Nanobeam Line Research Articles

Comparison of experimental proton-induced fluorescence spectra for a selection of thin high-Z samples with Geant4 Monte Carlo simulations

The general purpose Geant4 Monte Carlo simulation toolkit is able to simulate radiative and non-radiative atomic de-excitation processes such as fluorescence and Auger electron emission, occurring after interaction of incident ionising radiation with target atomic electrons. In this paper, we evaluate the Geant4 modelling capability for the simulation of fluorescence spectra induced by 1.5MeV proton irradiation of thin high-Z foils (Fe, GdF3, Pt, Au) with potential interest for nanotechnologies and life sciences. Simulation results are compared to measurements performed at the Centre d’Etudes Nucléaires de Bordeaux-Gradignan AIFIRA nanobeam line irradiation facility in France. Simulation and experimental conditions are described and the influence of Geant4 electromagnetic physics models is discussed.

Aifira: An ion beam facility for multidisciplinary research

During the last decade, the CENBG (Centre d’Études Nucléaires de Bordeaux Gradignan) commissioned a new facility called AIFIRA (Applications Interdisciplinaires des Faisceaux d’ions en Région Aquitaine). It allowed the development of a multidisciplinary activity based on the “in-house” expertise of CENBG in ion beam analysis. The great flexibility offered by the five beam lines confers a lot of possibilities for chemical analysis and nuclear physics. Indeed, not only the macrobeam and the external beam lines provide the full set of IBA techniques for routine sample analysis but an additional beam line is devoted to the production of monoenergetic neutrons through the interaction of the incoming ion with selected targets. In addition, the two high-resolution microbeam lines are used for chemical analyses, 2D/3D imaging, and targeted cell irradiation. Besides, the combination of the nanobeam line flexibility, the uniqueness of the micro-irradiation design completed by the internal CENBG expertise confers a great specificity to AIFIRA in biomedical field. After a detailed technical overview of the platform, the article focuses on the two high-resolution lines as they tap most of the activity. Thus a quick overview of the most significant results concerning biomedical samples is proposed in order to highlight the analytical possibilities of AIFIRA microbeam lines. A summary of the development status of the micro-irradiation line is also done.

The power ofin situpulsed laser deposition synchrotron characterization for the detection of domain formation during growth of Ba0.5Sr0.5TiO3on MgO

A highly sophisticated pulsed laser deposition (PLD) chamber has recently been installed at the NANO beamline at the synchrotron facility ANKA (Karlsruhe, Germany), which allows for comprehensive studies on the PLD growth process of dielectric, ferroelectric and ferromagnetic thin films in epitaxial oxide heterostructures or even multilayer systems by combining in situ reflective high-energy diffraction with the in situ synchrotron high-resolution X-ray diffraction and surface diffraction methods. The modularity of the in situ PLD chamber offers the opportunity to explore the microstructure of the grown thin films as a function of the substrate temperature, gas pressure, laser fluence and target-substrate separation distance. Ba0.5Sr0.5TiO3 grown on MgO represents the first system that is grown in this in situ PLD chamber and studied by in situ X-ray reflectivity, in situ two-dimensional reciprocal space mapping of symmetric X-ray diffraction and acquisition of time-resolved diffraction profiles during the ablation process. In situ PLD synchrotron investigation has revealed the occurrence of structural distortion as well as domain formation and misfit dislocation which all depend strongly on the film thickness. The microstructure transformation has been accurately detected with a time resolution of 1 s. The acquisition of two-dimensional reciprocal space maps during the PLD growth has the advantage of simultaneously monitoring the changes of the crystalline structure as well as the formation of defects. The stability of the morphology during the PLD growth is demonstrated to be remarkably affected by the film thickness. A critical thickness for the domain formation in Ba0.5Sr0.5TiO3 grown on MgO could be determined from the acquisition of time-resolved diffraction profiles during the PLD growth. A splitting of the diffraction peak into two distinguishable peaks has revealed a morphology change due to modification of the internal strain during growth.

