3)X-ray Spectrometry– HVC Capacitor, HV Ceramic Capacitor to build All kinds of X-ray machine.
The first industrially applied spectrometer was reviewed by
Hollerith et al. (B4), who used an Ir/Au TES in a scanning electron
microscopy (SEM). The superconductor layer of the detector is
400 400 mm
2
with a 250 250 mm
2
Au absorber with a
thickness of 500 nm. Due to the 500 times smaller detector area
of this TES compared to the conventional Si(Li) detectors, the
solid angle has to be decreased by mounting a polycapillary lens
in front of the Ir/Au sensor. Using this X-ray optics, the detectable
count rate was improved by a factor of 5 at the Si-K R energy.
Three American authors (B5) outlined the general and specific
properties of the microcalorimeters and their applicability to SEM
analysis. They called the attention to the following facts: (i) the
spectral resolution of the microcalorimeters is better than the best
alternative detection technology in wavelength-dispersive spec-
trometry (WDS), (ii) this energy-dispersive property is signifi-
cantly better than what Si(Li) technology can provide, (iii) the
detection efficiency is between Si(Li) and WDS modes, (iv) the
disadvantageous detection characters of this cryogenic detector
are the limited count rate and the limited geometrical efficiency
capabilities compared to WDS and Si(Li) detection. These nonideal
working characteristics can be avoided by the development of
appropriate microcalorimeter array detector system that should
be the ideal detector for EPMA of low atomic number elements.
Bechstein and co-workers ( B6) characterized a cryogenic super-
conductive tunnel junction detector set that consists of Nb/Al/
AlO x/Al/Nb layers segmented in four individual structures having
an area between 70 70ím
2
and 200 200 ím
2
. The aim of
their investigation was to clarify the dependence of the detection
efficiency and the energy resolution properties on the impinging
X-ray energy (up to 1500 eV) and the count rate and its influence
on the detector response function. The X-ray microbeam had a
5- ím diameter, and this size allowed scanning the beam vertically
and irradiating different parts of the detector surface. The authors
found an unexpected degradation of the energy resolution in a
wide edge zone. The laterally resolved measurements provide a
better understanding of the physical processes in STJs and
promote design of an improved detector layout. A Japanese
research group ( B7) developed a new design for a set of STJ
detectors, capable of providing multispectra of X-rays for purposes
of X-ray computer tomography in the energy range below 1 keV.
The typical size of each individual STJ on the multipixel chip is
100 100 ím
2
. An energy resolution of 41 eV fwhm was
observed at 5.9-keV energy, and that value is three times better
than the theoretical limit of conventional Si detectors. The authors
carried out experiments with their STJ chip in the 5-25-keV
energy range and concluded that this type of cryogenic detector
is a promising candidate for 3-D X-ray absorption and fluorescence
CT imaging. Bruijn et al. reported (B8) a new development of a
cryogenic 5 5 matrix-shaped array of microcalorimeters using
Ti/Au TES with Cu/Bi absorber and Si3N4
cooling connector. The
array was tested with irradiation of 5.9-keV monoenergetic X-ray,
and the response spectra had a 6 -7 eV fwhm. An Italian research
group reviewed (B9) a similar experiment with TES that consists
of a 300 400 ím
2
thin and 25-ím-thick polycrystalline Sn foil
acting as an energy absorber. The TES surface was protected
against possible chemical damaging during the photolithographic
procedure. The TES microcalorimeter was tested at radiation
beamline GILDA of the European Synchrotron Radiation Facility
(ESRF), detecting X-ray fluorescence spectra emitted by a Renais-
sance gold luster on ceramic; during this analysis, the energy
resolution of the TES was found to be 70 eV between 6- and 9-keV
X-ray energy. On the basis of their experimental results, the
authors concluded that the TES calorimeters are very applicable
for the synchrotron based X-ray fluorescence analysis. A special
monolithic X-ray detector based on the connection of an SDD and
a CsI(Tl) scintillation device was reviewed by Marisaldi et al.
