6)X-ray Spectrometry– HVC Capacitor, HV Ceramic Capacitor to build All kinds of X-ray machine.
INSTRUMENTATION AND X-RAY OPTICS
The ultimate goals of focusing X-ray beams are to produce the
highest possible flux in the focal point and produce magnified
X-ray images. The state-of-the-art focused spots of X-rays are of
the order of 50 nm, provided by beam-compressing capillaries;
transmission refractive lenses achieved 210 nm and the best values
were reached by Fresnel-zone plates. Jark et al. proposed (C1)a
very simple and optimized form of compound refractive lenses
(CRL) for focusing X-rays by reducing the optically passive
material. A single lens was composed of two large prisms of
millimeter size touching each other, and each individual large
prism contained a highly regular inner structure of smaller
identical prismlike segments. The focusing device allowed using
a larger aperture comparing to other microfocusing X-ray optical
elements in the millimeter range, and the smallest image size was
2.8 ím while the photon flux enhancement was 25. The most
effective materials for refractive lenses are such materials that
have an as low as possible atomic number; low- Z elements have
a low absorption and high refraction index. The first lenses were
fabricated from Al and later from Be and Li; these devices required
special treatment because of their toxicity and dangerous chemical
properties. To avoid this fundamental problem, the research group
of Artemiev ( C2) proposed and developed a new design of a planar
compound refractive lens made from glassy carbon; that lens
focuses in one direction and its curvature radius is between 5 and
200 ím. The lens has some advantageous properties, e.g.: (i) the
lens material can be fabricated by laser beam technology, (ii) it
has excellent thermal and radiation stability. The smallest focal
spot was of 1.4-ím size at 25-keV X-ray energy, while the measured
gain was 3. The first possible application of this newly developed
compound lens will be micro-XRF and micro-EXAFS experiments.
The most effective focusing devices for high-energy X-ray (25-
100 keV) are the compound refractive lenses due to their lower
absorption coefficient and high refractive index compared to the
lower energy range. Shastry describes (C3) a combined X-ray
optical setup consisting of an Al CRL, tunable in-line monochro-
mator of two vertical diffracting bent Laue crystals inserted
tangentially on a Rowland circles, a Si(111) high-resolution
monochromator. The author showed a few examples with different
combinations of these optical elements and discussed their
experimental properties: the best focal spot size was67ímin
line focus and the transmittance was between 50 and 60% at 67-
and 81-keV X-ray energies. For the low-energy X-ray range (<10
keV), Pereira et al. ( C4) fabricated a Li CRL having 90% transmis-
sion at 10.87-keV X-ray energy, while the gain was up to 40 and
the geometrical fwhm of the focal blurred was 20ím at 2.13-m
focal distance. The prototype lens has 80 individual lens sets with
two parabolic surfaces of 0.253-mm nominal radius, and its
transmission efficiency was found between 49 and 90%. A soft X-ray
microscope with excellently high spatial resolution (better than
15 nm) was constructed recently by Chao et al. (C5)atthe
Advanced Light Source, based on two Fresnel-zone plates. The
improvement of spatial resolution of the fabrication zone plates
is fundamentally limited due to the electron nanofabrication
restriction, namely, the electron beam broadening. The electron
beam that forms the nanopatterns of the zone plate scatters in
the recording medium, and this process leads to a loss of image
contrast. The novel idea of the authors was that they subdivided
the zone plate pattern into two individual complementary patterns,
which had less dense patterns, and they were manufactured
separately. The combined zone plate used in their X-ray micro-
scope was set by overlaying both zone plates with high accuracy,
and in such a way higher, a pattern density was achievable, several
times better than it would be using a single zone plate. The
microscope was assembled by these precisely fitted zone plates,
a pinhole system, and a CCD camera to transmit the X-ray image
to visible. The authors predict a promising future for this plate
fabrication technique, especially in life science, to localize quan-
titatively proteins in a 3D image of a cell, permitting the study of
genes. Recently, the Fresnel zone plates and waveguides are on
the top in the high-resolution X-ray optical elements. Michette
and co-workers (C6) reported a new possibility for the structure
of modified reflection zone plates and Bragg -Fresnel lens, which
pass below the 10-nm resolution limit of transmission zone plates
