Wide-gap CdTe strip detectors for high-resolution imaging in hard X-rays
Wide-gap CdTe strip detectors for high-resolution imaging in hard X-rays
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用于硬 X 射线高分辨率成像的宽间隙 CdTe 条状探测器
DOI：
10.1016/j.nima.2023.168175
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Takahashi Tadayuki
中科院分区：
文献类型：
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作者：
Nagasawa Shunsaku;Minami Takahiro;Watanabe Shin;Takahashi Tadayuki
我们提出了一种新的CdTe x射线探测器的条带结构，称为“宽间隙CdTe条带探测器”，其中相邻条带之间的间隙远远大于每个条带的宽度。已知，当且仅当入射x射线光子引起的电荷云被分割成多个条带并精确测量其能量时，可以利用相邻条带中入射光子的观测能量来获得比条带间距更精细的位置分辨率。然而，现有的碲化镉条带探测器，这种电荷共享事件的比例是有限的。一个潜在的突破，以大大提高电荷共享事件的比率的想法是扩大探测器上的条带之间的间隙。为了验证这一概念，我们开发了一种宽间隙CdTe条带探测器，该探测器在阴极侧有64个铂带电极，条带间距从60 μ m （30 μ m带和30 μ m隙宽）到80 μ m （30 μ m带和50 μ m隙宽）不等。我们通过在探测器上照射241 Am的x射线来评估其性能。由于探测器上更宽的间隙导致的电荷损失被发现是显著的，在某种程度上，假设电荷共享事件的入射光子的能量是相邻条带中检测到的能量的简单总和，导致累积光谱中的能量分辨率显著下降，与具有标准间隙宽度的前辈相比。然后，我们开发了一种新的能量重建方法来补偿电荷损失。该方法对数据的应用产生了与前一代光谱分辨率相当的光谱。17.8 keV事件的电荷共享事件比率从24.3%提高到49.9%，是前一代的两倍。我们用基于肖克利-拉莫定理的理论模拟评估了结果，发现它们是一致的。
We propose a new strip configuration for CdTe X-ray detectors, named “Wide-gap CdTe strip detector”, in which the gap between adjacent strips is much wider than the width of each strip. It has been known that the observed energies of an incoming photon in adjacent strips can be utilized to achieve a position resolution finer than the strip pitch, if and only if the charge cloud induced by an incoming X-ray photon is split into multiple strips and their energies are accurately measured. However, with existing CdTe strip detectors, the ratio of such charge-sharing events is limited. An idea for a potential breakthrough to greatly enhance the ratio of charge-sharing events is to widen the gaps between strips on the detector. To test the concept, we developed a wide-gap CdTe strip detector, which has 64 platinum strip electrodes on the cathode side with some variations in strip pitches from 60 μ m (30 μ m strip and 30 μ m gap width) to 80 μ m (30 μ m strip and 50 μ m gap width). We evaluated the performance depending on the strip pitches by irradiating X-rays from 241 Am on the detector. The charge loss due to the wider gaps on the detector was found to be significant to the extent that the assumption that the energy of an incoming photon for a charge-sharing event was the simple sum of the energies detected in adjacent strips lead to a significant degradation in the energy resolution in the accumulated spectrum, compared with those obtained with its predecessor having standard gap-widths. We then developed a new energy-reconstruction method to compensate for the charge loss. Application of the method to the data yielded a spectrum with a comparable spectral resolution with that of the predecessor. The ratio of the charge-sharing events for 17.8 keV events was doubled from that of the predecessor, from 24.3 to 49.9 percent. We assessed the results with a theoretical simulation based on the Shockley–Ramo theorem and found that they were in agreement.