We are propose a technique for measuring of a focal spot size directly during the shot of a radiographic facility based on a linear induction accelerator. The key feature of the proposed method is the penumbral imaging in the direction backward to the electron beam propagation. Diagnostic has been installed in a backward hemisphere of the target chamber of a linear induction accelerator. It consists of two parallel edge-knife (roll-bars with 500 mm radius of curvature), a thin BGO scintillator, and a CCD camera with a 7 microseconds shutter. The performance and operability of the diagnostic was demonstrated on the linear induction accelerator with energy of electrons of 4 MeV. The first experimental results of the beam spot measurements are presented. A radiation transport modeling of the diagnostic scheme was performed using Monte-Carlo code PRIZMA. The effect of the scattered bremsstrahlung on the penumbral image in the backward direction was analyzed.

中文翻译：

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通过光束向后传播的X射线测量目标上LIA光斑尺寸的技术

我们提出了一种基于线性感应加速器的，在放射线照相设备拍摄期间直接测量焦斑大小的技术。所提出方法的关键特征是半影成像在电子束传播的反方向。诊断程序已安装在线性感应加速器目标室的后半球中。它由两个平行的边缘刀（曲率半径为500 mm的滚动杆），一个薄的BGO闪烁体和一个具有7微秒快门的CCD照相机组成。在线性感应加速器上以4 MeV的电子能量证明了该诊断仪的性能和可操作性。给出了束斑测量的第一个实验结果。使用蒙特卡洛代码PRIZMA对诊断方案进行了辐射传输建模。分析了散射的direction致对后向半影图像的影响。