Investigation of the Non-Linear Variation in the Photo-Peak Area of Prompt Gamma Rays in NaCl Aqueous Solutions Using the PGNAA Technique

A Prompt Gamma-ray Neutron Activation Analysis (PGNAA) setup, comprising a radionuclide AmBe neutron source and an HPGe detector, was employed for the quantitative analysis of aqueous samples in University of Rajasthan laboratories. Various samples containing different amounts of sodium chloride (NaCl) solution, ranging from 10 to 1000 g, were dissolved in 5 liters of deionized water. For each sample, prompt gamma-ray data had been collected over a period of half an hour. The measurement outputs indicated that the prompt gamma-ray emission from chlorine did not increase linearly with NaCl concentrations above 100 g, due to neutron self-shielding effects. However, in the 10 to 100 g range, the counts showed an approximately linear dependence on concentration. Methodology for the minimum detectable concentration (MDC) of chlorine has been developed and adopted using the 6110.8 keV prompt gamma peak. The determined MDC of our setup was found to be $781 \pm 273 \text{ppm}$ in aqueous solution.