Precision Study of Son-Linear QED by Observing an Energy-Angular 2D-Distribution

我们成功地观测到了通过非线性QED过程产生的X射线的角分布。在我们的实验之前，美国SLAC的E144实验是唯一观测到在线QED效应的实验（布拉等人，Phys.Rev.Lett.76，3116（1996））。实验中测量了反冲电子的能量，证实了反冲电子的能量与非线性QED理论的预言是一致的，但是仅仅测量反冲电子的能量并不足以建立非线性QED理论。非线性QED过程的理论计算表明，非线性QED过程产生的X射线角分布与线性QED过程产生的X射线角分布有很大不同。我们的实验首次观察到了非线性QED过程产生的X射线的特征角分布。实验在BNL（USA）的线性加速器上进行。60 MeV电子束与高功率CO_2激光器的激光束发生碰撞。我们测量了碰撞产生的X射线。非线性过程产生能量高于线性过程的运动学极限的X射线。我们用薄银片阻挡低能X射线，然后只观察高能X射线。使用CCD检测器来观察通过银板的这些高能X射线的空间分布。X射线呈哑铃形分布，这是非线性QED预言的特征。这些结果发表在Physical Review Letters、Laser Physics和International Journal of Modern Physics上。我们还开发了一种设备，可以进行更高精度的测量。该装置由曲面多层反射镜和X射线像增强器组成。用这个仪器我们可以同时测量角度和能量分布。该装置的研制是成功的，我们向核仪器和物理方法研究提交了研制报告。

We successfully observed the angular distribution of X-rays generated through non-linear QED processes.Before our experiment, the E144 experiment at SLAC (USA) was only experiment which observed an effect of on-liner QED (Bula et al., Phys.Rev.Lett.76,3116 (1996)). In this experiment, the energy of recoil electrons were measured and confirmed that it was consistent with prediction of non-linear QED.However energy measurement alone is not sufficient to establish non-linear QED. The theoretical calculation of non-linear QED predict that the angular distribution of X-rays generated by non-linear QED process significantly is different from that of linear QED process. Our experiment firstly observed a characteristic angular distribution of X-rays generated by non-linear QED process. The experiment was performed at a linear accelerator at BNL (USA). A 60 MeV electron beam made collision with a laser beam from a high power CO2 laser. We measured the X-rays created in this collision. A non-linear process creates X-ray which energy is higher than the kinematical limit of the linear process. We used thin silver plate to stop low energy X-rays then observed only high energy X-rays. A CCD detector was used to observed spatial distribution of these high energy X-rays which passed the silver plate. The X-ray shows dumbbell-shaped distribution which is characteristic in prediction of non-linear QED. Those results were published in Physical Review Letters, Laser Physics, and International Journal of Modern Physics.We also developed an apparatus which allows us to perform much high precision measurement. The apparatus consists of a curved multilayer reflector and a X-ray image intensifier. Using this apparatus we can measure both angle and energy distribution at once. The development of the apparatus was successful and we submitted the report of the development to the Nuclear Instruments and Methods in Physics Research.