Preliminary comparison of monolithic and aperture optics for XRMF Page: 3 of 8
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Preliminary Comparison of Monolithic and Aperture Optics for XRMF
George J. Havrilla and Christopher G. Worley
Los Alamos National Laboratory
Los Alamos, New Mexico 87545
Comparisons between standard aperture optics and a custom designed monolithic
capillary x-ray optic for the Kevex Omicron are presented. The results demonstrate the feasibility
of retrofitting an Omicron with a monolithic capillary. Increased flux is observed especially at
lower energies which results in an increase in sensitivity and potentially an increase in spatial
resolution. Alignment is a critical factor in achieving optimal performance of the monolithic
capillary. Further improvements in flux output, spot size and overall sensitivity are expected with
Capillary optics for x-ray spectrometry have developed rapidly within the last 10 years
[1-4]. Most applications have centered on research instruments, rotating anodes, synchrotrons or
new commercial instruments. The most obvious application would be to retrofit an Omicron to
both increase x-ray flux at the sample and increase spatial resolution. The Omicron instrument
manufactured by Kevex, is based on aperture optics and suffers from loss of flux as smaller
apertures are inserted in front of the x-ray tube. This paper presents preliminary comparisons of a
monolithic capillary designed for the Omicron geometry with the instrument aperture optics and
some of the difficulties associated with retrofitting. The monolithic capillary is best suited for
retrofit applications due to the constrained geometry of the Omicron. The monolithic capillary
consists of an assembly of glass capillaries formed into an ellipse. This allows a compact, high
efficiency x-ray lens to collect and focus x-rays and provide an increase in x-ray flux at the
sample relative to using an aperture.
A Kevex Omicron (Valencia, CA) equipped with a 50 W (50 kV, 1 mA maximum)
rhodium x-ray tube and apertures with diameters from 3 mm to 50 microns is used in this work.
A monolithic capillary (X-ray Optical Systems (XOS), Albany, NY) was designed specifically
for the Omicron geometry. Figure 1 is a diagram of the optic with the appropriate dimensions.
The advantages of the XOS monolithic capillary are determined by the collection distance, 25.4
mm, and the focal distance, 6 mm. The total distance from x-ray tube to sample within the
Omicron optical kernel is just under 61 mm. The body of the optic is 29 mm long encased in a
stainless steel tube with the ends sealed with beryllium windows. The predicted focal spot size is
about 23 microns when properly aligned.
Results and Discussion
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Havrilla, G.J. & Worley, C.G. Preliminary comparison of monolithic and aperture optics for XRMF, article, August 1, 1997; New Mexico. (digital.library.unt.edu/ark:/67531/metadc685505/m1/3/: accessed June 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.