The targeted acquisition of the radioactive element content or radioactivity in a radioactivity is an important task in geological exploration and radioactive pollution investigation. During the process of targeted gamma radiation sampling, gamma rays from non-target areas significantly interfere with the measurement results.

This study aims to design a dual-energy targeted gamma radiation sampling probe that uses a cerium bromide scintillation detector on the basis of the difference in the linear attenuation coefficients of the high- and low-energy gamma rays from the same radioactive decay series in the lead shielding layer of the detector.

Firstly, Monte Carlo (MC) numerical simulations were employed to determine the optimal lead shielding layer thickness for the dual-energy targeted gamma radiation sampling probe detecting targets of the 0.609 MeV and 1.764 MeV gamma rays emitted by ²¹⁴Bi. Then, the directional proportionality coefficients were calculated and applied to obtaining 0.609 MeV gamma ray counts of dual energy γ radiation probe within lead shielded angle. Finally, MC numerical simulations with four types of interfering radiation sources and physical experiments with two radium sources were conducted to validate the results that calculated using the directional proportionality coefficients.

The simulation result of optimal lead shielding layer thickness for the dual-energy targeted gamma radiation sampling probe is 6 mm, and the calculated directional proportionality coefficients of a and A are 0.268 and 0.451, respectively. Validation results show that the relative error between the counts for the 0.609 MeV gamma rays within the shielded angle and the net peak area counts measured with the dual-energy targeted gamma radiation sampling probe for two radium sources is within ±2.52% with average relative error of 0.63%. The relative errors between the measured uranium content and recommended values in the tested models are all less than 5%.

The dual-energy targeted gamma radiation sampling results for a radioactive mixed standard model and three radioactive models indicated that the designed dual-energy targeted gamma radiation sampling probe is capable of targeted gamma radiation sampling.