Research for the development of the vertex detector using fully-depleted fine-pixel CCD

我们已经进行了研究的顶点探测器的发展，使用全耗尽精细像素CCD（FPCCD）的直线对撞机（ILC）的实验。研究内容包括：使用FPCCD的顶点探测器的预期性能的模拟研究、标准像素尺寸全耗尽CCD的开发和表征、FPCCD的辐射耐受性研究、FPCCD的辐射硬度研究仪器的开发以及薄化CCD的机械研究。我们发明并证明了通过使用命中簇形状来有效地拒绝背景命中的方法的有效性，这是精细像素的优点之一。在ILC实验中，验证了FPCCD顶点探测器可以满足对跟踪效率和碰撞参数分辨率的要求。随着全耗尽CCD的发展，我们制作了几种不同外延层厚度和电阻率的背照式CCD样品。这些CCD用聚焦成线形的激光照射，线形的宽度小于像素的宽度。我们测量了传播到前表面附近的势阱的信号的扩展。结果发现，具有24 μ m厚的高阻外延层的样品可以完全耗尽，而与栅电压无关。我们还测量了磁场中的洛仑兹角，发现在3T磁场中使用时不会出现严重问题，有望应用于实际实验中，通过本研究，我们证明了FPCCD顶点探测器原则上可以用于ILC实验。在硬件研发方面，我们已经实现了样品CCD的完全耗尽。

We have carried out a study for the development of the vertex detector using fully-depleted fine-pixel CCDs (FPCCD) for the linear collider (ILC) experiments. The study issues are simulation studies of the expected performance of the vertex detector using FPCCD, development and characterization of standard pixel-size fully-depleted CCDs, study of radiation tolerance of FPCCDs, development of apparatus for the radiation hardness study of FPCCDs, and mechanical study of thinned CCDs.In the simulation studies, we invented and demonstrated the validity of a method of effective rejection of background hits by using the hit cluster shape, which is one of the advantages of the fine pixels. We also demonstrated the FPCCD vertex detector can satisfy the requirement for the tracking efficiency and the impact parameter resolution in the ILC experiment.As the development of fully depleted CCDs, we fabricated several kinds of sample back-illuminating CCDs which have different thickness and resistivity of the epitaxial layers. These CCDs were illuminated with LASER light focused in line shape which has the width less than the width of the pixels. We measured the spread of the signal which travels to the potential well near the front surface. As a result, we have found that a sample which has 24gm-thick high-resistive epitaxial layer can be fully depleted independent of the gate voltage. We also measured the Lorentz angle in the magnetic field, and found that there will be no serious problem when used in 3T magnetic field which is expected to be used in the actual experiment.Through this study, we demonstrated that the FPCCD vertex detector can, in principle, be used for the ILC experiment. As for the hardware R＆D, we have achieved the fully depletion of the sample CCD.