  The DIRAC experiment at CERN aims to measure the lifetime of the pionium atom
($A_{2\pi}$), a $\pi^+\pi^-$ bound state with an accuracy of 10%. The
experimental setup consists of a high precision magnetic double arm
spectrometer, located at the high intensity proton beam of the CERN Proton
Synchrotron. This measurement will provide - in a model independent way - the
S-wave pion scattering length difference $|a_0 - a_2|$ with 5% precision.
