ALICE: A Large Ion Collider Experiment

  • CMS
  • LHCb
  • MoEDAL
  • Linear accelerators for protons (p ) or lead nuclei (Pb)
  • Proton Synchrotron Booster (PSB )
  • Proton Synchrotron (PS )
  • Super Proton Synchrotron (SPS )

ALICE is the acronym for A Large Ion Collider Experiment. It is a particle physics experiment that is designed to reproduce the state of matter just after the Big Bang. ALICE is part of the Large Hadron Collider at the CERN research center near Geneva. With 1,000 employees ( physicists, engineers and technicians ) is one of the largest current ALICE (2011 ) Single experiments. The ALICE detector is about 25 meters long and 16 meters wide and has a total weight of about 10,000 tons.

Goal of ALICE is the generation and measurement of a quark-gluon plasma. Immediately after the Big Bang, the universe for a few millionths of a second was in a state of extreme density and temperature, the quark -gluon plasma. By means of collisions of accelerated nuclei lead to this condition are briefly generated. To study the quark- gluon plasma is ALICE from a large number of individual detectors.

Inner Tracking System

The Inner Tracking System ( ITS) consists of six cylindrically arranged silicon detector layers. It thus surrounds the collision point and determines this with high precision. In addition, the ITS is used to identify and track reconstruction of particles with small pulses. The Inner Tracking System in turn consists of the detectors SSD, SDD, SPD and FMD.

Time Projection Chamber

The ALICE Time Projection Chamber (TPC / track drift chamber ) is the part that mainly the particle trajectories are determined in the. In this case, charged particles ionize the TPC- filling gas. The free electrons are then extracted via the applied voltage and make it possible to reconstitute the particle path.

Transition Radiation Detector

The ALICE Transition Radiation Detector (TRD / transition radiation detector ) closes the outside directly to the TPC. It consists of 540 different sub-detectors, which are arranged over a length of about 7 meters annularly around the beam axis, wherein the individual chambers are six layers in the radial direction one after the other. The TRD is used for particle identification, it should inter alia help to distinguish electrons and pions.

Flight time

To identify charged particles, the velocity can be measured in addition to the pulse, and thus the mass of the particles are determined. To determine how long it takes the particles from the collision point to the outer areas of the detector. In order to obtain a precise time measurement, ALICE uses about 160,000 MRPCs (English for Multi -gap Resistive Plate Chamber ). In these exploits that charged particles can ionize a gas. If this happens simultaneously in several areas along the particle path, gives a visible signal whose time can be determined very precisely.