(TZPs). The authors showed that in the case of coaxial elliptical
reflection structures, the different diffraction orders will focus into
the same focal point; in the case of a Au Fresnel structure placed
on a Si crystal, the resolution limit at the first diffraction order is
6 nm. The authors emphasized that this new potentially sub-
nanometer resolution focusing element can be utilized at the free-
electron laser and they cannot substitute the “conventional” TZPs
because of their optical aberrations. The Fresnel zone plates
consist mainly of a concentrically positioned periodical alternation
of transparent and absorbing parts to form the X-ray image. The
basic practical problem of this optical element is that the
background level is comparable to the signal level resulting
sometimes in 10% error. Tamari and Azechi published a new
solution (C7) for neglecting this undesirable effect by designing
a FZP with variable thickness and width of transparent and
absorber zones and optimized these parameters for achieving a
better signal-to-background ratio, four times better than for
conventional two layers FZP. For focusing X-rays in the hard-
energy range (5 -120 keV), the CRLs are the most suitable optical
elements due to their compact and robust construction and
mechanically simple alignment. These types of X-ray devices
operate as conventional glass lenses in the optical range of the
electromagnetic waves; the principle difference is that the refrac-
tion index for X-rays is less than 1 with a very small quantity;
therefore, the CRLs must consist of series of individual units in
order to produce the expected focusing effect. The research group
of Lengerer in Aachen (C8) reviewed a novel type of CRLs made
from B, Be, Al, and Si, with a rotational parabolic profile, for
focusing in two dimensions and to avoid the spherical aberration
that is a characteristic property of the other types of CRLs with
spherical profile. As a material of the CRLs, the low-Z elements
are ideal due to the low absorption properties, and they must resist
the high heat load in the lens material induced by the high X-ray
flux. The author tested a cooled Be CRL with 100-W mm
-2
heat
load in ESRF at the ID-10 beamline, and the highest temperature
was 65 °C during continuous operation. That value is optimal for
Be because its melting point is 1285 °C and the recrystallization
occurs over 600 °C. The authors reviewed the experimental results
of a nanofocusing Be lens that was assembled from two planar
CRLs; each focuses into one dimension, and the best focal spot
was achieved as 115 160 nm
2
at 47-m focal distance from the
undulator X-ray source (the energy was 15.2 keV) at ID-13 in the
ESRF. The authors predict that the parabolic CRLs will be the
key optical devices for scanning microscopy and microanalysis,
diffraction, fluorescence analysis, absorption measurements, and
XRF tomography experiments with high X-ray energy and high
spatial resolution. The main technical problem in manufacturing
of CRLs is to arrange the uniform shape of the individual lens
and precisely assemble them into one lens set; however, these
problems can be avoided with a bubble-type CRL. This is basically
a series of air bubbles embedded in epoxy (that is involved in a
glass capillary) forming spherical individual lenses. Piestrup et
al. published ( C9) on experiments with this type of CRL for
imaging of biological objects and found 20-ím resolution using
a conventional Cu anode X-ray tube and applying 600-W power;
that value is far from the best resolution achieved at synchrotron
facilities with parabolic CRLs but it equals the best of the
microtomography devices currently on the market. A newly
designed refractive Fresnel-like X-ray lens was published in ref
C10 , constructed by a triangular array of prisms whose optical
element operates with the phase shift of the X-rays. Each identical
prism is shifted off the optical axis of the lens and that structure
allows focusing the transmitted X-rays. The one-dimension focus-
ing device was fabricated with deep reactive ion etching of Si; it
was tested at a synchrotron beamline, and it provided a focal line
width of 1.4ím at 13.4-keV X-ray energy. The authors outlined
the advantageous optical properties of this type of X-ray lens. If
the displacement of the prism columns is sufficiently small
compared to the prism height, a parabolic correction is not
necessary; they expect this design as the future lens for hard
X-rays. One of the most spectacular and promising X-ray optical
devices, which can provide narrow and small-diameter X-ray
beams down to less than 10 nm, are the 1D or 2D X-ray
waveguides. The thin-film slab waveguides can confine the
prefocused incident X-ray beam and guide it, and at the output
side, the diameter of the X-ray beam can be reduced to 10 nm.
