High-pass x-ray filter device and methods of making thereof
A high-pass x-ray filter device is disclosed that includes a substrate defining an elongated opening. A reflecting membrane is positioned across the opening and supported, along all sides, by the substrate. The reflecting membrane is configured to transmit, from an incident x-ray beam, x-ray photons having an energy above about a threshold energy level and reflects, from the incident x-ray beam, x-ray photons having an energy below about the threshold energy level. The elongated opening of the substrate defines an exit path for the transmitted x-ray beam. A high-pass x-ray filter system including the high-pass filter device and a method of fabrication of the high-pass filter device are also disclosed.
1. A high-pass x-ray filter comprising:
a substrate defining an elongated opening; and
a reflecting membrane positioned across the opening and supported, along all sides, by the substrate, the reflecting membrane configured to transmit, from an incident x-ray beam, x-ray photons having an energy above about a threshold energy level and to reflect, from the incident x-ray beam, x-ray photons having an energy below about the threshold energy level, wherein the elongated opening of the substrate defines an exit path for the transmitted x-ray beam.
2. The high-pass x-ray filter of claim 1 , wherein the substrate comprises a silicon wafer.
3. The high-pass x-ray filter of claim 2 , wherein the reflecting membrane comprises a film formed on at least a second side of the silicon wafer.
4. The high-pass x-ray filter of claim 3 , wherein the thin reflecting membrane comprises Si 3 N 4 .
5. The high-pass x-ray filter of claim 4 , wherein the elongated opening in the substrate comprises an etched window in the substrate from a first side of the substrate to a Si 3 N 4 layer formed on the second side of the substrate.
6. The high-pass x-ray filter of claim 3 , wherein the thin reflecting membrane comprises polymethyl methacrylate (PMMA), SU-8, Parylene C or a poly(p-xylylene) polymer.
7. The high-pass x-ray filter of claim 6 , wherein the elongated opening in the substrate comprises an etched window in the substrate from a first side of the substrate to the thin reflecting membrane formed on the second side of the substrate.
8. The high-pass x-ray filter of claim 1 , wherein a thickness of the thin reflecting membrane is between about 10 nm to about 600 nm.
9. The high-pass x-ray filter of claim 8 , wherein a thickness of the thin reflecting membrane is between about 200 nm to about 400 nm.
10. The high-pass x-ray filter of claim 1 , wherein the elongated opening is between about 0.5 mm to about 10 mm in width.
11. The high-pass x-ray filter of claim 1 , wherein the elongated opening is between about 70 mm to about 300 mm in length.
12. The high-pass x-ray filter of claim 1 , wherein the elongated opening is between about 1.0-2.0 mm in width and is between about 250-300 mm in length.
13. The high-pass x-ray filter of claim 1 , wherein the thin reflecting membrane comprises a composite structure.
14. The high-pass x-ray filter of claim 13 , wherein the thin reflecting membrane comprises a thin film of a metal coating.
15. The high-pass x-ray filter of claim 14 , wherein the thin film of a metal coating is about 10 nm thick.
16. The high-pass x-ray filter of claim 1 , wherein the substrate defines a plurality of elongated openings, each of the plurality of elongated openings including a thin reflecting membrane positioned across the respective opening and supported, along all sides, by the substrate, each of the thin reflecting membranes to transmit, from an incident x-ray beam, x-ray photons having an energy above about a threshold energy level and to reflect, from the incident x-ray beam, x-ray photons having an energy below about the threshold energy level, wherein each of the plurality of elongated openings defines an exit path for the transmitted x-ray beam.
17. The high-pass x-ray filter of claim 16 , wherein each of the thin reflecting membranes is different than other ones of the thin reflecting membranes.
18. A high-pass x-ray filter system, comprising:
a synchrotron source configured to generate an x-ray beam; and
an x-ray filter including a substrate defining an elongated opening and including a thin reflecting membrane positioned across the opening so as to be supported along all sides by the substrate, the reflecting membrane configured to transmit, from an incident x-ray beam of the synchrotron source, xray photons having an energy above about a threshold energy level and to reflect, from the incident xray beam, x-ray photons having an energy below about the threshold energy level, the elongated opening of the substrate defining an exit path for the transmitted x-ray beam.
19. The high-pass x-ray filter system of claim 18 , wherein the synchrotron source includes insertion device magnets.
20. The high-pass x-ray filter system of claim 19 , wherein the insertion device magnets comprise an undulator.
21. The high-pass x-ray filter system of claim 20 , wherein the x-ray beam generated by the undulator comprises a narrow-band fundamental harmonic and a series of higher energy harmonics.
22. The high-pass x-ray filter system of claim 18 , wherein the incident x-ray beam comprises a broadband x-ray spectrum.
23. The high-pass x-ray filter system of claim 18 , wherein the thin reflecting membrane is configured to reflect x-ray photons with energies below a critical angle of incidence from the incident x-ray beam.
24. The high-pass x-ray filter system of claim 18 , wherein the incident x-ray beam is at a grazing angle relative to the thin reflecting membrane, the grazing angle being between about 0° to about 0.5°.