precession-type x-ray diffraction camera (Mark II, first version)
Date: 1941-1944
Inventory Number: 1996-1-0185
Classification: X-Ray Diffraction Camera
Subject:
Maker: Martin J. Buerger (1903 - 1986)
Maker: Charles Supper Company ? (1941-present)
Maker: (motor) Bodine Electric Company (1905-present)
Cultural Region:
Place of Origin:
Dimensions:
32 x 35 x 33 cm (12 5/8 x 13 3/4 x 13 in.)
Material:
Accessories: film holder (a); metal screen (b); small rectangular metal counterweight (c)
DescriptionThe instrument consists of several parts aligned on a metal beam which itself can be rotated horizontally on an arch of a triangular base with levelling screws.
At one end of a beam on a platform is an electric motor, which transfers rotational motion to an axle parallel to the beam base. This axle connects to an arc-shaped arm with angle graduations. The next two components both are coupled at the same point with the arc-shaped arm, and this point can be moved to change the angle at which this happens. The first component is the photographic film holder, which couples to the arc-shaped arm via a metal bar followed by an arrangement in the shape of a parallelogram, The second component is the sample holder, which connects to the arc-shaped arm via a curved, hacksaw-shaped metal arm which goes around the photographic film holder. The sample holder is fixed in place by a separate arm attached to the base, but in a way that allows the transmission of movement from the arc-shaped arm, which is rotated by the motor. The orientation of the sample can be adjusted very precisely with several dials, but in this particular instrument, the last section of the sample holder, the goniometer head, is not present. It would normally extend to stand between the photographic plate and the x-ray source. The final component of the instrument is the x-ray collimator, which is a tapering metal piece held by a fixed vertical beam attached to the base.
Accessories present include a metal screen and a rectangular metal counterweight.
The entire instrument rests on an enameled metal base.
At one end of a beam on a platform is an electric motor, which transfers rotational motion to an axle parallel to the beam base. This axle connects to an arc-shaped arm with angle graduations. The next two components both are coupled at the same point with the arc-shaped arm, and this point can be moved to change the angle at which this happens. The first component is the photographic film holder, which couples to the arc-shaped arm via a metal bar followed by an arrangement in the shape of a parallelogram, The second component is the sample holder, which connects to the arc-shaped arm via a curved, hacksaw-shaped metal arm which goes around the photographic film holder. The sample holder is fixed in place by a separate arm attached to the base, but in a way that allows the transmission of movement from the arc-shaped arm, which is rotated by the motor. The orientation of the sample can be adjusted very precisely with several dials, but in this particular instrument, the last section of the sample holder, the goniometer head, is not present. It would normally extend to stand between the photographic plate and the x-ray source. The final component of the instrument is the x-ray collimator, which is a tapering metal piece held by a fixed vertical beam attached to the base.
Accessories present include a metal screen and a rectangular metal counterweight.
The entire instrument rests on an enameled metal base.
Signedunsigned
Inscribedon paper, taped to base: ADD 1.5 to reading
FunctionX-ray diffraction cameras are used to determine the atomic arrangement of crystals. They were first used to determine the structure of simple substances and minerals, and later were central for the determination of the structure of biomolecules such as proteins and DNA.
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 particular type of diffraction camera is called a precession camera, and was developed by Martin J. Buerger at MIT. In this type of camera, the crystal's orientation is made to precess around the direction of the x-ray beam, requiring a clever movement of both the crystal holder and the photographic film.
The precession method simplified the process required to determine the arrangement of a crystal based on their x-ray diffraction photographs. According to Clifford Frondel (see obituary in Related Works), it "permitted the undistorted photography of the reciprocal lattice".
Martin J. Buerger called this particular design the "Mark II, First Version". Its main feature is a three-dimensional parallelogram which is used to keep the crystal sample and film parallel as they precess about the direction of the x-ray beam. This feature ended up being difficult to manufacture commercially, and he designed a simpler, commercial type called the "Mark II, Second Version" (1998-1-1673). The First Version also allowed adjusting the distance between the sample and the photographic film, a feature that was dropped as unnecessary for the Second Version.
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 particular type of diffraction camera is called a precession camera, and was developed by Martin J. Buerger at MIT. In this type of camera, the crystal's orientation is made to precess around the direction of the x-ray beam, requiring a clever movement of both the crystal holder and the photographic film.
The precession method simplified the process required to determine the arrangement of a crystal based on their x-ray diffraction photographs. According to Clifford Frondel (see obituary in Related Works), it "permitted the undistorted photography of the reciprocal lattice".
Martin J. Buerger called this particular design the "Mark II, First Version". Its main feature is a three-dimensional parallelogram which is used to keep the crystal sample and film parallel as they precess about the direction of the x-ray beam. This feature ended up being difficult to manufacture commercially, and he designed a simpler, commercial type called the "Mark II, Second Version" (1998-1-1673). The First Version also allowed adjusting the distance between the sample and the photographic film, a feature that was dropped as unnecessary for the Second Version.
Historical AttributesThis is a prototype of the precession-type x-ray crystallography camera devised by Professor Martin Buerger at MIT. It was the second one ever made -- the first went to W. L. Bragg.
This second instrument was given by Martin Buerger to his colleague and friend, Professor Clifford Frondel at Harvard.
This second instrument was given by Martin Buerger to his colleague and friend, Professor Clifford Frondel at Harvard.
Primary SourcesMartin J. Buerger, The Precession Method in X-ray Crystallography (New York, Wiley and Sons, 1964). This camera is explained in detail in Chapter 4, "The Mark II precession instrument", pp. 30-34. The chapter features multiple detailed photographs and diagrams of the instrument.
ProvenanceFrom the Department of Earth and Planetary Sciences, Harvard University.
Given by Professor Clifford Frondel.
Given by Professor Clifford Frondel.
