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The ORNL 10‐meter small angle X‐ray scattering camera
Author(s) -
Hendricks R. W.
Publication year - 1978
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889878012613
Subject(s) - optics , detector , minicomputer , sample (material) , collimated light , physics , image resolution , position (finance) , computer science , laser , finance , economics , thermodynamics , operating system
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 × 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 × 200 mm and has up to 200 × 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 10 5 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 × 10 6 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.