Transverse emittance measurement with a rapid wire scanner at the CERN SPS

A simple almost non-destructive device has been built to accurately measure the transverse emittances of the proton and antiproton beams in the CERN SPS collider. A fine wire passing rapidly through the beams acts as a target for the production of high energy secondary particles. Use is made of the strong directivity of the particle production to separately record the profiles of the two beams using scintillators and photomultipliers placed close to the beam pipe in the downstream proton and antiproton directions. The wire scanners are also used to measure the emittance of high-intensity proton beams during normal fixed-target operation using the secondary emission (depletion) current leaving the wire since in this case the directivity is not required. (orig.)