How many different experimental configurations does the Large Hadron Collider have? I understand that the LHC can collide protons with protons, heavy ions with heavy ions, or protons with heavy ions, giving three main configurations. But, I'm wondering: is that the only property that physicists would vary in order to perform different experiments?
For example, might they run the LHC at less than the maximum energy in order to facilitate a certain kind of experiment? Or, use different heavy ions? Or, vary the beam collision parameters in some way?
If not, then do they just fire up the LCH and continuously collect data for months at a time, only stopping to switch the particles used?
(Note that I'm not talking about the probably millions of properties that must be tweaked to get it running at its best; I'm only asking about properties where the optimal value depends on the experiment being run.)
 A: Components:
Muon Spectrometer:
     (1) Monitored Drift Tube
     (2) Thin Gap Chamber
Magnet system:
     (3) End-Cap Toroid Magnet
     (4) Barrel Toroid Magnet
Inner Detector:
     (5) Transition Radiation Tracker
     (6) Semi-Conductor Tracker
     (7) Pixel Detector
Calorimeters:
     (8) Electromagnetic Calorimeter
     (9) Hadronic Calorimeter
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 charged particles in the Inner Detector and the Muon Spectrometer, allowing their momenta to be measured.
The only established stable particles that cannot be detected directly are neutrinos; their presence is inferred by measuring a momentum imbalance among detected particles. For this to work, the detector must be "hermetic", meaning it must detect all non-neutrinos produced, with no blind spots. Maintaining detector performance in the high radiation areas immediately surrounding the proton beams is a significant engineering challenge.
