Mats Ahlberg

Elimination of Charging in the Proton-Induced X-Ray Emission Analysis of Insulating Samples

Anomalous background due to charging in the proton-induced X-ray analysis of insulators is eliminated by inserting a heated carbon filament or by raising the pressure in the sample chamber.

Enhancement in PIXE analysis

Abstract The enhancement in proton induced X-ray emission analysis (PIXE) due to secondary excitation by bremsstrahlung, secondary electrons, target—target collisions, Auger electrons and primary induced X-rays is discussed. Primary induced X-rays are concluded to be the only source of importance. The enhancement is investigated as a function of proton energy and sample thickness, and the calculated values are shown to be within 5% agreement with experimental results obtained from a NBS Standard Steel sample.

Proton-induced X-ray emission in the trace analysis of human tooth enamel and dentine

In this study the feasibility of applying proton-induced X-ray emission spectroscopy (PIXE) to the trace element analysis of human tooth enamel and dentine is investigated. Detection limits on the order of 1–10 ppm are obtained. Depth yields for different elements and proton energies are discussed. Enhancement calculations show that the effect for PIXE analysis is less important than for X-ray induced X-ray analysis. However, for elements with an absorption edge just below an intense X-ray line from a major element the enhancement effect is significant, and, due to the 40% calcium in the enamel matrix, it is estimated to be 15% for potassium. The importance of a smooth sample surface is discussed.

Proton-Induced X-Ray Analysis of Steel Surfaces for Microprobe Purposes

A study of the detection limits for the elements with Z = 15-92 in thick target steel surfaces using proton-induced X-ray technique has been performed. Samples were irradiated with a broad proton beam of 2 mm diameter and the X-rays were detected by a Si(Li) detector. Detection limits at levels down to the order of 10 ppm were achieved with simultaneous measurement of several elements. Mylar and chromium absorbers were introduced in front of the semiconductor detector and irradiations at two different proton energies (1.0 and 2.5 MeV) were carried out in order to elucidate their effects on detection limits. The results are valid for microbeam analysis.

Comparison of yield versus depth for particle induced and photon induced x-ray emission analysis

Abstract The depth sensitivity using 1.0, 2.5 and 5.0 MeV protons and Ti, Mo and Sm K α X-rays for excitation is compared in the elemental analysis by X-ray emission of cellulose, fluorapatite and stainless steel samples.

The chemical state of particulate sulfur in ambient aerosols determined by pixe analysis

Abstract By a combination of relative humidity control during aerosol particle sampling by cascade impactors and of elemental analysis for S and other elements by proton induced X-ray emission, ammonium sulfate may be distinguished from sulfuric acid as the principal chemical form of sulfur in fine aerosol particles of aerodynamic diameter 〈2 μm. In a laboratory test, two impactors sampled air simultaneously, one by first passing the air at a measured rate over a water surface in a horizontal tube, thus adjusting the relative humidity upward to a predetermined value, e.g. 98%, depending on tube length, and the other impactor by sampling the laboratory air directly. The dependence of mass median aerodynamic diameter on relative humidity indicated that ammonium sulfate, rather than sulfuric acid, is more abundant on the average in the 〈2 μm fine particle mode in these samples.

Analytical Use of Proton-Induced X-Ray Emission

Proton-induced X-ray emission, PIXE, is capable of simultaneous quantitative determination of 10–15 elements. An introduction to the physical properties of the method is given and detection limits are shown for a routine analysis of a thin aerosol sample. Examples of applications to both thick and thin samples are presented. Human tooth dentine is analysed for lead, with simple sample preparation, indicating lead values of a few ppm for Swedish children. Quantitative analyses of several other elements are obtained simultaneously. Cascade impactors are used for sampling aerosols in work environment during welding operations giving information of size distribution and concentrations of the elements present. The aerosol is dominated by particle sizes between 0.5 and 2 μm as measured by the impactor, but the size distributions are different for different elements and welding techniques and depend on the distance from the welding source. The relative abundance of the elements found in the aerosol indicates the presence of fractionation mechanisms.