Patent Number: 
Section: claims

1. A multilayer structure for reflecting x-rays comprising: at least one triad of layers including a first layer, a second layer, and a third layer;  wherein the first layer includes one of lanthanum (La), lanthanum oxide (La 2 O 3 ), or a lanthanum-based alloy, the second layer includes one of carbon (C), boron (B), silicon (Si), boron carbide (B 4 C) or silicon carbide (SiC), and the third layer includes one of boron (B) or boron carbide (B 4 C), and  wherein the second layer is disposed between the first layer and the third layer. 2. The multilayer structure of  claim 1  wherein the first layer includes one of lanthanum (La) or lanthanum oxide (La 2 O 3 ). claim 1 3. The multilayer structure of  claim 1  wherein the third layer consists of boron carbide (B 4 C). claim 1 4. The multilayer structure of  claim 1  wherein the second layer includes one of carbon (C), boron (B), or silicon (Si). claim 1 5. The multilayer structure of  claim 1  wherein the second layer includes one of boron carbide (B 4 C) or silicon carbide (SiC). claim 1 6. The multilayer structure of  claim 1  wherein the first layer consists of lanthanum (La), the second layer consists of silicon carbide (SiC), and the third layer consists of boron carbide (B 4 C). claim 1 7. The multilayer structure of  claim 1  wherein the first layer consists of lanthanum oxide (La 2 O 3 ), the second layer consists of silicon (Si), and the third layer consisting of boron carbide (B 4 C). claim 1 8. The multilayer structure of  claim 1  wherein the first layer consists of lanthanum oxide (La 2 O 3 ), the second layer consists of carbon (C) and the third layer consists of boron carbide (B 4 C). claim 1 9. The multilayer structure of  claim 1  characterized in that the structure consists of between 1 and 100 of the triads of layers. claim 1 10. The multilayer structure of  claim 1  characterized in that the structure consists of between 30 and 60 of the triads of layers. claim 1 11. The multilayer structure of  claim 1  characterized in that the structure is laterally graded. claim 1 12. The multilayer structure of  claim 1  characterized in that the structure is depth graded. claim 1 13. The multilayer structure of  claim 1  wherein a thickness of the first layer, a thickness of the second layer, and a thickness of the third layer are substantially identical. claim 1 14. The multilayer structure of  claim 1  wherein a thickness of the first layer, a thickness of the second layer, and a thickness of the third layer are variable. claim 1 15. The multilayer structure of  claim 1  characterized in that the structure is elliptically curved. claim 1 16. The multilayer structure of  claim 1  characterized in that the structure is parabolically curved. claim 1 17. The multilayer structure of  claim 1  characterized in that the structure is spherically curved. claim 1 18. The multilayer structure of  claim 1  wherein the at least one triad of layers is between 5 and 60 nanometers in thickness. claim 1 19. A method of x-ray fluorescence spectroscopy comprising: providing a field x-ray radiation;  irradiating a sample to be analyzed with the field of x-ray radiation, thereby inducing a field of fluorescence radiation;  directing the field of fluorescence radiation from a multilayer reflector including at least one triad of layers, the at least one triad of layers including a first layer, a second layer, and a third layer, the first layer including one of lanthanum (La), lanthanum oxide (La 2 O 3 ), or a lanthanum-based alloy, the second layer including one of carbon (C), boron (B), silicon (Si), boron carbide (B 4 C) or silicon carbide (SiC), and the third layer including one of boron (B) or boron carbide (B 4 C). 20. The method of  claim 19  further comprising the step of analyzing the field of fluorescence radiation after it has irradiated the sample. claim 19 21. An x-ray fluorescence spectroscopy system comprising: an x-ray source emitting an x-ray radiation field on a sample;  a multilayer structure having at least one period of individual layers, wherein the number of individual layers in the period is either three or four, a first layer including one of lanthanum (La), lanthanum oxide (La 2 O 3 ), or a lanthanum-based alloy, a second layer including one of carbon (C), boron (B), silicon (Si), boron carbide (B 4 C) or silicon carbide (SiC), and a third layer including one of boron (B) or boron carbide (B 4 C);  wherein the sample emits a fluorescent radiation field in response to the x-ray radiation field, and wherein further the multilayer structure selectively reflects the fluorescent radiation field. 22. A multilayer structure for reflecting x-rays comprising: at least one quartet of layers;  wherein a first layer includes one of lanthanum (La), lanthanum oxide (La 2 O 3 ), or a lanthanum-based alloy, a second layer includes one of boron (B) or boron carbide (B 4 C), a third layer includes one of carbon (C), boron (B), silicon (Si), boron carbide (B 4 C) or silicon carbide (SiC), and a fourth layer includes one of carbon (C), boron (B), silicon (Si), boron carbide (B 4 C) or silicon carbide (Sic); and  wherein the third layer is disposed between the first layer and the second layer, end wherein the second layer is disposed between the third layer and the fourth layer. 23. The multilayer structure of  claim 22 , characterized in that the structure consists of between 1 and 100 of the quartets of layers. claim 22 24. The multilayer structure of  claim 22  characterized in that the structure consists of between 80 and 60 of the quartets of layers. claim 22 25. The multilayer structure of  claim 22  characterized in that the structure is laterally graded. claim 22 26. The multilayer structure of  claim 22  characterized in that the structure is depth graded. claim 22 27. The multilayer structure of  claim 22  wherein a thickness of the first layer, a thickness of the second layer, a thickness of the third layer, and a thickness of the fourth layer are substantially identical. claim 22 28. The multilayer structure of  claim 22 , wherein a thickness of the first layer, a thickness of the second layer, a thickness of the third layer, and a thickness of the fourth layer are variable. claim 22 29. The multilayer structure of  claim 22  characterized in that the structure is elliptically curved. claim 22 30. The multilayer structure of  claim 22  characterized in that the structure is parabolically curved. claim 22 31. The multilayer structure of  claim 22  characterized in that the structure is spherically curved. claim 22 32. The multilayer structure of  claim 22  wherein the at least one quartet of layers is between 5 and 60 nanometers in thickness. claim 22