The xraylib library for X-ray-matter interactions. Recent developments

This white paper, directed to the Stars and Stellar Evolution panel, has three objectives: 1) to provide the Astro2010 Decadal Survey with a vista into the goals of the nuclear physics and nuclear astrophysics community; 2) to alert the astronomical community of joint opportunities for discoveries at the interface between nuclear physics and astronomy; and 3) to delineate efforts in nuclear physics and describe the observational and theoretical advances in astrophysics necessary to make progress towards answering the following questions in the Nuclear Science 2007 Long Range Plan: 1) What is the origin and distribution of the elements? 2) What are the nuclear reactions that power stars and stellar explosions? 3) What is the nature of dense matter? The scope of this white paper concerns the specific area of "low energy" nuclear astrophysics We define this as the area of overlap between astrophysics and the study of nuclear structure and reactions Of the questions listed above, two -- What is the origin of the elements? and What is the nature of dense matter? -- were specifically listed in the National Academies Study, "Connecting Quarks with the Cosmos"

Nuclei in the Cosmos

A small number of naturally occurring, proton-rich nuclides (the p-nuclei) cannot be made in the s- and r-processes. Their origin is not well understood. Massive stars can produce p-nuclei through photodisintegration of pre-existing intermediate and heavy nuclei. This so-called γ-process requires high stellar plasma temperatures and occurs mainly in explosive O/Ne burning during a core-collapse supernova. Although the γ-process in massive stars has been successful in producing a large range of p-nuclei, significant deficiencies remain. An increasing number of processes and sites has been studied in recent years in search of viable alternatives replacing or supplementing the massive star models. A large number of unstable nuclei, however, with only theoretically predicted reaction rates are included in the reaction network and thus the nuclear input may also bear considerable uncertainties. The current status of astrophysical models, nuclear input and observational constraints is reviewed. After an overview of currently discussed models, the focus is on the possibility to better constrain those models through different means. Meteoritic data not only provide the actual isotopic abundances of the p-nuclei but can also put constraints on the possible contribution of proton-rich nucleosynthesis. The main part of the review focuses on the nuclear uncertainties involved in the determination of the astrophysical reaction rates required for the extended reaction networks used in nucleosynthesis studies. Experimental approaches are discussed together with their necessary connection to theory, which is especially pronounced for reactions with intermediate and heavy nuclei in explosive nuclear burning, even close to stability.

/pdf/constraining-the-astrophysical-origin-of-the-p-nuclei-1mykm0l1zh.pdf

Constraining the astrophysical origin of the p-nuclei through nuclear physics and meteoritic data

Laser-induced breakdown spectroscopy (LIBS) has emerged in the past ten years as a promising technique for analysis and characterization of the composition of a broad variety of objects of cultural heritage including painted artworks, icons, polychromes, pottery, sculpture, and metal, glass, and stone artifacts. This article describes in brief the basic principles and technological aspects of LIBS, and reviews several test cases that demonstrate the applicability and prospects of LIBS in the field of archaeological science.

Laser-induced breakdown spectroscopy (LIBS) in archaeological science--applications and prospects.

https://oem.bmj.com/content/oemed/26/3/249.1.full.pdf

Dangerous Properties of Industrial Materials

The proton induced Kα X-ray emission spectra of pure and some compound targets of sulfur were measured with a crystal spectrometer in Johansson geometry, which enables energy resolution below the natural linewidth of the measured Kα line. From these measurements the absolute energies of the S-Kα 1,2 lines were experimentally determined. In addition, the energies of the KαL 1 X-ray satellite lines, appearing in these spectra as a result of the radiative decay of atomic states with one hole in the K shell and one in the L subshells, were also measured. The measured Kα diagram and satellite line energies depend crucially on the S chemical state. The measured diagram line energies, as well as their relative intensity ratios obtained from the X-ray spectra of different S compounds, allow the deconvolution of X-ray spectra of mixed targets containing two different S compounds and the accurate determination of their mass ratio. Finally, the proton induced S-Kα X-ray spectrum from an aerosol sample was collected and the measured energies of the Kα 1,2 lines were used to specify the chemical state of S in the aerosol as a sulfate ([SO 4 ] 2− ). In conclusion, the results of the present paper demonstrate that the S-Kα 1,2 emission energies depend on the S chemical state and, therefore, their determination allows the chemical state speciation of S in a given sample.

Chemical state analysis of sulfur in samples of environmental interest using high resolution measurement of Kα diagram line

Within the framework of the project “Jewelmed” (ICA3-1999-10020), the chemical composition of 34 gold and four silver jewels was examined. These jewels belong to the Benaki museum's collection in Athens, Greece and are dating from the 7th to the 1st century BC. The compositional analysis of the jewels was performed by means of a “home-made” portable X-ray fluorescence (XRF) spectrometer. The XRF results have shown that the gold jewels can be categorized in two groups, which include artifacts made by native and by high purity gold, respectively. For the silver jewels the results have provided interesting information regarding the manufacturing technology, the authenticity of the jewels and the raw materials used. The potential and the limitations of the XRF technique, applied in the chemical analysis of archaeological metal artifacts, are also discussed.

A compositional study of a museum jewellery collection (7th–1st BC) by means of a portable XRF spectrometer

Determination of uranium in human urine by total reflection X-ray fluorescence

The differential cross-sections of the 12 C(d, p 0 ) 13 C reaction (applied to the determination of the depth distribution of carbon in near-surface layers of materials) were determined in the projectile energy region E d, lab  = 900–2000 keV (in steps of 25 keV) and for detector angles between 135° and 170° (in steps of 5°) using as targets 99.9% purity self-supported natural carbon (98.9% 12 C–1.1% 13 C) foils of nominal thickness ca. 1 × 10 18  at/cm 2 . The overall error in the absolute differential cross-section measurements varied between ∼6% and 22%. The results were compared with already published data and the occurring differences were explained.

A detailed study of the 12C(d, p0)13C reaction at detector angles between 135° and 170°, for the energy range Ed, lab = 900–2000 keV

A high-energy resolution crystal spectrometer in Johansson geometry, which allows energy resolution below the natural linewidth of the Ka diagram lines, was employed in the measurements of proton-induced Ka x-ray emission spectra of titanium and sulfur pure and compound targets. The results demonstrate a clear dependence of the Ka energy shifts on the chemical state of the element in the sample. This dependence permits the chemical state speciation of low-Z elements in an unknown sample by employing high-resolution PIXE measurements of the Ka line. The potential of the technique in speciation studies is demonstrated in the case of an aerosol sample. The analysis of the Ka line obtained from the high-energy resolution proton-induced S Ka x-ray spectrum allowed the identification of sulfur in the aerosol sample as sulfate ([SO 4 ] 2- ).

Ch. Zarkadas

Papers

Chemical state analysis of sulfur in samples of environmental interest using high resolution measurement of Kα diagram line

A compositional study of a museum jewellery collection (7th–1st BC) by means of a portable XRF spectrometer

Determination of uranium in human urine by total reflection X-ray fluorescence

A detailed study of the 12C(d, p0)13C reaction at detector angles between 135° and 170°, for the energy range Ed, lab = 900–2000 keV

Chemical state analysis employing sub‐natural linewidth resolution PIXE measurements of Kα diagram lines