CEBAF Large Acceptance Spectrometer (CLAS) is a nuclear and particle physics detector located in the experimental Hall B at Jefferson Laboratory in Newport News, Virginia, United States.
Electrons or photons in the incoming beam collide with the nuclei of atoms in the physics "target" located at the center of CLAS.
Teams of physicists analyze the events, looking for new kinds of particles or information related to the underlying structure of the proton.
The particles then traverse three packages of drift chambers which are used to track their paths though the magnetic field, and thereby allow determination of their momentum.
Experiments using electron scattering primarily probe the structure of protons and their excitations at various sub-nuclear "length scales".
Experiments using real photon beams primarily probe the production and decay of mesons and excited baryons.