Tins are marketed as containing nine cherries. To fill the tins, cherries are fed into a drum containing twelve holes through which air is sucked; either zero, one or two cherries stick in each hole. Dielectric measurements are then made on each hole. Three outcomes are distinguished: empty hole (which is reliable); one cherry (which indicates one cherry with high probability, or two cherries with a complementary low probability known from calibration); or an uncertain number (which also indicates one cherry or two, with known probabilities that are quite similar). A choice can be made from which holes simultaneously to discharge contents into the tin. The sum and product rules of probability are applied in a Bayesian manner to find the distribution for the number of cherries in the tin. Based on this distribution, ways are discussed to optimise the number to nine cherries.

The technique of correspondence analysis was applied to a set of data obtained from X-ray elemental analysis by nuclear microscopy. Hydroponic experiments simulating tropical acid soil conditions were carried out to determine possible mechanisms of Al-toxicity stress on specific varieties of the genus Brachiaria. In particular the species Brachiaria brizantha was tested for gradient variation along the central cylinder of selected root tips. Single-point irradiations by nuclear microscopy gave some indication of a possible trace element profile gradient along the root axis. To be able to extrapolate the possible correlation and trace elemental concentrations gradients to a more confident level, this nuclear microscopy data obtained was analysed by correspondence analysis. A clear gradient on the plot of the first two axes of the correspondence analysis was found. The correlation of Ca and Cu as well as that of K and Cl were established.

Individual particle analysis using micro-PIXE and proton backscattering was performed for selected aerosol samples collected over Siberia. Point analyses were complemented by x-ray mapping for complex particles. Hierarchical cluster analysis of 124 particles identified in general the same particle groups, as found by automated electron microprobe analyses of approximately 25000 particles from the same locations. However, owing to the superior sensitivity of micro-PIXE, a number of heavy metals were identified, suggesting an anthropogenic origin of particles. These metals remained undetected by EPXMA owing to its inferior sensitivity. Elemental mapping of single aerosol particles yielded important information on the chemical heterogeneities. Copyright (C) 2001 John Wiley & Sons, Ltd.

It has been shown that Bayesian statistics is a powerful tool in the analysis of ion beam analysis (IBA) data. Past work has shown its applicability to the deconvolution of the detector response function from micro-Rutherford backscattering spectrometry (RBS) and micro-proton-induced X-ray emission (PIXE) spectra, subtraction of the background from PIXE spectra, the extraction of depth profiles from PIXE spectra using two detectors and the extraction of depth profiles from RBS spectra. However, the method has some drawbacks, e.g. numerical integration, α-marginalisation, etc., all of which result in very long computation times. In this paper, preliminary results are presented from the application of the Bayesian theory to the automatic extraction of depth profiles from RBS spectra with the aim of creating an online RBS analysis program, which has the advantage of minimal user input while still being as computationally intensive as conventional RBS analysis packages to extract a depth profile.

Electron backscattering has been performed using a Centaurus detector, developed especially for low-energy electron backscattering. A H2+ beam of energy 5 MeV was used, with each proton having 2.5 MeV, and the accompanying electron having an energy of 1.3 keV. The backscattered electrons were measured simultaneously with the particle-induced X-ray emission (PIXE) and Rutherford backscattering (RBS) signals, as complementary information. Results show that the electron backscattering signals indeed offer elemental information in imaging at least an order of magnitude faster than PIXE. This may result in novel applications in imaging of geological grains, with subsequent trace element analysis.

The use of micro-capillaries and micro-light guides has revolutionised optical microscopy, enabling the spatial resolution to become orders of magnitude less than allowed by the diffraction limit. This has led to a new field of application or near-field optical microscopy. These capillaries consist of glass tubes with exit apertures of the order of some tens of nanometre. Micro-capillaries have been tested as ultra-collimators for nuclear microscopic applications. The obvious application is for use in single event studies, such as STIM and IBIC, as well as single event upsets, both in semiconductors and biological systems. The possibility of application of micro-capillaries in high-resolution imaging using traditional ion-beam techniques, such as PIXE and RBS, is also discussed.

