One of the building blocks of the CMS Silicon Tracker: a part of the detector that reconstructs the trajectories of charged particles emerging from the proton-proton collisions. A lightweight structure, made mostly of carbon fibre, supports silicon detectors and their readout electronics. These detectors generate an electrical pulse when they are traversed by a charged particle, and they are segmented into fine strips (in this case the strips are 180 microns wide, about the size of a human hair) that collect those pulses, such that the position of the strip provides a coordinate on the particle trajectory. In this “rod” silicon detectors are arranged in back-to-back pairs, where the two detectors of each pair have the strips oriented at an angle, such that the crossing point of the strips provides a two-dimensional coordinate in the rod plane. Three pairs of detectors are mounted on each side of the rod structure, to fully cover its surface. In the Tracker, rods are arranged to form cylindrical layers in the central “barrel” region.

One of the building blocks of the CMS Silicon Tracker: a part of the detector that reconstructs the trajectories of charge particles emerging from the proton-proton collisions. A lightweight structure, made mostly of carbon fibre, supports silicon detectors and their readout electronics. These detectors generate an electrical pulse when they are traversed by a charged particle, and they are segmented into fine strips (in this case the strips are 180 microns wide, about the size of a human hair) that collect those pulses, such that the position of the strip provides a coordinate on the particle trajectory.

The CMS (Compact Muon Solenoid) Tile Calorimeter is a pivotal component of the CMS detector, which is one of the major experiments at the Large Hadron Collider (LHC) at CERN. Designed to measure the energy of particles, the calorimeter plays an essential role in the study of high-energy physics.

LHCb measures muons using gold plated tungsten wires stretched over read-out pads. A high voltage is applied across the wires and pads and the set-up is bathed in a gas mixture. Passing muons interact with the gas, knocking out electrons from its atoms in a process called ionization. Both the ionized atoms and the electrons then drift in the electric field. This movement creates an electric signal in the wires and pads that is used to identify where the muon has passed. In total, the LHCb muon detectors contain about 2 million wires and are capable of making measurements 40 million times a second – every time the particle beams collide.

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.

Each of these straws is a complete mini–detector in its own right. Every one is filled with a gas mixture and threaded with a wire. Imagine assembling 300’000 fragile drinking straws up to 144 cm long, with no bends or kinks allowed! This layer of tracker plays two important roles. Firstly, it makes more position measurements, giving more dots for the computers to join up to recreate the particle tracks. Then it also helps distinguish between different types of particles depending on whether they emit radiation as they make the transition from the surrounding foil into the straws. An electric field is applied between the wire and the outside wall of the straw. As particles pass through, they collide with atoms in the gas, knocking out electrons. The avalanche of electrons is detected as an electrical signal on the wire in the centre.

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.

The innermost layers of all four LHC detectors are made of silicon. This piece comes from the ATLAS detector where its job is to record the paths of the particles close to the collision. Here, hundreds of particles spray outwards and the silicon detectors must identify the exact points from which the particles originate and make an accurate measurement of the curvature of every particle track. Inside ATLAS, the first layer is made of 80 million silicon pixels, each smaller than a grain of sand. Surrounding the pixels are six million silicon strips, each about the thickness of a hair. The object on display here contains 1536 such silicon strips. Together, the layers of tracking detectors are like a giant 92 mega pixel camera taking a photo 40 million times every second.

The first layer of the ATLAS detector’s calorimeter is made of 8’200 lead plates and electrodes folded into an accordion shape and immersed in liquid argon. ATLAS (A Toroidal LHC ApparatuS) is the largest, general-purpose particle detector experiment at the Large Hadron Collider (LHC). As particles cross the folds and interact with the lead atoms, electrons and photons are ejected. There is a knock-on effect and as they continue on into the argon, a whole shower of secondary particles is produced. The electrodes register a signal that gives a measurement of the energy of the initial particle. As with most of the LHC detectors, the structural design challenge is to hold the heavy elements in place without affecting the measurements of the particles. Here, the layers of honeycomb spacer are designed to do just that. They separate the copper electrode layer from the lead and stainless steel absorber, allowing the liquid argon to flow freely in between.