This type of X-ray microoptical element is one of the most
promising devices for X-ray microscopes at the third-generation
synchrotron beamlines and for free electron lasers. Warner and
Fonzo published ( C11 ) theoretical calculation of the transmission
properties of 1D and 2D waveguides and tutored the reader
through a simple representation of their calculation model, giving
a simple comparison with other X-ray optical devices. On the basis
of calculations, they predicted that the transmission efficiency of
the one-dimensional waveguides is 50% for the incident coherent
radiation and 28% was found for the two-dimensional version. Two-
dimensional X-ray waveguide arrays were reviewed by Ollinger
et al. ( C12 ); these devices are in fact a serial of one-dimensional
waveguides. The authors fabricated this 2D version by electron
beam lithography in Si, and the 1D element is really a nanotube
having typical entrance sizes of 34 60 nm
2
. The monochroma-
tized X-ray beam for testing was set at E ) 8.94 keV, 1.6 10
9
photons mm
-2
s
-1
per 100 mA, and they measured the far-field
pattern of the waveguide. They emphasized that it is not necessary
to prefocus the input X-ray beam for their 2D device, and hopefully
soon, the entrance sizes of the device can be reduced down to
the critical value of 30 nm. Jarre et al. reviewed ( C13 ) waveguides
prepared by sputtering Ni as a cladding and C as a guiding layer
on a Si wafer (thicknesses of Ni/C/Ni layers were 5, 32, and 20
ím, respectively) with roughness less than 1 nm. The authors
were able to produce an X-ray beam with a diameter between 10
and 100 nm in one dimension in the case of spatially coherent
and divergent white synchrotron beams at the energy-dispersive
reflectivity dipole magnet beamline of BESSY II. The confocal
measuring setup for 3D XRF analysis is one of the most effective,
simple, and fast methods. An international research group
reviewed ( C14 ) new confocal XRF measurements on historical
and modern paintings using an 21-keV X-ray beam and Si(Li)
detector. The main idea of this method is that a microvolume of
the sample is excited by using polycapillary optics between the
X-ray source and the sample, and an other identical polycapillary
is mounted in front of the detector (between sample and detector)
in order to detect only those characteristic X-rays emitted from
the selected small interaction microvolume. During the analysis
the excitation and detection setup was stable and the sample was
moved in x-y direction in the front of the X-ray beam and detector
to excite and analyze different geometric places in the sample
material. The geometrical resolution was determined by the
scanning step unit and that was set 10 í m for each step. The
authors presented a theoretical calculation for the sample com-
position based on the polycapillary filtering properties, the average
sample composition, and the use of same Etalon samples. Malzer
and Kanngiesser (C15 ) published new results as well in the
confocal measuring technique for 3D analysis with micrometer-
sized spatial resolution. The authors described a detailed calcula-
tion model based on the fundamental parameter approach for a
confocal measuring setup for both thin and thick samples. The
model needs the knowledge of the correct description of the
characteristic of the spectrometer, the sensitivity values, and the
fluorescence intensity profile. Janssens et al. (C16 ) published their
confocal measuring setup at beamline L at HASYLAB and
demonstrated its analytical capabilities in 3D elementary analysis
where a 1.2-T bending magnet provided polychromatic SR and a
narrow energy band (¢E/E 10
-4
) in the monochromatic mode.
The authors demonstrated that, in the confocal XRF mode,
elements in the atomic range from Fe to Zr can be measured with
a spatial resolution of 15 -30ím down to 0.3-1.0 fg or 0.1-0.3
ppm.