An original method has been developed to measure the lateral straggling of sub-micron proton and alpha beams after passing through polymer foils of different thickness. For this purpose, the microbeam line at CENBG has been used in scanning transmission ion microscopy (STIM) configuration to deliver the ions in normal incidence on foils. The lateral spreading of the beam was measured using a collimated charged particle detector centred on the beam axis and placed 6.3 mm behind the foil. When the beam was horizontally scanned in front of the collimator, its lateral distribution was measured step by step detecting particles passing trough the small aperture. Regular gaussian shapes were obtained and data were compared to the result of simulations carried out using the SRIM Monte-Carlo code for 2.5 MeV protons and alphas in Mylar and Formvar thin films.

A single event facility is currently under development at CENBG for applications in radiation biology. The aim is to induce the response of living cells by hitting selected individual specimens or specific sub-cellular compartments with an exact number of light ions. In order to avoid the construction of a complete beam line, it was decided to adapt the existing microprobe system. The line has been equipped with a removable final irradiation stage constituting a versatile system working on demand either in external beam mode or classical analysis under vacuum. The beam blanking is ensured by particle detectors which have been specifically designed to control MeV proton or alpha beams in a single event mode. This paper presents the overall experimental setup and first in-air experimental tests.

The use of particle-induced x-ray emission (PIXE) in conjunction with a scanning nuclear microprobe (SNM) offers one of the few microanalytical techniques capable of studies of elemental concentrations at the ppm level, with a spatial resolution of the order of 1 mum. Beam scanning capabilities and advanced data treatment make it a technique of choice for quantitative two-dimensional studies of elemental distribution. Although the ultimate aim is to obtain true quantitative elemental maps, free of concentration or thickness artifacts, some compromises are necessary owing to experimental and computational restrictions. Some approaches currently used are discussed with emphasis on true elemental imaging using the dynamic analysis method. Examples of applications in geology and biology are shown to illustrate its benefits and limitations. Copyright (C) 2001 John Wiley & Sons, Ltd.

The nuclear microprobe (NMP) unit of the National Accelerator Centre (NAC) has initiated a focused research programme on studies of biological material, ranging from applications in medicine to agriculture and botany. During this period a state-of-the-art cryo-preparation laboratory was also developed. This research programme has resulted in a wide range of projects, and has shown how well suited the NMP is for studies of biological material in general. This paper reports on some of the problems and demands in this field, as well as some of the results obtained using particle induced X-ray spectroscopy (PIXE) and Rutherford backscattering (RBS). True elemental imaging is routinely performed using the dynamic analysis (DA) method, which forms part of the GeoPIXE suite of programmes. A collaborative project, together with the CENBG group of Bordeaux–Gradignan in France, on the development of a facility with the aim of studying effects of single-events of radiation in living cells was recently established and is discussed.

Whereas the concept of remote control is not new, the required equipment and data link have typically been costly and specialized. With the growing availability of reliable Internet connection, it has however become possible and increasingly attractive to be able to control complex equipment remotely over the Internet. Some methods of Internet Remote control are discussed, bearing in mind the specific needs of nuclear microprobe control. One such system has been implemented at the NAC nuclear microprobe, and even though improvements are envisaged, it is already functioning satisfactorily.

The nuclear microprobe (NMP) is an established analytical instrument for the determination of minor and trace elements, It allows measurements with a spatial resolution of the order of 1 mu m and minimum detection limits down to few ppm by weight, with excellent scanning capabilities. The nuclear microprobe of the National Accelerator Centre, South Africa, is being used in a wide number of applications in the biosciences. The complementarity of proton-induced x-ray emission and backscattering spectrometry in a wide range of biological applications is shown. The advantages and restrictions of true elemental imaging are also discussed. Copyright (C) 1999 John Wiley & Sons, Ltd.