CRionScan: A stand-alone real time controller designed to perform ion beam imaging, dose controlled irradiation and proton beam writing

High resolution ion microbeams, usually used to perform elemental mapping, low dose targeted irradiation or ion beam lithography needs a very flexible beam control system. For this purpose, we have developed a dedicated system (called “CRionScan”), on the AIFIRA facility (Applications Interdisciplinaires des Faisceaux d’Ions en Région Aquitaine). It consists of a stand-alone real-time scanning and imaging instrument based on a Compact Reconfigurable Input/Output (Compact RIO) device from National Instruments™. It is based on a real-time controller, a Field Programmable Gate Array (FPGA), input/output modules and Ethernet connectivity. We have implemented a fast and deterministic beam scanning system interfaced with our commercial data acquisition system without any hardware development. CRionScan is built under LabVIEW™ and has been used on AIFIRA’s nanobeam line since 2009 (Barberet et al., 2009, 2011) [1,2]. A Graphical User Interface (GUI) embedded in the Compact RIO as a web page is used to control the scanning parameters. In addition, a fast electrostatic beam blanking trigger has been included in the FPGA and high speed counters (15MHz) have been implemented to perform dose controlled irradiation and on-line images on the GUI. Analog to Digital converters are used for the beam current measurement and in the near future for secondary electrons imaging. Other functionalities have been integrated in this controller like LED lighting using Pulse Width Modulation and a “NIM Wilkinson ADC” data acquisition.

First results obtained using the CENBG nanobeam line: Performances and applications

A high resolution focused beam line has been recently installed on the AIFIRA (“Applications Interdisciplinaires des Faisceaux d’Ions en Région Aquitaine”) facility at CENBG. This nanobeam line, based on a doublet–triplet configuration of Oxford Microbeam Ltd. OM-50™ quadrupoles, offers the opportunity to focus protons, deuterons and alpha particles in the MeV energy range to a sub-micrometer beam spot. The beam optics design has been studied in detail and optimized using detailed ray-tracing simulations and the full mechanical design of the beam line was reported in the Debrecen ICNMTA conference in 2008. During the last two years, the lenses have been carefully aligned and the target chamber has been fully equipped with particle and X-ray detectors, microscopes and precise positioning stages. The beam line is now operational and has been used for its first applications to ion beam analysis. Interestingly, this set-up turned out to be a very versatile tool for a wide range of applications. Indeed, even if it was not intended during the design phase, the ion optics configuration offers the opportunity to work either with a high current microbeam (using the triplet only) or with a lower current beam presenting a sub-micrometer resolution (using the doublet–triplet configuration).The performances of the CENBG nanobeam line are presented for both configurations. Quantitative data concerning the beam lateral resolutions at different beam currents are provided. Finally, the first results obtained for different types of application are shown, including nuclear reaction analysis at the micrometer scale and the first results on biological samples.

Technical developments for computed tomography on the CENBG nanobeam line

The use of ion microbeams as probes for computed tomography has proven to be a powerful tool for the three-dimensional characterization of specimens a few tens of micrometers in size. Compared to other types of probes, the main advantage is that quantitative information about mass density and composition can be obtained directly, using specific reconstruction codes. At the Centre d’Etudes Nucléaires de Bordeaux Gradignan (CENBG), this technique was initially developed for applications in cellular biology. However, the observation of the cell ultrastructure requires a sub-micron resolution. The construction of the nanobeam line at the Applications Interdisciplinaires des Faisceaux d’Ions en Region Aquitaine (AIFIRA) irradiation facility has opened new perspectives for such applications.The implementation of computed tomography on the nanobeam line of CENBG has required a careful design of the analysis chamber, especially microscopes for precise sample visualization, and detectors for scanning transmission ion microscopy (STIM) and for particle induced X-ray emission (PIXE). The sample can be precisely positioned in the three directions X, Y, Z and a stepper motor coupled to a goniometer ensures the rotational motion. First images of 3D tomography were obtained on a reference sample containing microspheres of certified diameter, showing the good stability of the beam and the sample stage, and the precision of the motion.

