The article deals with the experimental study of the relationship of parameters of combined discharge low temperature plasma with the parameters of its formation process: input SHF power and displacement potential. The purpose of the study is to increase the efficiency of the plasma impact on the surface of parts or products according to the criterion of the formation in the surface layer of composite structures enhancing their operational reliability.
The study results revealed that, firstly, the level of input SHF power is responsible for the intensity of ionization processes at the outer boundary of the plasma; the potential supplied to the product is responsible for generating a compensated flow at the inner boundary of the plasma, and secondly, the processes occurring in the plasma must be controlled. This will ensure consistency of the desired speed and, consequently, the degree of surface heating within a set time, and, on this basis, the increase in the reproducibility of the composite structure synthesis in the surface layer of parts or products, including structures with desired properties.
Basic features of combined-discharge low-temperature plasma formation around the surfaces of complex-contoured metal units are considered. It is shown that it makes the possibilities for synthesis of hardened high-durable coatings of hard tools appropriate for material processing in extreme load-temperature conditions. Experimental study of the coating formation was carried out in combination with the analysis of emission spectra of a low-temperature plasma cloud. Some practical examples of the coating applications are presented.
Rigaku Innovative Technologies (RIT) produces x-ray optics based on multilayer mirrors. A multilayer mirror is deposited on a wafer and mounted on a solid backing plate in an elliptical shape to focus x-rays. The wafer surface imperfections, defects from the multilayer deposition, and figure errors induced by the mounting process result in some focal spot widening for the final optics. An AFM is used in the spatial period range 0.1 - 10 microns, and a "ZYGO"
interferometric microscope is used in the spatial period range 1 micron - 5 mm, to study these imperfections determining the influence of each technological step on the focal spot quality. AFM analysis shows dramatically different roughness between 1 x 1 micron and 20 x 20 micron field of view on super-polished substrates from some suppliers and only a little difference from others. A smoothing effect of a multilayer coating at spatial periods less than one micron as well as defects in multilayer coatings have been observed with power spectral density analysis. Machining marks on the surface
of wafers are clearly seen at ZYGO microscope pictures. Ray-tracing simulations based on the ZYGO data show the focal spot shape changes due to the figure errors introduced at the step of a multilayer coated wafer mounting and only background scattering with no focal spot widening from defects induced at the step of multilayer deposition.
A double multilayer monochromator with each multilayer composed of four stripes with different d-spacing providing spectral resolution of 0.3% to 0.8% in the energy range of 6keV to 19keV has been developed. Test multilayer structures with d-spacing from 2.3nm to 10.6nm have been deposited by magnetron sputtering. X-ray characterization has been performed at OSMIC by using a recently upgraded diffractometer setup and Cu-Kα radiation and at the APS. The following material combinations were studied before the final choice of materials for the high energy resolution monochromator has been made: Al2O3/B4C, SiC/Si, SiC/B4C and SiC/C. To minimize the effect of internal stress built in multilayer structure on X-ray characteristics flat and thick 1" diameter silicon substrates supplied by Wave Precision Inc. were used for all calibration coatings. Final coatings were deposited on two 145mm long, 60mm wide and 30mm thick silicon substrates. Resolution of SiC/Si structures with d1=2.3nm, N1=1000 and d2=3nm, N2=700 was measured at Cu-Kα with X-ray beam divergence of 14 arcsec to be 0.216% and 0.34% respectively. For plane waves the resolution is expected to be 0.13% and 0.19%, respectively.
We introduce a method for the determination of the thickness variation through the stack of multilayer structures deposited by magnetron sputter deposition. The deposited structure is determined by minimizing a merit function based on the difference between actual x-ray reflectivity data and the theoretical calculation of the reflectivity from a multilayer structure. This method uses only four parameters and is independent of the total number of layers deposited. Further, this simple method provides a good initial guess if one wishes to increase the number of independent parameters in order to investigate finer detail of the structure. We illustrate the usefulness of this method through comparison of a desired and deposited Ni/C multilayer. The thickness distribution through the stack was designed in such a way as to maximize integrated reflectivity over some angular range. Finally, we determine the dependence of layer thickness with annealing temperature for the depth graded Ni/C multilayer by use of our method.
Two approaches have been explored to cover existing gap in energy resolution between traditional multilayers (1 to 2%) and perfect crystals (0.01%). The first approach is based on low contrast (Al2O3/B4C) multilayers where we measured the width of the reflectivity curve as low as 17 arc sec, a spectral resolution of 0.27% and a reflectivity of 40% from a 26 Å d-spacing multilayer with 800 bi-layers. The second approach is based on using structures with small d-spacing using traditional W/B4C and Mo/B4C materials. A W/B4C multilayer with 14.8Å d-spacing showed a resolution of 0.5% and a reflectivity of 58.5%. Two Mo/B4C samples with d-spacings of 15Å and 20Å showed energy resolutions of 0.25% and 0.52% with corresponding reflectivities of 39% and 66% correspondingly.
The experimental fabrication of a Fabry-Perot interferometer for the x-ray region is reported. Based on state of the art thin film deposition technology at Osmic Inc., challenging requirements for making the interferometer for x-rays have been met.
We report here the development of a hard x-ray multilayer grating that has achieved an absolute efficiency of 34% at a wavelength of 1.54A. The W-C multilayer itself has a reflectivity of 57% and
the grating has a 0th order absolute efficiency of 36%. The origin of this extraordinarily high efficiency is that the short period and highly asymmetric structure of the grating combined with its deep grooves allows light to interact with a large number of layer pairs. This increases angular separation of the diffraction orders and reduces the multilayer bandwidth to the point where there is little or no order to order overlap in the grating structure, and hence maximum intensity can be diffracted into a selected order. This paper reports on the development of an optimized multilayer grating and some of its unique characteristics.
A beamline for high resolution spectroscopy with elliptically polarized X-rays is described. The working energy range is large, from 20 eV to above 1800 eV. The resolving power is on the order of 10,000 at low energies (20 eV - 200 eV) and 6000 at high energies (200 eV - 1800 eV). This is achieved using a variable deviation angle plane grating monochromator. A single grating, with one line density and a varying groove depth, is used to cover the entire energy range. The beamline has been designed to operate with either one or two x-ray beams propagating simultaneously through the monochromator and to the experimental station. Switching between polarizations at rates of 0.1 Hz and slower is accomplished in the single beam mode by alternating the output of the elliptically polarized undulator source between left and right polarization. Fast polarization switching, at rates of 100 - 1000 Hz, is provided in the two beam mode by mechanical chopping between two photon beams, one of which is right circularly polarized, and the other left circularly polarized.
A beamline for circularly polarized radiation produced by an elliptical wiggler has been designed at the ALS. It covers a broad energy range from 50 eV to 2000 eV. The rigorous theory of grating diffraction efficiency has been used to maximize throughput. This is a challenging optical problem due to the nature of the elliptical wiggler insertion device. The wiggler has a large source size in the vertical and horizontal directions, and the monochromator requires high resolution (small slits), a wide tuning range, and cooling for high heat loads. These problems have been solved by using a variable included angle monochromator with high demagnification onto the entrance slit, aberration correction of the grating for the large vertical aperture, and cooled optics.
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