ALICE and the time projection chamber

26 April 2000

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Looking rather like the inside of a whale (or a futuristic rabbit hole?), this image is of a prototype detector for the ALICE experiment being prepared at CERN, Europe's centre for research in particle physics near Geneva. ALICE (A Large Ion Collider Experiment) will study high-energy head-on collisions between ions of lead in the Large Hadron Collider (LHC), which should start up at CERN in 2005. The experiment will search for signs of quark gluon plasma, a state of matter that should have existed in the energetic early Universe. Experiments at CERN have already glimpsed signs that this matter may be formed in heavy-ion collisions, but ALICE will observe collisions at energies 300 times higher than has been achieved so far.

Rather than transporting ALICE into another dimension, the Time Projection Chamber (TPC) will track charged particles produced in the collisions. The chamber will be filled with gas and an electric field will be applied across it. When charged particles pass through, they will knock electrons out of atoms in the gas and these will drift in the electric field to the end of the chamber. By measuring the position and arrival of electrons at the end, the TPC will reconstruct the paths of the original particles.

Credit: CERN Photo