航空数字γ能谱测量系统的研制

The development of a digital airborne gamma-ray spectrometry

航空数字化γ能谱测量系统以NaI(Tl)晶体(10 mm×10 mm×40 mm)和光电倍增管构成的闪烁计数器为γ射线探测器,采用4条下测晶体和1条上测晶体组合成航空γ能谱测量系统的探头,设计了温度传感器、电流反馈型前置放大器和低纹波高压供电电路,实现了γ光子与核信号的转换;采用Y/U双通道数控增益放大器、双回路自动稳谱电路和算法实现了谱漂的精细调节和自动稳谱,通过高速ADC与CPLD实现模拟核信号的数字化。该系统可接入NaI(Tl)闪烁计数器γ探测器数20条,可探测能量范围0.02–10.0 MeV,采样周期0.5–1 s,最大计数通过率>100 k/s,1024道谱漂<±1道。

In this paper, we report a newly developed AGS instrument. The probe is composed of five 5 NaI（T1） scintillators of 10 mm×10 mm×40 mm size. Four of them detect the ground, and the fifth detects the sky. A temperature sensor, a preamplifier with circuit negative feedback and a high voltage supply with lower noise are designed. A Y/U double channel digital controlled gain amplifier for fine adjustment of the spectral drift, and high speed ADC and CPLD, are designed to perform digital spectroscopy and improve the energy resolution and pulse through output rate （〉100 k/s）. Two self-stabilization spectrum loops are designed for spectrum stability. The first loop performs rough adjustment （temperature）, and the second loop does the fine adjustment by a Kalman filter. The AGS system has the following specifications： energy range of detection, 0.02-10.0 MeV; the spectral drift, ±1 channel; and spectrum collection time of 0.5-1 s. The 20 NaI（T1）＋PMT scintillation counters can be operated at the same time.