Absolute measurement of 198Au activity in gold foil using plastic scintillators and a well-type NaI(Tl) detector

A beta-gamma coincidence system has been developed for measuring 198Au activity in gold foils. The system was validated by Monte Carlo simulations and by measuring the activity of a 60Co point-source. To study effects such as self-shielding of beta particles in gold foils, 198Au activity measurements and simulations were performed for various scintillators and foil sizes. The measured 198Au activities were ~1% above the reference activity, which might be due to self-shielding of beta particles. The measured and simulated 198Au activities agreed, suggesting feasibility of precise activity measurement.