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

在KEK加速器实验装置(KEK-ATF)上进行了一项研究狭缝靶的光学衍射辐射(ODR)的实验，作为一种可能的非侵入性电子束尺寸诊断工具。实验装置已安装在提取管路的诊断部分。我们首次从狭缝目标上进行了非相干ODR观测。测得的角分布与理论预期符合得很好。观察到了束流尺寸对ODR角方向图的影响。此外，还实现了对光束尺寸的灵敏度，最小为14μm。目标安装在45度。到光束的轨迹。目标是一块尺寸为7.9 mm的硅晶片，上面覆盖着黄金，以获得更好的反射率。该板有0.26x5mm2的矩形孔。由于靶子没有被完全切割，所以它的两半自然是共面的。由于目标是倾斜的，所以有效狭缝尺寸a=0.26Sin(45)=185μm。目标Thi…最大切割度为0.3 mm。我们的主要想法是，电子束必须完全不接触靶子。为此，缝隙边缘具有倾斜的形状。它使我们能够减小狭缝尺寸，增加ODR光子产额。我们的最终目标是测量单发光束的大小。为此，我们正在考虑一种新的基于图像增强型CCD相机的探测器系统。观测到来自上游弯曲磁体的巨大同步辐射(SR)背景。对于束流诊断来说，排除背景是极其必要的，因为它严重扭曲了ODR角模式。为此，我们在靶前安装了SR掩模，并切断了SR光子的主要部分，实现了对14μm光束尺寸的灵敏度。但我们假设存在系统误差，这可能是由SR光子的左侧部分引起的，即实验厅X射线背景。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，用光电倍增管进行的测量不是单次测量。但是，毫无疑问，这是实现最终目标的合理的第一步。较少

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