Currently indexing
X-ray powder camera in test chamber
Date: circa 1950
Inventory Number: 2004-1-0334
Classification: X-Ray Diffraction Camera
Subject:
User: Mineralogical Museum, Harvard University (founded circa 1775)
Maker: Clifford Frondel (1907 - 2002)
Maker: Dunbar Laboratory, Harvard University (founded c. 1931)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
23 × 34 × 20 cm (9 1/16 × 13 3/8 × 7 7/8 in.)
Description:
X-ray powder camera in wood-lined, aluminum test chamber with a thermal coil and external motor. Inside the box there is an X-ray powder camera made out of an upright circular chamber fixed on a solid base mounted on a slider. The cylindrical part has two diametrically opposed orifices in which collimators can be screwed in to refine the X-ray beam. Inside the camera, there is an X-ray rectangular collimator with a length of roughly two-thirds of the cylinder diameter. The second orifice, where the sample is supposed to be mounted, can be connected to the external motor to rotate the sample.
Signedunsigned
FunctionAn X-ray diffraction camera can be used to determine the atomic arrangement of crystals. The wavelength of an X-ray is similar in size to the distance between atoms in crystalline substances. Thus, by recording how a material scatters X-rays, and causes variation in their intensity, one may determine its crystal structure - the pattern by which its atoms are arranged as well as the precise distance between them.
The X-ray camera is placed in an insulating boxed, while a heating or cooling liquid can be circulated through the coil pipes to change the temperature of the sample. Variable temperature X-ray crystallography aims to determine the thermal expansion properties of crystals.
This particular X-ray powder camera is a variation of the standard Debye-Scherrer model (see 1997-1-1721), developed by Prof. Clifford Frondel at Harvard, and described in an article (See Primary Sources).
It consists of a light-tight cylindrical enclosure which holds a strip of X-ray film accurately fixed on its perimeter. The specimen, usually a fine powder, is accurately placed not on the axis of the cylinder (as in the standard powder cameras) but on its periphery, diametrically opposed to the X-ray collimator. A fine beam of X-rays, produced by passing the beam through a metal collimator, is scattered on the sample. The sample is successively photographed on the peripheral positions at opposite ends of a diameter, the film remaining unmoved during the operation. This gives two back-reflection photographs that are symmetrically opposed on the same strip of film. The measurements can be repeated using the second collimator. The pattern of lines on the photograph represents possible values of the Bragg angles that satisfy Bragg's law .
The X-ray camera is placed in an insulating boxed, while a heating or cooling liquid can be circulated through the coil pipes to change the temperature of the sample. Variable temperature X-ray crystallography aims to determine the thermal expansion properties of crystals.
This particular X-ray powder camera is a variation of the standard Debye-Scherrer model (see 1997-1-1721), developed by Prof. Clifford Frondel at Harvard, and described in an article (See Primary Sources).
It consists of a light-tight cylindrical enclosure which holds a strip of X-ray film accurately fixed on its perimeter. The specimen, usually a fine powder, is accurately placed not on the axis of the cylinder (as in the standard powder cameras) but on its periphery, diametrically opposed to the X-ray collimator. A fine beam of X-rays, produced by passing the beam through a metal collimator, is scattered on the sample. The sample is successively photographed on the peripheral positions at opposite ends of a diameter, the film remaining unmoved during the operation. This gives two back-reflection photographs that are symmetrically opposed on the same strip of film. The measurements can be repeated using the second collimator. The pattern of lines on the photograph represents possible values of the Bragg angles that satisfy Bragg's law .
Historical AttributesThis is likely to be one of the cameras described in the article by Clifford Frondel in American Mineralogist. See Primary Sources.
Curatorial RemarksThe X-ray powder camera inside the box is the same design as 1997-1-1722.
Primary SourcesClifford Frondel, "Precision X-Ray Powder Camera" ( American Mineralogist , 40, 1955)
ProvenanceCarl Francis, Mineralogical Museum, Harvard University