2)X-ray Spectrometry– HVC Capacitor, HV Ceramic Capacitor to build All kinds of X-ray machine.
having three-dimension wiring layers, cryogenic multiplexing
schemes, complex and flexible electronics, and finally an as low
as possible mass.
SR is widely used for all fields of XRS for the characterization
of materials for basic research and for practical aims. In view of
the lack of a detailed description of this analytical technique for
the nonsynchrotron-expert forensic community, Kempson and co-
workers (A8) published a review paper on application of synchro-
tron radiation in forensic trace analysis. The authors pointed out
the benefits of SR and discuss XRF techniques, described the
tomographic method, X-ray diffraction, and scattering applications,
and finally, they highlighted the X-ray absorption near edge
structure (XANES) and extended X-ray absorption fine-structure
(EXAFS) methods and their significant contribution to the
characterization of materials. They outlined the unique advanta-
geous spectroscopic characters of the synchrotron beams: high
brightness, energy tenability, nearly 100% of polarization and
coherence, and possibility of time-resolved measurements; finally
they showed some examples demonstrating the benefit of ap-
plication of the SR in this practical field.
A general tutorial paper was published by Van der Veen and
Pfeiffer ( A9) about the properties of coherent hard X-ray beams
and their use in structural analysis of solid materials. Because of
a fully coherent X-ray beam is provided by SR, it is suitable for
such experiments where the interference of the X-ray beam gives
information on the inner structure of the investigated object
material. In the near-forward scattering direction, the differences
in the phases between waves traversing different parts of the
object enable imaging the object structure into a phase contrast.
In larger scattering angles the interference provides coherent
diffractive imaging without lenses and it is called holography
without reference beam. The authors give a simple mathematical
description of the investigated effects: transverse coherence,
longitudinal coherence, phase contrast, X-ray photon correlation
spectroscopy, diffracting imaging, and waveguide analysis on the
basis of the Fraunhoffer diffraction pattern.
In this last review period, an increasing number of papers were
published on the 1D and 2D waveguides due to the strong needs
of a microsized X-ray beam, which has a high flux density, for
the analysis of submicrometer-sized objects. Egorov and Egorov
published a tutorial on state-of-art of X-ray waveguides ( A10), with
the general description of the operating principles and the
spectroscopic characteristic properties and possible applications.
X-ray microanalytical methods are more widely applied in
archaeometry and in cultural heritage conservation research,
especially nondestructive micro-X-ray analytical methods. Selected
presentations of the 7th International Conference on Nondestruc-
tive Testing and Microanalysis for the Diagnosis and Conservation
of the Cultural and Environmental Heritage, dealing with different
types of instrumental analysis of materials and artifacts of cultural-
historical value, were published in Cultural Heritage Conservation
and Environmental Impact Assessment by Non-Destructive Testing
and Micro-Analysis(A11). The publication gives a survey of the
possible solutions for analytical problems in the cultural heritage
sector, using portable energy-dispersive XRF spectrometers,
TXRF, microfocus X-ray tomography, confocal micro-XRF, and
micro-XAS.
The in-field analysis of hazardous material and environ-
mental samples obviously requires portable XRF spectrometers.
Melquiades and Appoloni published a review article (A12) about
the basic methodology aspects of laboratory and portable X-ray
spectrometers. Laboratory measurements can be slow, sometimes
laborious, and of course more expensive; however, they are more
precise in comparison with portable XRF spectrometers. The use
of portable spectrometers allows rapid mapping and ranking of
contaminated sites, and a large number of semiquantitative data
can be generated on site in nearly real time. The authors overview
the possible detector types that are suitable for the portable
technique and concluded that the Peltier cooled detectors (Si-
PIN, CdZnTe, Si drift) are the most appropriate devices because
no cryogenic cooling is required. The most significant applications
and portable designs were summarized in a separate table
involving the characteristic parameters: excitation source, re-
quired sample preparation technique, possible matrixes for sample
bulk, and minimum detection levels for different elements. The
authors give some examples for applications published in the
literature, and they discuss the main steps of in-field analysis such
as preconcentration techniques and data evaluation methods.
Finally, in this introductory section, we mention an article about
the direct analysis of biological samples applying TXRF analysis,
published Marco and Herna´ ndez-Caraballo (A13). They claim that,
for the purpose of direct analysis of biological origin samples, the
most suitable XRS method is TXRF due to the limited matrix effect
and the multielement character. TXRF is used mostly after a
sample digestion procedure; however, in some cases, the biologi-
cal wet samples can be analyzed without preparation due to the
low matrix interference. This technique has advantageous proper-
ties such as shorter analysis time, low reagent consumption, and
simplified analysis procedure.
DETECTION
Cryogenic energy-dispersive (ED) detectors have a superior
energy resolution due to the very low operating temperature, that
reduces the thermal noise, and to the appearance of low excitation
states of electron energies. The working principle is based on the
fact that one absorbed X-ray photon (the energy is 1 keV)
generates an 100 times higher number of charge carriers in the
superconductive-type detectors than in conventional Si sensors.
This effect leads to the excellent 2 -4-eV energy resolution in the
X-ray energy range of several kiloelectronvolts, while the best
energy resolution of the conventional Si(Li) detectors is 120 eV
at 5.9-keV energy. The microcalorimeters are principally very
sensitive solid-state thermometers changing their temperature
through the absorption of X-ray energy quanta. The construction
of the STJs is based on two superconductive electrodes separated
by a tunneling barrier. The tunneling current between the
electrodes depends on the absorbed X-ray energy in the barrier
layer, and this changing of current can be applied as a signal of
detected X-ray quanta. Metallic magnetic calorimeters (MMC) for
high-resolution XRS were developed by Fleischmann and co-
workers (B1); they show an fwhm of 3.4 eV for X-ray energies up
to 6.5 keV. This type of detector is based on a paramagnetic sensor
placed in a magnetic field and in contact with a metallic absorber.
The magnetization of the sensor indicates the temperature of the
absorber calorimeter. The spectroscopic capability of this cryo-
genic MMC detector was demonstrated by
55
Fe spectra with
separation of the Mn-KR1 and Mn-KR2
peaks. A German physics
research group (B2) developed a prototype of a new construction
of an STJ detector having two thin electrode layers separated by
a thin tunnel barrier, and on this layer a lead absorber is layered.
Due to the high absorption properties of the Pb layer, the quantum
efficiency of the STJ detector increased considerably from 1% up
to 50% of X-ray energy of 6 keV. This structure helps reduce the
doubling of the peaks. The achieved energy resolution of the
detector was 10.8 eV at an energy of 5.9 keV, at a working
temperature of 70 mK. The authors are going to install this type
of detector into a new high-resolution cryogenic spectrometer used
in an electron microscope. The microcalorimeters offer the most
impressive energy resolution, 2 -3 eV, in the energy range of 2 -6
keV ( B3). However, their detectable count rate is low, 500
counts/s. In contrast with these operating properties the STJs have
a little bit less resolution capability, which is 3-12 eV in the
energy range of 2 -6 keV, but their maximum count rate should
be 10 times higher than in the case of the microcalorimeters. The
authors developed a new STJ with structure of Nb -Al -AlO x-
Al – Nb for high count rate detection of synchrotron radiation.
They produced an impressive count rate at 10 000 counts/s with
an energy resolution between 7 and 15 eV fwmh. Their device
was able to detect 100 000 counts/s as well, but then the energy
resolution deteriorated to 43 eV.