K-shell X-ray Research Articles

K-shell X-ray production cross sections in Ti by 0.3–1.0 MeV/u 12C and 28Si ions for heavy ion PIXE

An inhibiting factor in the implementation of heavy ion PIXE is that heavy ion X-ray production cross sections are not well known for many materials. This contribution reports on work carried out at iThemba LABS to measure X-ray production cross-sections in Ti thin films irradiated with 12C and 28Si ions within the 0.3–1.0MeV/u energy range. Experimental data are compared to predictions by the PWBA, SCA-UA and ECPSSR theories. For the C–Ti asymmetric collision, ECPSSR theory describes experiment fairly well, but fails for the nearly symmetric Si–Ti collision, even after correction for multiple ionisation effects. The SCA-UA calculations tend to agree with data only at low (<0.5MeV/u) energies for the lighter 12C incident ions, but like ECPSSR, fail in the case of 28Si projectiles. The PWBA predictions grossly overestimate experiment in both cases.

First-principles calculations of K-shell X-ray absorption spectra for warm dense nitrogen

X-ray absorption spectrum is a powerful tool for atomic structure detection on warm dense matter. Here, we perform first-principles molecular dynamics and X-ray absorption spectrum calculations on warm dense nitrogen along a Hugoniot curve. From the molecular dynamics trajectory, the detailed atomic structures are examined for each thermodynamical condition. The K-shell X-ray absorption spectrum is calculated, and its changes with temperature and pressure along the Hugoniot curve are discussed. The warm dense nitrogen systems may contain isolated nitrogen atoms, N2 molecules, and nitrogen clusters, which show quite different contributions to the total X-ray spectrum due to their different electron density of states. The changes of X-ray spectrum along the Hugoniot curve are caused by the different nitrogen structures induced by the temperature and the pressure. Some clear signatures on X-ray spectrum for different thermodynamical conditions are pointed out, which may provide useful data for future X-ray experiments.

Electron temperature measurements inside the ablating plasma of gas-filled hohlraums at the National Ignition Facility

The first measurement of the electron temperature (Te) inside a National Ignition Facility hohlraum is obtained using temporally resolved K-shell X-ray spectroscopy of a mid-Z tracer dot. Both isoelectronic- and interstage-line ratios are used to calculate the local Te via the collisional–radiative atomic physics code SCRAM [Hansen et al., High Energy Density Phys 3, 109 (2007)]. The trajectory of the mid-Z dot as it is ablated from the capsule surface and moves toward the laser entrance hole (LEH) is measured using side-on x-ray imaging, characterizing the plasma flow of the ablating capsule. Data show that the measured dot location is farther away from the LEH in comparison to the radiation-hydrodynamics simulation prediction using HYDRA [Marinak et al., Phys. Plasmas 3, 2070 (1996)]. To account for this discrepancy, the predicted simulation Te is evaluated at the measured dot trajectory. The peak Te, measured to be 4.2 keV ± 0.2 keV, is ∼0.5 keV hotter than the simulation prediction.

Validation of modelled imaging plates sensitivity to 1-100 keV x-rays and spatial resolution characterisation for diagnostics for the "PETawatt Aquitaine Laser".

Thanks to their high dynamic range and ability to withstand electromagnetic pulse, imaging plates (IPs) are commonly used as passive detectors in laser-plasma experiments. In the framework of the development of the diagnostics for the Petawatt Aquitaine Laser facility, we present an absolute calibration and spatial resolution study of five different available types of IP (namely, MS-SR-TR-MP-ND) performed by using laser-induced K-shell X-rays emitted by a solid silver target irradiated by the laser ECLIPSE at CEntre Lasers Intenses et Applications. In addition, IP sensitivity measurements were performed with a 160 kV X-ray generator at CEA DAM DIF, where the absolute response of IP SR and TR has been calibrated to X-rays in the energy range 8-75 keV with uncertainties of about 15%. Finally, the response functions have been modeled in Monte Carlo GEANT4 simulations in order to reproduce experimental data. Simulations enable extrapolation of the IP response functions to photon energies from 1 keV to 1 GeV, of interest, e.g., for laser-driven radiography.

XRF-measured bone lead (Pb) as a biomarker for Pb exposure and toxicity among children diagnosed with Pb poisoning

Childhood lead (Pb) poisoning remains a global issue, especially in industrial areas. In this study, 115 children with average age 5.7 years were recruited as either patient diagnosed with Pb poisoning or controls at Xinhua Hospital in China. The subjects’ bone Pb was measured with a K-shell X-ray fluorescence (KXRF) and a portable X-ray fluorescence (XRF) system. A significant correlation between KXRF bone Pb and blood Pb and portable XRF and KXRF measurements were observed. The half-life of blood-lead was calculated to be 9.96 ± 3.92 d. Our results indicate that bone is a useful biomarker for Pb in children.

