Editing ATLAS experiment (section)

===Calorimeters===
[[File:ATLAS HCal.jpg|thumb|September 2005: The main barrel section of the ATLAS [[hadronic]] calorimeter, waiting to be moved inside the toroid magnets.]]
[[File:CERN-Rama-33.jpg|thumb|One of the sections of the extensions of the hadronic [[Calorimeter (particle physics)|calorimeter]], waiting to be inserted in late February 2006.]]
[[File:ATLAS Tile Calorimeter.png|thumb|The extended barrel section of the hadronic calorimeter.]]

The [[calorimeter (particle physics)|calorimeters]]<ref name=fact_sheets/><ref name=the_bible/><ref name="TPoveralldetector"/> are situated outside the solenoidal [[magnet]] that surrounds the Inner Detector.  Their purpose is to measure the energy from particles by absorbing it.  There are two basic calorimeter systems: an inner electromagnetic calorimeter and an outer [[hadronic]] calorimeter.<ref name="TPcalorimetry">{{cite book| year=1994| title= ATLAS Technical Proposal| chapter=Calorimetry| publisher=CERN| chapter-url=http://atlas.web.cern.ch/Atlas/TP/NEW/HTML/tp9new/node9.html#SECTION00432000000000000000}}</ref>  Both are ''sampling calorimeters''; that is, they absorb energy in high-density metal and periodically sample the shape of the resulting [[particle shower]], inferring the energy of the original particle from this measurement.

====Electromagnetic calorimeter====
The electromagnetic (EM) calorimeter absorbs energy from particles that interact [[Electromagnetism|electromagnetically]], which include charged particles and photons.  It has high precision, both in the amount of energy absorbed and in the precise location of the energy deposited.  The angle between the particle's trajectory and the detector's beam axis (or more precisely the [[pseudorapidity]]) and its angle within the perpendicular plane are both measured to within roughly 0.025&nbsp;[[radian]]s. The barrel EM calorimeter has accordion shaped electrodes and the energy-absorbing materials are [[lead]] and [[stainless steel]], with liquid [[argon]] as the sampling material, and a [[cryostat]] is required around the EM calorimeter to keep it sufficiently cool.

====Hadron calorimeter====
The [[hadron]] calorimeter absorbs energy from particles that pass through the EM calorimeter, but do interact via the [[strong force]]; these particles are primarily hadrons.  It is less precise, both in energy magnitude and in the localization (within about 0.1&nbsp;radians only).<ref name="PhysicsatLHC"/>  The energy-absorbing material is steel, with scintillating tiles that sample the energy deposited.  Many of the features of the calorimeter are chosen for their cost-effectiveness; the instrument is large and comprises a huge amount of construction material: the main part of the calorimeter – the tile calorimeter – is 8&nbsp;metres in diameter and covers 12&nbsp;metres along the beam axis.  The far-forward sections of the hadronic calorimeter are contained within the forward EM calorimeter's cryostat, and use liquid argon as well, while copper and tungsten are used as absorbers.