Charged Particle Detectors

The Charged Particle Detectors

Three charged particle detectors are present in the PADME setup to detect:

• the positrons that have radiated a high energy photon in the target (PVeto);
• the electrons from the beam interactions in the target or from particles which decay to final states with electrons (EVeto);
• the positrons which have lost a relatively low energy in the target (HEPVeto).

All three detectors are made of plastics scintillator bars with approximate dimensions 1 × 1 × 178 cm³. The scintillators are grooved longitudinally and the light is taken by a 1.2 mm diameter BCF-92 wave-length shifter fiber, glued in the groove with BC-600 optical cement. The optical readout is performed with a 3 × 3 mm² Hamamatsu S13360 silicon photomultiplier (SiPM), whose contact with the fiber  is realized with a Momentive RTV615 silicone rubber compound. The SiPMs are mounted on a custom designed PCB housing the front-end electronics and a control circuit, which allows to adjust and measure for each SiPM the bias voltage.

All three detector are placed inside the PADME vacuum chamber: the EVeto and the PVeto, consisting of 96 elements each, are located along the walls of the chamber inside the dipole magnet, while the HEPVeto, made of 16 elements, is installed close to the beam exit window.