Research and Development of the Non-invasive Beam Diagnostics on High Quality Electron Beam Using Optical Diffraction Radiation

在KEK-加速器试验装置（KEK- atf）上进行了一项研究狭缝靶的光学衍射辐射（ODR）作为非侵入性电子束尺寸诊断工具的研究。实验装置已安装在萃取线的诊断段。我们在狭缝目标上进行了首次非相干ODR观测。测得的角分布与理论预期基本一致。观察到光束尺寸对ODR角图的影响。此外，还实现了对光束尺寸小至14μm的灵敏度。目标与光束轨迹成45度角安装。目标是一块7.9毫米尺寸的硅晶片，上面覆盖着金，以获得更好的反射率。该板具有0.26x5mm2的矩形孔。由于目标没有被完全切割，它的两半自然是共面。由于目标是倾斜的，因此有效狭缝尺寸a =0.26 sin(45) = 185μm。目标是…更大的宽度是0.3毫米。我们的主要想法是电子束一定不能碰到目标。为了这个目的，狭缝的边缘有一个倾斜的形状。它使我们能够减小狭缝尺寸并增加ODR光子产率。我们的最终目标是测量单射光束的尺寸。为此，我们正在考虑一种基于图像增强CCD摄像机的新型探测器系统。观测到来自上游弯曲磁体的巨大同步辐射背景。对于波束诊断，抑制背景是非常必要的，因为它严重地扭曲了ODR角图。为此，我们在目标前面安装了SR掩模，并切断了SR光子的优势部分。我们已经实现了对光束尺寸小至14μm的灵敏度。然而，我们假设存在系统误差，这可能是由SR光子的左侧部分，实验霍尔x射线背景引起的。为了能够测量小于10μm的光束尺寸，我们必须了解并减小系统误差。显然，PMT的测量不是单次的。但是，毫无疑问，这是实现最终目标的合理的第一步。少

An experiment on investigation of optical diffraction radiation (ODR) from a slit target as a possible tool for non-invasive electron beam size diagnostics has been performed at KEK - Accelerator Test Facility (KEK-ATF). The experimental setup has been installed at the diagnostics section of the extraction line. We have performed the first incoherent ODR observation from a slit target. The measured angular distributions are in reasonable agreement with the theoretical expectation. The beam size effect onto the ODR angular pattern has been observed. Moreover, the sensitivity to the beam size as small as 14μm has been achieved. The target is mounted at 45 deg. to the beam trajectory. The target is a silicon wafer with 7.9mm dimensions covered with gold for better reflectivity. The plate has rectangular hole of 0.26x5mm2. As the target is not completely cut, two halves of it are naturally coplanar. Since the target is tilted, the effective slit size a =0.26 sin(45) = 185μm. The target thi … More ckness is 0.3mm. Our main idea is that the electron beam must not touch the target at all. For that purpose the slit edges have an oblique shape. It allowed us to reduce the slit size and increase the ODR photon yield.The our final goal is the single shot beam size measurements. To this purpose we are considering a new detector system based on an image intensified CCD camera. A huge synchrotron radiation (SR) background from the upstream bending magnet was observed. For beam diagnostics it was extremely necessary to reject the background, because it significantly distorted the ODR angular pattern. For that purpose we installed SR mask in front of the target and cut off the dominant part of the SR photons.We have achieved the sensitivity to the beam size as small as 14μm. However, we suppose that a systematic error exists, which might be caused by the left part of SR photons, experimental hall X-ray background. To be able to measure the beam size smaller than 10μm, we shall have to understand and reduce the systematic error. Obviously the measurements with the PMT are not single shot ones. But, undoubtedly that is the reasonable first step of the ultimate goal. Less