Dosimetry for radiobiology experiments at GANIL

Mainly encouraged by the increasing application of ion beams for cancer treatment (hadron-therapy) including carbon beams, the use of heavy ion facilities for radiobiology is expanding rapidly today. As an alternative to dedicated centers for treatment and medical research, accelerators like GANIL offer the possibility to undertake such experiments.Since 20 years, CIMAP, reinforced 15 years ago by the biological host laboratory LARIA, has been receiving researchers in radiobiology and assisted them in performing experiments in different fields such as hadron-therapy, space radioprotection and fundamental biological and physico-chemical mechanisms. We present here a short description of the beam line and the on-line equipments that allow the automatic irradiation of up to 24 biological samples at once.We also developed an original on-line beam monitoring procedure for low ion flux (low dose rates) based on the measurement of the K-shell X-rays emitted from a thin iron foil. This detector is calibrated on an absolute scale before each experiment by counting etched tracks on an irradiated CR39 polymer plate. We present the performances and limits of this method and finally give typical fluence (dose) uncertainties for a standard irradiation in radiobiology.

Angular distributions of differential X-ray production cross sections for Cu and Ta in photoionization

Abstract The characteristic K-shell X-ray emission of Cu and L X-rays of Ta in photoionization has been measured at excitation energy of 15.9 keV. The differential X-ray production cross sections of Kα and Kβ for Cu and Lα, Lβ1, Lβ2, Lγ1 for Ta are derived at emission angles ranging from 100° to 150°. The ratio of Kβ and Kα X-ray production cross sections, Kβ/Kα, is calculated for Cu and it is found to be consistent with other work even at different incident energy. While the ratios of Lα/Lβ, Lα/Lγ1 and Lβ/Lγ1 for Ta are found to be different with other results at different excitation energy. The reasons giving rise to this discrepancy are clarified with thorough analysis.

X-ray emission from 424-MeV/u C ions impacting on selected target**Project supported by the National Basic Research Program of China (Grant No. 2010CB832902), the National Natural Science Foundation of China (Grant Nos. 11505248, 11375034, U1532263, 11275241, 11205225, 11105192, and 11275238), and the Scientific Research Program of Education Bureau of Shaanxi Province, China (Grant No. 15JK1793).

The K-shell x-rays of Ti, V, Fe, Co, Ni, Cu, and Zn induced by 424-MeV/u C6+ ion impact are measured. It is found that the K x-ray shifts to the high energy side and the intensity ratio of Kβ/Kα is larger than the atomic data, owing to the L-shell multiple-ionization. The x-ray production cross sections are deduced from the experimental counts and compared with the binary encounter approximation (BEA), plane wave approximation (PWBA) and energy-loss Coulomb-repulsion perturbed-stationary-state relativistic (ECPSSR) theoretical predictions. The BEA model with considering the multiple-ionization fluorescence yield is in better consistence with the experimental results. In addition, the cross section as a function of target atomic K-shell binding energy is presented.

K-shell X-ray production in Silicon (Z2 = 14) by (1 ⩽ Z1 ⩽ 53) slow ions

K-shell X-ray emission of Silicon induced by near-Bohr-velocity ions was systematically investigated in collision systems for which the ratio of projectile-to-target atomic numbers (Z1/Z2) ranged from 0.07 to 3.79. The results show that, in asymmetric collisions, the measured K-shell X-ray production cross sections of Silicon fit very well with the predictions of different direct ionization models depending on the atomic number of projectile. In the case of near-symmetric collisions (Z1/Z2∼1), an obvious enhancement of the X-ray production cross section was observed, which can be attributed to the vacancy transfer within the framework of quasi-molecular model.

