HOW BIG ARE CHARGE CLOUDS INSIDE THE CHARGE-COUPLED DEVICE PRODUCED BY X-RAY PHOTONS?
HOW BIG ARE CHARGE CLOUDS INSIDE THE CHARGE-COUPLED DEVICE PRODUCED BY X-RAY PHOTONS?
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X 射线光子在电荷耦合器件内产生的电荷云有多大？
DOI：
10.1143/jjap.37.4627
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发表时间：
1998
影响因子：
1.5
通讯作者：
M. Ohtani
中科院分区：
文献类型：
--
作者：
J. Hiraga;H. Tsunemi;K. Yoshita;E. Miyata;M. Ohtani
本文报道了X射线光子在电荷耦合器件（CCD）中产生的电荷云形状及其测量方法，测量采用多间距网格，不仅对单个事例，而且对分裂事例，都能以亚像素分辨率确定X射线的相互作用位置。当X射线相互作用位置接近像素边界时，生成分裂事件。该区域的宽度取决于表观电荷大小。最后，根据X射线的相互作用位置测量像素输出的信号。通过对该函数的微分，我们得到了可以用非对称高斯函数很好地表示的电荷云形状。Al-K X射线的电荷云尺寸为0.7×1.4 µm2，而Mo-L X射线的电荷云尺寸为0.8×1.4 µm2。这些X射线在Si中产生的光电子的尺寸约为0.04微米。考虑到这些X射线在Si中的平均吸收长度，耗尽区的扩散过程不能解释电荷云的大小。电荷云的不对称性可能是由CCD中电场的不对称性引起的。
We report here the charge cloud shape produced by an X-ray photon inside the charge-coupled device (CCD) as well as a method to measure it. The measurement is carried out by using a multi-pitch mesh which enables us to specify the interaction position of X-rays with subpixel resolution not only for single events but also for split events. Split events are generated when the X-ray interaction position is close to the pixel boundary. The width of this area depends on the apparent charge size. Finally, we measured the signal output from the pixel according to the interaction position of X-rays. By differentiating this function, we obtain, in detail, the charge cloud shape which can be well represented by an asymmetric Gaussian function. The charge cloud size for Al-K X-rays is 0.7×1.4 µm2 while that for Mo-L X-rays is 0.8×1.4 µm2. The size of the photoelectron in Si produced by these X-rays is about 0.04 µm. Taking into account the mean absorption length for these X-rays in Si, diffusion process in the depletion region cannot explain the charge cloud size. The asymmetry of the charge cloud probably arises from the asymmetry of the electric field in the CCD.