  The aim of this work was to test the impact of the lightguides insertion in
the J-PET detection system and to choose the best of available solutions. At
the two strip J-PET test system a series of measurements was performed with
different combinations concerning the length of the lightguides (3 mm and 3 cm)
and scintillators (3, 15 and 30 cm), shape of lightguides (trapezoidal and
cylindrical, with and without a cut matching the scintillator size) and optical
connection between elements (optical gel and glue). It was proven that the
insertion of the thin lightguide does not spoil the time resolution and the
light output. Additionally,the correlation between the time resolution and the
light output was confirmed.
