8)X-ray Spectrometry– HVC Capacitor, HV Ceramic Capacitor to build All kinds of X-ray machine.
An Australian research group (D18 ) published theoretical
calculations for the estimation of the contribution of X-ray
scattering and second-order fluorescence effects on the absorption
measurements, using differently sized apertures to admit varying
amounts of the scattered and fluorescence X-ray flux into the
detector. The authors emphasized that the magnitude of this
contribution effect is specified by the applied X-ray optics, i.e.,
collimators, the X-ray energy, the response function of the detector
and the atomic number, quality, and geometrical parameters of
the absorber sample. They found the contribution from Rayleigh
scattering to be less than 2% above the absorption edge; however,
it can reach 10% below the edge, The contribution of the Compton
scattering was found less than 1% in the studied energy range.
For PIXE, exact information about the X-ray production cross
section is essentially needed for the application of any calculation
model. For this reason, a research group in Mexico (D19 )
reviewed their experimental results for the L shell X-ray produc-
tion cross section of rare earth elements (Ce, Nd, Sm, Eu, Gd,
Dy) excited by
12
C
4+
,
16
O
4+
ions at 0.75 MeV. Several L lines’
intensities (L R1,2,Lâ1,3,4,Lâ2,15 ,Lç1,5) were subtracted from each
obtained EDXRF spectra (AXIL software was used for spectrum
evaluation) collected by a LEGe detector (fwhm ) 150 eV at 5.9-
keV energy). In the evaluation procedures of EDXRF, the
analytical shape of the XRF peaks is an ultimate problem in which
one of the important parameters is the so-called Fano factor that
is defined as a parameter in the expression for the contribution
of the electron-hole pair creation in the detector crystal. Papp et
al. ( D20 ) published their new results on the determination of the
Fano factor and its dependence on the detected X-ray energy in
the low-energy range and found the value of this parameter to be
varying between 0.059 and 0.083; those numbers are less than
generally determined values. They performed experiments with
a HPGe detector, which is almost free from low-energy tailing,
irradiated by an 8.36-keV X-ray beam and with a Si(Li) (with 122-
eV energy resolution) irradiated by X-rays of a
55
Fe radioactive
source. The escape peaks in the EDXRF spectra may give
significant and disturbing contributions to the low-intensity peaks,
necessitating more complex spectra evaluation algorithms.
Due to the lack of papers on the problem of escape processes
in Ge(Li) and HPGe detectors, Yilmaz and Can studied (D21 ) the
photoelectron, Compton and X-ray escape processes for these
types of detectors in the energy range from 8 to 52 keV and their
dependence on the X-ray energy. For the measurements, char-
acteristic X-rays of Cu, Rb, Mo, Ag, Ba, and Tb were used, the
energy loss caused by all three processes was observed in the
case of Ba and Tb, and only the X-ray and photoelectron escape
effects were measured for other elements. The authors applied a
Monte Carlo program for simulating all the interactions between
X-ray photons and atoms. They found a reasonable agreement
between their measured data and similar data sets published by
other researchers. However, between the simulation and mea-
sured values, a larger discrepancy was observed.
The relevant description of the low-energy tailing effect for
EDXRF spectrum analysis has great importance; this motivated
Shariff and co-workers (D22 ) to investigate this detection problem,
describing mathematically the low-energy tailing in PIXE spectra
using a combination of Hypermate-type functions. For their
experiments, they used Ge and Si(Li) detectors, in 1.3 -9.2-keV
X-ray energy range, with a PIXE set up with 2550-keV proton
energy. They found an energy dependence of the low-energy
tailing parameters for the Ge detector; most had a maximum value
at 1.48 keV (Al-KR) and decreased rapidly. A similar behavior was
found for the Si(Li) detector. In the comparison of Ge and Si
detectors, the Ge shows more intense low-energy tailing than the
Si(Li) detector, but the tailings become negligible at much lower
X-ray energies than for Si(Li) detectors.