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Large Hadron Collider

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The Large Hadron Collider (LHC) is the largest and highest-energy particle accelerator in the world.

Location Large Hadron Collider
Location Large Hadron Collider

It is a massive scientific instrument designed to probe the fundamental structure of the universe. By colliding subatomic particles at extreme speeds, physicists can study the basic laws of nature. This research helps scientists understand how forces work and how the universe began. The LHC is managed by the European Organization for Nuclear Research, also known as CERN. It represents one of the most complex engineering feats in human history.

To understand how the LHC works, one must first understand the particles it moves. The machine primarily accelerates protons, which are a type of hadron. Hadrons are composite particles made of smaller units called quarks, held together by the strong force.

CERN LHC Proton Source
CERN LHC Proton Source

The process begins with a series of smaller accelerators. First, the Linac4 generates negative hydrogen ions. These ions move to the Proton Synchrotron Booster, where electrons are stripped away to leave single protons. The protons then move through the Proton Synchrotron and the Super Proton Synchrotron. Finally, they enter the main LHC ring to be accelerated to their peak energy.

The LHC uses a circular tunnel to guide these particles. This tunnel has a circumference of 27 kilometers and sits deep underground.

LHC magnet types
LHC magnet types

The depth varies to avoid digging under the Jura Mountains. The tunnel crosses the border between France and Switzerland at four different points. Inside the tunnel, two parallel beam pipes hold beams of particles traveling in opposite directions. To keep these beams on a circular path, the LHC uses 1,232 dipole magnets. These magnets are massive, with each one weighing 35 tonnes. Additionally, 392 quadrupole magnets are used to focus the beams. This focusing is vital to ensure the particles actually hit each other at the crossing points.

Maintaining these magnets requires extreme conditions. The LHC contains about 10,000 superconducting magnets made of copper-clad niobium-titanium. To function, these magnets must be kept at a temperature of 1.9 Kelvin.

LHC quadrupole magnets
LHC quadrupole magnets

To achieve this, the facility uses 96 tonnes of superfluid helium-4. This makes the LHC the largest cryogenic facility in the world operating at liquid helium temperatures. During operation, the site draws about 200 megawatts of electricity from the French grid. This is roughly one-third of the power used by the entire city of Geneva. The particles move at incredible speeds, reaching about 99.9999991% of the speed of light.

There are several distinct types of collisions performed at the LHC. Most experiments involve proton-proton collisions to test the Standard Model of particle physics. However, the LHC also performs heavy-ion collisions. During these runs, the machine accelerates ions like lead instead of protons.

These heavy-ion collisions allow scientists to study quark-gluon plasma. This is a state of matter thought to have existed in the very early universe. By studying these collisions, researchers can recreate conditions similar to those just after the Big Bang.

The history of the LHC is marked by massive international cooperation and major discoveries. Construction took place between 1998 and 2008, involving over 10,000 scientists from more than 100 countries. In 2010, the machine achieved its first collisions at 3.5 tera-electronvolts (TeV) per beam. This was four times higher than the previous world record. A landmark moment occurred in 2012 when the LHC discovered the Higgs boson.

CMS Higgs-event
CMS Higgs-event

This particle is essential to the Standard Model because it explains how elementary particles acquire mass. Following this, the machine underwent upgrades to reach even higher energies.

After upgrades between 2013 and 2015, the collision energy increased to 13 TeV. The LHC is equipped with nine specialized detectors located at the four crossing points.

View inside detector at the CMS cavern LHC CERN
View inside detector at the CMS cavern LHC CERN

Two of these are large, general-purpose detectors called ATLAS and CMS. Other detectors, such as ALICE and LHCb, have more specific research roles. These machines catch the byproducts of collisions, which often decay very quickly. The amount of information produced is staggering, with 140 terabytes of data generated every single day. To manage this, the LHC Computing Grid connects hundreds of computing centers across the globe.

The scientific significance of the LHC extends to many unsolved mysteries in physics. Scientists use the data to search for dark matter, which accounts for 27% of the universe's mass-energy. They also look for evidence of supersymmetry, which predicts a large family of new particles. Another goal is to investigate whether there are extra dimensions, as suggested by string theory. The LHC also helps researchers study the relationship between quantum mechanics and general relativity. By testing these theories, the LHC helps us map the deep structure of space and time.

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🖼️ Images & Media (11)
File:Location Large Hadron Collider.PNG
Location Large Hadron Collider.PNG
File:LHC quadrupole magnets.jpg
LHC quadrupole magnets.jpg
File:LHC magnet types.jpg
LHC magnet types.jpg
File:CERN LHC Proton Source.JPG
CERN LHC Proton Source.JPG
File:View inside detector at the CMS cavern LHC CERN.jpg
View inside detector at the CMS cavern...
File:Lyn Evans - pictures donated by CERN-1 (cropped).jpg
Lyn Evans - pictures donated by CERN-1...
File:Jean Iliopoulos (Ecole Normale Supérieure) - Philippe Binant Archives.jpg
Jean Iliopoulos (Ecole Normale...
File:Views of the LHC tunnel sector 3-4, tirage 2.jpg
Views of the LHC tunnel sector 3-4, tirage 2.jpg
File:New hadrons at the LHC.svg
New hadrons at the LHC.svg
File:BosonFusion-Higgs.svg
BosonFusion-Higgs.svg
File:CMS Higgs-event.jpg
CMS Higgs-event.jpg
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