In this paper

we report a newly developed AGS instrument.The probe is composed of five 5 NaI(Tl) 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(Tl)+PMT scintillation counters can be operated at the same time.