X-ray powder diffraction camera
Date: circa 1955
Inventory Number: 2004-1-0319
Classification: X-Ray Diffraction Camera
Subject:
User: Mineralogical Museum, Harvard University (founded circa 1775)
Maker: American
Cultural Region:
City of Use:
Dimensions:
21 × 23 × 10 cm (8 1/4 × 9 1/16 × 3 15/16 in.)
Material:
Description:
Upright circular chamber fixed on a solid base that can be mounted on a slider. The back of the base is protected by a plexiglass shield. The cylindrical part has two diametrically opposed orifices, with a pinhole collimator screwed in one of them. The top of the cylinder has a detachable round lid. In the center of the cylinder there is an improvised specimen holder where the sample is to be mounted, consisting of a heavy triangular metal piece (perhaps lead), to which a small test tube is glued. The role played by test tube is uncertain. The top part of the camera's perimeter holds two pairs metal plates (black and brass colored) that were probably used to fix the X-ray film.
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.
This back-reflection X-ray powder camera consists of a light-tight semicylindrical enclosure which holds a strip of X-ray film accurately fixed on its perimeter. The specimen, usually a fine powder, is accurately placed on the diameter side of the semicircle. A fine beam of X-rays, produced by passing the beam through a metal collimator, is scattered on the sample. The pattern of lines on the photograph produced by the back-reflection represents possible values of the Bragg angles that satisfy Bragg's law .
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.
This back-reflection X-ray powder camera consists of a light-tight semicylindrical enclosure which holds a strip of X-ray film accurately fixed on its perimeter. The specimen, usually a fine powder, is accurately placed on the diameter side of the semicircle. A fine beam of X-rays, produced by passing the beam through a metal collimator, is scattered on the sample. The pattern of lines on the photograph produced by the back-reflection represents possible values of the Bragg angles that satisfy Bragg's law .
Curatorial RemarksThe location of the test tube behind the triangular metal piece might be to shield it from direct exposure to x-rays, especially if the triangular piece is made of lead.
ProvenanceCarl Francis, Mineralogical Museum, Harvard University