R. Flagmeyer

The novel ultrastable HVEE 3.5 MV Singletron™ accelerator for nanoprobe applications

Abstract Recently, HVEE has completed a novel 3.5 MV single ended accelerator (Singletron™) for the University of Leipzig, Germany. For one of the main applications, the system will be connected to a nanobeamline to achieve submicron resolution. Because the energy stability and ripple of the beam, and beam brightness are of vital importance for the performance of a nanoprobe, special care has been taken in optimizing these parameters. The system consists of an RF source which is directly mounted on the accelerator tube, a switching magnet to bend the beam into a chamber for standard analysis purposes and an analysis magnet that directs the beam into the nanoprobe. The stability of the beam energy was measured at a terminal voltage of 1.881 MV. These measurements were taken during factory acceptance with large production equipment operational, which negatively influenced the stability of the mains. The measured stability was found to be approx. ±50 eV over 5 h, but it is anticipated that this figure will be as good as ±20 eV (i.e. ∼ 10−5) under normal laboratory conditions. The terminal voltage ripple was measured at 2.25 MV to be 25 Vpp (i.e. ∼ 1.1 × 10−5). Finally, the beam brightness of a 2.25 MeV hydrogen beam was measured by the use of two micrometer slit systems. A brightness of approx. 18 Amps · rad−2 m−2 eV−1 was obtained. In this article we will describe the considerations which have led to the layout of the present system.

The Leipzig high-energy ion nanoprobe: A report on first results

Abstract The high-energy ion nanoprobe LIPSION at the University of Leipzig has been operational since October 1998. Its magnetic quadrupole lens system, arranged as a separated Russian quadruplet, has been developed by the Microanalytical Research Centre (MARC), Melbourne. The ultrastable single-ended 3.5 MV SINGLETRON™ accelerator (High Voltage Engineering Europa) supplies H+ and He+ ion beams with a beam brightness in the range of 10–20 A rad −2 m −2 eV −1 [D.J.W. Mous, R.G. Haitsma, T. Butz, R.-H. Flagmeyer, D. Lehmann, J. Vogt, Nucl. Instr. and Meth. B 130 (1997) 31]. Due to this high brightness, the excellent optical properties of the focusing system of the nanoprobe and the suppression of mechanical vibrations, lateral resolutions of 100 nm for the low current mode (STIM) and 340 nm at a current of 10 pA (PIXE, RBS, SEI modes) were achieved. Further improvements are expected.

A comparative study of swelling, strain and radiation damage of high-energy proton-bombarded GaAs, GaP, InP, Si and Ge single crystals

Abstract Swelling is studied on GaAs, GaP, InP, Si and Ge implanted with 0.3 and 1.2 MeV protons in the range of fluences D = 1015-8 × 1017cm−2, for several proton energies, implantation and annealing temperatures (T = 300–650 K). Within t the “buried” damaged layer all materials exhibit a volume dilation whereas in the near-surface layer only GaAs, GaP and Ge show considerable expansion and InP contracts due to the proton bombardment. For the interpretation of the results additional measurements of strain and damage density are taken into consideration.

Identification of air pollution sources by single aerosol particle fingerprints - micro-PIXE spectra

Abstract A new method for direct assessment of air pollution is developed by using nuclear microprobe techniques to analyse single aerosol particles (SAP). Every particle is characterized by its PIXE spectrum which can be considered to be its fingerprint. The strategy for fingerprint classification and identification is used to trace a measured aerosol particle to its original source. Most of the particles have a size of up to 3 μm . The particles are separately attached to a clean thin foil. The Leipzig Nanoprobe, LIPSION, is used for this study. There are two steps in the new method. First, collect samples from different sources, measure them and compile their characteristic spectra into a library. Then, assess the environmental samples by comparing their spectra with those in the library. An artificial neural network (ANN) package is used for spectrum comparison.

