Improving the resolution in soft X-ray emission spectrometers through photon-counting using an Electron Multiplying CCD
Improving the resolution in soft X-ray emission spectrometers through photon-counting using an Electron Multiplying CCD
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DOI：
10.1088/1748-0221/7/01/c01063
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发表时间：
2012-01
影响因子：
1.3
通讯作者：
D. Hall;M. Soman;J. Tutt;N. Murray;A. Holland;T. Schmitt;J. Raabe;V. Strocov;B. Schmitt
中科院分区：
文献类型：
--
作者：
D. Hall;M. Soman;J. Tutt;N. Murray;A. Holland;T. Schmitt;J. Raabe;V. Strocov;B. Schmitt
2007年，一项用于软x射线光子探测的背光电荷耦合器件（ccd）的研究表明，基于衍射光栅和位置敏感探测器的x射线光谱仪的传统微通道板探测器可以带来改进。据报道，虽然空间分辨率得到了显着提高，但由于CCD中产生的电荷云在几个像素上的扩散，发现了大约25微米的固有限制。为了克服这一分辨率限制，有必要摆脱当前的集成成像方法，考虑光子计数方法，将光子相互作用位置记录到亚像素水平。为了利用光子计数技术，重要的是单个事件是可分离的。为了保持光谱仪对高强度谱线的吞吐量，需要更高的帧速率，因此需要更高的读出速度。对于基于CCD的系统，在高读出速度下增加的噪声会限制光子计数性能。电子倍增CCD与标准CCD共享类似的架构，但合并了一个“增益寄存器”。这种新颖的附加功能允许在引入读取噪声之前将可控增益应用于信号，因此即使在更高的读出速率下，也可以在噪声之上解决单个事件。在过去，EM-CCD只能用于成像区域太小，无法在软x射线发射光谱仪中实际应用。目前对大面积电子倍增ccd的驱动使该技术向新的光子计数应用开放，需要对所涉及的过程和技术进行深入分析。早期的结果表明，通过引入光子计数技术，这种系统的分辨率可以显着提高。
In 2007, a study of back-illuminated Charge-Coupled Devices (CCDs) for soft X-ray photon detection demonstrated the improvements that could be brought over more traditional micro-channel plate detectors for X-ray spectrometers based on diffraction gratings and position sensitive detectors. Whilst the spatial resolution was reported to be improved dramatically, an intrinsic limit of approximately 25 micrometers was found due to the spreading of the charge cloud generated in the CCD across several pixels. To overcome this resolution limit, it is necessary to move away from the current integrated imaging methods and consider a photon-counting approach, recording the photon interaction locations to the sub-pixel level. To make use of photon-counting techniques it is important that the individual events are separable. To maintain the throughput of the spectrometer for high intensity lines, higher frame rates and therefore higher readout speeds are required. With CCD based systems, the increased noise at high readout speeds can limit the photon-counting performance. The Electron-Multiplying CCD shares a similar architecture with the standard CCD but incorporates a "gain register". This novel addition allows controllable gain to be applied to the signal before the read noise is introduced, therefore allowing individual events to be resolved above the noise even at much higher readout rates. In the past, the EM-CCD has only been available with imaging areas too small to be practical in soft X-ray emission spectrometers. The current drive for large area Electron-Multiplying CCDs is opening this technology to new photon-counting applications, requiring in-depth analysis of the processes and techniques involved. Early results indicate that through the introduction of photon-counting techniques the resolution in such systems can be dramatically improved.