A Large Ion Collider Experiment
From Wikipedia, the free encyclopedia
 The accelerator chain of the Large Hadron Collider (LHC) |
|
| LHC experiments | |
| ATLAS | A Toroidal LHC ApparatuS |
| CMS | Compact Muon Solenoid |
| LHCb | LHC-beauty |
| ALICE | A Large Ion Collider Experiment |
| TOTEM | Total Cross Section, Elastic Scattering and Diffraction Dissociation |
| LHCf | LHC-forward |
| LHC preaccelerators | |
| p and Pb | Linear accelerator for proton and Lead |
| (not marked) | Proton Synchrotron Booster |
| PS | Proton Synchrotron |
| SPS | Super Proton Synchrotron |
ALICE (A Large Ion Collider Experiment) is one of the six detector experiments being constructed at the Large Hadron Collider at CERN. It is optimized to study heavy ion collisions. Pb-Pb nuclei collisions will be studied at a centre of mass energy of 5.5 TeV per nucleon. The resulting temperature and density are expected to be large enough to generate a quark-gluon plasma, a state of matter wherein quarks and gluons are deconfined.
Contents |
[edit] Inner Tracking System
The Inner Tracking System (ITS) consists of six cylindrical layers of silicon detectors. The layers surround the collision point and measure the properties of the emerging particles, pin-pointing their positions to a fraction of a millimetre. The ITS will recognize particles containing heavy quarks by identifying the points at which they decay
[edit] Time Projection Chamber
The ALICE Time Projection Chamber (TPC) is the main particle tracking device in ALICE. Charged particles crossing the gas of the TPC knock electrons out of their atoms, which then drift in the electric field. By measuring the arrival of electrons at the end of the chamber, the TPC will reconstruct the paths of the original charged particles.
[edit] Transition Radiation Detector
Electrons and positrons can be discriminated from other charged particles using the emission of transition radiation, X-rays emitted when the particles cross many layers of thin materials. To develop such a Transition Radiation Detector (TRD) for ALICE many detector prototypes were tested in mixed beams of pions and electrons.
[edit] Time of Flight
Charged particles are identified in ALICE by Time-Of-Flight (TOF); heavier particles are slower and so take longer to reach the outer layers of the detector. For its TOF system ALICE uses detectors called Multigap Resistive Plate Chambers (MRPC). There are approximately 160 000 of them distributed over 150 square meters. Using the tracking information from other detectors every track firing a sensor is identified.
[edit] Photon Spectrometer
The Photon Spectrometer (PHOS) is designed to measure the temperature of collisions by detecting photons emerging from them. It will be made of lead tungstate crystals. When high energy photons strike lead tungstate, they make it glow, or scintillate, and this glow can be measured. Lead tungstate is extremely dense (denser than iron), stopping most photons that reach it.
[edit] High Momentum Particle Identification Detector
The High Momentum Particle Identification Detector (HMPID) is a RICH detector to determine the speed of particles beyond the momentum range available through energy loss (in ITS and TPC, p = 600 MeV) and through time-of-flight measurements (in TOF, p = 1.2 − 1.4 GeV). Its momentum range is up to 3 GeV for pion/kaon discrimination and up to 5 GeV for kaon/proton discrimination. It is world's largest caesium iodide RICH detector, with an active area of 11 m². A prototype was successfully tested at CERN in 1997 and currently takes data at the Relativistic Heavy Ion Collider at the Brookhaven National Laboratory in the US.
[edit] Muon spectrometer
The muon spectrometer measures pairs of muons, in particular those coming from the decays of J/ψ and Upsilon particles. Tracking chambers to detect the muons and reconstruct their trajectories will be made from a special composite material, which is highly rigid but very thin. A set of resistive plate chambers (RPC) will act as a triggering device.
[edit] Forward Multiplicity Detectors
The Forward Multiplicity Detector (FMD) consist of 5 large Si disks with each 10 240 individual detector channels to measure the charged particles emitted at small angles relative to the beam. The forward detectors also comprise the main trigger detectors for timing (T0) and for collision centrality (V0).
[edit] Electro-Magnetic Calorimeter
The Electro-Magnetic Calorimeter (EM-Cal) will add greatly to the high momentum particle measurement capabilities of ALICE.
[edit] External links
- Official ALICE Public Webpage at CERN
