Fig. 1.

Photo of the Jagiellonian positron emission tomograph (J-PET). The J-PET detector is made of three cylindrical layers of EJ-230 plastic scintillator strips (black) with dimension of $7\times 19\times 500\text{mm}{}^3$ and Hamamatsu R9800 vacuum tube photomultipliers (grey). The signals from photomultipliers are probed in the voltage domain at four thresholds with the timing accuracy of 30 ps [10] and the data acquisition is working in the trigger-less mode [11, 12]