- Am-241 peaks at ch 134=13.8, ch 163=17.8, ch 218=26.3 keV - Calibration: E = 0.397 + 0.0995 × ch (previously wrong) - Kurie fit endpoint 425 keV vs Q=297.5 keV — spectrum extends beyond MCA range (407 keV), simple extrapolation unreliable - Proper endpoint extraction requires theory model + detector convolution (fitter module), not simple Kurie plot