The design and construction of an experimental MgO cold cathode X-ray tube for use in XRF spectrometry.
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Date
2000
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Abstract
An introduction to the fundamental concepts of X-ray physics and X-ray tube design is given.
This discussion also includes a brief description of various X-ray tube types available
commercially for a number of different industrial applications.
The design of a high-energy MgO cold cathode X-ray tube, which is to be used in an X-ray
fluorescence (XRF) spectrometer, is described in detail with emphasis placed on the electron
beam focusing mechanism and the theory of operation as well as the construction of the X-ray
tube MgO cold cathode, which functioned as the electron emitter of the device. A detailed
account is also given of the output characteristics of the X-ray tube power supply, which has a
direct effect on the design requirements and consequently the performance of the X-ray tube.
An investigation into the manufacture of the vacuum envelope with particular attention focused
on the production of reliable metal-to-ceramic seals was performed. A number of tests were
conducted especially with regard to the maximum temperature that such seals may withstand
without becoming permanently damaged. These tests were essential, since high temperature
gradients tend to develop in an X-ray tube during operation, which the metal-to-cerarnic seals of
the tube must be capable of withstanding if damage to the device is to be avoided.
The set-up of the XRF spectrometer in which the completed X-ray tube was tested is discussed, in
which the X-ray current and voltage measuring techniques are described. Furthermore a detailed
account of the operation of the X-ray detector system and the multichannel analyser is given,
which was used to detect and record spectra of the sample elements excited by the primary
radiation of the X-ray tube.
Finally the measured X-ray tube performance characteristics are discussed and compared to the
predicted results.
Description
Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.
Keywords
Cold cathode tubes., X-ray tubes., Magnesium oxide., Theses--Electronic engineering.