Study of the provenance of Belgian Merovingian garnets by PIXE at IPNAS cyclotron

Recent archaeological excavation in Belgium reveals one of the biggest Merovingian necropolis ever found in this country. This necropolis contains 436 tombs with a period of occupation of almost two centuries. Some of these tombs were very rich, especially two of them, and delivered an important funerary furniture. About 60 jewels inlaid with red garnets have been found, most of them of “cloisonné” style (namely about 450 garnets). The new extracted beam set-up of the IPNAS cyclotron (University of Liège, Belgium) has been improved in order to analyse by PIXE these garnets and try to determine their provenance. These analyses reveal that the garnets found in the necropolis of Grez-Doiceau are very homogeneous in composition (almandine garnets) and are coming almost from a unique source.These results have been compared to previous studies led in France during these past five years. This permits to identify the source of almandine garnet situated in India and to highlight differences in garnet supply between France and Belgium in Merovingian times.     

Particle induced X-ray emission (PIXE) analyses on metal samples with structured surfaces

The X-ray yields obtained in PIXE measurements from metal samples with bent or relief surface have been investigated experimentally and by a computer simulation. It was found, that in the fundamental parameter method correct analytical results will be obtained, if two conditions are fulfilled: (1) the inclination of the tangential plane of the bent surface at the point where the ion beam hits this surface has to be known; and (2) the radius of curvature of the surface structure must be larger than 3 to 4 times the ion beam radius used.     

Experimental and theoretical calibration of a PIXE setup for K and L X-rays

K and L line calibration has been performed for a PIXE setup by the independent use of experimental and theoretical methods. In the former case, thin film standards of known thicknesses were applied, while in the latter one cross section values were derived from different theoretical models.Programs REV5S and PIXEKL developed here were used for spectrum evaluation and concentration determination, respectively. They proved to be reliable and especially appropriate for routine serial evaluation of spectra measured on samples of nearly identical matrices.As a result of the work, an accurate calibration of the setup has been obtained and it was shown that experimental and theoretical techniques used lead to calibration curves which fit each other reasonably well.     

Routine PIXE at the University of Aarhus

The setup currently in use at the Aarhus PIXE facility is described, with the emphasis on features necessary for fast and reliable routine operation.     

A setup for radiation-thermal investigations

L. Ya. Karpov Physicochemical Scientific Research Institute. Translated from Atomnaya Énergiya, Vol. 72, No. 3, pp. 288–290, March, 1992.     

A quantitative basis for hair analysis using PIXE

The PIXE technique offers the possibility of scanning a single hair strand longitudinally with a millimetre proton beam for trace elements. However, the accuracy of the method has been questioned since the quantification of the mass concentration has been a serious problem. In this paper a specific beam-hair-detector geometry is assumed, and the correction factor accounting for the proton energy loss and the X-ray absorption in a regular hair is calculated. 43 hair segments from 8 individuals, ranging from 45 to 110 μm in in diameter were analyzed giving a mean value of 4.32% (standard deviation 0.25%) for sulphur, and a mean value of 149 ppm (standard deviation 35 ppm) for zinc. It is shown that the correction is important not only for the determination of the absolute elemental concentrations but also for the determination of their relative longitudinal distributions. The secondary corrections accounting for the inhomogeneous elemental distribution over the cross section and the irregular shape and/or the differing mass density of a hair are also calculated. It is concluded that the accuracy and precision of the PIXE method does not become considerably lower when it is applied to single hair strands, and accuracy and precision below 10% may be reached by implementing the procedure described.     

Thick target PIXE analyses of the elemental distributions across the surface and inside human fingernails

The energy dispersive spectrometry of thick target proton-induced X-ray emission (thick target PIXE) was used to determine the distributions of 11 elements (S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn) across the surface and at a certain depth inside human fingernails. The respective profiles are discussed and preliminary interpretations are given. The results are compared with data from other authors.     

