Taking a closer look at LHC


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 A L I C E

ALICE (A Large Ion Collider Experiment), will study relativistic heavy ion interactions. The aim of the ALICE collaboration is to study the physics of strongly interacting matter at extreme densities where the formation of a new phase of matter, the quark-gluon plasma, is expected.

In some way ALICE will be reproducing the Big Bang.

Lead ions are produced from a highly purified lead sample heated to a temperature of about 550°C. The lead vapour is ionized by an electron current. Many different charge states are produced with a maximum around Pb27+. These ions are selected and accelerated to 4.2 MeV/u (energy per nucleon) before passing through a carbon foil, which strips most of them to Pb54+. The Pb54+ beam is accumulated, then accelerated to 72 MeV/u in the Low Energy Ion Ring (LEIR), which transfers them to the PS. The PS accelerates the beam to 5.9 GeV/u and sends it to the SPS after first passing it through a second foil where it is fully stripped to Pb82+.

The SPS accelerates it to 177 GeV/u then sends it to the LHC, which accelerates it to 2.76 TeV/u.

The detector consists of two main components: the central part composed of detectors dedicated to the study of hadronic signals and electrons, and the forward muon spectrometer dedicated to the study of quarkonia behaviour in dense matter.
The central part is embedded in a large solenoid magnet with a weak field (full current of 6000 amps and magnetic field of 670 millitesla). The innermost part of the detector is the tracking system, which consists of the inner tracking system (ITS) and the outer tracking system (TPC).

TPC is the principal component of ALICE and it's a time projection chamber. A cylindrical device filled with gas and incorporating uniform electric and magnetic fields, a TPC is ideal for separating, tracking, and identifying thousands of charged particles in a dense environment — such as the thousands of particles produced in an energetic heavy-nuclei collision. It is the main detector in many high-energy physics experiments.

Some calculations...

Alice collaboration: 29 countries, 86 institutes, 1000 members.
