X-ray or gamma ray systems or devices – Specific application – Diffraction – reflection – or scattering analysis
Reexamination Certificate
1999-02-12
2001-05-22
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Diffraction, reflection, or scattering analysis
C378S082000
Reexamination Certificate
active
06236710
ABSTRACT:
BACKGROUND—FIELD OF THE INVENTION
This invention relates to devices having a doubly curved crystal for the diffraction of x-rays in spectrometers or instruments for microanalysis and also relates to a method of fabricating such crystal devices with high quality.
BACKGROUND—PRIOR ART
Doubly curved crystals are known to be useful as a means of focusing monochromatic x-rays or as a wavelength dispersive device in x-ray spectrometers. For example: (1) a toroidally curved crystal can provide point-to-point focussing of monochromatic x-rays, (2)crystals curved to spherical or ellipsoidal shape can be used as dispersive devices for parallel detection of x-rays, and (3) crystals with atomic planes spherically curved and the surface toroidally curved can provide high collection efficiency when used in scanning x-ray monochromators as described in U.S. Pat. No. 4,882,780.
Some of the prior art for doubly curved crystals and their mounting are described in U.S. Pat. Nos. 4,807,268, 4,780,899 and 4,949,367. U.S. Pat. No. 4,807,268 describes a “Wittry geometry” curved crystal formed by plastic deformation at elevated temperature. The crystals so made have low reflection efficiency and can not focus to a high degree of accuracy because of the increase of the crystal's rocking curve width due to the plastic deformation. Subsequent work has shown that in order to preserve a crystal's narrow rocking curve width, elastic, not plastic deformation must be used.
U.S. Pat. No. 4,807,268 describes a curved crystal for scanning monochromators formed by plastic deformation at elevated temperature and having unique spherically curved planes and toroidally curved surface (this has sometimes been called the “Wittry geometry” after it's inventor). These devices have a serious drawback, namely the smoothness of the crystal surface and crystal planes is strongly affected by irregularities in the bonding layer. The irregularities can result from the lack of uniform initial thickness of the adhesive layer on the substrate or it can occur during mounting of the crystal even if the initial adhesive layer is highly uniform. In addition, the use of a precision concave substrate is disadvantageous because a new substrate which must be made with great precision and expense is required for each new crystal device.
OBJECTIVES OF THE PRESENT INVENTION
The objectives of the invention are as follows: (1) to provide an x-ray crystal device which can be fabricated so that the crystal is doubly curved with a smoother surface and smoother crystal planes than is obtained by other methods of fabrication, 2) to provide an x-ray crystal device whose planes are more accurately curved to a predetermined theoretically-optimum shape, (3) to obtain smaller focal spot sizes when the crystal device is used for focusing x-rays than the spot sizes previously obtained, (4) to provide a method of fabrication that will allow the fabrication of many identical crystal diffracting devices by use of only one mold, and (5) to provide a crystal device that can be aligned for use with a minimum of adjustments, and (6) to provide a crystal device which, when used in x-ray instruments, can be readily removed and replaced with minimal requirement for realignment.
BRIEF DESCRIPTION OF THE INVENTION
This invention achieves some of the desired objectives by bonding the crystal to its substrate by a thick bonding agent that has high viscosity in it's initial state and hardens to a solid in its final state. The crystal is bent to its final state by bending it to conform to a convex mold that has the desired shape of the surface of the crystal using pressure that is applied to the crystal by the viscous bonding agent which receives pressure from a force applied to the backing plate during fabrication. Additional features of the invention include special configurations of the mold containing the surface used for bending, and special characteristics of the crystal and backing plate that make the crystal device more convenient to use and easier to align.
REFERENCES:
patent: 4599741 (1986-07-01), Wittry
patent: 4649557 (1987-03-01), Hornstra et al.
patent: 4780899 (1988-10-01), Adema et al.
patent: 4807268 (1989-02-01), Wittry
patent: 4882780 (1989-11-01), Wittry
patent: 4949367 (1990-08-01), Huizing et al.
U.S. application No. 09/149,690, Wittry, filed Sep. 8, 1998.
“Microprobe X-Ray Fluorescence With the Use of Point Focusing Diffractors” Z. W. Chen and D. B. Wittry, Appl. Phys. Lett. 71 (Sep. 29, 1997) pp. 1884-1886.
“Microanalysis by Monochromatic Microprobe X-Ray Fluorescence . . . ” Z. W. Chen and D. B. Wittry, J. Appl. Phys. 84 (Jul. 15, 1998) pp. 1064-1073.
Dunn Drew A.
Kim Robert H.
LandOfFree
Curved crystal x-ray optical device and method of fabrication does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Curved crystal x-ray optical device and method of fabrication, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Curved crystal x-ray optical device and method of fabrication will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2514292