用PIXE研究经络穴位元素浓度的异常分布

采用外束质子激发Ｘ荧光发射技术测定了与穴位位置相对应的结缔组织结构中元素浓度的特异性分析,初步发现,穴位区富集有Ｃａ,Ｐ,Ｋ,Ｆｅ,Ｚｎ等元素。     

A 40 keV cyclotron for radioisotope dating

We have built and begun testing a small low energy negative ion cyclotron for direct detection of ¹⁴C. At present, the cyclotron is operated in a high resolution mode at the 31st harmonic, with 1–2 kV on the dees. The high harmonic and a minimum number of turns of approximately 100, should give a fwhm mass resolution of about $\text{1}\text{30000}$ — sufficient to suppress the background from molecular ions such as ¹³CH^?. Background such as scattered ions of ¹²C^? and ¹³C^? should be totally suppressed by the cyclotron acceleration process. (At the 88″ cyclotron at LBL we found that ions only 1% off-resonance are suppressed by more than a factor of 10¹⁷.) A miniature Cs sputter source located at the center of the cyclotron is expected to provide more than 1 μA of negative carbon ions. Negative ions are used in order to eliminate the interference from ¹⁴N. Unlike high energy cyclotrons, focussing is obtained solely from the axial components of the accelerating electric field. The magnetic field is kept flat to within 1 part in 10⁴ in order to maintain exact isochronism throughout the several thousand accelerating rf cycles. The low final energy of 40 keV eliminates any danger from radiation or need for shielding, and the final orbit radius of only 10.5 cm, reduce the size and cost of the machine to that of conventional mass spectrometers.     

Cell irradiation setup and dosimetry for radiobiological studies at ELBE

The radiation source ELBE delivers different types of secondary radiation, which is used for cell irradiation studies in radiobiological research. Thereby an important issue is the determination of the biological effectiveness of photon radiation as a function of photon energy by using low-energetic, monochromatic channeling radiation (10-100 keV) and high-energetic bremsstrahlung (up to 40 MV). Radiobiological studies at the research facility ELBE demand special technical and dosimetric prerequisites. Therefore, a cell irradiation system (CIS) has been designed, constructed and installed at the beam line. The CIS allows automatic irradiation of a larger cell sample number and the compensation of spatial inhomogeneity of the dose distribution within the beam spot. The recently introduced GafChromic^® EBT radiochromic film model has been used to verify the cell irradiation dose deposition achieving a dose uncertainty of <5%. Both, the installed cell irradiation system and the developed dosimetric procedure based on the use of the EBT film have been experimentally tested at ELBE. The biological effectiveness of 34 MV bremsstrahlung with respect to 200 kV X-rays from a conventional X-ray tube has been determined. An RBE value of 0.75 has been measured in good agreement with literature.     

An improved beam chopper setup at the Budapest PGAA facility

Modulating neutron beams with a beam chopper enables the investigation of time-dependent processes following neutron capture, such as emission of decay-gamma-radiation from short-lived nuclides. For this purpose, a redesigned beam chopper and controller electronics have been recently installed at the PGAA facility of the Budapest Research Reactor. The new electronics provides accurate timing and better control of routing of the signals. The upgraded instrumentation is capable of recording the events in the beam-on and beam-off phases in parallel. Simplified formulae were derived to relate the areas of prompt- and decay peaks to the partial γ-ray production cross-sections. Finally, preliminary results obtained with Ag- and Na-containing targets are presented.     

用于超灵敏小型迴旋加速器质谱计的微通道板粒子探测器

我们制造并测试了为超灵敏小型通旋加速器质谱计研究设计的单粒子探测系统。探测器由Al_2O_3打拿极、微通道板电子倍增器和阳极三部分组成。入射离子沿80°角方向轰击打拿极,以0.8电子/keV的转换系数产生数目与离子能量成正比的次级电子,每个电子在不同的通道管内单独放大至饱和,阳极收集的电荷数与入射离子能量成正比。用选择甄别阈的方法可以有效地将离子计数与本底分开。从实测数据外推到40keV K或Ar离子时可知:相应于90％计数效率的本底率为10~(-3)/S。探测系统的能量分辨△E=6.5keV,可以用于测量极低能量的重离子谱。     

Quantitative PIXE analyses of ferromanganese oxide deposits from different locations of the Indian Ocean and a deposit from the Pacific Ocean

