Precision Spectroscopy of X and Gamma Radiation Using the Focusing Crystal Principle. A Determination of the Luminosity in the Wavelength Range 10 to 500 X.U. and a Preliminary Measurement of Gamma Radiation from Au¹⁹⁸

Citation

Lind, David Arthur (1948) Precision Spectroscopy of X and Gamma Radiation Using the Focusing Crystal Principle. A Determination of the Luminosity in the Wavelength Range 10 to 500 X.U. and a Preliminary Measurement of Gamma Radiation from Au¹⁹⁸. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/yfjh-gj31. https://resolver.caltech.edu/CaltechTHESIS:05302025-213209046

Abstract

The principles of the curved crystal transmission type spectrometer are discussed with an analysis of the constructional tolerances which are necessary for spectroscopy of x-rays and gamma radiation to 1.7 Mev. energy. A description of the spectrometer which was completed and put into operation is given. The spectrometer has a two-meter focal distance with a dispersion of one mm. per X. U. at the sine screw and has a constant resolution equal to 0.1 X. U. The (310) planes of a quartz plate one mm. thick are used in the transmission arrangement. The wave-length range is from 7 X. U. to 500 X. U. with a precision of 0.01 X. U. The theoretical results of the diffraction theory in ideal and real crystals are summarized. Using these results the absolute intensity in the diffracted beam (luminosity function) is calculated as a function of wave-length under certain simplifying assumptions. An experimental determination of the luminosity function between 500 X. U. and 11 X. U. was made; the integrated reflection coefficient was found to be a function of λ² between these limits. These data indicate that a quartz crystal under an inhomogeneous stress behaves as would a mosaic crystal. A comparison of the reflection coefficients with theoretical values shows good agreement. At 0.4 Mev. only 0.3% of the incident quanta are diffracted by the crystal. Sources of 50 mc. or greater are needed since at present only one quantum in 10⁸ will register in a spectral line. A precision determination of one gamma-ray line in the radio-gold Au¹⁹⁸ spectrum was made with the result

E = 0.4112 ± 0.0002 Mev.

This represents the first precision determination of any gamma radiation energy. Finally, design requirements and limitations of the focusing crystal method are discussed to indicate the range of usefulness and the results which may be obtained with such an instrument.

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