The zigzag grating is one of the newly proposed optical dispersive elements which has an excellent diffraction characteristics and has important applications in the spectrum measurement and analysis. The simulation results of the diffraction pattern of the zigzag grating for X ray are presented using a new numerical method based on the convolution theorem, and comparison of its diffraction pattern with those of the traditional grating and sinusoidal grating are studied. It is seen from the results that all higher order diffractions of the zigzag grating are suppressed below the level of four orders of magnitude compared with the first order diffraction, which is superior to the traditional grating, being consistent with the theoretical expectations. Moreover, the impact caused by the absorber is analyzed, which eventually confirms that the zigzag grating has perfect practical application feasibility. The conclusions provide a potential alternative for the physical design of the zigzag gating, which is expected to replace the traditional transmission grating in applications to the soft X-ray spectrum measurement.

No abstract

No abstract

To accelerate the electrons efficiently in the laser wake-field accelerator, it is necessary to suppress the instability induced by the diffraction and the defocusing of the laser pulse. The gas-filled capillary discharge waveguide can generate an approximately parabolic density distribution, which can guide the laser pulse efficiently and suppress the instability. Using the Stark effect, this plasma density distribution is measured in this paper, and the relationship between plasma density and filled pressure is presented. By using the MHD code CRMHA, the formation of the capillary waveguide is simulated and researched in detail.

No abstract