. It is this density (4.06 gcm-3) that makes lead glass attractive to physicists. The refractive index of the glass is 1.708 at 400nm (violet light), meaning that light travels in the glass at about 58% its normal speed. At CERN, the OPAL detector uses some 12000 blocks of glass like this to measure particle energies.

This is a calorimeter, a detector which measures the energy of particles. When in use, it is filled with liquid krypton at -152°C. Electrons and photons passing through interact with the krypton, creating a shower of charged particles which are collected on the copper ribbons. The ribbons are aligned to an accuracy of a tenth of a millimetre. The folding at each end allows them to be kept absolutely flat. Each shower of particles also creates a signal in scintillating material embedded in the support disks. These flashes of light are transmitted to electronics by the optical fibres along the side of the detector. They give the time at which the interaction occurred. The photo shows the calorimeter at NA48, a CERN experiment which is trying to understand the lack of anti-matter in the Universe today.

Part of the IBM computer that was used for physics simulations in preparation for experiments at LEP. When installed in 1985, it was considered to be very powerful. Nowadays, a PC can outperform it by a factor of ten.

Empire scientific corporation. U.S.A. Série 3432

Hewlett Packard. 419A

central region of the ion source for the synchro-cyclotron