3 accelerating cavities.
Particles are accelerated using radio-frequency cavities. These contain an electric field which oscillates at just the right frequency to give a kick to the charged particles passing through.
Sin títuloA short section of the LHC beam-pipe including beam screen. In the LHC, particles circulate under vacuum. The vacuum chamber can be at room temperature (for example, in the experimental areas), or at cryogenic temperature, in the superconductive magnets. This piece is located in the superconductive magnets. The outer pipe is the vacuum chamber, which is in contact with the magnets, at cryogenic temperature (1.9K). It is called the “cold bore”. The inner tube is the beam screen. Its main goal is to protect the magnets from the heat load coming from the synchrotron radiation. Indeed, when high energy protons’ trajectory is bent, photons are emitted by the beam. They are intercepted by the beam screen. The temperature of the beam screen is kept between 5 and 20K by a circulation of gaseous helium in the small pipes on both sides of the beam screen. As those surfaces are at cryogenic temperature. The residual gas present in the accelerator is sticking on the surfaces. This phenomenon called “adsorption” is used to maintain a very low pressure in the vacuum chamber of the accelerator. About materials: The cold bore is in stainless steel. The beam screen is in stainless steel with colaminated copper. Both those material have a low outgassing rates, which means that they release few molecules in the vacuum chamber. About beam and impedance: The goal of the copper, which has a good electrical conductivity, is to facilitate the circulation of the image current. The beam is composed of charged particules circulating: it is an electric current. When it is circulating, an image current is produced. It is called induction. If the image current cannot circulate properly, the beam is slowed down. About adsorption process: When the beam circulates, photons from synchrotron radiation are emitted and hit the beam screen. By doing so, they desorb molecules from the walls. The molecules are then pumped down on the outer pipe (where they cannot be reached by the photons anymore), through the small holes in the beam screen.
If all molecules in this bottle could be used, this hydrogen bottle contains enough protons to feed the Large Hadron Collider for 200’000 years of continuous operation! But since there are losses inside the source, in and between the accelerators, such a bottle only lasted for 4 to 6 months of operations and needed then to be replaced.
42 modules like this one surround the collision point inside the LHCb detector. Their role is to measure the tracks of short-lived particles spraying out from the collision and to pinpoint the exact spots where they decay into secondary particles. Some exist for just trillionths of a second before decaying! The silicon modules operate so close to the collision point, they can only be moved into position once the circling particle beams are at their most focused. Otherwise, peripheral particles on the outside of the finer-than-a-hair beam would bore a hole right through them.
A magnet surrounding the detectors bends the paths of charged particles. This shows if they are positively - or negatively- charged and also allows their momentum to be measured. Inside ATLAS, the solenoid magnet surrounding the tracking detectors must be as thin as possible, so as not to affect their measurements. 9 km of superconducting wires, support casing, cooling fluids and insulation is squeezed into the 4.5 cm gap between the tracking detectors and the calorimeters. ATLAS is one of the 4 large experiments surrounding collision points at the Large Hadron Collider.
This detector is part of the ALICE experiment's Time Projection Chamber (TPC). With incredible precision, the TPC records the thousands of tracks of charged particles spraying out from the collision, allowing each particle to be identified. In such a dense, electronics-filled environment, it is rare to find a relatively empty space - yet most of the TPC's 88m3 volume is filled with just gas, with read-out detectors, like this one located on the outer surface.
A half shell of the barrel CMS Pixel Phase-0 that was installed at the start-up of the Large Hadron Collider (2009-2016 in operation) and has been involved in the discovery of the Higgs boson.
Dipole Magnet - Guiding the protons around the ring This is a cut-through of the coil of a dipole magnet, that generates the magnetic field used to bend the paths of circulating protons. Looking closely, you can distinguish insulated cables made of individual wires. High and extremely stable magnetic fields are needed for guiding the proton beams, so a superconducting material called Niobium-Titanium was chosen for the wires. At very low temperatures, superconductors have no electrical resistance and therefore no power loss. They carry a very stable current of 13.000 amps, about 20.000 times that used to power this screen. In addition to dipole magnets, the Large Hadron Collider contains quadrupoles and other higher order magnets, used to prepare the proton beams for collision. Dipoles are two pole magnets used for bending the beams of protons around the ring. Quadrupoles have four magnetic poles and are used for focusing the beam, squeezing protons closer together to increase the chance of collision when the beams cross inside the experiments. In total, the LHC uses more than 50 different types of magnet to adjust the particle beams even more finely. The Beam-Pipe - Where the beams of protons circulate Proton beams can circulate for over 10 hours in the Large Hadron Collider. Over this time, protons make four hundred million revolutions of the 27 km machine, traveling a distance equivalent to the diameter of the solar system. They must travel in a pipe that is emptied of air, to avoid collisions with molecules of gas. The beam-pipes are therefore pumped down to an air pressure similar to that on the surface of the moon. There are two pipes, one for each direction of the circulating beams. The two beams only meet inside the four experiments where collisions take place. Liquid Helium - Bringing in the cooling fluid This pipe carries liquid helium through the Large Hadron Collider magnets to keep them at 1.9 degrees above absolute zero - about 300 degrees below room temperature. 800'000 litres of superfluid helium are used to cool down the 36'000 tonnes of equipment. This is the world's biggest cryogenic installation and its reliability and efficiency is essential for the magnets. The pipe connects to the main cryogenic line that you can see running along behind the blue magnets via "jumper connections" like the one to your right. Support Post - Insulating and extremely tough The magnet supports bridge a difference in temperature of nearly 300 degrees! Electrical connections, instrumentation and the posts on which the magnets stand are the only points where heat transfer can happen through conduction. They are all carefully designed to draw off heat progressively. The posts are made of 4 mm thick glass-fibre - epoxy composite material. Each post supports 10'000 kg of magnet and leaks just 0.1 W of heat. There are three per magnet. Magnet Collars - Preventing the wires from moving The LHC accelerates two proton beams moving in opposite directions, so it is really two accelerators in one. To keep the machine as compact and economical as possible, two magnets are built into a single housing that must withstand enormous electromagnetic forces. These forces tend to open-up the coils, and squeeze them. At full field, the force on one metre of coil is comparable to the weight of a jumbo jet. Great care must be taken to prevent movements as the field changes - any friction could create hot spots that would cause the wire to lost its superconducting stage. Magnet collars made from reinforced steel keep the coils firmly in place. Insulation - Preventing heat from leaking In The LHC, beam-tube and magnets are inside a vacuum tank to reduce to a minimum the heat flowing in through convection. To prevent heat inflow through radiation, they are surrounded by a super insulator - multi-layer, reflective, aluminized Mylar. Then to prevent heat flow via conduction, ingenious solutions had to be found for the electrical connections and the support posts. Iron Yoke - Shielding the magnetic field The LHC magnet cables are surrounded by a layered iron yoke that shields the powerful magnetic field - 100'000 times stronger than the Earth's - so that stray fields outside the magnet are negligible. This action also helps enhance the magnetic field within the beam-pipe, where it is needed for control of the proton beams. In addition, the layers of iron yoke, called laminations, play a role together with the magnet collars in keeping cables from moving when the magnet powers up. The technical challenge of manufacturing the laminations centred on ensuring both strength and magnetic homogeneity across a large-scale production. Over 6 million laminations are needed for the 1232 dipole magnets installed around the LHC's 27km ring.