Abstract The Pulse shape discrimination (PSD) technique for single crystal CVD diamond detector (SDD) was applied to the real-time thermal neutron measurement during the 3rd campaign of Deuterium-Deuterium (D-D) plasma experiment in the Large Helical Device (LHD). The PSD method is based upon the different shape of electrical pulses produced in diamond by gamma-ray (triangular-shaped pulse) and energetic ions (rectangular-shaped pulse), respectively. An improved PSD was developed which makes use of the full width at half maximum (FWHM) and the full width at 2/3 of the peak height (FW2/3 PH). These two parameters reflect the difference in the pulse shape produced by gamma-rays and energetic ions. The performance of this improved PSD technique was first tested irradiating the SDD by gamma-rays from 60Co and alphas from 241Am radiation sources, respectively. Then, using a 6LiF thermal neutron converter, a successful discrimination between gamma-rays and alpha particles and tritons generated by the 6Li(n,α)3H reaction induced by neutrons from 252Cf spontaneous fission neutron source was achieved. Thanks to this PSD processing technique, the thermal neutron detection efficiency increased about 1.7 times compared to previous measurements performed without the PSD technique. The real-time thermal neutron measurement by SDD with this enhanced PSD processing was also used during D-D plasma discharges in the Large Helical Device (LHD). It was found that both the time integrated counts and the time evolution count rate measured by the SDD reproduced well that of the fission chamber used as official LHD neutron monitor. The capability of the SDD detector using the PSD technique of precise real-time thermal neutron measurement in LHD was demonstrated.

中文翻译：

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单晶CVD金刚石探测器热中子测量在LHD氘等离子体实验中应用脉冲形状鉴别

摘要 将单晶CVD金刚石探测器（SDD）的脉冲形状鉴别（PSD）技术应用于大型螺旋装置（LHD）中氘-氘（DD）等离子体实验第三阶段的实时热中子测量。PSD 方法基于伽马射线（三角形脉冲）和高能离子（矩形脉冲）分别在金刚石中产生的不同形状的电脉冲。开发了一种改进的 PSD，它利用了半峰全宽 (FWHM) 和峰高 2/3 处的全宽 (FW2/3 PH)。这两个参数反映了伽马射线和高能离子产生的脉冲形状的差异。这种改进的 PSD 技术的性能首先通过来自 60Co 的伽马射线和来自 241Am 辐射源的 α 射线照射 SDD 进行测试，分别。然后，使用 6LiF 热中子转换器，成功区分了伽马射线和 α 粒子以及由 252Cf 自发裂变中子源中子引起的 6Li(n,α)3H 反应产生的氚。由于采用了这种 PSD 处理技术，与之前没有使用 PSD 技术进行的测量相比，热中子探测效率提高了约 1.7 倍。在大型螺旋装置 (LHD) 中的 DD 等离子体放电期间，也使用了具有这种增强型 PSD 处理的 SDD 实时热中子测量。发现由 SDD 测量的时间积分计数和时间演化计数率都很好地再现了用作官方 LHD 中子监测器的裂变室。