A high‐resolution X‐ray fluorescence spectrometer and its application at SSRF

A high‐resolution X‐ray fluorescence spectrometer based on Rowland circle geometry was developed and installed at BL14W1 XAFS beamline of Shanghai Synchrotron Radiation Facility. The spectrometer mainly consists of three parts: a sample holder, a spherically curved Si crystal, and an avalanche photodiode detector. The simplicity of the spectrometer makes it easily assembled on the general purpose X‐ray absorption beamline. X‐ray emission spectroscopy and high‐resolution X‐ray absorption near edge spectroscopy can be carried out by using this spectrometer. X‐ray emission preliminary results with high‐resolution about 3 eV of Mn compounds were obtained, which confirmed the feasibility of the spectrometer. The application about Eu (III) retention on manganese dioxide was also studied using this spectrometer. Compared with conventional X‐ray absorption fine structure spectroscopy technique, the fluorescence peak of probed element [Eu (III) Lα] and matrix constituents (Mn Kα) were discriminated using this technique, indicating its superiority in fluorescence detection. Copyright © 2013 John Wiley & Sons, Ltd.     

A gas‐filled electroluminescence detector for EDXRF Spectrometry

The design and features of a sealed‐off proportional scintillation gas‐filled detector (GSPC) are described. The use of a 50 µm Be window and an Xe‐based gas mixture provides high efficiency of registration in the range 1.5–25 keV. The energy resolution changes from 18% for Al Kα (1.49 keV) to 4.2% for Ag Kα (22.2 keV). When the count rate on the unit output is 5 × 10⁴ s^?1, the energy resolution at the Mn Kα line does not exceed 9% at an entrance window area near 3 cm 2 . The detector is operated at room temperature and does not require maintenance during operation. The service life of the detector is over 5 years and the radiation lifetime is practically unlimited. The detector is designed for use in EDXRF spectrometers instead of gas‐filled proportional counters. Copyright © 2005 John Wiley & Sons, Ltd.     

Recording X‐ray spectra with an audio digitizer

X‐ray spectra were recorded with a notebook computer and analyzed by software on the computer, without a pulse height analyzer (PHA) or a digital signal processor (DSP). An audio (microphone or line) input on a personal computer has a built‐in analogue‐to‐digital converter (ADC) for digital audio recording. The output signal of the X‐ray detector is recorded through the audio input of the computer and then analyzed by software on the computer. On the basis of this method, X‐rays from a radium source were measured with a cadmium telluride detector. K X‐rays of bismuth were detected. Full width at half maximum (FWHM) was 5.6 keV at Kα of bismuth (77.1 keV), enough to separate Kβ (87.3 keV) from Kα of bismuth. The present method achieved almost equal energy resolution as that of the regular method (5.3 keV FWHM at 77.1 keV). Copyright © 2010 John Wiley & Sons, Ltd.     

A fast energy‐dispersive multi‐element detector for X‐ray absorption spectroscopy

In this paper results are presented from fluorescence‐yield X‐ray absorption fine‐structure spectroscopy measurements with a new seven‐cell silicon drift detector (SDD) module. The complete module, including an integrated circuit for the detector readout, was developed and realised at DESY utilizing a monolithic seven‐cell SDD. The new detector module is optimized for applications like XAFS which require an energy resolution of ～250–300 eV (FWHM Mn Kα) at high count rates. Measurements during the commissioning phase proved the excellent performance for this type of application.     

Kβ/Kα x‐ray intensity ratios for bromine and iodine compounds

Kβ/Kα x‐ray intensity ratios of some Br and I compounds were studied. The samples were excited by 59.5 keV γ‐rays emitted from an Am‐241 radioisotope source and characteristic K x‐rays emitted from the samples were counted by means of an Si(Li) detector which has a resolution 155 eV at 5.9 keV. The experimental values were compared with the calculated theoretical values for elemental Br and I. Copyright © 2003 John Wiley & Sons, Ltd.     

