Editing ATLAS experiment (section)

===Detector systems===
[[File:ATLAS Drawing with Labels.svg|thumb|upright=1.5|Computer generated cut-away view of the ATLAS detector showing its various components. <br>
[[#Muon Spectrometer|Muon Spectrometer]]: <br>
&nbsp;&nbsp; (1) Forward regions (End-caps) <br>
&nbsp;&nbsp; (1) Barrel region <br>
[[#Magnet System|Magnet System]]: <br>
&nbsp;&nbsp; (2) Toroid Magnets <br>
&nbsp;&nbsp; (3) Solenoid Magnet <br>
[[#Inner Detector|Inner Detector]]: <br>
&nbsp;&nbsp; (4) Transition Radiation Tracker <br>
&nbsp;&nbsp; (5) Semi-Conductor Tracker <br>
&nbsp;&nbsp; (6) Pixel Detector <br>
[[#Calorimeters|Calorimeters]]: <br>
&nbsp;&nbsp; (7) Liquid Argon Calorimeter <br>
&nbsp;&nbsp; (8) Tile Calorimeter <br>
]]

The ATLAS detector<ref name=fact_sheets/><ref name=the_bible/><ref name="TPoveralldetector"/> consists of a series of ever-larger concentric cylinders around the [[interaction point]] where the proton beams from the LHC collide. Maintaining detector performance in the high radiation areas immediately surrounding the proton beams is a significant engineering challenge.  The detector can be divided into four major systems: 
# Inner Detector; 
# Calorimeters; 
# [[Muon]] Spectrometer; 
# Magnet system.  
Each of these is in turn made of multiple layers.  The detectors are complementary: the Inner Detector tracks particles precisely, the calorimeters measure the energy of easily stopped particles, and the muon system makes additional measurements of highly penetrating muons.  The two magnet systems bend [[electric charge|charged]] particles in the Inner Detector and the Muon Spectrometer, allowing their [[electric charge]]s and [[momentum|momenta]] to be measured.
The only established stable particles that cannot be detected directly are [[neutrino]]s; their presence is inferred by measuring a momentum imbalance among detected particles.  For this to work, the detector must be "[[Hermetic detector|hermetic]]", meaning it must detect all non-neutrinos produced, with no blind spots.

The installation of all the above detector systems was finished in August 2008. The detectors collected millions of cosmic rays during the magnet repairs which took place between fall 2008 and fall 2009, prior to the first proton collisions. The detector operated with close to 100% efficiency and provided performance characteristics very close to its design values.<ref>{{cite journal|title= Performance of the ATLAS Detector using First Collision Data|journal=JHEP|volume=1009|year=2010|pages=056|doi= 10.1007/JHEP09(2010)056|arxiv = 1005.5254 |bibcode = 2010JHEP...09..056A|last1= Aad|first1= G.|author2=  (ATLAS Collaboration)|issue= 9|s2cid=118543167|display-authors=etal}}</ref>