Vanadium K-shell X-ray emission induced by xenon ions at near the Bohr velocity

The X-ray emission spectra produced by 2.4-6.0 MeV Xe20+ ions impacting on vanadium surface were measured. The V K-shell X-ray production cross sections were extracted from the experimental yield data and compared with the theoretical predictions of the binary encounter approximation (BEA), the plane wave born approximation (PWBA), and the energy-loss coulomb-repulsion perturbed-stationary-state relativist (ECPSSR). In order to predict reasonably the inner-shell ionization induced by highly charged heavy ions during the asymmetric collisions at near the Bohr velocity, the corrections of BEA model are discussed. It is found that the X-ray production cross section induced by highly charged heavy ions moving at near the Bohr velocity is on the magnitude of 1 barn, which is almost four orders of magnitude larger than that induced by proton. The ECPSSR, which is regarded as the best model to simulate the inner-shell ionization by light ions, may underestimate the experimental data at least three orders of magnitude. The PWBA model presents a prediction to the results on an order of magnitude better than the ECPSSR simulation, but gives a worse tendency than the BEA model. The BEA calculations, corrected both by Coulomb repulsion and effective nuclear charge, present the best agreement with the experimental results. It is proposed, that in the energy region near the Bohr velocity, during the asymmetric collisions of Xe20+ ions with V atoms, the K-shell electron of V is ionized by direct ionization, and that it can be described by the binary encounter process between the xenon ions and the bound electrons. The X-ray production cross section can be simulated by BEA model, but the corrections of Coulomb repulsion and effective nuclear charge must be considered.

Feasibility of measuring arsenic and selenium in human skin using in vivo x-ray fluorescence (XRF)—a comparison of methods

In recent years, in vivo measurement systems of arsenic in skin by K-shell x-ray fluorescence (XRF) have been developed, including one which was applied in a pilot study of human subjects. Improved tube-based approaches suggest the method can be further exploited for in vivo studies. Recently, it has been suggested that selenium deficiency is correlated with arsenic toxicity. A non-invasive measurement of both elements could therefore be of potential interest. The main aim of this current study was to evaluate and compare the performance of an upgraded portable XRF system and an advanced version of the benchtop XRF system for both selenium and arsenic. This evaluation was performed in terms of arsenic and selenium Kα detection limits for a 4W gold anode Olympus InnovX Delta portable analyzer (40 kVp) in polyester resin skin-mimicking phantoms. Unlike the polychromatic source earlier reported in the literature, the benchtop tube-based technique involves monochromatic excitation (25 W silver anode, manufactured by x-ray optics, XOS) and a higher throughput detector type. Use of a single exciting energy allows for a lower in vivo dose delivered and superior signal-noise ratio. For the portable XRF method, arsenic and selenium minimum detection limits (MDLs) of 0.59 ± 0.03 ppm and 0.75 ± 0.02 ppm respectively were found for 1 min measurement times. The MDLs for arsenic and selenium using the benchtop system were found to be 0.35 ± 0.01 ppm and 0.670 ± 0.004 ppm respectively for 30 min measurement times. In terms of a figure of merit (FOM), allowing for dose as well as MDL, the benchtop system was found to be superior for arsenic and the two systems were equivalent, within error, for selenium. We shall discuss the performance and possible improvements of each system, their ease of use and potential for field application.

K β to K α X-ray intensity ratios and K to L shell vacancy transfer probabilities of Co, Ni, Cu, and Zn

The K to L shell total vacancy transfer probabilities of low Z elements Co, Ni, Cu, and Zn are estimated by measuring the Kβ to Kα intensity ratio adopting the 2π-geometry. The target elements were excited by 32.86 keV barium K-shell X-rays from a weak 137Cs γ-ray source. The emitted K-shell X-rays were detected using a low energy HPGe X-ray detector coupled to a 16 k MCA. The measured intensity ratios and the total vacancy transfer probabilities are compared with theoretical results and others’ work, establishing a good agreement.

K-shell X-ray production cross sections of Ni induced by protons, alpha-particles, and He+

The proton, alpha-particle, and He+ induced X-ray emissions of Ni were measured on mono-elemental thin films in order to obtain the K-shell X-ray production cross section in the energy range of 0.7–2.0MeV for protons, 4.0–6.5MeV for alpha-particles, and 3.0–4.0MeV for He+. The proton-induced X-ray production cross section for Ni agreed well with the theoretical values, endorsing the quality of the measurements. The X-ray production cross section induced with alpha-particles is in good agreement with ECPSSR theory in the complete range of energies, while for He+ that quantity is systematically below. Kβ/Kα ratios were evaluated and compared with experimental and theoretical values.

A Review of the Gas-Puff &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$Z$ &lt;/tex-math&gt;&lt;/inline-formula&gt;-Pinch as an X-Ray and Neutron Source

Fisher and collaborators at the University of California, Irvine, invented the gas puff $Z$ -pinch in the late 1970s using a 200-kA generator. The implementation of gas puffs as a copious source of X-rays has encountered major challenges, such as disruptive instabilities and the quest for long implosion times. During nearly four decades of experimental and theoretical efforts, those challenges have been successfully met to a great extent. This success is a result of the efforts of a large number of researchers. Today, the gas-puff $Z$ -pinch has evolved into a powerful source of X-rays and neutrons, and is fielded on multi-Mega-Ampere generators. The basic force imploding a pinch is straightforward, but the operation of a gas puff requires specialized hardware and a thorough understanding of the radiation physics involves magnetohydrodynamics coupled with nonequilibrium ionization kinetics. The goal of this review is to document the experiments and theory that have led to the success of the gas puff as a K-shell X-ray and neutron source. Consequently, this review takes a historical approach to the covered material, but also provides a broad introduction to relevant scientific concepts.

