Abstract: To meet the needs of online monitoring of α/β radioactive aerosols for dynamic variation of high γ radiation in nuclear power stations and emergency monitoring environments, ion implanted semiconductor detector with passivated surface is redesigned and improved, based on the characteristics of the source term of the monitoring scene. Monte Carlo method was used to simulate the angular response of the optimized dual PIPS detector, and then the structure of the probe was improved. In order to decrease relative standard deviation for angle response, the structure of detection system is improved. Optimized equipment is placed in the ⁶⁰Co and ¹³⁷Cs reference radiation field. Linearity, energy and angular response experiments were performed. It is shown that: 1) The newly designed integrated dual detector has better performance in angular response. 2) Due to anisotropy of the structure and density of assembly material, the construction of probe is optimized, the angular response is no more than 5%, thereby the weight of equipment is effectively reduced. In addition, the linearity and energy response data of the equipment are fitted and the formula is input into the data processing program. Finally, the operating equipment was placed in a ¹³⁷Cs reference radiation field with 10 μGy/h. The test data have shown that the minimum detection limit (MDL) is less than 0.03 Bq/cm³ (for α aerosol) and 0.4 Bq/cm³ (for β aerosol), respectively. As a result, false alarm is significantly avoided.

Key words: aerosol monitoring, nuclear power plant, γ compensation, angular response, minimum detection limit