The present studies on ferromanganese nodules and encrustations from the Indian Ocean and a sediment from the Pacific ocean, were carried out to investigate the role of Mn and Fe in the uptaking of various trace elements from seawater. The Indian Ocean samples comprised eight iron rich ferromanganese nodules and four ferromanganese encrustations, out of which two are from Mid Indian Ocean Ridge (MIOR) and one each from Afanasiy Nikitin seamount and topographically elevated region. The Pacific Ocean sample was a metalliferrous sediment from Lau Basin. The Proton Induced X-ray Emission (PIXE) measurements were carried out on all the samples using 3 MeV proton beam from a 3 MV Pelletron accelerator for quantitative multielemental analysis. The spectral data were analysed using GUPIX software. Quantitative estimate of nearly 21 elements, e.g., K, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Sr, Y, Zr, Nb, Mo, Ba, Tl, Pb, and Bi have been made. The classification of the deposits into hydrogenous and hydrothermal types was carried out on the basis of their Mn/Fe ratios and subsequently, the distribution of various minor and trace elements were studied. The growth rate of these deposits are estimated. The findings show that, the concentrations of various elements in hydrogenous deposits are higher compared to that in hydrothermal ones. The reason for this behaviour is attributed to suitable physico-chemical oceanic conditions prevailing at the depositional sites and the growth rate of these deposits. The variation in the concentrations of Co, Ni and Cu is shown to be dependent on ocean depth. It was found that the Co content is significantly high for the deposit from the Afanasiy Nikitin seamount. It has also been shown and discussed that the hydrothermal processes seem to be more controlling in the uptake of V and As than the hydrogenous processes.     

CFD analyses of liquid metal flow in sub-channels for Gen IV reactors

Some of the limitations of Reynolds Averaged Navier Stokes (RANS) based Computational Fluid Dynamics CFD codes in computing the flow and temperature field in a rod-bundle are well known. An in-house validation campaign has indicated that the Baseline Reynolds Stress Model (BSL-RSM) with automatic wall treatment is preferred for RANS analyses of a rod-bundle using the CFX code.As a first step in the present paper, the employed CFX code has been assessed with the analyses of a liquid sodium flow in a rod-bundle as in the TEGENA (TEmperatur- und GEschwindigkeitsverteilungen in Stabbündel mit turbulenter NAtriumströmung) experiment. For this RANS analysis, the full cross-section is modelled to avoid numerical issues associated with symmetric boundary conditions.The influence of pitch-to-diameter ratio (p/d) and rod arrangements on thermal-hydraulics is analyzed by applying the assessed modeling approach. For this purpose, rod-bundles with different p/d are arranged in a square and triangular lattice. The computational sub-channels make use of periodic boundary conditions. RANS computed axial velocity normalized with the friction velocity shows the presence of a logarithmic outer region for both arrangements. Similar behavior was reported based on a Large Eddy Simulation (LES) approach. The analyses reveal that the intensity of secondary flow increases with decreasing p/d for both arrangements. RANS analyzed normal Reynolds stresses normalized with centerline velocity in the smallest gap of rod-bundle reveal their anisotropy. Furthermore, the analyses show that the Nusselt numbers increase with p/d for described flow conditions and for both arrangements. Following observations of flow oscillations in a tight lattice rod-bundle as in Hooper's experiment, as a final step, unsteady RANS simulations for hydraulic analyses using a rod-bundle with small p/d are presented with two commercial CFD codes, namely, CFX and STAR-CCM+. In particular, the analysis of Hooper's hydraulics experiment with a tight lattice rod-bundle having a p/d of 1.1 demonstrates the existence of flow oscillations or instabilities as inferred in the experiment.     

A spray technique for preparing uniform large-area PIXE calibration standards from aqueous solutions

We describe a procedure for preparing reference standards that can be used to calibrate PIXE spectra of aerosol deposits collected on suitable backing films made, for example, of synthesised polymers (polypropylene, polycarbonate etc.) or chemically modified biopolymers (e.g., cellulose actetate). Aqueous solutions of well defined concentration were prepared from metal salts. The solutions were spray-deposited on cellulose acetate backings using a nebuliser. Lateral uniformity of the deposited layer over areas ranging from several mm to several cm was accomplished by raster scanning the table on which the backing was mounted. By optimising the experimental parameters, deposition could be accomplished without any detectable wetting of delicate substrates like paper. The areal density of the deposited material was calculated from the concentration of the solute, the volume of the consumed solution and the raster scanned area. The reference standards were analysed by PIXE using an external beam chamber backfilled with helium. The Si(Li) based detection system contained a thin funny filter so that X-ray spectra could be measured down to 1 keV. The proton energy on impact was 1.1 MeV. This relatively low probe energy has the advantage of producing favourable elemental X-ray peak heights relative to the bremsstrahlung-background, notably at energies between 2 and 7 keV. Under the same conditions sufficiently high X-ray yields were achieved for heavy elements like Zn and Pb. Using large area beams, bombardment-induced stress in the backing films could be kept at a low level so that very reproducible background spectra were obtained. Hence a straightforward background subtraction routine could be employed. Sensitivities were determined for 23 elements ranging from Na to Pb. Advantages and problems associated with the different metal salts are discussed briefly.     