Petrochemical investigation of the Cape Granite Suite illustrated that three major granitoid types exist namely S-, I-and A-types. Studies of zircon typologies of these granites confirmed that the three major types and their subtypes could be distinguished with relative ease. Using the typological classification as a base, zircons from the three granite groups were analysed by proton microprobe. The proton microprobe was utilized to enable the detection of elements normally present in low quantities in zircon. The results clearly illustrated that PIXE analyses may readily be used to discriminate zircons from S-, I- and A-type granites using the elements Th, Y and Yb.

A new plasma-based ion implantation (PBII) facility consisting of a dedicated PBII chamber plus characterization equipment has been established at the Van de Graaff Group, National Accelerator Centre, Faure. The implantation unit has an aluminum vacuum chamber with a volume of 1 m3, and it incorporates conventional plasma generation capability for gas plasmas, such as a set of multifilaments. The implantation power supply is capable of delivering 30 kV, with a pulse duration of up to 1000 μs, and a repetition rate of 1 kHz. This allows a maximum average load of 12 J to the target. The facility is being used at the outset for the fundamental study of plasmas, time-dependent x-ray generation during the implantation pulse, and plasma immersion implantation. The facility is supported by a 6 MV Van de Graaff accelerator equipped with the ion-beam analytical tools necessary for characterization of modified surfaces.

This paper presents some of the microanalytical problems and challenges in minerals research and the geosciences in general. It deals with the evolving possibilities for advanced analysis in the geological end mineralogical field, with emphasis on ion-beam based techniques. The geosciences have a large array of analytical techniques that they rely on, but there are still a number of areas where problems persist. The different analytical techniques have also been more complementary than competitive up to now, but this is set to change as new techniques evolve and are optimized. The strengths and weaknesses of ion-beam techniques are highlighted, with emphasis on minerals characterization.

A ΔE–E telescope was used in coincidence to analyse diamond samples by recoil of hydrogen (ERDA) using 4.1 MeV He+. Comparison of the results from silicates with known H-abundances suggested sensitivities of <50 atomic ppm. A slice of type Ib diamond was prepared and implanted with known amounts of hydrogen (1000, 150, 40 and 10 atomic ppm). The analysis of this manufactured standard by ERDA showed that the 1000 and 150 ppm implants were resolvable. The presence of intrinsic hydrogen in the diamond prevented resolution of the lower H implants. A number of diamonds from southern Africa were analysed for their H-content using ERDA and Fourier transform infrared (FTIR) techniques. There was no correlation between the results of both techniques. It was concluded that much of the hydrogen in diamond (typically 100–4000 atomic ppm in the specimens analysed) was not infrared active (i.e. not bonded to C or N in the diamond lattice).

Glass bottles, used for sparkling wine, are treated with freon during manufacturing to harden the inside surface. Although this type of treatment normally improves the properties of the glass, in this case the occurrence of “egg” formations (egg-shaped rough areas) on distinct areas of bottles, as well as yeast sticking to the insides of bottles at specific areas pointed to the possibility of different areas showing different properties in the same bottle. The question was whether the correct gas was used for the treatment, and secondly, whether the process was controlled well enough to obtain the correct properties for the inside of the glass. We present results of an optical microscopy and nuclear microprobe (NMP) investigation.

Molecular hydrogen ions were first used in nuclear microprobe STIM imaging to enhance contrast. These beams have also been used for PIXE and other techniques of microprobe imaging, although the high-energy electrons associated with the molecules caused problems with charge integration. This paper discusses the use of asymmetric molecular ion beams, to utilise the properties of molecular break-up for enhanced materials analysis. In particular the use of the deuterium-hydrogen (DH+) molecule for STIM imaging to provide increased image contrast and improved density measurement for specimens of widely varying areal densities is discussed.