Synchrotron‐induced EDXRF determination of uranium and thorium in mixed uranium–thorium oxide pellets

Uranium and thorium in their mixed oxides were determined by synchrotron‐induced energy dispersive X‐ray fluorescence (EDXRF) spectrometry. Mixed oxide calibration mixtures containing uranium and thorium in different relative amounts and approximately fixed amount of yttrium were prepared in the form of pellets. The EDXRF spectra of the pellets were measured at the microfocus XRF (BL‐16) beam line of Indus‐2 synchrotron radiation facility (Raja Ramanna Centre of Advanced Technology, Indore, India). Characteristic X‐ray lines U Lα, Th Lα, and Y Kα were used as analyte lines. Calibration plot for the determination of uranium was prepared by plotting amount ratios of U and Y against the intensity ratios of U Lα and Y Kα. Similarly, a calibration plot for thorium analysis was also made. The amounts of uranium and thorium in the sample mixtures prepared in similar way as the calibration mixtures were determined using the aforementioned calibration plots. The precision values obtained for uranium and thorium determinations were found to be 0.3 and 0.2% (relative standard deviation, 1σ), respectively. The EDXRF results deviated from the expected values by 1% for uranium and 0.9% for thorium determinations. These analytical features are much superior compared with laboratory‐based analysis results. Copyright © 2012 John Wiley & Sons, Ltd.     

High‐resolution x‐ray analysis with multilayer gratings

Periodic multilayers are nowadays widely used to perform x‐ray analysis in the soft x‐ray range (photon energy lower than 1 keV). However, they do not permit to obtain high‐resolution spectra such as natural or synthetic crystals. Thus, multilayers cannot resolve interferences between close x‐ray lines. It has been shown and demonstrated experimentally that patterning a grating profile within a multilayer structure leads to a diffractive optics with improved resolving power. We illustrate the use of an Mo/B₄C multilayer grating in the Fe L and C K spectral ranges, around 700 and 280 eV, respectively. First, in the Fe L range, the improved spectral resolution enables us to distinguish the Fe Lα and Lβ emissions (separated by 13 eV). In addition, using a sample made of a mix of LiF and an iron ore, we show that it is possible to easily resolve the F K and Fe L emissions. These examples demonstrate that an improved x‐ray analysis can be obtained with multilayer gratings when there is the need to study samples having elements giving rise to close emission lines. Second, in the C K range, by comparing C Kα spectra from B₄C and cellulose, we show that the shape of the emission band is sensitive to the chemical state of the carbon atom. Copyright © 2009 John Wiley & Sons, Ltd.     

L x‐ray fluorescence cross‐sections of heavy elements in the atomic region 57 ≤ Z ≤ 71 excited by 17.78 keV photons

L x‐ray fluorescence cross‐sections (σ_Lα, σ_Lβ, and σ_Lγ) were measured with an accuracy of 6% (except for the Lγ x‐ray line around 8%) for La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb and Lu at an excitation energy of 17.78 keV. Relative intensities I_Kβ/I_Kα and I_Lγ/I_Lα were also measured for the same elements. The measured cross‐sections were compared with experimental and theoretical values. Measurements of the emitted x‐rays were performed using an Si(Li) detector. Copyright © 2004 John Wiley & Sons, Ltd.     

Trace elemental determination by portable total reflection X‐ray fluorescence spectrometer with low wattage X‐ray tube

A specimen containing nanograms of Sb, rare earth elements, Pb, and Bi and a specimen containing a few nanograms each of As and Pb were measured using a portable total reflection X‐ray fluorescence spectrometer. Nanograms of Sb, rare earth elements, Pb, and Bi were detected. Although the As Kα line (10.54 keV) overlapped with the Pb Lα line (10.55 keV) in a spectrum of the specimen containing nanograms of As and Pb, the Pb Lβ line was detected. Therefore, the net intensity of the As Kα line was calculated using the Pb Lα/Lβ intensity ratio in a spectrum of a Pb standard solution and the net intensity of the Pb Lβ line in the spectrum of the specimen containing As and Pb. This result indicates that these two elements can be quantified by using the portable spectrometer. Commercially available bottled drinking water was also measured. The portable spectrometer detected several tens of ppb of V in the drinking water sample. Copyright © 2013 John Wiley & Sons, Ltd.     

