Characterization of a GEM-based fast neutron detector
Characterization of a GEM-based fast neutron detector
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DOI：
10.1016/j.nima.2013.11.103
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发表时间：
2014-03
影响因子：
1.4
通讯作者：
B. Esposito;D. Marocco;R. Villari;F. Murtas;R. Rodionov
中科院分区：
文献类型：
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作者：
B. Esposito;D. Marocco;R. Villari;F. Murtas;R. Rodionov
设计用于聚变装置中快速中子测量的基于气体电子倍增器（GEM）的探测器的中子效率是通过结合使用蒙特卡罗（MCNPX）计算和氘-氘和氘-氚中子辐照实验的分析来确定的。该探测器的特点是采用 Ar/CO2/CF4–45/15/40 气体混合物冲洗的三重 GEM 结构，具有数字读出系统，并具有两个子单元，用于检测 2.5+14 MeV 中子和 14 MeV 中子（分别为 UDD 和 UDT）。脉冲高度谱 (PHS) 根据实验效率曲线确定，作为探测器高电压的函数 (HV) 和 MCNPX 模拟的 PHS 使用拟合例程进行比较，该例程通过假设 HV（决定探测器增益）和气体中沉积的能量之间关系的参数模型来找到实验和模拟 PHS 之间的最佳匹配。这导致将实验中子效率表示为沉积能量（能量阈值）上设置的辨别水平的函数。还分析了探测器对 γ 射线的灵敏度，并确定了 γ 射线对信号的贡献不可忽略的操作范围。研究发现，该探测器在 2.5 MeV（UDD 子单元）下可以达到~1×10−3counts/n 的最大中子效率，在 14 MeV（UDT 和 UDD 子单元）下可以达到~4×10−3counts/n 的最大中子效率。
The neutron efficiency of a Gas Electron Multiplier (GEM)-based detector designed for fast neutron measurements in fusion devices was determined through the combined use of Monte Carlo (MCNPX) calculations and analysis of deuterium–deuterium and deuterium–tritium neutron irradiation experiments. The detector, characterized by a triple GEM structure flushed with a Ar/CO2/CF4– 45/15/40 gas mixture, features a digital read-out system and has two sub-units for the detection of 2.5+14 MeV neutrons and 14 MeV neutrons (UDDandUDT, respectively).The pulse height spectra (PHS) determined from the curves of experimental efficiency as a function of the detector's high voltage (HV) and the MCNPX-simulated PHS were compared using a fitting routine that finds the best match between the experimental and simulated PHS by assuming a parametric model for the relation between HV (that determines the detector's gain) and the energy deposited in the gas. This led to express the experimental neutron efficiency as a function of the discrimination level set on the deposited energy (energy threshold). The detector sensitivity to γ-rays was also analyzed and the operational range in which the γ-ray contribution to the signal is not negligible was determined. It is found that this detector can reach a maximum neutron efficiency of ~1×10−3counts/n at 2.5 MeV (UDDsub-unit) and of ~4×10−3counts/n at 14 MeV (UDTandUDDsub-units).