A Point Focusing Monochromator for the Study of Low-Angle X-Ray Diffraction: Determining the Size Distributions of Carbon Blacks and a Precision Determination of the Size of Dow Latex Particles
Abstract
A point focusing x-ray monochromator was designed and constructed for low angle scattering studies. The anastigmatic point focus is achieved by means of two cylindrically bent quartz crystals whose focal circles are mutually perpendicular. The beam, emanating from the copper target of an x-ray tube, is reflected in succession, first from the crystal defining the horizontal focal circle and, second from the crystal defining the vertical focal circle following which it comes to a mono chromatic point focus of wavelength 1.537 A (Cu Ko(1). The sample to be studied is placed between the second crystal and the point focus, and the scattered beam is detected by means of a photographic plate placed at the point focus, at right angles to the undeviated beam, the latter being suppressed by means of an absorber. Mathematical analysis, in which a ray was traced through the two crystal system, revealed correctly the shape and size of the point focus, and the possibility of reducing the latter in size by stopping down the beam emerging from the target. The instrument and its lining up procedure is described in detail, particularly the latter since the orientation of the two crystals relative to each other and the x-ray tube involve twelve degrees of freedom. Suggestions for improving the intensity of the instrument are made . These consist of (1) substitution of topaz crystals for quartz, (2) use of helium atmosphere instead of air to surround the x-ray beam (3) reorientation of the x-ray tube to permit smaller angles of emergence of the beam. As a trial run for the instrument, the scattering patterns of two kinds of carbon black (good scatterers) were obtained from which the average particle sizes and size distributions were calculated.
Additional Information
I wish to take this opportunity to thank Professor Jesse W.M. DuMond for suggesting this thesis project and for taking a keen interest in the course of its development. His helpful suggestions have been instrumental in the success of this work. In the three years that I have worked for him as a graduate student, I have profited considerably from his vast experience and have learned a good deal of the practical side of physics, the sort of thing one does not find in textbooks. For this, I wish to express my deepest gratitude. To Warren E. Danielson, who shares equally in the design and construction of the point focusing monochromator, I wish to extend my hearty thanks and the hope that he will find many interesting applications of the instrument. This project was supported jointly by the Office of Naval Research and the Atomic Energy Commission. Leon Shenfil The undersigned wishes to take this opportunity to express his gratitude to the Office of Naval Research for their generous permission to include financing of this development under Contract N6onr-244, T.O. IV. He also wishes to thank Prof. L. Pauling for his encouragement and supporting recommendation of the proposal to the O.N.R. when the primary idea was in a nascent stage. He is very deeply indebted to the two graduate students whose patience, skill and diligence have so successfully brought the initial ideas to concrete realization in spite of many d1fficulties and uncertainties. Respectfully submitted, Jesse W. M. DuMond Fundamental Research in Spectroscopy of Short Wave-Length X-Rays and Gamma Rays.Attached Files
Accepted Version - A_Point_Focusing_Monochromator_for_the_Study_of_Low-Angle_X-ray_Diffraction.pdf
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Additional details
- Alternative title
- Office of Naval Research Special Technical Report No. 15
- Eprint ID
- 46562
- Resolver ID
- CaltechAUTHORS:20140629-201517483
- N6onr-244
- Office of Naval Research (ONR)
- NR 017-602
- Office of Naval Research (ONR)
- Atomic Energy Commission
- Created
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2014-07-08Created from EPrint's datestamp field
- Updated
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2019-10-03Created from EPrint's last_modified field