to noise and to optimize the response for low energies. Electro-Magnetic Calorimeter The EMCal is a lead-scintillator sampling calorimeter comprising almost 13,000 individual towers that are grouped into ten super-modules. The towers are read out by wavelength-shifting optical fibers in a shashlik geometry coupled to an avalanche photodiode. The complete EMCal will contain 100,000 individual scintillator tiles and 185 kilometers of optical fiber, weighing in total about 100 tons. The EMCal covers almost the full length of the ALICE Time Projection Chamber and central detector, and a third of its azimuth placed back-to-back with the ALICE Photon Spectrometer – a smaller, highly granular lead-tungstate calorimeter. The super-modules are inserted into an independent support frame situated within the ALICE magnet, between the time-of-flight counters and the magnet coil. The support frame itself is a complex structure: it weighs 20 tons and must support five times its own weight, with a maximum deflection between being empty and being fully loaded of only a couple of centimeters. Installation of the eight-ton super-modules requires a system of rails with a sophisticated insertion device to bridge across to the support structure. The Electro-Magnetic Calorimeter (EM-Cal) will add greatly to the high momentum particle measurement capabilities of ALICE. It will extend ALICE's reach to study jets and other hard processes. Photon Multiplicity Detector The Photon Multiplicity Detector (PMD) is a Particle shower detector which measures the multiplicity and spatial distribution of photons produced in the collisions. It utilizes as a first layer a veto detector to reject charged particles. Photons on the other hand pass through a converter, initiating an electromagnetic shower in a second detector layer where they produce large signals on several cells of its sensitive volume. Hadrons on the other hand normally affect only one cell and produce a signal representing minimum-ionizing particles. Forward Multiplicity Detector The Forward Multiplicity Detector (FMD) extends the coverage for multiplicity of charge particles into the forward regions - giving ALICE the widest coverage of the 4 LHC experiments for these measurements. The FMD consist of 5 large silicon discs with each 10 240 individual detector channels to measure the charged particles emitted at small angles relative to the beam. FMD provides an independent measurement of the orientation of the collisions in the vertical plane, which can be used with measurements from the barrel detector to investigate flow, jets, etc. Muon spectrometer The ALICE forward muon spectrometer studies