Search Results - (Author, Cooperation:K. D. Finkelstein)

2018-02-24

Wiley-Blackwell

Chemistry and Pharmacology

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2013-10-25

Nature Publishing Group (NPG)

0028-0836

1476-4687

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Physics

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

A system of diffracting perfect crystals for the generation of variable, elliptically polarized x rays was tested at the Cornell High Energy Synchrotron Source under the conditions of a standard undulator source. The phase retarding optical component was a 4-bounce, Ge(220) Bragg reflection channel-cut crystal. The full polarization state of the output beam, including the circular polarization purity P3, was determined using the multiple-beam Bragg diffraction technique. In addition to measuring the optics' efficiency, the ability to scan the system in energy, while frequently reversing the circular helicity, was demonstrated at the vicinity of the Fe K edge at 7.1 keV. The setup was applied to a circular magnetic x-ray dichroism measurement. © 1995 American Institute of Physics.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

We show that the Stokes–Poincaré polarization parameters for an x-ray beam can be completely determined using the method of multiple-beam Bragg diffraction. We first summarize the principles of this technique, and then show results from an experiment in which we applied the method to characterize an x-ray phase plate. © 1995 American Institute of Physics.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

We present a simple method for complete determination of the x-ray polarization state, using just one Bragg reflection from a single-crystal analyzer. For the linear polarization components P1 and P2, we show that the usual method of using a 90° Bragg reflection can be extended to using any Bragg reflection with 2θ≠90°. For circular component P3, we use the intensity modulation profile in an azimuthal rotation caused by the phase-sensitive interference around a multiple-beam Bragg reflection. The combination of the two measurements allows a straightforward complete determination of x-ray polarization, including an unpolarized component, in a broad applicable energy range.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

A 25-pole permanent magnet hybrid wiggler has been built at CHESS and installed on the CESR (Cornell Electron Storage Ring). This device has a magnetic period of 19.6 cm, a peak on-axis field of 1.2 T at the nominal operating gap of 4.0 cm, and a K parameter of 22. The wiggler has been designed to provide radiation for two new experimental stations with approximately four times the flux available from the present CHESS six-pole electromagnet wiggler. Under normal running conditions at 100 mA currents, the total power radiated should exceed 6 kW making this one of the highest flux x-ray sources below 1 A(ring) critical wavelength. In this paper an overview of the development of the wiggler is given, including the unique features in its design and construction as well as results of measurements obtained on its magnetic and spectral properties.

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

When hard x-ray focusing optics require segmented bending, the focal spot can be minimized by matching segment size to the synchrotron source size and focal ratio. At modern sources this implies features etched or cut into silicon on the 100 μm scale. We describe our experience using photolithography and high aspect ratio reactive ion etching (RIE) to produce sagittal focusing crystals. The work was carried out at the Cornell Nanofabrication Facility. RIE has been of great utility for the manufacture of microelectromechanical systems (MEMS) which contain features typically a few microns in size. We have learned that because of the very large dielectric constant of silicon, a number of important considerations must go into a successful design when features are scaled up for x-ray optics applications. Nevertheless, we have designed, built and tested x-ray optical devices produced using MEMS techniques, and in fact they are in regular use at CHESS. We describe our results from the point of view of mechanical robustness and focus quality, and offer general guidelines for future designers. © 2002 American Institute of Physics.

Electronic Resource