Claims
- 1. A method for producing a monochromatic beam, the method comprising:
- generating a plurality of beams from a polyenergetic source;
- transmitting the beams through a bent crystal having non-cylindrical shape;
- positioning the bent crystal with respect to the polyenergetic source to emit a plurality of divergent monochromatic beams from the bent crystal wherein the bent crystal is differentially bent in a logarithmic spiral shape;
- wherein the logarithmic spiral shape is achieved by mounting and differentially bending the crystal in a four-bar bender;
- wherein the two outer bars of the four-bar bender each is moved a same distance with respect to a corresponding one of two inner bars of the four-bar bender to bend the crystal into a cylindrical shape and then the outer bars are differentially displaced with respect to each other;
- wherein the outer bars are differentially displaced with respect to each other by displacing one of the outer bars by a differential .DELTA.z to at least partially unbend the bent crystal and further displacing another of the outer bars by the differential distance .DELTA.z to further bend the bent crystal.
- 2. A method according to claim 1 wherein the beams generated have a wavelength in a X-ray bandwidth.
- 3. A method according to claim 1 wherein the beams are first transmitted through a concave surface of the bent crystal and then through a convex surface of the bent crystal.
- 4. A method according to claim 1 wherein the different distance .DELTA.z bending is governed by: ##EQU1## where 2L.sub.c is a first distance between the two inner bars and L.sub.s is a second distance between one of the outer bars and a corresponding one of the inner bars.
- 5. A method according to claim 1 wherein the bent crystal is rocked in a plane of diffraction until the divergent monochromatic beams are emitted from the bent crystal.
- 6. A method according to claim 1 wherein a plurality of white beams are transmitted through the bent crystal and the divergent monochromatic beams are separated from the white beams by a fixed angle of diffraction.
- 7. A method according to claim 1 wherein the divergent monochromatic beams have a two-dimensional solid angle of at least about 5 degrees by at least about 5 degrees.
- 8. A method according to claim 1 wherein the divergent monochromatic beams are two-dimensional.
- 9. A method according to claim 1 wherein an energy bandwidth (.DELTA.E/E) of the divergent monochromatic beams is about 2%.
- 10. A method according to claim 1 wherein the divergent monochromatic beams are tuned to above and below a K-edge of a radiographic contrast element.
- 11. A method according to claim 10 wherein the tuned divergent monochromatic beams are used for dual energy digital subtraction radiography.
- 12. A method according to claim 1 wherein the divergent monochromatic beams are tuned to above a K-edge of a radiographic contrast element.
- 13. A method according to claim 12 wherein the tuned divergent monochromatic beams are used to enhance an image contrast.
- 14. A method according to claim 1 wherein the bent crystal is a bent Laue crystal.
- 15. A method according to claim 1 wherein the divergent monochromatic beams are transmitted through the bent crystal with asymmetric transmission geometry.
- 16. A method according to claim 1 wherein the polyenergetic source is an X-ray rotating anode source.
Government Interests
This work was supported in part by U.S. Army Grant DAMD17-96-1-6143; U.S. Department of Energy Contract DE-AC02-76CH00016; and U.S. Department of Defense Advanced Research Projects Agency, ARPA Contract AOB227.
US Referenced Citations (18)
Non-Patent Literature Citations (2)
Entry |
Monochromatic energy-subtration radiography using a rotating anode source and a bent Laue monochromator, a paper pulbished in Phys. Med. Biol., 42 (1997), pp. 1751-1762. |
A bent Laue crystal monochromator for monochromatic radiography with an area beam, a paper published in Nuclear Instruments and Methods in Physics Research, Section A, 399 (1997), pp. 489-498. |