Photon counting performance of amorphous selenium and its dependence on detector structure.
Photon counting performance of amorphous selenium and its dependence on detector structure.
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非晶硒的光子计数性能及其对探测器结构的依赖性。
DOI：
10.1117/1.jmi.5.4.043502
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Zhao,Wei
中科院分区：
文献类型：
--
作者：
Stavro,Jann;Goldan,AmirH;Zhao,Wei
光子计数探测器（PCD）具有改善X射线成像的潜力;然而，它们仍然受到高成本和性能限制的阻碍。通过使用非晶硒（a-Se），与现代晶体半导体相比，PCD的成本可以显著降低，并且能够实现大面积沉积。我们正在研制一种直接转换场成形多阱雪崩探测器（SWAD），以克服a-Se中低载流子迁移率和低电荷转换增益的限制。SWAD的双栅极设计创建了独立的非雪崩相互作用（体）和雪崩检测（井）区域，实现了与深度无关的雪崩增益。单极性时间差分（UTD）电荷感测与阱区中的可调谐雪崩增益相结合允许快速响应和高电荷增益。我们开发了一个基于概率的数值模拟来研究UTD电荷感测和雪崩增益对不同a-Se探测器配置的光子计数性能的影响。模拟了59.5和30 keV光子的脉冲高度谱（PHS）。我们观察到我们的模型和以前公布的PHS测量平面探测器之间的良好协议。能量分辨率从平面探测器的33 keV显著提高到SWAD的107 keV。发现SWAD具有接近200 kcps /像素的线性响应。
Photon counting detectors (PCD) have the potential to improve x-ray imaging; however, they are still hindered by high costs and performance limitations. By using amorphous selenium (a-Se), the cost of PCDs can be significantly reduced compared with modern crystalline semiconductors, and enable large-area deposition. We are developing a direct conversion field-shaping multiwell avalanche detector (SWAD) to overcome the limitation of low carrier mobility and low charge conversion gain in a-Se. SWAD’s dual-grid design creates separate nonavalanche interaction (bulk) and avalanche sensing (well) regions, achieving depth-independent avalanche gain. Unipolar time differential (UTD) charge sensing, combined with tunable avalanche gain in the well region allows for fast response and high charge gain. We developed a probability-based numerical simulation to investigate the impact of UTD charge sensing and avalanche gain on the photon counting performance of different a-Se detector configurations. Pulse height spectra (PHS) for 59.5 and 30 keV photons were simulated. We observed excellent agreement between our model and previously published PHS measurements for a planar detector. The energy resolution significantly improved from 33 keV for the planar detector to ∼7 keV for SWAD. SWAD was found to have a linear response approaching 200 kcps / pixel.