Th. Beier

Provenance determination of Mycenaean sherds found in Tell el Amarna by Neutron Activation Analysis

Abstract Trace elemental analysis of ceramics found in archaeological excavations is known to give information about its provenance. Using Neutron Activation Analysis (NAA) the production site of several Mycenaean sherds excavated in Amarna in Egypt is located somewhere in the northern Argolid, probably in the region of Mycenae-Berbati.

Precision studies in traps: Measurement of fundamental constants and tests of fundamental theories

Experiments on single atomic particles confined in Penning ion traps have contributed significantly to the improvements of fundamental constants and to tests of the theory of Quantum Electrodynamics for free and bound electrons. The most precise value of the fine structure constant as well as the electron mass have been derived from trap experiments. Numerous atomic masses of interest for fundamental questions have been determined with precisions of 10 � 9 or below. Further progress is envisaged in the near future.

The fundamental parameter method applied to X-ray fluorescence analysis with synchrotron radiation

Abstract Quantitative X-ray fluorescence analysis applying the fundamental parameter method is usually restricted to monochromatic excitation sources. It is shown here, that such analyses can be performed as well with a white synchrotron radiation spectrum. To determine absolute elemental concentration values it is necessary to know the spectral distribution of this spectrum. A newly designed and tested experimental setup, which uses the synchrotron radiation emitted from electrons in a bending magnet of ELSA (electron stretcher accelerator of the university of Bonn) is presented. The determination of the exciting spectrum, described by the given electron beam parameters, is limited due to uncertainties in the vertical electron beam size and divergence. We describe a method which allows us to determine the relative and absolute spectral distributions needed for accurate analysis. First test measurements of different alloys and standards of known composition demonstrate that it is possible to determine exact concentration values in bulk and trace element analysis.

A PIXE mini-beam setup at the bonn cyclotron for archeometric metal analyses

The exact analysis of the elemental composition at and around a soldering joint of an antique piece of jewelry can elucidate the joining technologies and give hints of the genuineness of the object. As analytical method we use PIXE, which is nondestructive, multielemental and with fundamental parameter calculations gives absolute concentration values. To obtain the necessary spot size of the H2+ beam at the Bonn cyclotron we use a piezo-controlled diaphragm, whose demagnified image is focussed on the target by two magnetic quadrupole triplets. With an electrostatic deflector the beam spot of 0.1 × 0.3 mm2 size can be moved 2 mm in each direction on the target. With a laser beam, which simulates the ion beam, an irregularly shaped archeological object can be positioned. The laser is also used to obtain the alignment of the target surface to the ion beam direction and the small beam size makes it easier to find a flat part on the surface of the object; both of these are important preconditions for using the fundamental parameter method. A scan over a joint of modern gold alloys demonstrates the ability to detect soldering joints. The analysis of four pieces of Roman gold jewelry found in the area of Cologne and Bonn shows examples of brazing with a solder as well as diffusion soldering.

PIXE analysis of Bronze and Iron Age weapons from Bactria

Abstract PIXE analyses with α-particles of an energy of 30 MeV have been performed with the Bonn cyclotron for more than a decade. In this paper we summarize recent improvements of our experimental setup and the data evaluation system. The ion beam is collimated by a remotely controlled diaphragm and exits the vacuum system. This facilitates sample handling and reduces limitations of the requirements for the samples. To obtain quantitative results the fundamental parameter method is applied which gives precise results for minor and main elements of thick samples particularly at higher ion energies. As an archaeometric application we analysed alloys used for the manufacture of Bronze and Iron Age weapons from Bactria.

A monitor for the spectral distribution of white synchrotron radiation

To analyze nondestructively the elemental composition of expensive and sensitive objects pertaining to the history of art and civilization, X-ray fluorescence analysis (SYXRF) can be performed at the electron storage ring ELSA, University of Bonn, using synchrotron radiation (SR) as a powerful source of X-ray radiation. The calibration by standards is cumbersome for targets of different types, therefore, quantitative analyses should be performed by the fundamental parameter method [1]. Using known experimental and theoretical parameters, like X-ray production and absorption cross sections, the elemental abundances in thick targets can be determined from the measured Xray fluorescence intensities emitted. One basic information needed for these calculations is the spectral distribution of intensity of the exciting SR at the target position. Accelerated electrons with energies of several GeV emit a continuous spectrum of SR reaching energies possible to excite Kand/or L-shells of all elements. SR is focused in the direction of the electron motion with opening angles of about 0.15 mrad in the X-ray energy region. For one electron on an ideal orbit, the spectral and angular distribution of the SR is given by the Schwinger equation [2, 3]. In existing electron storage rings many electrons oscillating around the ideal orbit are contributing to the emitted radiation. Therefore, a quantification of the SR spectrum has to take into account this finite size and divergence of the electron beam. Calculations [4] show that the spectral distribution of SR, seen through a diaphragm of definite size, depends on the vertical position and size of the diaphragm, the effective vertical size of the electron beam rerf (FWHM of the

On the importance of line shift and peak broadening corrections in the evaluation of spectra in neutron activation analysis

The evaluation of γ-ray spectra achieved by Instrumental Neutron Activation Analysis (INAA) is improved if effects of line shift and peak broadening are taken into account, comparing the corresponding γ-lines in spectra from samples and standards. An algorithm which handles both effects is proposed and its realization in a computer program for routine analysis of archaeological ceramic samples is presented.