Development of a Liquid Scintillator and of Data ... - Borexino - Infn

6 Test of a PXE based scintillator for Borexino
Energy Resolution
The energy resolution can be derived from the width of the Po alpha peak (see fig. 6.9):
¡
Ideally, the relative energy resolution should be directly proportional to Ô ÒÔ, where ÒÔ is
the number of photoelectrons. This leads to
¡
Ô ÒÔ
or ¡
Ô Î
The energy resolution can also be obtained by the fit tothe C spectrum, which gives
¡
Ô ¦ Î
Res01℄
Again, the values obtained in two different energy regions are in good agreement.
Spatial Resolution
The spatial resolution can be derived without introducing a radioactive source using the correlated
decays of Bi and Po, which due to the short lifetime of the Po must occur at
the same place. Plotting the distance between the x-coordinates of the reconstructed positions
of the Bi and the following Po event gives a distribution with a resolution of Ü ¡ Ô .
This resolution is averaged over the energy range of the Bi ¬ events (0 - 3.2 MeV) and the
Po « events (0.7 - 1.2 MeV). The result is shown in fig. 6.10. As the Rn is distributed
homogeneously inside the scintillator, this method gives the position resolution averaged over
the whole scintillator volume. The results are
94
Ü ¦ Ñ
Ý ¦ Ñ
Þ ¦ Ñ