Toward sub‐micro‐XRF working at nanometer range using capillary optics

Capillary optics are used for X‐ray fluorescence micro‐analysis using the Cu Kα line provided by a rotating anode. The excitation beam is focused using a polycapillary lens on a Co–Ti sample. Cylindrical glass capillaries of various diameters are fitted to the X‐ray detector (Energy Dispersive X‐Ray (EDX) analyzer) and displaced along the irradiated zone of the sample. The fluorescence is studied as a function of capillary position. Good agreement is found between experimental and calculated lateral widths of the fluorescence collection, taken into account the cylindrical capillary critical angles relevant in the experiment. The influence of the cylindrical capillary diameter on the signal level detected is studied to estimate the possibility of lateral resolution increase of X‐ray fluorescence technique both in‐lab and in synchrotron environment. Copyright © 2013 John Wiley & Sons, Ltd.     

Combining CdTe and Si detectors for Energy‐Dispersive X‐Ray Fluorescence

Most energy‐dispersive X‐ray fluorescence (EDXRF) instruments use Si diodes as X‐ray detectors. These provide very high energy resolution, but their sensitivity falls off at energies of 10–20 keV. They are well suited for measuring the K lines of elements with Z < 40, but for heavier elements, one must use K lines at low efficiency or use L or M lines that often overlap other lines. Either is a challenge for accurate quantitative analysis. CdTe detectors offer much higher efficiency at high energy but poorer energy resolution compared with Si diodes. In many important EDXRF measurements, both high and low Z elements are present. In this paper, we will compare the precision and accuracy of systems using the following: (1) a high resolution Si detector, (2) a high efficiency CdTe detector, and (3) a composite system using both detectors. We will show that CdTe detectors generally offer better analytical results than even a high resolution silicon drift detectors for K lines greater than 20 or 25 keV, whereas the high resolution Si detectors are much better at lower energies. We will also show the advantages of a combined system, using both detectors. Although a combined system would be more expensive, the increased accuracy, precision, and throughput will often outweigh the small increase in cost and complexity. The systems will be compared for representative applications that include both high and low Z elements. Copyright © 2012 John Wiley & Sons, Ltd.     

Fabrication of superconducting tunnel junctions for soft X‐ray spectroscopy

Superconducting tunnel junction (STJ) array detectors with a new design, which has a minimum junction edge coverage of an SiO₂ insulation, passivation layer and an asymmetric tunnel junction layer structure, have been fabricated for a soft X‐ray region between 100 eV and 1 keV. The sensitive area was patterned by removing the SiO₂ deposition layer by a lift‐off technique that ensured no contamination layer on the top Nb electrode surface. The width of the passivation rim was as narrow as 0.5 µm at the junction edge. The clean Nb surface and the narrow SiO₂ rim resulted in almost no artifact photon events in a low‐energy region. The asymmetric layer design is effective in solving a problem of double peak response to monochromatic X‐rays, which is commonly observed in STJ detectors. The performance of a 100 pixel array detector was investigated by the fluorescent X‐ray analysis of oxides and nitrides: an energy resolution of about 30 eV for the total absorption of the Kα lines of oxygen and nitrogen. We plan to realize an energy resolution of better than 20 eV and a counting rate of over 1 Mcps for fluorescence‐yield X‐ray absorption spectroscopy for light trace elements. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of in‐target Compton‐scattering in lanthanum fluorescence spectra

