A Monte Carlo Code for Simulation of Pulse Pile-up Spectral Distortion in Pulse-height Measurement

The Monte Carlo simulation code CEARPPU has been improved to obtain better accuracy for predicting pulse-height spectra measured at high counting rates. Experimental verification was carried out by measuring an Fe-55 spectrum with a Si(Li) X-ray spectrometer. Based on the spectrum measured at low counting rate, which is considered to be the “true” spectrum with no pulse pile-up distortion, the predicted high counting-rate spectrum by CEARPPU is in excellent agreement with the measured one for all of the folded regions due to pulse pile-up. This code is available for public dissemination at Oak Ridge National Laboratory (ORNL) through RSICC. By iteratively using this code, a Monte Carlo approach MCPUT has been proposed and demonstrated for solving the “inverse problem” to make pulse pile-up corrections for pulseheight spectra measured at high counting rates. INTRODUCTION Pulse pile-up distortion is a common problem for pulse-height measurement at high counting rates. High counting rates are “a must” for many medical and industrial applications of radiation measurement to ensure good counting statistics in the shortest possible diagnosis or on-line measurement times. The electronics of a spectrometer for pulse-height measurement are illustrated in Figure 1. Two signal acquisition options are now available, analog and digital pulse processing. Figure 1. Schematic diagram of a generalized chain of electronics for energy pulse-height measurement Current Pulses Detector Preamplifier Linear Amplifier Tail Pulses MCB (ADC+Memory) Display MCA Shaped Pulses Tail Pulses Analog Digitizer Display Digitized Pulses Digital Copyright ©JCPDS International Centre for Diffraction Data 2005, Advances in X-ray Analysis, Volume 48. 246