CAS Center for Excellence in Comparative Planetology, University of Science and Technology of China, Hefei 230026, China.
State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei 230026, China.
Rev Sci Instrum. 2021 Mar 1;92(3):033301. doi: 10.1063/5.0038534.
In situ radioactivity measurements in a deep ocean environment are essential for marine environmental pollution monitoring and seabed geological exploration. In the past, the most widely used gamma spectrometers were based on towed instrumentation, which could only be operated underwater at a depth of less than 1500 m. In this study, a compact gamma spectrometer with small-size, light weight, and low power consumption was designed for working in a marine in situ environment. This spectrometer, with two essential parts: detector and electronics, was designed to work on different underwater platforms in the real-time control mode or autonomous operation mode. Multiple small volume avalanche photodiodes were coupled with NaI(Tl), which can significantly reduce the spectrometer volume compared with the option of the photomultiplier tube. Integrated readout electronics were employed to digitize all detector signals for miniaturization and low power consumption. The field programmable gate array (FPGA) was used to obtain the energy spectrum in real-time and an online multi-channel summation with temperature calibration algorithm was employed to improve detection efficiency. Relevant tests were also conducted in the laboratory to evaluate critical techniques and system performance. Results show that the energy resolution (full width at half maximum over the peak position) was ∼7.5% at 662 keV, verifying the online multi-channel summation with temperature calibration based on the FPGA. Moreover, the compact prototype spectrometer worked well in the power-on hydraulic test.
在深海环境中进行原位放射性测量对于海洋环境污染监测和海底地质勘探至关重要。过去，最广泛使用的伽马谱仪基于拖曳式仪器，只能在水深不超过 1500 米的水下操作。在这项研究中，设计了一种紧凑的伽马谱仪，具有体积小、重量轻、功耗低的特点，可用于海洋原位环境。该谱仪由探测器和电子学两部分组成，旨在以实时控制模式或自主操作模式在不同的水下平台上工作。多个小体积雪崩光电二极管与 NaI(Tl)耦合，可以显著减小谱仪体积，与光电倍增管的选择相比具有优势。采用集成读出电子学对所有探测器信号进行数字化，以实现小型化和低功耗。现场可编程门阵列 (FPGA) 用于实时获取能谱，采用在线多道求和温度校准算法来提高检测效率。还在实验室中进行了相关测试，以评估关键技术和系统性能。结果表明，在 662keV 处能量分辨率（半峰全宽相对于峰位）约为 7.5%，验证了基于 FPGA 的在线多道求和温度校准。此外，紧凑型原型谱仪在通电水压测试中运行良好。
