Which part of a CCD pixel is sensitive to the proton damage
Which part of a CCD pixel is sensitive to the proton damage
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CCD像素的哪一部分对质子损伤敏感
DOI：
10.1016/s0168-9002(03)01910-7
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发表时间：
2003
影响因子：
1.4
通讯作者：
T. Minamisono
中科院分区：
文献类型：
--
作者：
J. Hiraga;H. Tsunemi;E. Miyata;H. Kouno;K. Miyaguchi;K. Matsuta;M. Fukuda;M. Mihara;T. Minamisono
到目前为止，网格实验是研究电荷耦合器件(CCD)亚像素分辨率响应的唯一实用技术。由于钱德拉ACIS在轨道上受到低能质子的严重破坏，我们用相对低能的质子束进行了网格实验。所使用的CCD是为计划于2007年登上国际空间站的全天X射线图像监视器(MAXI)任务所使用的固体狭缝相机(SSC)而设计的。它由1024x1024像素组成，每个像素24μm正方形。每个像素的中心都有一个“凹槽”结构，使其不易受到辐射。选择了质子束能量，使穿过直径为2μm的网孔的质子将穿透到ccd芯片并破坏传输通道。在实验开始时，我们使用了低强度的质子束，并在质子计数模式下操作电荷耦合器件，以精确确定网格与电荷耦合器件之间的相互对准。然后，我们用强质子束辐照电荷耦合器件，使电荷转移效率从10−6提高到10−4。质子辐照后，我们去除网格，用X射线测量电荷转移效率。通过这种方式，我们确定了单个像素的CTI。我们看到有一个从上到下贯穿像素中心的高CTI区域。这对应于电荷转移的凹槽区域。缺口结构受损的像素的CTI值为∼3×10−4，约为缺口区域外受损像素的3倍。当质子在缺口结构中破坏时，信号电荷很容易被俘获，从而导致高CTI。我们的结果清楚地表明，CTI的不均匀是由于缺口结构造成的。这一结果与其他实验结果一致，表明了缺口结构的有效性。
A mesh experiment is, so far, the only practical technique to study charge-coupled devices (CCD) response with subpixel resolution. Since the Chandra ACIS was seriously damaged by low-energy protons in orbit, we undertook a mesh experiment with a relatively low-energy proton beam. The CCD used was designed for the Solid Slit Camera (SSC) employed by the Monitor of All-sky X-ray Image (MAXI) mission that is scheduled to be onboard the International Space Station in 2007. It consists of 1024×1024 pixels, each 24 μm square. Each pixel is equipped with a ‘notch’ structure in the center to make it radiation hard. A proton beam energy has been selected so that the protons passing through the mesh holes, 2 μm in diameter, will penetrate into the CCD chip and damage the transfer channel. At the beginning of the experiment, we used a low intensity proton beam and operated the CCD in proton count mode in order to precisely determine the mutual alignment between the mesh and the CCD. Then, we irradiated the CCD with a strong proton beam, which increased the charge transfer inefficiency (CTI) from 10−6to 10−4. After the proton irradiation, we removed the mesh and measured the CTI with X-rays. In this way, we determined the CTI for individual pixels. We see that there is a high CTI region running through the center of the pixels from top to bottom. This corresponds to the notch region where the charge is transferred. Pixels whose notch structures are damaged show a CTI of ∼3×10−4that is about three times worse than those damaged outside the notch regions. When the proton damages in the notch structure, the signal charges are easily trapped, resulting in a high CTI. Our results clearly show that the non-uniformity of the CTI is due to the notch structure. This result is consistent with other experiments showing the effectiveness of the notch structure.