K-series X-rays Research Articles

Rare-earth element comparative analysis in chosen geological samples using nuclear-related analytical techniques

In this study, four analytical techniques for the detection of Sc, La, Ce, Nd, Sm, Eu, Tb and Lu in volcanic rock specimens from Ghana have been compared. These rock samples were examined using inductively coupled plasma mass spectrometry, X-ray fluorescence spectrometry, and instrumental neutron activation analysis. The Am-241 excitation-based X-ray fluorescence accuracies were good for Y, La, Ce, Nd, Eu, and the results were comparable to inductively coupled plasma mass spectrometry and instrumental neutron activation analysis except Silver-anode X-ray tube X-ray fluorescence. This demonstrates the limitations of the tube-based X-ray fluorescence excitation system for rare earth elements analysis, primarily caused by interference between the K-series X-ray emission from the transition metals and the relatively low intensities of L-series lines of the rare earth elements. Data on the precision and accuracy of these methods were based on IAEA SOIL-7 reference material.

The effect of fluorescence on surface dose with superficial X-rays incident on tissue with underlying lead.

An Advanced Markus chamber on the surface of solid water phantom was used to determine surface dose reduction, with either a lead or air interface, as a function of surface-interface separation (t). The beam quality dependence of dose reduction was investigated using the 50kV, 100kV and 150kV beams of an Xstrahl 150 superficial X-ray unit. For each beam the dose correction factor, DCF(t), namely the ratio of surface dose (t) to surface dose (t = 100mm), was determined. Monte Carlo simulations of DCF(t) with a lead interface were compared with corresponding measured values. Simulated spectra were calculated at the phantom surface for full backscatter (t = 100mm) and with either a lead or air interface at 2mm or 8mm depth. For each depth and beam quality lead fluorescent radiation at the surface was evident. The variation of DCF(t) for each beam and field size exhibits a minima at t ≈ 5mm and in the range 1mm ≤ t ≤ 40mm surface dose reduction is larger for 100kV than 150kV. Monte Carlo simulated DCF(t) are consistent with corresponding measured DCF(t). From simulated spectra L-series fluorescent X-rays (≈ 15keV) emanating from lead at t = 2mm are evident for all beams and fluorescent K-series X-rays only occur with 100kV and 150kV beams.

K-series X-ray yield measurement of kaonic hydrogen atoms in a gaseous target

We measured the K-series X-rays of the K−p exotic atom in the SIDDHARTA experiment with a gaseous hydrogen target of 1.3 g/l, which is about 15 times the ρSTP of hydrogen gas. At this density, the absolute yields of kaonic X-rays, when a negatively charged kaon stopped inside the target, were determined to be 0.012−0.003+0.004 for Kα and 0.043−0.011+0.012 for all the K-series transitions Ktot. These results, together with the KEK E228 experiment results, confirm for the first time a target density dependence of the yield predicted by the cascade models, and provide valuable information to refine the parameters used in the cascade models for the kaonic atoms.

Testing the Pauli Exclusion Principle for Electrons at LNGS

High-precision experiments have been done to test the Pauli exclusion principle (PEP) for electrons by searching for anomalous K-series X-rays from a Cu target supplied with electric current. With the highest sensitivity the VIP (VIolation of Pauli Exclusion Principle) experiment set an upper limit at the level of 10−29 for the probability that an external electron captured by a Cu atom can make the transition from the 2p state to a 1s state already occupied by two electrons. In a follow-up experiment at Gran Sasso, we aim to increase the sensitivity by two orders of magnitude. We show proofs that the proposed improvement factor is realistic based on the results from recent performance tests of the detectors we did at Laboratori Nazionali di Frascati (LNF).

A new measurement of kaonic hydrogen X-rays

The K¯N system at threshold is a sensitive testing ground for low energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we have measured the K-series X-rays of kaonic hydrogen atoms at the DAΦNE electron–positron collider of Laboratori Nazionali di Frascati, and have determined the most precise values of the strong-interaction energy-level shift and width of the 1s atomic state. As X-ray detectors, we used large-area silicon drift detectors having excellent energy and timing resolution, which were developed especially for the SIDDHARTA experiment. The shift and width were determined to be ϵ1s=−283±36(stat)±6(syst) eV and Γ1s=541±89(stat)±22(syst) eV, respectively. The new values will provide vital constraints on the theoretical description of the low-energy K¯N interaction.