Technical description of the CENBG nanobeam line

Two years ago, the CENBG has commissioned the AIFIRA (Application Interdisciplinaire des Faisceaux d’Ions en Aquitaine) facility for the development of an interdisciplinary research program based on a 3.5 MV Singletron ™ accelerator (HVEE, The Netherlands). In addition to the existing beam lines, this facility is being equipped with a high demagnification focused beam line allowing the focusing of protons, deuterons and alpha particles down to a sub-micrometer resolution. This so-called “nanobeam line”, based on a long working distance doublet–triplet of Oxford Microbeams Ltd., OM-50 ™ quadrupoles, is at its final stage of development. The chosen layout of the beam line has been computed in details using the GEANT4 simulation toolkit. In the simulations, experimental measurements of the beam emittance at the entrance slits have been used to obtain more realistic beam distributions and intensities along the full beam line. According to these simulations, a beam resolution of about 300 nm in high current mode and below 100 nm in STIM mode is expected. The components of the beam line have been mounted at the 0° output of the Singletron ™ switching magnet and the fine alignment will be performed using the ion beam in the coming weeks. In the present paper, all the major components of the CENBG nanobeam line are described in details.

A detailed ray-tracing simulation of the high resolution microbeam at the AIFIRA facility

The AIFIRA (Applications Interdisciplinaires des Faisceaux d’Ions en Région Aquitaine) ion beam facility at the CENBG (Centre d’Etudes Nucléaires de Bordeaux-Gradignan) is being equipped with a high demagnification focused microbeam line. This beam line, which is under its final stage of development, should allow focusing of protons and alpha particles down to a sub-micrometer resolution, and is therefore referred to as a “nanobeam line” in the following paper.We present the complete beam transport simulation along the chosen configuration for the nanobeam line, which consists of a long working distance doublet–triplet of Oxford Microbeam Ltd. OM-50® quadrupoles. These simulations have been performed using the Geant4 Monte Carlo simulation toolkit, which has been previously validated for ray-tracing studies in the design of quadrupole microbeam systems. They include a fine modelling of the quadupole magnetic field, based on the analytical Enge’s model, which is compared to a classical square field model and to a high granularity tri-dimensional field map computed with the OPERA3D® software. The beam emittance model is parameterized from experimental measurements performed directly on the HVEE Singletron® at the AIFIRA facility, allowing the computation of the beam transmitted current along the nanobeam line. Grid shadow images, acquired from simulations, for system alignment purposes and beam deflection studies on target are presented as well.

Monte Carlo simulation of the CENBG microbeam and nanobeam lines with the Geant4 toolkit

A single-ended HVEE ® 3.5 MV Singletron electrostatic accelerator has been installed since October 2005 at the Centre d’Etudes Nucléaires de Bordeaux-Gradignan (CENBG) in France. This facility is equipped with a microbeam line dedicated to ion beam analysis (scanning transmission ion microscopy – STIM, particle induced X-ray emission – PIXE, Rutherford back scattering) and cellular irradiation in single event mode. A high demagnification nanobeam line will be installed on the same facility in the near future. This paper focuses on the simulation of the microbeam and nanobeam lines performances using the Geant4 Monte Carlo simulation toolkit. Comparisons with experimental data collected on the microbeam line are presented.

Geant4 simulation of the new CENBG micro and nanoprobes facility

The Centre d’Etudes Nucléaires de Bordeaux-Gradignan (CENBG) will soon be equipped with a new state of the art accelerator facility including a single-ended HVEE® 3.5MV Singletron. Its performance in terms of brightness and energy stability will provide the unique opportunity to develop a high spatial resolution nanobeam line. The actual microbeam line dedicated to ion beam analysis (scanning transmission ion microscopy, particle induced X-ray emission and Rutherford backscattering spectrometry) and to cellular irradiation will be reinstalled on the new machine. In this paper, expected performances of the two beam lines are presented from ray tracing simulations using the Geant4 toolkit, capabilities of which at the sub-micron scale have been investigated and validated previously.