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

点击翻译按钮获取中文摘要

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.