Determination of strain in MBE (In, Ga)As films grown on GaAs(100) substrate by ion channeling

Abstract The structure of In x Ga 1− x As films grown on GaAs(100) substrate is analysed by 1.7 MeV He + Rutherford backscattering and channeling. Angular scans along the off-normal 〈112〉 direction permit the direct measurement of tetragonal strain in the pseudomorphic films with thicknesses up to 50 nm.

Study of metal bioaccumulation by nuclear microprobe analysis of algae fossils and living algae cells

Abstract Microscopic ion-beam analysis of palaeo-algae fossils and living green algae cells have been performed to study the metal bioaccumulation processes. The algae fossils, both single cellular and multicellular, are from the late Neoproterozonic (570 million years ago) ocean and perfectly preserved within a phosphorite formation. The biosorption of the rare earth element ions Nd3+ by the green algae species euglena gracilis was investigated with a comparison between the normal cells and immobilized ones. The new Leipzig Nanoprobe, LIPSION, was used to produce a proton beam with 2 μm size and 0.5 nA beam current for this study. PIXE and RBS techniques were used for analysis and imaging. The observation of small metal rich spores ( μm ) surrounding both of the fossils and the living cells proved the existence of some specific receptor sites which bind metal carrier ligands at the microbic surface. The bioaccumulation efficiency of neodymium by the algae cells was 10 times higher for immobilized algae cells. It confirms the fact that the algae immobilization is an useful technique to improve its metal bioaccumulation.

RBS analysis of heteroepitaxial layered structures

Abstract Rutherford backscattering and channeling of energetic ions is applied to III–V semiconductor epitaxial systems. Grazing incidence RBS is employed to observed in-depth profiles of chemical composition, especially the well width L z , of AlGaAs/GaAs and InGaAs/InP single quantum well (SQW) structures. In case of highly lattice-mismatched materials, RBS/channeling analyses reveal the pseudomorphic or relaxed state of the corresponding crystal lattices. Some new aspects in determining the elastic strain and in locating the misfit dislocation array in InGaAs/GaAs single heterostructures and superlattices are discussed. Finally, attention is drawn to the “internal” lattice distortion in epilayers of pseudobinary alloys, and the high sensibility of dechanneling to the intrinsic atomic displacements is demonstrated.

Ion microprobe analyses of ancient human bone

Abstract At the Rossendorf nuclear microprobe facility, a beam of protons with MeV energy was used to analyse ancient human bones of the Merowingian period (6–8th century AD). Emitted X-rays were detected to determine the elemental composition of the bones and to estimate the influence of the burial environment on the elemental content of the skeletons. In cross sections of human femora, a different behaviour of the radial distributions of the main and trace elements like P, Ca, Mn, Fe, Zn, Br, and Sr was observed using lateral-resolved μPIXE. This result indicates post mortem mineral exchange processes and diagenetic alteration during burial of bone tissue in soil.

Radiation damaging behaviour of GaP by MeV ion implantation

Abstract The creation of defects in GaP bombarded with energetic ions has been studied and compared with TRIM calculations. To investigate the influence of the relation of nuclear to electronic energy deposition and of the size of displacement cascades on defect production, the atomic species and projectile energies were varied from Z = 1 to 20 and E = 0.3 to 175 MeV. It has been found that not only the nuclear energy deposition but also the electronic energy deposition influences the defect production.

Location of misfit dislocation networks and channeling stopping power measurements in strained-layer superlattices by RBS

A backscattering angle-dependent dechanneling analysis is presented for the location of a misfit dislocation network in strained layers and strained-layer superlattices. Simultaneously this RBS/channeling method permits the determination of the ratio of channeling to the random stopping cross section. An In0.18Ga0.82As/GaAs strained-layer superlattice on (100) GaAs layer superlattice is analyzed with 1.7 MeV He ions. The misfit dislocation network is located at the superlattice-substrate interface. The ratio of 〈100〉 channeling to the random stopping cross section γ = 0.61 is determined at the He ion energy of 1.63 MeV.