The Large Hadron Collider

By Kathleen McKay

What is the LHC?

• The most powerful particle accelerator in the world.

• A synchrotron (ring-shaped particle accelerator)

• Built by the European Organization for Nuclear Research (CERN)

• A part of the CERN accelerator complex

History of the LHC

• The LEP (Large Electron-Positron Collider)– Built in the tunnels the LEP used to occupy

• Approved by CERN Council in 1994• Built 1996- 2008• Opened April 5th 2008• Technical difficulties–Magnetic failures and a helium leak

• 2010 first successful experiment

What does it do?

• It accelerates two beams of hadrons at 99% the speed of light.– Particles of Matter

• Uses 9,600 magnets to collide the two beams at six sites around its circumference.

• Observes and studies the collisions.

What it’s looking for…

• A mini Big Bang– Atomic subparticles– Matter v. Antimatter

• Dark Matter• The Standard Model– Higgs Boson Particle

• String Theory– 11 dimensions– Supersymmetry

Six Collision Sites

ATLAS• A Toroidal LHC ApparatuS• 46m long, 25m tall, 25m

wide• Inner tracker

– Detect & analyze momentum

• Calorimeter– Measures energy by

absorption, shows path

• Moun spectrometer– Measures momentum of

particles too heavy to be caught by calorimeter

CMS• Compact Moun

Solenoid• General purpose• Contained inside

solenoid magnet– Field is 100,000 times

stronger than Earth’s

Six Collision Sites cont.

ALICE• A Large Ion Collider

Experiment• Studies the collisions

of iron ions• Moun spectrometer• Time Projection

Chamber (TPC)– Tracks particle

trajectories

LHCb• Large Hadron Collider

beauty• Search for antimatter

– Beauty/bottom quarks

• 20 meters of detectors around the site to catch the quarks

The Two Small Collision Sites

TOTEM• TOTal Elastic and

diffractive cross section Measurement

• Measures the size of protons

• Measures luminosity (how precisely an accelerator produces collisions)

LHCf• Large Hadron Collider

forward• Stimulates cosmic

rays• Tries to make

experiments where naturally occurring cosmic rays can be observed and studied

• 27 km circumference• 100 m underground• 8 arches, 8 insertions• Insertions- long

straight sections, control coming and going of particles– Injection– Beam dumping– Beam cleaning

• 3 vacuum systems– Beam vacuum– Insulation for

cryomagnets– Insulation for helium

distribution line

How It Works

Magnets•9,600 magnets•Guides the particle beams into collisions and through insertions.•3 Kinds

•Quadrupole- focuses beam•Accelerating Cavities- accelerate particles and keep them at constant speed•Dipole- keep the beams going in a circle

•8.33 T

Cooling System

• Designed so that the magnets can conduct electricity with almost no resistance and generate a high enough magnetic field.

• 120 tons of super fluid helium

• 5 cryogenic ‘islands’• Colder than outer

space: 1.9 K (-456.25 F)

Helium is cooled to 80 K, using 10,000

tons of liquid nitrogen.

Helium is cooled to 4.5 K, using refrigerator

turbines and is injected to the

magnets.

Refrigerator cools magnets further down, to 1.9 K.

Strip electrons from hydrogen atoms or lead ions to produce protons.

Protons enter LINAC 2 then the PS Booster. • Use radio frequency cavities to accelerate the protons to

form beams.• Control is transferred from the radio-frequency electric

fields to the magnets.

Sent to the Super Proton Synchotron (SPS).• Accelerated and divided into bunches• 2808 bunches in a beam, 1.1 x 1011 protons in a bunch.

Then takes 20 minutes for beams to reach top speed of 11,245 trips around the LHC per second.

Beams are positioned to collide at one of the six collision sites.

Particle Process

Collision Results

• Quarks- subatomic particles• Gluon- mitigating force• Photons- particles of light• Positrons- the anti-particles to

electrons• Muons- negatively charged, heavier

version of electrons

LHC Computing Grid

Tier 0CERN’s computing system

Processes information and divides it into chunks for the other two tiers.

Tier 112 sites in various countries

Receives data over dedicated computer connections at 10 gigabytes per second.

Divides the information again.

Tier 2Thousands of computers at universities all over

the world.Receives data through standard network

connection.Processes and analyzes the data.

Sends data back through the tiers to CERN.

•150 million sensors in the LHC•700 megabytes of data per second•15 petabytes per year•2001- EDG (European Data Grid project)•2004- EGEE (Enabling Grid for E-sciencE)•Divides the data into chunks to be analyzed separately•Uses midware•Uses identification and authorization procedures to keep the information safe.

Question 1

What does LHC stand for?1. Luminosity Higgs Controller2. Large Higgs Chamber3. Low Helium Cryomagnet4. Large Hadron Collider

Question 2

Who created the LHC?1. CMS2. CERN3. TOTEM4. EDG

Question 3

What are the names of the six detector sites?

1. CMS, ALICE, TPS, TOTEM, LEP, LHCb2. LHCf, LEP, CMS, ATLAS, LHCb, SPS3. ATLAS, CMS, ALICE, LHCb, TOTEM,

LHCf4. EDG, ATLAS, SPS, LEP, LHCf, CMS

Question 4

What does the LHC do?1. Measures momentum of particles too

heavy to be caught by calorimeter.2. Guides the particle beams into

collisions and through insertions.3. Collides two beams of particles.4. Measures energy of particles through

absorption.

Question 5

What temperature are the magnets cooled to?

1. 1.9 K2. 3.9 C3. 4.8 K4. -354.25 F