核能谱分析仪中，常采用模拟滤波成形电路处理探测器的输出信号，以满足后级电路对信号波形的需要并滤除噪声。由模拟电路实现的高斯成形系统，改变成形参数必须对硬件进行调整，灵活性及稳定性均不理想。为实现数字滤波成形，根据模拟Sallen－Key高斯滤波成形电路，推导出模拟高斯成形系统的冲激响应；再根据采样定理推导出了数字高斯成形系统的冲激响应。用该数字高斯成形系统对实测核脉冲信号进行处理的结果显示，数字核脉冲信号被滤波成形为准高斯信号，为核脉冲信号数字滤波成形的实现提供了一种新的实现方法。%In order to give the uncertainty of activity concentration of radio xenon which leaked into air after nu -clear fission happened , it was supposed that the radio xenon leakage was instantaneous , and the radio xenon leaked into a confined space ,the distribution was uniform .After decay correction and in principle that the theo-retical value of the average activity is consistent with the measuring values ,the mathematical model of the air-borne radio xenon monitoring was derived .By analyzing the sources of uncertainty ,the uncertainty components evaluation , synthesis ,and the mathematics model was evaluated under the certain condition .In the sources of uncertainty ,radio xenon peak net count rate and efficiency value are the main sources ,the concentration ,volume of xenon in air and gamma -ray emission rate of radio xenon are smaller ,the decay constant and time measure-ment are the least .
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