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Silicon nitride transmission X-ray mirrors.

Cornaby S, Bilderback DH - J Synchrotron Radiat (2008)

Bottom Line: Transmission X-ray mirrors have been fabricated from 300-400 nm-thick low-stress silicon nitride windows of size 0.6 mm x 85 mm.The energy cut-off can be adjusted from 8 to 12 keV at an angle of 0.26 degrees to 0.18 degrees , respectively.The observed mirror transmittance was above 80% for a 300 nm-thick film.

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Affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.

ABSTRACT
Transmission X-ray mirrors have been fabricated from 300-400 nm-thick low-stress silicon nitride windows of size 0.6 mm x 85 mm. The windows act as a high-pass energy filter at grazing incidence in an X-ray beam for the beam transmitted through the window. The energy cut-off can be selected by adjusting the incidence angle of the transmission mirror, because the energy cut-off is a function of the angle of the window with respect to the beam. With the transmission mirror at the target angle of 0.22 degrees , a 0.3 mm x 0.3 mm X-ray beam was allowed to pass through the mirror with a cut-off energy of 10 keV at the Cornell High Energy Synchrotron Source. The energy cut-off can be adjusted from 8 to 12 keV at an angle of 0.26 degrees to 0.18 degrees , respectively. The observed mirror transmittance was above 80% for a 300 nm-thick film.

No MeSH data available.


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(a) Transmission of a 300 nm-thick silicon nitride film at angles ranging from 0.18° to 0.26°. (b) Transmission of a second 300 nm-thick silicon nitride film at angles 0.22° and 0.24°. The small peaks between 8 and 9 keV in the transmission curves are a result of both copper and zinc fluorescent contamination in the signal that we were unable to eliminate, which most likely originated as trace elements within the Kapton tape.
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fig3: (a) Transmission of a 300 nm-thick silicon nitride film at angles ranging from 0.18° to 0.26°. (b) Transmission of a second 300 nm-thick silicon nitride film at angles 0.22° and 0.24°. The small peaks between 8 and 9 keV in the transmission curves are a result of both copper and zinc fluorescent contamination in the signal that we were unable to eliminate, which most likely originated as trace elements within the Kapton tape.

Mentions: The silicon nitride TMs were tested in the B1 station white beam at CHESS with the full energy spread from a bending magnet with 10 keV critical energy. The only other elements in the beamline were two beryllium windows between an air/vacuum and vacuum/vacuum environment, a few Kapton windows on helium-filled flight tubes, and the TM chamber. The beam was slitted down to 0.2 mm × 0.2 mm and was then put through the TM. The X-ray beam travelled 2.25 m in a helium flight path, then through a 1 mm-diameter lead clean-up aperture, and finally through a 0.5 mm-thick film of Kapton tape. An XFlash diode detector was used to measure the Compton scattering from the Kapton tape in order to observe the energy spectrum of the beam. The effects of transmission of windows, flight paths, detector efficiency etc. were normalized by taking a scan with the TM in the beam, then dividing it by a scan taken without the TM in the beam. Fig. 3 ▶ shows the observed transmission curves, along with the predicted transmission from two different mirrors. Fig. 3(a) ▶ shows the transmission curves for a 300 nm-thick silicon nitride membrane at angles from 0.18° to 0.26° in steps of 0.02°, along with the predicted curves, which assume a 5 nm r.m.s. roughness. The actual curves track well with the predicted curves. Angles below 0.18° were not reasonable because the beam started to be clipped by the glued-on silicon wafer support. We did not go above 0.26° because the cut-off edge started to be obscured by impurity X-ray fluorescent signals from the scattering Kapton tape. Fig. 3(b) ▶ shows a curve from a second window at 0.22° and 0.24°, which is also well matched to the predicted transmission curves.


Silicon nitride transmission X-ray mirrors.

Cornaby S, Bilderback DH - J Synchrotron Radiat (2008)

(a) Transmission of a 300 nm-thick silicon nitride film at angles ranging from 0.18° to 0.26°. (b) Transmission of a second 300 nm-thick silicon nitride film at angles 0.22° and 0.24°. The small peaks between 8 and 9 keV in the transmission curves are a result of both copper and zinc fluorescent contamination in the signal that we were unable to eliminate, which most likely originated as trace elements within the Kapton tape.
© Copyright Policy
Related In: Results  -  Collection

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fig3: (a) Transmission of a 300 nm-thick silicon nitride film at angles ranging from 0.18° to 0.26°. (b) Transmission of a second 300 nm-thick silicon nitride film at angles 0.22° and 0.24°. The small peaks between 8 and 9 keV in the transmission curves are a result of both copper and zinc fluorescent contamination in the signal that we were unable to eliminate, which most likely originated as trace elements within the Kapton tape.
Mentions: The silicon nitride TMs were tested in the B1 station white beam at CHESS with the full energy spread from a bending magnet with 10 keV critical energy. The only other elements in the beamline were two beryllium windows between an air/vacuum and vacuum/vacuum environment, a few Kapton windows on helium-filled flight tubes, and the TM chamber. The beam was slitted down to 0.2 mm × 0.2 mm and was then put through the TM. The X-ray beam travelled 2.25 m in a helium flight path, then through a 1 mm-diameter lead clean-up aperture, and finally through a 0.5 mm-thick film of Kapton tape. An XFlash diode detector was used to measure the Compton scattering from the Kapton tape in order to observe the energy spectrum of the beam. The effects of transmission of windows, flight paths, detector efficiency etc. were normalized by taking a scan with the TM in the beam, then dividing it by a scan taken without the TM in the beam. Fig. 3 ▶ shows the observed transmission curves, along with the predicted transmission from two different mirrors. Fig. 3(a) ▶ shows the transmission curves for a 300 nm-thick silicon nitride membrane at angles from 0.18° to 0.26° in steps of 0.02°, along with the predicted curves, which assume a 5 nm r.m.s. roughness. The actual curves track well with the predicted curves. Angles below 0.18° were not reasonable because the beam started to be clipped by the glued-on silicon wafer support. We did not go above 0.26° because the cut-off edge started to be obscured by impurity X-ray fluorescent signals from the scattering Kapton tape. Fig. 3(b) ▶ shows a curve from a second window at 0.22° and 0.24°, which is also well matched to the predicted transmission curves.

Bottom Line: Transmission X-ray mirrors have been fabricated from 300-400 nm-thick low-stress silicon nitride windows of size 0.6 mm x 85 mm.The energy cut-off can be adjusted from 8 to 12 keV at an angle of 0.26 degrees to 0.18 degrees , respectively.The observed mirror transmittance was above 80% for a 300 nm-thick film.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.

ABSTRACT
Transmission X-ray mirrors have been fabricated from 300-400 nm-thick low-stress silicon nitride windows of size 0.6 mm x 85 mm. The windows act as a high-pass energy filter at grazing incidence in an X-ray beam for the beam transmitted through the window. The energy cut-off can be selected by adjusting the incidence angle of the transmission mirror, because the energy cut-off is a function of the angle of the window with respect to the beam. With the transmission mirror at the target angle of 0.22 degrees , a 0.3 mm x 0.3 mm X-ray beam was allowed to pass through the mirror with a cut-off energy of 10 keV at the Cornell High Energy Synchrotron Source. The energy cut-off can be adjusted from 8 to 12 keV at an angle of 0.26 degrees to 0.18 degrees , respectively. The observed mirror transmittance was above 80% for a 300 nm-thick film.

No MeSH data available.


Related in: MedlinePlus