CaLIPSO: An novel detector concept for positron annihilation detection

The CaLIPSO project focuses on the development of an innovative energetic-photon detector. The detector uses a 'heavy' organometallic liquid: the Trimethyl Bismuth (TMBi), 82% by weight of Bismuth. TMBi efficiently converts through the photo-electric effect photons of energies below 1 MeV. The ionisation signal and light produced in the liquid are both detected. Beyond the measurement of gamma photon energies, this detector will allow locating photon interactions in the detector in three dimensions down to 1 mm³ and a sub nanosecond timing accuracy. All these desirable properties can be obtained simultaneously with liquid TMBi detector. The optical properties relevant for particle detection are measured. Preliminary results on TMBi ionization properties are shown. (authors)