Recently, the research team led by Xu Zhizhan and Li Ruxin, the State Key Laboratory of Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, made breakthrough progress in the study of ultra-high brightness gamma (g) radiation sources based on super short laser driving. Ultra-short laser-driven cascaded wakefield acceleration to obtain high-performance high-energy electron beam and laser collisions to produce ultra-high brightness quasi-monochromatic MeV level gamma ray source, the maximum peak brightness of 3 × 1022 photons s- 1 mm-2 mrad-2 0.1% BW, which is more than one order of magnitude higher than the luminance of the same type of gamma ray source reported in the world, which is 100,000 times higher than that of the traditional gamma ray source. Relevant findings are published in Scientific Report [Scientific Report 6, 29518 (2016)].
The inverse Compton scattering based on the relativistic electron beam and laser collisions is the most effective way to generate high energy gamma ray source. High-energy gamma ray sources have extremely important application value in many fields such as nuclear physics and nuclear photonics, particle physics, non-destructive testing, material science, medical diagnosis, nuclear energy and space technology. Many countries in the world, including China, are actively establishing However, the gamma ray source device based on the traditional accelerator is bulky and expensive, greatly limiting its development and application. Super short laser driven plasma wake wave field electron acceleration is a new electronic acceleration mechanism, the acceleration gradient compared to the traditional electron accelerator increased by more than three orders of magnitude, which can greatly reduce the system size and cost, to achieve Compton Gamma ray source device miniaturization. In addition, the relativistic electron beams generated by the super short laser accelerating have the properties of femtosecond pulse width and micron order size, which make the gamma ray pulse have the significant advantages such as ultrashort pulse and ultra-high brightness, which are difficult to obtain by traditional methods.
In recent years, the research team at Shanghai Institute of Optics and Electronics carried out a unique research on the electron acceleration of the laser tail wave field. For the first time in the world, a new scheme of quasi-single-energy high-energy electron acceleration with cascaded two-wavy fields was successfully achieved. Phys. Rev. Lett. 107, 035001 (2011); Appl. Phys. Lett. 103, 243501 (2013)]. In the development of this Compton g-ray source, by using the super-short laser device with high repetition frequency of 200TW developed by ourselves, the peak energy is obtained by optimizing the electron injection phase in the electron acceleration of cascaded wavefield. ~ 500 MeV range, capable of dissipating ~ 1%, power ~ 50pC, divergence angle <0.4 mrad, pulse width ~ 10fs high-performance quasi-single electron beam. And the use of plasma mirror reflection drive laser with the electron beam to achieve self-synchronization accurate collision, resulting in a peak energy tunable in the range of 0.2-2 MeV quasi-monochromatic gamma ray source. The highest peak brightness of 3 × 1022 photons s-1 mm-2 mrad-2 0.1% BW, than the traditional gamma ray source with the peak energy of the same region to improve 100,000 times the same time, the number of single-photon gamma photons reach 5 × 107 photons .
The reviewers commented highly on this result. "... This paper very fully characterizes a fully light driven quasi-monochrome Compton source with a record peak intensity in the soft gamma range. .. "and" ... The authors gave very complete physical images by taking a full range of measurements, considering possible background effects and detailed simulations ... ". This miniaturized ultra-high brightness quasi-monochromatic MeV graded gamma ray source will have a wide range of applications in nuclear physics and nuclear photonics, materials science, non-destructive testing and medical diagnosis.
Note: In the diagnostic measurement of gamma ray sources in this study, a close cooperation has been carried out with the Northwest Institute of Nuclear Technology (NPPN), a joint project of the State Key Laboratory of Laser Physics of Strong Field,
(Ac) Gamma ray beam spot distribution measured experimentally, beam spot distribution and background radiation after passing through different attenuation plates; (df) Corresponding (ac) gamma ray photon spatial distribution; (h) Radiation source and background The intensity distribution in the transverse and longitudinal directions; (i) the reconstructed energy spectrum of the gamma ray source.
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