Patent Number: 
Section: description

As shown in FIG. 1, an x-ray fluoroscopy analyzing system 10 includes a radiation generator or source, such as x-ray tube 12, that generates a beam of radiation along a first direction, such as a beam of x-rays 14. The x-rays 14 have a wavelength that ranges from 0.3-1.0 nm. The x-rays 14 generated from x-ray tube 12 are received by and interact with the object or sample 16 so that x-ray fluorescence radiation 18 is generated from the object 16. The x-rays 18 are directed through a slit 19 and received by a multilayer grating/mirror 20, which reflects only a zeroth order of diffraction of x-rays 22 of a particular wavelength, such as 0.71 nm. The x-rays 22 are then received by a detector system 24, such as a proportional counter detector. The detected radiation is then analyzed in a well known manner. As shown in FIG. 2, the multilayer grating/mirror 20 includes a multilayer structure 26 deposited on a substrate 28. The multilayer structure 26 is made out of alternating layers of materials with large and small atomic numbers. The material with large atomic number can be selected from the materials W, Ni, Fe, Mo, V, Cr and the material with small atomic numbers can be selected from the materials C, Si, B4C. For example, the multilayer structure 26 can be made out of alternating layers of W (10 xc3x85) and C (10 xc3x85) layers. Thus, the period, d, of the alternating W and C layers is 20 xc3x85. In this embodiment, the number of periods, d, of alternating W/C bi-layers in the multilayer structure 26 is 500. Note that the number of bi-layer depends on a spectral resolution/bandpass requirements. For 500 bi-layers, the bandpassxcex/xcex94xcexxcx9cN xcx9c500. The period of the multilayer depends on a required Bragg angle and typically ranges from 15 A to 100 A for different wavelengths. In addition, other materials and thicknesses for the layers of materials with large and small atomic numbers are possible depending on the specific needs for wavelength and Bragg angle. As shown in FIG. 2, a plurality of grooves 30 are formed randomly on the multilayer grating/mirror 20. The grooves 30 are positioned between lands 32 of the multilayer structure 26, wherein each land 32 has a width of approximately 1 micron and contains 500 periods of alternating W/Si bilayers. The starting points or positions xi of the lands 30 can be determined by a formula given below: xi=(d*i)+[ki*(dxe2x88x92Wland)], xe2x80x83xe2x80x83(2) where d=effective period of the grating/mirror 20, i=1, 2, 3, . . . ,; Wland=width of land and ki=a random number from 0 to 1. Note that the widths of the lands and depths of the grooves are constant for the entire area of the grating. Furthermore, the lands are placed randomly inside each period according to the formula (2) above. One of the benefits of using a multilayer grating/mirror 20 with a random pattern of grooves is that all diffraction orders, except the zeroth order, are suppressed. In other words, only the direct beam is reflected by the grating/mirror 20. The suppression of diffraction orders is shown by analogy to the single layer random structure transmission grating diffraction intensity distribution shown in FIG. 4. Obviously, if a single layer transmission grating with a random structure suppresses multiple diffraction orders, then a multi-layer transmission grating with a random structure will also suppress multiple diffraction orders. In the above-described mode of randomizing the grating/mirror 20, the land widths and the grooves depths are selected so that a desired width of the peak of the rocking curve of the grating/mirror 20, which is the same as an energy bandpass or spectral resolution of the grating/mirror 20, is achieved. Thus, the ability to change the bandpass allows the spectral resolution to be adjusted to specific requirements and so as to optimize flux and resolution. While the above description constitutes the preferred embodiments of the present invention, it will be appreciated that the invention is susceptible of modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims. For example, the grating 20 can also be used as a monochromator.