High-speed embossed radiography utilizing a quasi-monochromatic spherical-plasma flash X-ray generator

Embossed radiography is an important technique for imaging target region by decreasing absorption contrast of objects. The high-speed embossed radiography (HER) system consists of a computed radiography (CR) system, an intense plasma flash X-ray generator, and a two-dimensional computer program for shifting the image pixel. In the flash X-ray generator, a high-voltage condenser of 150 nF is charged to 80 kV, and the electric charges in the condenser are discharged to the flash X-ray tube through a four-cable transmission line after closing the gap switch. The molybdenum-target evaporation leads to the formation of weakly ionized spherical plasma, and intense molybdenum K-series X-rays were produced utilizing angular dependence of bremsstrahlung X-ray intensity. High-speed monochromatic radiography was performed using molybdenum flash K-rays, and a two-dimensional HER was carried out utilizing single-energy subtraction after the image shifting. The minimum spatial resolution was equal to the sampling pitch of the CR system of 87.5 μm, and concavoconvex radiography such as phase-differential imaging was performed with X-ray durations of approximately 100 ns.

Calculations of the cascade characteristics for hadronic hydrogen atoms based on a quantum-classical approach

The quantum–classical Monte Carlo cascade calculation model for the muonic (non-hadronic) hydrogen atom has been modified for exotic pK − and \(p\bar p\) atoms with strong interaction. The radiative and collision transitions were taken into account only because in such a case of “heavy” atoms the effects of exotic molecule formation are not essential. The radiative cascade was considered within the framework of quantum mechanics whereas the collisions of exotic atoms in excited states with hydrogen were described by methods of classical mechanics. The yields for the K-series X-rays in pK − and \(p\bar p\) atoms have been calculated and compared with the experimental data.

X-ray fluorescence camera for imaging of iodine media in vivo

X-ray fluorescence (XRF) analysis is useful for measuring density distributions of contrast media in vivo. An XRF camera was developed for carrying out mapping for iodine-based contrast media used in medical angiography. Objects are exposed by an X-ray beam from a cerium target. Cerium K-series X-rays are absorbed effectively by iodine media in objects, and iodine fluorescence is produced from the objects. Next, iodine Kalpha fluorescence is selected out by use of a 58-microm-thick stannum filter and is detected by a cadmium telluride (CdTe) detector. The Kalpha rays are discriminated out by a multichannel analyzer, and the number of photons is counted by a counter card. The objects are moved and scanned by an x-y stage in conjunction with a two-stage controller, and X-ray images obtained by iodine mapping are shown on a personal computer monitor. The scan pitch of the x and y axes was 2.5 mm, and the photon counting time per mapping point was 2.0 s. We carried out iodine mapping of non-living animals (phantoms), and iodine Kalpha fluorescence was produced from weakly remaining iodine elements in a rabbit skin cancer.

Whole-body lifetime occupational lead exposure and risk of Parkinson's disease.

BackgroundSeveral epidemiologic studies have suggested an association between Parkinson’s disease (PD) and exposure to heavy metals using subjective exposure measurements.ObjectivesWe investigated the association between objective chronic occupational lead exposure and the risk of PD.MethodsWe enrolled 121 PD patients and 414 age-, sex-, and race-, frequency-matched controls in a case–control study. As an indicator of chronic Pb exposure, we measured concentrations of tibial and calcaneal bone Pb stores using 109Cadmium excited K-series X-ray fluorescence. As an indicator of recent exposure, we measured blood Pb concentration. We collected occupational data on participants from 18 years of age until the age at enrollment, and an industrial hygienist determined the duration and intensity of environmental Pb exposure. We employed physiologically based pharmacokinetic modeling to combine these data, and we estimated whole-body lifetime Pb exposures for each individual. Logistic regression analysis produced estimates of PD risk by quartile of lifetime Pb exposure.ResultsRisk of PD was elevated by > 2-fold [odds ratio = 2.27 (95% confidence interval, 1.13–4.55); p = 0.021] for individuals in the highest quartile for lifetime lead exposure relative to the lowest quartile, adjusting for age, sex, race, smoking history, and coffee and alcohol consumption. The associated risk of PD for the second and third quartiles were elevated but not statistically significant at the α = 0.05 level.ConclusionsThese results provide an objective measure of chronic Pb exposure and confirm our earlier findings that occupational exposure to Pb is a risk factor for PD.

Cascade Processes in Muonic Hydrogen Atoms

The QCMC scheme created earlier for cascade calculations in heavy hadronic atoms of hydrogen isotopes has been modified and applied to the study of cascade processes in the μp muonic hydrogen atoms. The distribution of μp atoms over kinetic energies has been obtained and the yields of K-series X-rays per one stopped muon have been calculated.

One approach for doublet deconvolution to improve reliability in spectra analysis for in vivo lead measurement

Calculation of lead concentration from K-series X-ray fluorescent studies uses a robust normalization technique based on the amplitude or area of the elastic signal. Parameter estimation of the elastic signal can be affected by the overlap of the K β2 line, especially for concentrations greater than 40 ppm where the K β2 amplitude can be greater than 1% of the elastic signal. We tested the combination of estimation by method of least moduli and doublet deconvolution. We found that the estimation of the area of the elastic signal is more robust to changes in the low-energy end of the region of interest with the combined method than with method of least-squares estimation and singlet processing. We recommend use of the combined method for creation of calibration curves at concentrations greater than or equal to 40 ppm.

