An electron beam is obtained using laser wakefield electron accelerator, and converted into a γ-ray source after undergoing bremsstrahlung radiation in a dense material. A quasi-monoenergetic structure is observed when the length of the plasma channel was modified. The structure has a 58-MeV peak energy, 15- mrad （full-width at half-maximum） divergence angle, and 340-pC charge. The γ-ray source generated by this high-quality electron beam is brighter and has higher spatial and temporal resolutions than other conventional sources. A γ-ray radiography demonstrational experiment is performed. Pictures of a ball with different layers made of different materials are taken. The results show a clear structure and density resolution.
Large deuterium clusters are generated using a cryogenic pulse valve with a cone nozzle （21 mm long, 4° open angle）. Rayleigh scattering experiment is carried out to obtain the scaling relation between scattering signal SR and backing pressure P0. A method using the Coulomb explosion model is proposed to verify that the clusters continue to grow after their leaving the nozzle. Our experiments suggest a tentatively optimized position for laser cluster interaction.
High-order interpolation algorithms for charge conservation in Particle-inCell(PIC)simulations are presented.The methods are valid for the case that a particle trajectory is a zigzag line.The second-order and third-order algorithms which can be applied to any even-order and odd-order are discussed in this paper,respectively.Several test simulations are performed to demonstrate their validity in two-dimensional PIC code.Compared with the simulation results of one-order,high-order algorithms have advantages in computation precision and enlarging the grid scales which reduces the CPU time.
