.13.9 Nm, Grating Beam Splitter And Related Issues

The plasma is widely used in economy, industry and society. Soft X-ray Mach-Zehnder interferometer is an invaluable tool to probe the electron density gradient and electron density of larger variety plasma. Hereby, it is very important to the plasma diagnosis, X-ray Laser and so on. Experiments were conducted using either a wavefront-division interferometer based on Lloyd's mirror, or an amplitude division interferometer. While simplicity is an advantage of the Lloyd's mirror interferometer, the amplitude division interferometer has the advantage of producing interferograms of significantly higher quality, which display high fringe visibility over the entire field of view.In this thesis, the author focuses on the Diagnosis of the Plasmas. And The soft x-ray diffraction grating Mach-Zehnder interferometer is the emphases. This work is supported by National Science Foundation of China, 863 Project. The piece resistance of the author work are:1, Laminar grating as the splitter grating in the Soft X-ray laser Mach-Zehnder interferometerThe diffraction grating interferometer (DGI) is based on a skewed Mach-Zehnder configuration. The diffraction gratings are designed to split the incoming soft x-ray laser beam evenly into two orders. Elongated grazing incidence mirrors are used to direct the beams towards the second grating, where they are recombined to produce the interference pattern. The diffracted zero and first order beams from a diffraction grating form the two arms of the interferometer. The grating is positioned at a small glancing incidence angle (<10°) with respect to the soft X-ray laser beam to generate zero and first diffracted order beams of approximately equal intensities. The zero and first diffracted order beams' diffraction efficiency product is similarly important, because it can make the DGI get a high throughput. So the diffraction grating used as a splitter grating is very important to the diagnosis result of the plasma. At the wavelength 13.9nm which our DGI uses, there must be a new pattern grating used as the splitter grating.Comparing with the one based on thin film beam splitters, the DGI based on the laminar grating splitters has the advantages of a high throughput and a high robustness. Comparing with interferometers based on the blaze grating splitters, its throughput is approximately equal (>6percent per arm) and the laminar grating is easy to be fabricated.The laminar grating as beam splitter of interferometer was designed for 13.9nm. Then the grating was fabricated by using the holographic ion beam etching method and measured by synchrotron radiation at the National Synchrotron Radiation Laboratory (NSRL) of China. The calculated and measured results of the grating efficiency and their efficiency product were compared.2, The pre-aligned of the system and the fabrication of the pre-aligned-gratingThe diffraction grating interferometer (DGI) is based on a skewed Mach-Zehnder configuration shown in Fig. 1. The diffraction gratings are designed to split the incoming soft x-ray laser beam evenly into two orders. Elongated grazing incidence mirrors are used to direct the beams towards the second grating, where they are recombined to produce the interference pattern. The diffracted zero and first order beams from a diffraction grating form the two arms of the interferometer. The grating is positioned at a small glancing incidence angle (<10°) with respect to the soft X-ray laser beam to generate zero and first diffracted order beams of approximately equal intensities. The diffraction grating interferometer must be pre-aligned by a visible light like a He-Ne laser, because soft X-ray laser(SXRL) is a sightless light. To ensure that the SXRL and the He-Ne laser beams follow the same path, the diffraction gratings were ruled with two vertically separated regions(pre-aligned grating region & SXRL grating region) with different line densities. The ratio of the line densities(50 multiples upwards) in these two regions corresponds to the ratio of the wavelengths between the SXRL and the He-Ne laser. At present, Grating Tilling Technology and Exposure Tilling Technology had been used in the fabrication process of the diffraction grating. Using this kind of diffraction grating, the DGI will obtain high pre-aligned precision, but the fabrication process of the diffraction gratings is complicated and difficult, in addition there are some other problems.Herein a soft x-ray laser interferometer using a double-frequency grating(DFG) as the pre-alinged grating. The wavelength of the SXRL in our DGI is 13.9nm, and the wavelength of the He-Ne laser is 632.8nm. Using DFGs, the fabrication process of the diffraction gratings will be predigested and the problems begot by Grating Tilling Technology and Exposure Tilling Technology will be avoid.