5)X-ray Spectrometry– HVC Capacitor, HV Ceramic Capacitor to build All kinds of X-ray machine.
Zhang and co-workers reviewed (B26 ) the development and a
test of a new CdZnTe (CZT) pixilated 3-d position-sensitive
detector for a wide energy range of X- and ç-rays, coupled to a
third-generation ASIC-VAS3.1/TAT3 readout system. The detector
bulk is a 1.5 1.5 1cm
3
CdZnTe crystal mounted on a ceramic
substrate with 11 11 pixellated anodes bonded to the readout
electronics. They achieved a 1.27 1.27 0.2 mm
3
geometrical
position resolution of single pixel events and a better than 1% fwhm
energy resolution for the ç line of
137
Cs (662 keV) at room
temperature, using an uncollimated source.
The research group of Fant ( B27 ) reviewed a new large-area
detector with a 500-ím-thick pixellated vertical-SSD bound to
seven readout integrated circuits. The whole module has 448
64 pixels; each item has a 150 150 ím
2
uniform pixel size
without dead region, and the electronic readout procedure was
controlled by a LabView-based routine. The authors tested their
new detector with a collimated X-ray beam emitted by a copper
target and 35-keV and 10-mA anode current and demonstrated
with some pictures the imaging capability of the area detector.
The excellent physical and chemical stability and high thermal
conductivity motivated the intense research (B28 ) of silicon
carbide as a candidate for a semiconductor X-ray detector. The
authors demonstrated the detection capability of the SiC X-ray
sensor in a wide temperature range up to 100 °C. This value is
now unachievable by any other semiconductor detector currently
available in the praxis of XRS. The extreme working properties
are because this material has wide gap energy (2.2 -2.3 eV). The
energy resolution between 60- and 70-keV energy at 27 °C
temperature was found to be 366 eV, at 95 °C. The time-resolved
X-ray experiments such as time-dependent X-ray scattering and
imaging measurements require high count rate capacity detectors
with large area and excellent time resolution, between a few
milliseconds and a few seconds.
The authors of ref B29 describe a new high-throughput X-ray
detector system for X-ray photon correlation spectroscopy and
small-angle X-ray scattering using a modified version of a com-
mercial CCD camera designed originally for optical purposes. In
this new setup, the X-rays were absorbed directly in the Si bulk
of a CCD. Because the integrated intensity of a single X-ray
absorption event spreads over three or four pixels and it was found
to be significantly above the noise level of single-photon events,
it was possible to identify the event’s coordinates by the detector
pixels. The conventional CCDs are not optimal for XRS; however,
the authors pointed out that the so-called “deep-depletion” type
CCDs should have a sufficiently thick depletion layer where the
X-rays mostly absorb and deposit their energies. For example, a
camera with a depletion layer that is 40ím thick has a quantum
efficiency of 67% at a 6.3-keV X-ray energy; this allows one to use
this camera for low-energy XRS. The ultimate goal of the
development of compound semiconductor detectors, GaAs, CdTe,
CdZnTe, or HgI2
, was to create X-ray sensors that can not only
operate at cryogenic temperature (like Ge detectors) but also have
a higher absorption, achieving a more reasonable detection
efficiency (like Si-based detectors).
Finally, in this section, we review new GaAs and SiC pixilated
detectors published by Bertuccio (B30 ). These unique detectors
provide a comparable leakage current that is less or in some cases
better that Si-based ED detector devices, which produce 1 nA/
cm
2
for GaAs and 1 pA/cm
2
for SiC and 240-310 eV fwhm at
room temperature. The author overviews the physical working
principles of these detectors and outlines the electronic possibili-
ties for decreasing the spectral degradation effects, e.g., physical
origin and limitation of the leaking current.