New Branches of Science
The hundred or so years since the discovery of X-rays in 1895 has seen the emergence of a diverse range of imaging and analytical X-ray technologies, exploiting every known property of these new rays.
Early advances
One of the remarkable features of the history of X-ray science was the speed with which a huge variety of applications was envisaged and investigated. The discovery of the X-ray created a sensation in the scientific world. Before the end of 1896, the first diagnostic radiographs had been made, with immediate applications in military radiography. Experiments had been conducted with moving samples, and even the first angiogram was attempted, with post-mortem injection of compounds of mercury. X-rays were also applied experimentally to a range of intractable disease conditions, including tuberculosis, lupus and cancer. It was not until the death of Clarence Dally, (an assistant to Thomas Edison who had turned his inventive skills to the lucrative market of X-ray tubes) in 1904, that due attention was given to the fact that X-rays could kill as well as cure, and the questions of operator shielding and patient dose rates were given proper consideration.
One of the first industrial applications was made during the first World War (1914-1918) for the nondestructive testing of airframe parts in a biplane.
In 1927, the Müller company (which had been granted patent rights for the manufacture of X-ray tubes as early as 1899) was bought by Philips, the Dutch manufacturing company. Philips had been involved in the X-ray business since 1916, when the first rotating-anode X-ray tube was made. By 1930 the industrial side of the X-ray business was separated from medical imaging applications.
Quantitative X-ray analysis
Early attempts were made to utilize the analytical and quantitative potential of X-rays. In 1913, Moseley demonstrated the relationship between atomic number and the reciprocal of wavelength for target elements, and saw at once that this provided a method of elemental analysis based on characterization of the spectra of each element.
In 1915, William H Bragg and his son W Lawrence Bragg jointly received the Nobel Prize in Physics for work on crystal structure based on the wavelength-dependence of X-ray diffraction in a crystal lattice. These insights also provided a means of resolving X-ray emission by wavelength dispersion, and the Braggs went on to build an analytical device.
Similar investigations were carried out by Max von Laue in 1914 and by P. Debye and P. Scherer in 1915, resulting in techniques for the analysis of structures of crystals, organic materials and biological specimens. Crystallography remains an important X-ray application, supporting investigation into more modern phenomena such as superconductivity. Interestingly, the equations for X-ray diffraction were also derived independently of Bragg in 1913, by Mr. Torahiko Terada at the Tokyo Imperial University, indicating how early the widespread development of X-ray technology proceeded.
At least seven Nobel Prizes in Physics or Chemistry were awarded before the second World War for work related to X-rays, and several more in the years since.
Hadding investigated X-ray fluorescence (XRF) as an analytical technique for mineral samples as early as 1922, but it was 1948 before Friedman and Birks built the first commercial XRF spectrometer. Early limitations imposed by air paths were subsequently overcome with the addition of dry gas paths and vacuum systems.
The more recent invention of semiconductor radiation detectors has permitted elemental analysis and advanced imaging techniques utilizing energy-dispersion (since wavelength and energy distributions are closely related by Planck’s equation) using appropriate electronic signal collection and processing.
This is an extract for the XuM Principles and Appllications manual, please email us if you would like a copy of the full document.
