Implementation of a machine learning technique for estimating gamma direction using a coaxial High Purity Germanium detector
Implementation of a machine learning technique for estimating gamma direction using a coaxial High Purity Germanium detector
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DOI：
10.1016/j.nima.2022.167067
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发表时间：
2022-07-11
影响因子：
1.4
通讯作者：
Chirayath, V. A.
中科院分区：
文献类型：
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作者：
Gladen, R. W.;Harvey, T. J.;Chirayath, V. A.
我们演示了使用标准同轴高纯锗（HPGe）探测器获得伽马射线方向的能力，该探测器使用嵌入在预放大的HPGe信号形状中的方向敏感信息。我们使用两步机器学习技术推导出信号形状和伽马射线进入探测器活动体积方向之间的复杂关系。在第一步中，我们收集了由于133Ba放射源放置在探测器周围四个不同位置而产生的脉冲，同时保持与探测器晶体中心的距离恒定。用放射源收集的脉冲中的一个子集保存在四个位置，用于训练一个称为自组织映射（SOM）的人工神经网络（ANN），根据它们的形状对HPGe波形进行聚类。然后利用训练好的SOM网络生成与133Ba源相对于探测器的特定位置产生的脉冲相对应的定向图。在第二步中，我们使用som生成的特定方向图来训练另一个由单个前馈层组成的网络，用于预测由于伽马能量沉积而由HPGe探测器产生的脉冲产生的伽马射线方向。我们的研究结果表明，即使不采用复杂的方法，一个标准的同轴HPGe探测器也可以估计入射伽马射线的方向，从而参考探测器对伽马发射辐射源方向提供初步指导。
We demonstrate the ability to obtain the direction of the gamma rays using a standard coaxial high purity germanium (HPGe) detector using the direction-sensitive information embedded in the shape of the pre -amplified HPGe signals. We deduced the complex relationship between the shape of the signal and the direction from which the gamma-ray enters the detector active volume using a two-step machine learning technique. In the first step, we collected pulses from the HPGe detector due to a 133Ba radioactive source placed in four distinct positions around the detector while keeping the distance from the center of the detector crystal constant. A subset of the pulses collected with radioactive source kept at the four positions was used to train an artificial neural network (ANN) called a self-organizing map (SOM) to cluster the HPGe waveforms based on their shape. The trained SOM network was then utilized to produce direction-specific maps corresponding to pulses generated when the 133Ba source is at a specific location with respect to the detector. In the second step, we used the SOM-generated direction-specific maps to train another network composed of a single feedforward layer for predicting the direction of the gamma ray from the pulses produced by the HPGe detector due to the gamma energy deposition. Our results show that even without employing complex methodologies, a standard coaxial HPGe detector can estimate the direction of incoming gamma rays and thus, provide initial guidance on the gamma-emitting radioactive source direction with reference to the detector.