计算机断层扫描在“双成像法”测量束流二维相空间中的应用

Beam 2-D Phase-Space Measurement with CT and Cerenkov Radiation "Double Imaging Method

文中分析了利用计算机断层扫描 (CT)测量束流二维相空间的物理原理 ,并从数学上证明了现有方法 (CT +四极铁磁场扫描 )存在Radon变换角度空档 ,需要假设某一束流模型进行插值 ,图像重建的精度不高甚至失真 ;而结合Cerenkov辐射“双成像法” ,可以同时得到束流横向剖面和散角分布的Radon投影 ,从而将Radon变换角的范围扩展到完整的 0—π .文中以一个不对称的束流二维相空间分布为例 ,给出了计算机模拟实验结果 。

This paper proposes a new method to measure the 2 D beam transverse phase space with computerized tomography (CT) technique and Cerenkov radiation 'double imaging method'. The usual method with CT technique entirely depends on the quadrupole scanning and can not get a full π Radon rotation angle, which is essential to the Radon transform, the mathematic fundamental of CT technique. Therefore, it has to prior assume a certain kind of phase space distribution to extrapolate the vacancy of Radon rotation angle, which makes the reconstructed image imperfect and yields errors especially when the phase space distributions practically are not ideal. In this paper, by means of Cerenkov radiation double image method and mathematical analysis, we obtain a full rotation angle of the beam phase space precisely from 0 to π. Hence we can measure the actual 2 D transverse phase space density without making any prior assumptions about phase space distributions. The simulation results show that this new method is feasible and with much higher precision.