(B10). In this coupled detector, the SDD worked as a direct X-ray
sensor for photons that interacted in the Si body of the SDD and
in parallel as a photodetector for photons generated in the
scintillation crystal. The source of the electronic signal is dis-
criminated on the basis of the pulse shape evaluation and that
process yields the correct determination of the deposited photon
energy in the complex detector for both X-ray andç-ray energy
ranges. The authors systematically tested the dependence of the
detector efficiency on the operating temperature and found that,
at 10°C, the energy efficiency is nearly 100% for the 8 -200 keV
of energy range. They concluded that this type of combined
detector would be of great interest in X- and ç-ray detection in
astrophysics due to the advantageous spectroscopic capabilities,
i.e., the high detection efficiency from low-energy X-rays up to
several hundred kiloelectronvolts. Goulon et al. published ( B11)
the spectroscopic properties of their advanced detector systems,
especially SDD arrays, used for XRF spectrometry at the ID12
beamline in ESRF in Grenoble in the last 15 years. An improved
energy resolution was achieved during this period: 82 eV at Si-
KR and 126 eV at Fe-K R, by means of mathematical spectral
deconvolution. Now, the SDD has become a commercial detector
in varying sizes and shapes, in large array form, including 200-
400 detection channels for different applications of conventional
and specific X-ray emission analysis such as XRF tomography and
holography or EXAFS analysis. They discussed the use of SDD
as ED detectors, the modes of minimization of the electronic
readout noise, and the first result of a 35-element SDD array
consisting of 7 7 individual cylindrical SDDs. A special annular
SDD, developed for PIXE analysis, was tested and reviewed ( B12).
PIXE always suffers from the small solid angle of detection;
therefore, this new Peltier-cooled SDD was designed with annular
shape in order to maximize the detection angle. The area of the
detector is 60 mm
2
, and the working distance is only 1 mm. This
commercial ED detector is able to collect at high rate of 1
Mcounts/s with an energy resolution better than 200 eV at 6.4-
keV X-ray energy. In comparison with conventional Si(Li) detec-
tors, the solid angle and the count rate capability are both larger
by 2 orders of magnitude. A novel SDD with integrated FET was
published by Lechner and co-workers ( B13); it has a new chip
layout that allows constructing the readout anode in a smaller
size than earlier designed, which reduced the anode capacitance
of 120 fF instead of 200-250 fF in the case of commercial SDDs.
This improved detector structure and properties yielded a better
energy resolution: 147 eV at 5.9-keV X-ray energy at -10°C
detector temperature. On the basis of these results, the authors
proposed a new SDD device with increased effective area in order
to achieve higher geometrical efficiency. Eggert and colleagues
(B14) also studied the improvement possibilities of SDDs with
enlarged active detector surface area, from 5 to 10 mm
2
; that
required more intensive cooling from -15°C down to -20°C,
reducing the leakage current that causes degradation of the
energy resolution. On the basis of their experimental results, they
concluded that instead of enlargement of the active area of the
SDD detector a group of segmented detectors with a small (5
mm
2
) sensitive surface is more reasonable to apply. On the other
hand, in cases when a low count rate is available, a large sensitive
area is more reasonable. The research group of Sokolov reviewed
their results (B15) of systematic study about Si(Li), Si PIN, and
CdZnTe X-ray detectors, cooled by Peltier effect devices in order
to develop a portable ED X-ray spectrometer. They found that
the spectroscopic characters of the Peltier-cooled Si(Li) detector
was similar to those of detector cooled with liquid nitrogen, and
it was selected as the most suitable type of detector for XRF
analysis. They showed in this article illustrative spectra from the
studied semiconductor detectors using
55
Fe and
241
Am radioactive
sources. Streli and co-workers (B16) published their experimental
comparison of Si(Li) detectors and SDD equipped both with a
thin polymer window in order to detect low X-ray energies from
200 eV. With the Si(Li), it was possible to detect down to the C
KR and the limit for SDD was O. The detection limit for this latter
element was found to be 36 ng in the case of SDD and 4 ng for
a Si(Li) detector, which shows the better applicability of the Si(Li)
detector for XRF analysis of low- Z elements. Their results suggest
that the SDDs should be a promising candidate as a future
detection device for low atomic X-ray radiation especially at the
case of a high X-ray flux. In refB17, Wright et al. emphasized
that there is a strong demand for more efficient, more radiation-
tolerant sensors in X- and ç-ray physics, SR applications and
medical imaging. For these detection tasks, an excellent solution
is offered by the 3-D detector architecture in which the electrodes
traverse the detector bulk, neglecting the limitation of the distance
between electrodes by the thickness of the wafer. This 3-D
structure allows faster charge collection and a very low depletion
voltage of 1 -20 kV; on the other hand, the planar pixel detectors
need80 V. The authors performed a simulation model calcula-
tion for the charge collection in these two types of detectors and
found that the current pulse was produced in 5 ns, and in case
of a pixilated planar detector, this value was found to be 80 ns.
The 3-D Medipix1 sensor was created on high-resistivity n-type
Si bulk, the electrodes were formed by photochemical etching,
and the p-type electrodes were etched and doped with B by
diffusion. Finally, the electrode pores were metallized with a Ti
layer and Au and Al.