X-ray florescence analysis is an excellent non-destructive tool for analysing the elemental composition of materials in a wide range of works of art. The Department of Dosimetry and Application of ...Ionising Radiation at CTU-FNSPE has used radionuclide or X-ray tube excited energy dispersive X-ray fluorescence for many kinds of artefacts, including frescos, paintings, manuscripts, metal sculptures and other objects, ceramics, jewellery, various archaeological finds, etc. The method used is more or less “traditional”, i.e., semiconductor spectrometry of excited X-rays, with some optional choices—capillary optics for collimation of exciting beams and two-dimensional scanning. The “hardware” complex is supplemented by techniques for estimating the depth distribution of measured elements, for suppressing surface effects, for in situ non-contact measurements, etc. Extending the measurable range to lighter elements and decreasing the detection limits is one of the achievements that has been attained by improving the instrumentation and techniques that are used. This paper gives a brief review of works carried out at the Department of Dosimetry and Application of Ionising Radiation at CTU-FNSPE.
► X-ray fluorescence analysis as a non-destructive tool for investigating various artefacts. ► Improving instrumentation and experimental techniques for analysis. ► Extending the measurable range to lighter elements and decreasing the detection limits.
The presence of heavy chemical elements in old pigments is possible to identify in historical paintings using X-ray fluorescence analysis (XRF). This is a non-destructive analytical method frequently ...used in examination of objects that require in situ analysis, where it is necessary to avoid damaging the object by taking samples. Different modalities are available, such as microanalysis, scanning selected areas, or depth profiling techniques. Surface scanning is particularly profitable since 2D element distribution maps are much more understandable than the results of individual analyses. Information on the layered structure of the painting can be also obtained by handheld portable systems. Results presented in our paper combine 2D element distribution maps obtained by scanning analysis, and depth profiling using conventional XRF. The latter is very suitable for objects of art, as it can be evaluated from data measured with portable XRF device. Depth profiling by conventional XRF is based on the differences in X-ray absorption in paint layers.
The XRF technique was applied for analysis of panel paintings of the Master of the St George Altarpiece who was active in Prague in the 1470s and 1480s. The results were evaluated by taking micro-samples and performing a material analysis.
•Panel paintings of the Master of the St George Altarpiece, Prague 15th century.•The depth of the layer was predicted by Kα/Kβ technique.•Comparison with 2D scanning X-ray fluorescence analysis was made.•Micro-destructive elemental analysis was used as a reference method.•Further work with reference pigments and Monte Carlo simulation is possible.
After having announced the statistically significant observation (5.6σ) of the new exotic πK atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding ...atom lifetime, based on the full πK data sample: τ=(5.5−2.8+5.0)×10−15 s. By means of a precise relation (≈1%) between atom lifetime and scattering length, the following value for the S-wave isospin-odd πK scattering length a0−=13(a1/2−a3/2) has been derived: |a0−|=(0.072−0.020+0.031)Mπ−1.
The observation of hydrogenlike πK atoms, consisting of π^{-}K^{+} or π^{+}K^{-} mesons, is presented. The atoms are produced by 24 GeV/c protons from the CERN PS accelerator, interacting with ...platinum or nickel foil targets. The breakup (ionization) of πK atoms in the same targets yields characteristic πK pairs, called "atomic pairs," with small relative momenta Q in the pair center-of-mass system. The upgraded DIRAC experiment observed 349±62 such atomic πK pairs, corresponding to a signal of 5.6 standard deviations. This is the first statistically significant observation of the strange dimesonic πK atom.
The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogenlike π^{+}π^{-} atoms, produced by protons hitting a beryllium target. A part of these atoms ...crossed the gap of 96 mm between the target and a 2.1 μm thick platinum foil, in which most of them dissociated. Analyzing the observed number of atomic pairs, n_{A}^{L}=436_{-61}^{+157}|_{tot}, the lifetime of the 2p state is found to be τ_{2p}=(0.45_{-0.30}^{+1.08}|_{tot})×10^{-11} s, not contradicting the corresponding QED 2p state lifetime τ_{2p}^{QED}=1.17×10^{-11} s. This lifetime value is three orders of magnitude larger than our previously measured value of the π^{+}π^{-} atom ground state lifetime τ=(3.15_{-0.26}^{+0.28}|_{tot})×10^{-15} s. Further studies of long-lived π^{+}π^{-} atoms will allow us to measure energy differences between p and s atomic states and so to discriminate between the isoscalar and isotensor ππ scattering lengths with the aim to check QCD predictions.
Use of MCNP code in energy dispersive X-ray fluorescence Trojek, T.; Čechák, T.
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
October 2007, 2007-10-00, Letnik:
263, Številka:
1
Journal Article
Recenzirano
Monte Carlo simulations enable us to improve the applicability of analytical techniques based on emission of characteristic radiation. In particular, the MCNP4C2 code was tested for interpretation of ...measured data obtained with the use of energy dispersive X-ray fluorescence analysis. This paper describes MCNP outputs and compares them with the results of analytical calculations or experiments. Then the application of Monte Carlo simulations to the prediction of measurement results is shown, and the MCNP results are verified.
The results of a search for hydrogen-like atoms consisting of π∓K± mesons are presented. Evidence for πK atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been ...seen in terms of characteristic πK pairs from their breakup in the same target (178±49) as well as in terms of produced πK atoms (653±42). Using these results, the analysis yields a first value for the πK atom lifetime of τ=(2.5−1.8+3.0) fs and a first measurement of the S-wave isospin-odd πK scattering length |a0−|=13|a1/2−a3/2|=(0.11−0.04+0.09)Mπ−1 (aI for isospin I).
This paper deals with difficulties in making a quantitative evaluation with the use of in-situ X-ray fluorescence analysis. Incorrect sample positioning and some properties of the surface of the ...sample have a negative effect on quantitative analyses. Monte Carlo simulations with the MCNPX code were used for classifying the disturbing effects that must be taken into account in-situ X-ray fluorescence analysis. The relation between the count rate and variations in the geometrical arrangement has been studied. The Monte Carlo calculations provide an interpretation of effects that had been ascertained experimentally and also imply the range of uncertainties in the count rates. The results enable us to find an optimal set-up for a given in-situ measurement.
After observing and investigating the double-exotic (a double-exotic atom is a bound system, in which both oppositely charged components are unstable particles like μ,π,K,…) π+π− atom with the ground ...state lifetime τ of about 3×10−15 s, the upgraded DIRAC experiment at the CERN PS accelerator observes for the first time long-lived states of the same atom with lifetimes of about 10−11 s and more. The number of characteristic pion pairs resulting from the breakup (ionisation) of long-lived π+π− atoms amounts to 436±61, corresponding to a signal-to-error ratio of better than 7 standard deviations. This observation opens a new possibility to measure energy differences between p and s atomic states and so to determine ππ scattering lengths.
Lu3Al5O12 (LuAG) films were grown from the BaO–B2O3–BaF2 flux on LuAG and YAG substrates using the liquid phase epitaxy method (LPE). They were doped with Pr3+, Sc3+, and eventually still with Ce3+ ...ions. Photoelectron yield, its time dependence, and energy resolution were measured under α-particle excitation. A sample of the Czochralski-grown bulk LuAG:Pr single crystal was measured as a reference. The best performing epitaxial films had low Sc3+ concentration and appeared comparable or superior to the Czochralski-grown crystal in terms of photoelectron yield and relative intensity of the fast component of scintillation response. High concentration of Sc3+ ions results in slowdown of response and lower photoelectron yield. Some samples with lower photoelectron yield than that of the Czochralski-grown crystal did exhibit better energy resolution.
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