The upgrade of the ASACUSA scintillating bar detector for antiproton annihilation measurements

Antiproton annihilations on matter nuclei are usually detected by tracking the charged pions emitted in the process. A detector made of plastic scintillating bars have been built and used in the ASACUSA experiment for the last 10 years. Ageing, movements and transports caused stress on the internal mechanical structure and impacted mostly on the optical readout system which was eventually upgraded: the so far used multi-anode photo-multiplier tubes (PMTs) have been replaced by silicon photomultipliers (SiPM) and the front-end electronics had to be adapted to cope with the new signal formation. This work describes the design and operations of the upgrade, as well as the validation tests with cosmic rays.