Editing ATLAS experiment (section)

===Magnet System===
[[File:Installing the ATLAS Calorimeter - edit1.jpg|thumb|The eight toroid magnets of the ATLAS detector]] 
[[File:ATLAS Above.jpg|thumb|The ends of four of the eight ATLAS toroid magnets, looking down from about 90&nbsp;metres above, in September 2005]]

The ATLAS detector uses two large superconducting magnet systems to bend the trajectory of charged particles, so that their momenta can be measured.<ref name=fact_sheets/><ref name=the_bible/><ref name="TPoveralldetector"/>  This bending is due to the [[Lorentz force]], whose modulus is proportional to the [[electric charge]] <math>q</math> of the particle, to its speed <math>v</math> and to the intensity <math>B</math> of the magnetic field:
:<math>F = q \, v \, B.</math>
Since all particles produced in the LHC's [[proton]] collisions are traveling at very close to the speed of light in vacuum <math>(v \simeq c)</math>, the [[Lorentz force]] is about the same for all the particles with same [[electric charge]] <math>q</math>:
:<math>F \simeq q \, c \, B.</math>
The radius of curvature <math>r</math> due to the [[Lorentz force]] is equal to
:<math>r = \frac{p}{q \, B}.</math>
where <math> p = \gamma \, m \, v </math> is the [[mass in special relativity|relativistic]] [[momentum]] of the particle. As a result, high-momentum particles curve very little (large <math>r</math>), while low-momentum particles curve significantly (small <math>r</math>). The amount of [[curvature]] can be quantified and the particle [[momentum]] can be determined from this value.

====Solenoid Magnet====
The inner [[solenoid]] produces a two [[Tesla (unit)|tesla]] magnetic field surrounding the Inner Detector.<ref name="TPmagnet">{{cite book| year=1994| title= ATLAS Technical Proposal| chapter=Magnet system| publisher=CERN| chapter-url= http://atlas.web.cern.ch/Atlas/TP/NEW/HTML/tp9new/node8.html#SECTION00431000000000000000}}</ref>  This high magnetic field allows even very energetic particles to curve enough for their momentum to be determined, and its nearly uniform direction and strength allow measurements to be made very precisely.  Particles with momenta below roughly 400 [[MeV]] will be curved so strongly that they will loop repeatedly in the field and most likely not be measured; however, this energy is very small compared to the several [[TeV]] of energy released in each proton collision.

====Toroid Magnets====
The outer [[toroid]]al magnetic field is produced by eight very large air-core [[superconducting]] barrel loops and two smaller end-caps air toroidal magnets, for a total of 24 barrel loops all situated outside the calorimeters and within the muon system.<ref name="TPmagnet"/>  This magnetic field extends in an area 26&nbsp;metres long and 20&nbsp;metres in diameter, and it stores 1.6&nbsp;[[gigajoule]]s of energy.  Its magnetic field is not uniform, because a solenoid magnet of sufficient size would be prohibitively expensive to build. It varies between 2 and 8 Teslameters.