A study was made of the continuum adjacent to the Kα₁ and Kα₂ peaks (the ‘shoulder’) in lanthanum fluorescence spectra. The fluorescence was induced by 59.537 keV γ‐rays from a ²⁴¹Am source. The spectra were observed with an La₂O₃‐loaded paraffin target (the ‘La target’). To limit the observations to the scattering in the target, a collimator was used in front of the germanium detector, which strongly reduced the near‐detector scattering. Changes in the shoulder spectra were observed on attaching additional mass to the La target and on changing its orientation with respect to the detector‐to‐target centre‐line. The measurements clearly show that the main cause of the shoulder spectra is the in‐target Compton scattering. A different distribution of mass in the vicinity of the fluorescing atoms with respect to the detector‐to‐target centre‐line results in different probabilities of the observed scattering at all angles. Since the energy of secondary Compton photons is directly related to the scattering angles, different distributions of mass cause changes in the shoulder spectra. Comparison of the calculated and measured shoulder spectra shows good agreement on an absolute scale. Copyright © 2006 John Wiley & Sons, Ltd.     

Influence of polymer dielectric surface energy on thin‐film transistor performance of solution‐processed triethylsilylethynyl anthradithiophene (TES‐ADT)

This study investigates the correlation between surface energy of polymer dielectrics and the film morphology, microstructure, and thin‐film transistor performance of solution‐processed 5,11‐bis(triethylsilylethynyl) anthradithiophene (TES‐ADT) films. The low surface energy polyimide (PI) dielectric induced large grains with strong X‐ray reflections for spin‐cast TES‐ADT films in comparison to high surface en‐ ergy poly(4‐vinyl phenol) (PVP) dielectric. Furthermore, thin‐film transistors based on spin‐cast TES‐ADT films on PI dielectric exhibited enhanced electrical performance, small hysteresis, and high stability under bias stress with carrier mobility as high as 0.43 cm²/Vs and a current on/off ratio of 10⁷. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fundamental parameter approach to XRF spectroscopy measurements of arsenic in polyester resin skin phantoms

A fundamental parameter (FP) approach that explicitly incorporates the energy‐broadening response of the detector was developed. The ratio between Kα fluorescence peak area and the sum of coherently and incoherently scattered peak areas was used as an indicator of trace element concentration. The peak ratio was theoretically calculated using the FP method. The energy‐broadening response curve of the Si(Li) detector was estimated by matching the theoretical and experimental values of this ratio. The method was implemented for the analysis of the K‐shell x‐ray fluorescence (K‐XRF) spectra of six polyester resin samples corresponding to six different arsenic concentrations. A ¹⁰⁹Cd radioactive source provided the excitation radiation for spectra acquisition. The predicted detector energy resolution expressed as full width at half‐maximum (FWHM) for Fe Kα fluorescence peak (208 ± 5 eV at 6.4 keV) and As Kα fluorescence peak (222 ± 5 eV at 10.5 keV) were in agreement with the experimental measurements. Copyright © 2008 John Wiley & Sons, Ltd.     

Experimental L x‐ray fluorescence cross‐sections for elements with 45 ≤ Z ≤ 50 at 7 keV by synchrotron radiation photoionization

L x‐ray fluorescence cross‐sections for elements with 45 ≤ Z ≤ 50 were measured at 7 keV using synchrotron radiation photoionization. The experimental set‐up provided a linearly polarized monoenergetic photon beam producing a low background and improving the signal‐to‐noise ratio. The data obtained for the L lines, Ll, Lα, Lβ_I, Lβ_II, Lγ_I and Lγ_II, were grouped considering the transition scheme, the energies of the emission lines and the detector resolution. Results for the experimental cross‐sections obtained were compared with theoretical values using two different data tables. In general, it was found that the experimental fluorescence cross‐sections are slightly higher (7–10%) than the theoretically calculated data and in some cases these differences are up to 40%. Copyright © 2005 John Wiley & Sons, Ltd.     