Detection limits of heavy elements obtained with K-series x-rays induced by electron accelerator bremsstrahlung

Estimates of detection limits for elements with atomic number 69 ≤ Z ≤ 92 in an Al matrix were obtained for Kα characteristic fluorescence excitation by Al braking target bremsstrahlung in a 5 MeV electron accelerator. The electron energy varied from 1 to 5 MeV. Relationships were obtained between detection limit and electron energy and between detection limit and atomic number of defined elements for an electron energy of 2 MeV. The results show that the chosen method of analysis makes it possible to determine heavy element concentrations down to 10−8–10−9%, which allows the solution of a great number of problems in ecology, geology, geochemistry and industrial technology for pure material production. Copyright © 2000 John Wiley & Sons, Ltd.

Measurement of X-rays from muon to alpha sticking and fusion neutrons in solid/liquid D-T mixtures of high tritium concentration

We measured the yields of K-series X-rays from (αμ)+ ion formed by muon to alpha sticking as well as the yields and the disappearance rates of fusion neutrons in 3He-free solid and liquid D-T mixtures. The effective sticking probability ωs obtained by neutron measurement is much smaller than any theoretical values so far published, while the discrepancy in αμ X-ray yield seems less significant.

Energy-dispersive X-ray fluorescence spectrometry technique as an efficient monitoring tool for mercury contamination

This paper illustrates the useful early-warning role of the energy-dispersive X-ray fluorescence technique against a potential health hazard being posed by dumping effluents from an industrial unit involved in the manufacture of lead-batteries, in a nearby water-canal used for irrigation purposes by surrounding villages. These effluents were shown to contain mercury at a potentially unsafe level, resulting in timely initiation of necessary preventive measures. The standard fundamental parameter method was invoked for a quantitative estimation of the mercury (Hg) concentration. In addition, L-series (rather than the usual K-series) X-rays were used for excitation, mainly on account of the type of the available excitation source.

K-series X-rays from anti-protonic hydrogen and deuterium

Energies and yields of K-series X-rays from pp atoms have been measured with two gas scintillation proportional detectors at target gas densities of 0.25 and 0.92 ρ STP. Values for the strong interaction shift and width of the 1s state obtained from the X-ray spectra are compared with the predictions of a variety of theoretical models. Upper limits for the yield of K-series X-rays from p̄d atoms have also been obtained.

X-rays from anti-protonic hydrogen and deuterium

Antiprotons from the LEAR facility at CERN were stopped in targets of gaseous H 2 or D 2. Yields of L X-rays were measured. K-series X-rays from p-p atoms were observed. The measured shift and width for the 1s level are ΔE 1s = −0.73±0.15 keV. and Γ 1s = 0.85±0.39 keV.

THE CHARACTERISTIC X-RAY INTENSITY FACTORS OF THE PURE ELEMENT BULK SAMPLES

The K-series X-ray intensities of eight pure elements (from Al to Ge) and the L-series X-ray intensities of four pure elements (from Ni to Ge) excited by 15-30 keV electrons have been measured. Using the modified and simplified "full diffusion" electron diffusion model the ratios of the characteristic X-ray intensities) of these pure elements have been calculated. The back scattering effect is included in this model itself and the absorption correction factors are obtained from the stepped intensity-depth distribution derived from this model. Moreover the continuum fluorescence effect is also considered. The calculated values are in agreement with the experimental data, therefore the reliability of the model is verified.

Isotope effects in light pionic atoms

Direct comparison of the pionic K-series X-ray transitions for 16O/ 18O and 6Li/ 7Li has been made and a new measurement of the same transitions in 3He has been performed.

Precision determination of the difference of the charge radii of 16O and 18O

The difference of the rms radii of the charge distribution of the oxygen isotopes was determined by a relative measurement of the muonic K-series X-rays. It is r( 18O) − r( 16O) = (0.076 ± 0.005) fm .

Shift ofKx-ray lines associated with valency change and with isomorphous phase transitions in rare earths

Studies are reviewed that employ the effect of an anomalously strong shift of the fundamental K-series x-ray lines associated with a change in the number of 4f electrons in a given atom for investigating the phenomenon of variable valency in compounds of the rare-earth elements in general, and the so-called isomorphous phase transitions in these compounds in particular. The mechanism of the shift effect and its theory are described. The available data on the shifts of the K-lines of the different compounds of all the rare-earth elements (except promethium) are discussed. A summary table gives the valencies (including the anomalous ones), the occurrence of which has been proved by this method. Application of the K-shift method for studying isomorphous (or isostructural) transitions allows one to establish unambiguously that the mechanism of these transitions involves a change in the number of 4f electrons, and to measure the magnitude of these changes. The review concludes with a brief description of the principles and design of the required experimental apparatus-crystal diffraction spectrometers.