A new natural gamma radiation measurement system for marine sediment and rock analysis

摘要

A new high-efficiency and low-background system for the measurement ofnatural gamma radioactivity in marine sediment and rock cores retrieved frombeneath the seabed was designed, built, and installed on the JOIDES Resolutionresearch vessel. The system includes eight large NaI(Tl) detectors that measureadjacent intervals of the core simultaneously, maximizing counting times andminimizing statistical error for the limited measurement times available duringdrilling expeditions. Effect to background ratio is maximized with passive leadshielding, including both ordinary and low-activity lead. Large-area plasticscintillator active shielding filters background associated with thehigh-energy part of cosmic radiation. The new system has at least an order ofmagnitude higher statistical reliability and significantly enhances dataquality compared to other offshore natural gamma radiation (NGR) systemsdesigned to measure geological core samples. Reliable correlations andinterpretations of cored intervals are possible at rates of a few counts persecond.