The potential of L-shell X-ray fluorescence CT (XFCT) for molecular imaging.

X-ray fluorescence CT (XFCT), a novel modality proposed for high-sensitivity high-resolution molecular imaging of probes labelled with a high atomic-number element, has been performed with high-energy K-shell X-rays. XFCT performed with low-energy L-shell X-rays could, in principle, result in an increase of XFCT imaging sensitivity; however, the significant L-shell X-ray attenuation limits its use for imaging of small objects. This commentary discusses the advantages and drawbacks of L-shell XFCT imaging.

Bright x-ray stainless steel K-shell source development at the National Ignition Facility

High x-ray conversion efficiency (XRCE) K-shell sources are being developed for high energy density experiments for use as backlighters and for the testing of materials exposed to high x-ray fluxes and fluences. Recently, sources with high XRCE in the K-shell x-ray energy range of iron and nickel were investigated at the National Ignition Facility (NIF). The x-ray conversion efficiency in the 5–9 keV spectral range was determined to be 6.8% ± 0.3%. These targets were 4.1 mm diameter, 4 mm tall hollow epoxy tubes having a 50 μm thick wall supporting a tube of 3 to 3.5 μm thick stainless steel. The NIF laser deposited ∼460 kJ of 3ω light into the target in a 140 TW, 3.3 ns square pulse. The absolute x-ray emission of the source was measured by two calibrated Dante x-ray spectrometers. Time resolved images filtered for the Fe K-shell were recorded to follow the heating of the target. Time integrated high-resolution spectra were recorded in the K-shell range.

First-principles calculation of principal Hugoniot and K-shell X-ray absorption spectra for warm dense KCl

Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics (FPMD) method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. It is shown that approximate description of ionization in FPMD has small influence on Hugoniot pressure due to mutual compensation of electronic kinetic pressure and virial pressure. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the 3p electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter.

Nondestructive rare earth element imaging of fish teeth from deep-sea sediments

X-ray fluorescence computed tomography is an emerging imaging modality that allows for the nondestructive reconstruction of the internal distribution of elements within a sample. The common use of X-ray excitation energy (up to approximately 20 keV) has necessitated the use of l-shell fluorescence for heavy elements. In this study, based on high energy X-ray at BL13W1 of the Shanghai Synchrotron Radiation Facility, we employed high-energy excitation for tomographic imaging of the heavy metals (rare earth elements) in fish teeth from deep-sea sediments on the micrometer scale using K-shell X-ray fluorescence. The virtual cross-sectional distribution of La, Ce, Pm, Pr, Nd, and Sm were obtained, thereby providing a feasible approach for analyzing the enrichment mechanism of rare earth elements. Copyright © 2015 John Wiley & Sons, Ltd.

The effect of gradients at stagnation on K-shell x-ray line emission in high-current Ar gas-puff implosions

Argon gas puffs have produced 330 kJ ± 9% of x-ray radiation above 3 keV photon energy in fast z-pinch implosions, with remarkably reproducible K-shell spectra and power pulses. This reproducibility in x-ray production is particularly significant in light of the variations in instability evolution observed between experiments. Soft x-ray power measurements and K-shell line ratios from a time-resolved spectrum at peak x-ray power suggest that plasma gradients in these high-mass pinches may limit the K-shell radiating mass, K-shell power, and K-shell yield from high-current gas puffs.

K-shell X-ray energy and width resonances of nitrogen and oxygen atoms

Abstract Energy positions and width resonances of nitrogen and oxygen atoms are reported using the Screening Constant per Unit Nuclear Charge (SCUNC) method. Calculations are performed for the 1s2s 2 2p 3 [ 5,3 S°] n p 4 P° and for the 1s2s 2 2p 3 [ 3 D°, 3 P°] n p 4 P° core-excited autoionizing resonances of atomic nitrogen converging respectively to the 5 S° and 3 S°, and to the 3 D° and 3 P° series limits of N + and for the 1s2s 2 2p 4 [ 2,4 P°] n p 3 P° Rydberg series converging to the 1s −1 4 P° and 1s −1 2 P° series limits of atomic oxygen. The results obtained agree very well with available high-resolution K -edge spectra of atomic nitrogen and of atomic oxygen. The present calculations provide benchmark data for X-ray spectra in connections with the modeling of astrophysical systems.