Evaluation of Fiber-Shaped LYSO for Double Readout Gamma Photon Detection

Recently, the development of the micro pulling-down method has allowed the growth of single inorganic scintillation crystals with a uniform fiber shape. The dimensions may vary from 0.3 to 3 millimeters in diameter with length up to 1 meter. This paper presents an experimental set up built in order to study the scintillation light propagation within fiber shaped crystals. The interaction position of a gamma photon in the fiber is determined by a coincidence method. Light yields measured by photomultipliers at both sides of the fiber are correlated to the photon interaction position and the scintillating properties of the crystals. X-ray excited luminescence experiments were also performed to study the process of light attenuation along the fibers. X-ray and gamma ray measurements are in good agreement. Two cerium doped lutetium yttrium orthosilicate Lu_2(1-x)Y_2x SiO₅:Ce³⁺ fibers have been studied. The first was a cylindrical crystal fiber of 6.9 cm in length and of 1 mm in diameter obtained by the micro pulling-down technique. The second was a squared shaped fiber crystal of 1times1times43 mm³ obtained from a bulk after cutting and polishing. The interaction localization can be determined with a precision from 4 to 12 mm depending on the fiber shape