Adsorption and decomposition of triethylsilane on Si(1 0 0)

The adsorption and decomposition of triethylsilane (TES) on Si(1 0 0) were studied using temperature programmed desorption (TPD), high resolution electron energy loss spectroscopy (HREELS), electron stimulated desorption (ESD), and X-ray photoelectron spectroscopy (XPS). TPD and HREELS data indicate that carbon is thermally removed from the TES-dosed Si(1 0 0) surface via a β-hydride elimination process. At high exposures, TPD data shows the presence of physisorbed TES on the surface. These species are characterized by desorption of TES fragments at 160 K. Non-thermal decomposition of TES was studied at 100 K by irradiating the surface with 600 eV electrons. ESD of mass 27 strongly suggests that a β-hydride elimination process is a channel for non-thermal desorption of ethylene. TPD data indicated that electron irradiation of physisorbed TES species resulted in decomposition of the parent molecule and deposition of methyl groups on the surface that desorbed thermally at about 900 K. Without electron irradiation, mass 15 was not detected in the TPD spectra, indicating that the production of methyl groups in the TPD spectra was a direct result of electron irradiation. XPS data also showed that following electron irradiation of TES adsorbed on Si(1 0 0), carbon was deposited on the surface and could not be removed thermally.     

Intensity correction of WD‐XRF spectra from 2θ to energy

Generally, the energy‐dispersive X‐ray fluorescence spectra are plotted as an equi‐energy interval with the constant energy resolution. On the other hand, the wavelength‐dispersive X‐ray fluorescence spectra are usually measured with an equi‐angle interval supposed the constant angular resolution. When the wavelength axis of wavelength‐dispersive X‐ray fluorescence spectra is converted into energy, the intensity should be also corrected. This intensity correction is important even for a narrow scan range such as Pb Lα and Lβ peaks. The intensity ordering is Lβ > Lα for 2θ plot, but it becomes Lα > Lβ for energy plot. The detailed conversion equations for abscissa and ordinate axes are presented. Copyright © 2012 John Wiley & Sons, Ltd.     

X‐ray tube spectral measurement method for quantitative analysis of X‐ray fluorescence analysis

Lα and Lβ X‐ray fluorescence spectra of a lead metallic sheet were measured using an energy dispersive X‐ray spectrometer by changing the X‐ray tube voltage and the material of the primary filter. The Lα to Lβ intensity ratio changed from Lα: Lβ = 3: 1 at 15 kV to Lα: Lβ = 1: 1 at 50 kV depending on the X‐ray tube voltage and the filter. The scattered X‐ray spectra of an acrylic slab instead of the sample in the sample holder were measured by changing the applied voltage and the material of the primary filter. The calculated values of the Pb Lα/Lβ intensity ratio of the metallic sheet using the Shiraiwa–Fujino formula by inserting the scattered X‐ray spectra of an acrylic plate as incident X‐ray spectra and the fundamental parameters taken from the Elam database were in good agreement with the experimental ones. We conclude that we can obtain an incident X‐ray spectrum approximately by measuring the scattered X‐ray spectrum without measuring the direct incident beam. Copyright © 2010 John Wiley & Sons, Ltd.     

Valence‐to‐core X‐ray emission spectroscopy of titanium compounds using energy dispersive detectors

X‐ray emission spectroscopy (XES) of transition metal compounds is a powerful tool for investigating the spin and oxidation state of the metal centers. Valence‐to‐core (vtc) XES is of special interest, as it contains information on the ligand nature, hybridization, and protonation. To date, most vtc‐XES studies have been performed with high‐brightness sources, such as synchrotrons, due to the weak fluorescence lines from vtc transitions. Here, we present a systematic study of the vtc‐XES for different titanium compounds in a laboratory setting using an X‐ray tube source and energy dispersive microcalorimeter sensors. With a full‐width at half‐maximum energy resolution of approximately 4 eV at the Ti Kβ lines, we measure the XES features of different titanium compounds and compare our results for the vtc line shapes and energies to previously published and newly acquired synchrotron data as well as to new theoretical calculations. Finally, we report simulations of the feasibility of performing time‐resolved vtc‐XES studies with a laser‐based plasma source in a laboratory setting. Our results show that microcalorimeter sensors can already perform high‐quality measurements of vtc‐XES features in a laboratory setting under static conditions and that dynamic measurements will be possible in the future after reasonable technological developments.