Intrinsic time resolution of detectors in a time-of-flight spectrometer

Abstract

Introduction of a third detector in a time-of-flight spectrometer permits us to measure the intrinsic time resolution of each detector. We have tested this method with a 212Pb source and we have obtained the curve of the time resolution of a solid state detector (SSD) vs the energy of alpha particles (from 2 to 8 MeV) and the curve of the time resolution of a thin scintillator foil detector (TFD) as a function of the energy loss of the α-particles in the TFD or the number of photoelectrons created. We have been able to conclude that the time resolution of the SSD is a function of 1/✓E ( E = energy of the α-particles in the SSD, from 2 to 8 MeV) and that of the TFD is dependent on the time characteristics of the scintillator and the number of photoelectrons created. Further, this experiment leads to the conclusion that to get the best time resolution with a TFD, SSD spectrometer, one should use the thickest possible scintillator foil. This was verified in a heavy ion reaction ( 40Ar+ 197Au at 220 MeV) with elastically scattered 40Ar. We got a resolution of 200 ps with a Ne 111 foil of 300 μg/cm 2. It was, thus, possible to separate the masses of the reaction products up to 60 amu in the same reaction.