薄型NaI(Tl)探测器信噪比的蒙特卡罗模拟

The Monte Carlo simulation of SNR for thin NaI(Tl) detector

本文用蒙特卡罗方法模拟了^133Xe、^133mXe和^135Xe在薄型NaI晶体中的沉积，并模拟计算了信噪比，以分析^40K、U系和Th系核素以及^137Cs在Xe测量能窗中造成的噪声影响。结果表明，信噪比的变化与射线能量相关；^133Xe在晶体厚度为2cm时信噪比最低^133mXe在晶体厚度1-4cm时信噪较低且随晶体厚度的变化不明显，^135Xe在晶体厚度0．2-5cm时信噪比没有极值且随着晶体厚度的增加而增加。

The energy deposition in a thin NaI crystal caused by ^133Xe,^133mXe,^135Xe are simulated with Monte Carlo method. The signal-to-noise ratio （SNR） is calculated to analyze the influences of Uranium series,Thorium series and ^40K as noise signal. As results, the variation of SNR is related to the energy of γ-ray. The SNRs of ^133Xe have the minimum value at the 2cm thickness. The SNRs of ^133mXe are smaller and have no obvious changes at the 1cm to 4cm thickness. The SNRs of ^135Xe have no extremums and increase along with the increase of crystal thickness at the 0. 2cm to 5cm thickness.