Prototype for the ALEPH Time Projection Chamber

This is a prototype endplate piece constructed during R&D for the ALEPH Time Projection Chamber (TPC). ALEPH was one of 4 experiments at CERN's 27km Large Electron Positron collider (LEP) that ran from 1989 to 2000. ALEPH's TPC was a large-volume tracking chamber, 4.4 metres long and 3.6 metres in diameter - the largest TPC in existance at the time. This object is one of the endplates of a “Kind” sector, the smallest of the three types of sectors. The patterns etched into the copper form the cathode pads that measured particle track coordinates in the r-phi direction. It included a laser calibration system, a gating system to prevent space charge buildup, and a new radial pad geometry to improve resolution. the ALEPH TPC allowed for precise momentum measurements of the high-momentum particles from W and Z decays. The following institutes participated: CERN, Athens, Glasgow, Mainz, MPI Munich, INFN-Pisa, INFN-Trieste, Wisconsin.