PIXE,PIGE and NMR study of the masonry of the pyramid of Cheops at Giza

The mystery of the construction of the great pyramids of Egypt could be elucidated by physico-chemical measurements on small pieces of the material. In this paper, we give several arguments against the present point of view of most Egyptologists who do not admit another method than hewn blocks. We give several pieces of evidence that the masonry was entirely built by a moulding procedure involving the use of ingredients that were all available in the region of Cairo.     

Detection of non-sea salt sulphate aerosol at a remote coastal site in South Africa: A PIXE study

An aerosol sampling site based on a single-stage streaker sampler with four-hour time resolution was established in 1993 at Brandt-se-Baai, on the north-western coast of South Africa (31.5°S 18°E, 50 m asl). The site was deployed to monitor the generation of dust from the local mining operations and in part to test the hypothesis of large-scale air mass recirculation over Southern Africa. Streaker samples were analysed by PIXE for the usual crustal derived elements and sulphur. Sulphate aerosols over southern Africa are produced in the atmosphere by oxidation of SO₂, from industry, or DMS, from the ocean. Industrial related sulphate plays a key role in tracing long-range transport of anthropogenic pollutants.

We present results from selected monthly samples collected during 1996. Measured particulate sulphur has been apportioned between contributions from sea spray and non-sea salt sulphate (NSS) aerosols. Marine particulate sulphur, present in the regional background, was traced by its correlation with Na and Cl, which were routinely detected. The NSS content of these air masses was enriched with respect to the expected sea salt sulphur by two orders of magnitude. Al, Si, K, Ca, Ti and Fe, the major crustal elements, were measured only episodically with the occurrence of strong south-easterly winds. These winds are associated with wind blown dust from a mine located 4 km from the site.

These results are the first direct aerosol characterisation of the remote region of the western seaboard of southern Africa. Specifically the sulphur measurements at this site provide insights into relative contributions of natural DMS, industrial and sea salt contributions of particulate sulphate.     

New directions in the Bartol PIXE system for studies in archaeometry

This paper describes, firstly, the physical processes of PIXE that underly its advantages as an analytical tool and the practical limitation met in the compositional patterning of ancient bronzes, irons and glasses. Controlled variation of the energy of the proton beam and the use of selective filters in the X-ray detection system allows certain background effects from the X-ray output of the dominant elements to be significantly reduced. Secondly, plans for a new beam line for the Bartol PIXE facility are described. This system will provide for a beam diameter as small as 20 μm with a laser-based optical system that will allow for the precise location of the proton beam on the artifact's surface. This system will enable one to study inhomogeneous materials, such as metal residues trapped in smelted slag, solder joints in classical jewelry and islands of metal in heavily corroded artifacts.     

Rutherford backscattering — A tool for quantification of the results of PIXE analysis of single hair strands

As shown in a companion paper the geometrical diameter of a hair strand is an important parameter for quantification of its trace element content after PIXE analysis. By analysing Rutherford backscattered protons simultaneously with PIXE analysis a reliable estimate of the hair diameter can be obtained. In this work the hypothesis that there exists a linearity between the geometrical diameter and the number of backscattered protons in a certain energy interval is developed, discussed and experimentally verified.     

The new Cyclone 18/9 beam transport line at the CNA (Sevilla) for high energy PIXE applications

The Cyclone 18/9 cyclotron system at the Centro Nacional de Aceleradores (Sevilla, Spain) is commonly used to create short life radioisotopes for PET applications. Besides, an external beam transport line has been recently installed in one of the target ports with two major purposes: to study the effects of 18 MeV protons irradiation on the behaviour of electronic devices for space applications and to complement the analysis of materials using our 3 MV tandem accelerator with the PIXE measurements at high energy.In this work, the main elements of our beamline will be briefly described and the first PIXE application will be presented. The usual PIXE, in the analysis of archaeological metallic objects, using around 3 MeV protons requires having a shiny area. Our purpose is to obtain a deeper determination of the bulk composition bombarding with 18 MeV protons through the corroded samples surfaces, without polishing the ancient object. To check this methodology high energy PIXE has been performed on two fibulae of the Later Bronze Age and First Iron Age, coming from the area around Sevilla.