The large-area micro-channel plate entrance detector of the heavy-ion magnetic spectrometer PRISMA

This paper describes the entrance detector of the magnetic spectrometer PRISMA recently installed at Legnaro. The detector is based on rectangular (80 100mm2) Micro-Channel Plates (MCP). It provides a fast time signal and its position-sensitive anode allows to extract the X and Y information. It exploits an electrostatic field for the acceleration of secondary electrons from a thin Carbon foil (’ 20 mg=cm2) onto the MCP assembly. The electrons are guided by a parallel magnetic field. Good performances were obtained in the laboratory tests. The detector is presently installed at the entrance of PRISMA and gives resolutions p400 ps in time, and 1mm in both X and Y-axes, with efficiency ’ 100%, in typical experiments with heavy-ion beams.