National intercomparison of environmental gamma radiation dose rate in China based on ice surface cosmic ray response measurements

This study reports the first national intercomparison of environmental gamma radiation dose rate in China where each device's response to the ubiquitous cosmic rays was measured on top of a frozen lake ice surface. A total of 78 ambient gamma dose rate instruments from 38 institutions were tested at four typical sites, including a low-terrestrial-background site on the ice surface of the Bosten Lake to measure the detector-specific cosmic ray responses, and wilderness, road, indoor sites nearby. The measured dose rates on the ice surface show significant variations for different detector types but exhibit good consistency within the same model. The cosmic ray responses were then subtracted from the measured dose rates at the other three environmental sites, and the corrected terrestrial gamma radiation dose rates are generally very similar for all instruments. A robust Z-score analysis was applied to evaluate proficiency and identify outliers. This work demonstrates the feasibility of ice-based measurement of the detector-specific apparent cosmic-ray response, and offers a practical technical reference for future intercomparison activities and quality assurance in environmental gamma radiation measurements.