Hi everyone, I am doing an experiment about alpha spectrum. I am using Model P-2000/1 (don't know if this matters), a NaI(Tl) scintillation probe. I selected energy range 3-8 MeV at the front panel and waited for 3000 counts at the peak, it took ~800 seconds. But when I selected energy range 4-6 MeV and did the same measurement, it took me ~17000 seconds to have 3000 counts at the peak! Does anyone know why? Thanks a lot!