While generating a high-energy electron beam with a size of micrometers (one-tenth of the diameter of the hair filament), another laser beam must be precisely focused to the same size as the electron beam, and within the micrometer space and femtosecond time scale, the electron beam and The laser beam collides precisely. Since both electrons and photons move at the speed of light, how to achieve such precise collisions in experiments has always been a challenge in this field. Although there are dozens of super-powerful laser pointer in the world at the watt level, it is the first time that such sophisticated experiments have been carried out under such super-high intensity. Through numerical simulation on the supercomputer π of the Shanghai Jiaotong University High-Performance Computing Center, the researchers have reproduced the experimental results very well in computer simulations.
Multi-photon Thomson scattering has very high application value. The first author of the paper, a former Ph.D. graduate of the Institute of Physics, Institute of Physics, Chinese Academy of Sciences, and now a postdoctoral fellow at the University of Nebraska, Dr. Yan Wenchao, the experimental leader of the project, said: “Our technology can be used The high-brightness X-gamma ray light source has a brightness comparable to that of the third-generation synchrotron light source, but the volume of the device is only tens or even one percent. It is expected to supplement the synchrotron light source in the future for medical imaging and materials research 3. Research on biological macromolecules, three-dimensional metrology provides cheaper light sources, and solves the problems of low number of existing synchrotron light sources, difficult scheduling, and high cost.
At the same time, high-energy gamma rays can penetrate extremely thick steel plates, which is expected to greatly help customs inspection of drug and weapon smuggling. Since our device can be made very small, it may be integrated into small container trucks in the future, further increasing the flexibility of using radiation sources. “The vehicle-mounted multi-photon Thomson scattering gamma-ray light source is expected to be used in customs inspections and other environments. Using gamma rays generated by the interaction of super-strong lasers and electrons, scientists have successfully photographed the internal structure of the Wi-Fi receiver. It is not possible to penetrate the metal for such clear and high-resolution imaging.
The entire physical process of multi-photon Thomson scattering also has extremely high basic scientific research value. In this physical process, multiple photons participate in an interaction event, which exhibits a completely different calibration law than the previous single-photon Thomson scattering. The corresponding author of this paper, the director of the extreme light laboratory, professor said: “Under the condition of super-strong collision laser, electrons will undergo extremely nonlinear motion, and the photon density is very high, so a single electron will interact with hundreds of photons. Effect, these photons are coherently coupled together at the same time to form an ultra-high-energy photon. In fact, theory shows that up to 1300 photons may have been scattered simultaneously in our experiments.
The multi-photon Thomson scattering theory has been around for decades, but it has never been thoroughly verified by experiments. This is the first time that Thomson scattering with the participation of so many photons has been realized in the laboratory, and the theory has been completely verified. Development is of great significance. “In addition, the peak intensity of the ultra-strong laser at the focus is estimated after various parameter measurements under low-energy laser pulse conditions, and there is currently no direct measurement method. The gamma rays generated by the interaction process in this experiment It has a unique spatial distribution, and the distribution is directly related to the intensity of the collision laser. Therefore, the peak intensity of the super-strong laser can be accurately calibrated according to the nature of the gamma rays generated during the experiment. This is also the only direct measurement of super-strong red laser pointer peak intensity method.
Changes in laser intensity cause changes in the trajectory of electrons, and changes in the spatial distribution of radiated gamma rays. When the laser is at its strongest, more than 500 photons are simultaneously scattered by a single electron. The researchers said that in the future, the laser will be further upgraded, the multi-photon scattering theory will be further studied, and the preliminary quantum electrodynamics research will be carried out. In addition, the quality of the gamma-ray light source will be optimized, hoping to realize its wide application value as soon as possible.