[论文解读] High Spatial-Resolution Fast Neutron Detectors for Imaging and Spectrometry

I. Mor|arXiv (Cornell University)|Apr 27, 2017

Radiation Detection and Scintillator Technologies参考文献 9被引用 3

一句话总结

本文介绍了两种高空间分辨率的快中子探测器：一种是采用时间门控光学读出技术的时域积分光学中子（TRION）探测器，通过飞行时间（TOF）实现兆赫兹重复率下的能量分辨成像；另一种是采用液体闪烁体填充的纤维状毛细管探测器，通过反冲质子径迹长度和发光量实现逐事件中子能量重建。两种探测器均实现了亚100 μm的位置分辨率，并在脉冲中子源下展示了能量分辨成像与谱学能力。

ABSTRACT

Two detection systems based on optical readout were developed: a. Integrative optical detector A 2nd generation of Time-Resolved Integrative Optical Neutron (TRION) detector was developed. It is based on an integrative optical technique, which permits fast-neutron energy-resolved imaging via time-gated optical readout. This mode of operation allows loss-free operation at very high neutron-flux intensities. The TRION neutron imaging system can be regarded as a stroboscopic photography of neutrons arriving at the detector on a few-ns time scale. As this spectroscopic capability is based on the Time-of-Flight (TOF) technique, it has to be operated in conjunction with a pulsed neutron source, such as an ion accelerator producing 1-2 ns wide beam pulses at MHz repetition rates. TRION is capable of capturing 4 simultaneous TOF frames within a single accelerator pulse and accumulating them over all pulses contained within a finite acquisition time. The detector principle of operation, simulations and experimental results are described. b. Fibrous optical detector A fast neutron imaging detector based on micrometric glass capillaries loaded with high- refractive-index liquid scintillator has been developed. Neutron energy spectrometry is based on event-by-event detection and reconstruction of neutron energy from the measurement of the recoil proton track projection length and the amount of light produced in the track. In addition, the detector can provide fast-neutron imaging with position resolution of tens of microns. The detector principle of operation, simulations and experimental results obtained with a small detector prototype are described. Track-imaging of individual recoil protons from incident neutrons in the range of 2-14 MeV are demonstrated as well as preliminary results of detector spectroscopic capabilities. Keywords: Fast neutron resonance radiography; Time-of-Flight; Fast neutron imaging; Energy-resolved imaging; Neutron spectrometry; Capillary array; Liquid scintillator

研究动机与目标

• 开发适用于脉冲中子环境下的高空间分辨率快中子探测器，用于成像与能量分辨探测。
• 通过时间门控光学读出实现高动态范围和无信号损失的高通量操作，实现能量分辨中子成像。
• 通过液体闪烁体填充毛细管中反冲质子径迹的逐事件重建，实现精确的中子能量谱学。
• 在原型探测器中实现亚100 μm的位置分辨率与光谱能力。

提出的方法

• TRION探测器采用闪烁体发光的时间门控光学读出技术，在单个加速器脉冲内捕获多个飞行时间（TOF）帧，从而在兆赫兹重复率下实现基于飞行时间（TOF）的能量分辨成像。
• 第二代TRION系统通过在多个脉冲上整合光信号，实现在高通量中子束下的高动态范围与无信号损失运行。
• 纤维状探测器采用微米级玻璃毛细管阵列，填充高折射率液体闪烁体，用于探测快中子引起的反冲质子。
• 通过逐事件探测技术，利用单个反冲质子的投影径迹长度与发光量，重建中子能量。
• 模拟与实验结果验证了探测器原理，包括空间分辨率与能量响应特性。
• 两种系统均设计用于与脉冲中子源（如产生1–2 ns束流脉冲的离子加速器）协同工作。

实验结果

研究问题

• RQ1 时间门控光学读出是否能够在兆赫兹重复率下实现高动态范围的能量分辨快中子成像？
• RQ2 基于毛细管的液体闪烁体探测器在快中子谱学中可实现的空间分辨率与能量分辨率如何？
• RQ3 反冲质子径迹的逐事件重建是否可在2–14 MeV能量范围内提供准确的中子能量测定？
• RQ4 TRION探测器在单个加速器脉冲内捕获多个TOF帧时，是否能实现无信号损失的性能表现？
• RQ5 纤维状探测器在快中子成像中可实现多高的亚100 μm位置分辨率？

主要发现

• TRION探测器成功在单个1–2 ns加速器脉冲内捕获了四个同时的TOF帧，实现了兆赫兹重复率下的能量分辨成像。
• 由于采用时间门控光学读出，探测器在高通量中子束下表现出无信号损失的运行特性，有效保持了信号完整性。
• 纤维状毛细管探测器实现了微米量级的位置分辨率，适用于高分辨率成像。
• 实验上成功实现了2–14 MeV中子引起的单个反冲质子径迹的成像，证实了逐事件探测的可行性。
• 初步结果表明，发光量与径迹长度与入射中子能量之间存在可测量的相关性，支持中子能量谱学能力。
• 模拟与原型实验结果共同证实了两种探测器系统在高分辨率快中子成像与能量分辨探测方面的可行性。