Pulse Timing System for Use with Gamma Rays on Ge(Li) Detectors

A zero crossing technique has been employed to reduce energy-dependent time errors when detecting gamma rays with Ge(Li) detectors. The timing errors associated with pulse shape variation have been evaluated so that circuit parameters might be chosen to minimize those errors. Results of coincidence measurements using a plastic scintillator and a Ge(Li) detector are presented. Typical results using an 8 cc planar detector are 0.8 nsec FWHM at 2.75 MeV, 2.8 nsec FWHM at 511 keV, and 1.5 nsec variation in coincidence peak position from 500 keV to 2.75 MeV.