The ORNL 10-meter small angle X-ray scattering camera

Abstract

A new small-angle X-ray scattering camera which utilizes a rotating-anode X-ray source, crystal monochromatization of the incident beam, pinhole collimation, and a two-dimensional position-sensitive proportional counter has been developed. Because the sizes of the X-ray focal spot, the sample and the resolution element of the detector are each approximately 1 x 1 mm, the camera was designed so that the focal spot-to-sample and sample-to-detector distances may each be varied in 0-5 m increments up to 5 m to provide a system resolution in the range 0.5 to 4.0 mrad. A large, general-purpose specimen chamber has been provided into which a wide variety of special-purpose specimen holders can be mounted. The detector has an active area of 200 x 200 mm and has up to 200 x 200 resolution elements. The data are recorded in the memory of a minicomputer by a high-speed interface which uses a microprocessor to map the position of an incident photon into an absolute minicomputer memory address. With this interface, over 105 events s-1 can be recorded. The data recorded in the computer memory can be processed on-line by a variety of programs designed to enhance the user's interaction with the experiment. Among these are routines for background and detector-sensitivity correction, contour and perspective plotting of the two-dimensional data, a variety of averaging schemes for determining circular averages and/or one-dimensional slices of the data, file-management programs to handle the large quantity of data produced by a two-dimensional detector, and an interactive package for communications with a central computing facility via a dedicated hardwired link. At the highest angular resolution (0.4 mrad) the flux incident on the specimen is 1.0 x 106 photons s-1 with the X-ray source operating at 45 kV and 100 mA. The performance of the instrument is demonstrated with several examples, among which are scattering patterns from voids in neutron-irradiated nickel, plastically deformed polyethylene and collagen fibrils. Results from a kinetic study of the crystallization of polyethylene are also reported.

Microporosity and micromineralogy of vitrinite in a bituminous coal

“…The transformation accurately takes into account intersections of circles with the finite detector resolution elements and partitions counts within the elements (Hendricks, 1978). A typical scattering curve is shown in Fig.…”

“…The SAXS measurements were made with the ORNL 10 m camera (Hendricks, 1978), which includes a 6 kW rotating anode X-ray generator (Cu target), a pyrolyticgraphite incident-beam monochromator, pinhole collimation, a two-dimensional position-sensitive proportional counter, and an on-line minicomputer for data acquisition and analysis. Owing to the rather high scattering intensity from coal, even when the X-ray tube was operated at relatively low power (45 kV, 30 mA), the measuring time was 1000 s or less per sample.…”

Position-Resolved Small-Angle X-ray Scattering of Complex Biological Materials

“…The method is based on a conventional X-ray pinhole camera (Hendricks, 1978) equipped with a two-dimensional position-sensitive detector (Siemens, Karlsruhe) and a rotating-anode X-ray generator. The set-up is shown schematically in Fig.…”

Phase separation in an Ni–12·5 at.% Al alloy at 575 K

“…The transformation anneals were carried out in a KNO3-NaNO3 salt bath, maintained at 575 K, then quenched to room temperature in water. Following mechanical polishing to about 0.1 mm, samples were prepared for SAXS measurements by electropolishing from both sides in an electrolyte consisting of a 1:1 volume mixture of orthophosphoric acid and water, using an applied potential Of 22-5 V. The SAXS measurements werecarried out at ORNL using the 10 meter X-ray scattering instrument (Hendricks, 1978). This instrument is of the pinhole type and utilizes a two-dimensional position-sensitive gas-filled proportional counter of the Kopp-Borkowski type (Borkowski & Kopp, 1978).…”