The WASA (Wide Angle Shower Apparatus) is a new detector system with very h
igh acceptance presently being commisioned at the CELSIUS storage ring loca
ted at The Svedberg Laboratory in Uppsala. It has been designed to study ra
re decays of light mesons with sensitivity down to 10(-9) in the branching
ratio. It will also allow for unprecedented quality measurements of differe
ntial cross sections of different reactions induced by protons and light nu
clei.