Nanosecond pulsed proton microbeam

We show the preparation of a pulsed 20 MeV proton beam at the Munich tandem accelerator which offers a fluence of more than 1 × 10⁹ protons/cm² being deposited in a beam spot smaller than 100 μm in diameter and within a time span of 0.9 ns fwhm. Such a beam is produced by an ECR type proton source using charge exchange in cesium vapor to obtain a beam of negative hydrogen of high brightness that is bunched, chopped, accelerated and then focused by the superconducting multipole lens of the microprobe SNAKE. Single beam pulses are generated in order to irradiate cell samples or tissue and to measure their biological effect in comparison to continuous proton or X-ray irradiation.     

Performance of the Sumy nuclear microprobe with the integrated probe-forming system

The integrated probe-forming system for the Sumy nuclear microprobe comprises two doublets of magnetic quadrupole lenses of new design. Each doublet has been made from a single piece of soft iron by electro-discharge machining. This paper describes the performance tests of the microprobe including the beam scanning control and data acquisition systems. In the first runs a spot size of about 2 μm (FWHM) was obtained for the high beam current mode (up to 200 pA) by scanning a conventional copper grid with 1000 meshes per inch. Simulated beam optics parameters are compared with the experimental data.     

External scanning micro-PIXE for the characterization of a polycapillary lens: Measurement of the collected X-ray intensity distribution

We developed a PIXE detection system for the analysis of medium-light elements which exploits a weakly focusing polycapillary lens for the transmission of the X-rays emitted from the target material to a Silicon Drift Detector. The polycapillary lens efficiently collects X-rays, while prevents back-scattered protons from impinging on the detector chip, thus avoiding electronics perturbation and consequent quality loss of PIXE spectra. The system is optimized for the detection of X-rays in the energy range 1–10 keV, when the emission from the target is induced by MeV proton beams with size of the order of a few hundreds of micrometers.This work reports the results of the lens characterization in terms of X-ray collection spot, i.e. the area of the sample actually “seen” by the lens, and its dependence on the X-ray energy. The lens properties have been measured using the external scanning microbeam facility of the Tandetron accelerator at LABEC-INFN in Florence. The detection system was used to detect X-rays from a set of pure elemental standards with an incident 3 MeV proton beam focused to a size of about 30 μm scanning an area of 1.9 × 1.6 mm². By measuring the spatial distribution of characteristic X-rays from each given material, the collection profile of the lens at the corresponding X-ray energy was obtained. Using several standards, the behaviour throughout the range 1–10 keV was examined. The sensitivity of the lens collection profile on the lens-sample out-of-focus distance was also investigated.     

Targeted irradiation of biological cells using an ion microprobe – Why a small beam spot is not sufficient for success

When people plan to adapt their ion microprobe for the targeted irradiation of biological cells, they often claim that they expect a targeting accuracy in the range of their beam spot diameter, because they assume that reaching a sub-μm beam spot is the most difficult part of the job.Although many microprobes have now a beam spot diameter of some hundred nano-meters or less, nobody reached a targeting accuracy below 1 μm. Besides obvious reasons, like mechanical or thermal instabilities, there is a more difficult problem to overcome: one still needs a light microscope to locate both the microbeam and the cells to be irradiated, and there are various light-optical effects, which can give misleading information about the position of the beam and the cells.     

A proposed nuclear nanoprobe with Angstrom resolution

An idea is presented for an entirely new point-projection nuclear microscope that theoretically would have sub-nanometer resolution, approaching one Angstrom. The concept involves using a Kalbitzer super tip as a source of low energy (～100 eV) He or H ions that would be transmitted through a molecular sample (e.g. buckyball, carbon nanotube, graphene sheet, DNA molecule, etc.) placed very near the tip (～1–100 nm), and then projected onto a microchannel plate (MCP) screen placed ～1 m from the tip. Small angle scattering of the incident ions with atoms in the sample result in the development of shadow cones with an increase in scattered ion intensity at the critical cone angle. The enhanced intensity patterns formed at multiple intersections of cone perimeters are called “threads”. The shadow cones and threads are projected onto a suitable low-energy ion position sensitive detector to create a “shadow or thread image” of the sample. Such point-projection microscopes have no aberrations that affect the image, and the magnification would be of the order 1 m/10 nm, or 1.E8! The feasibility of this scheme is currently being studied theoretically using a deterministic atomic scattering model and a Monte Carlo molecular dynamics code. The results of these calculations indicate that only very low energy (60–120 eV) incident hydrogen ions can be used to avoid displacing atoms in the sample. At these energies, the critical cone angles are quite large and it would be necessary to position the molecular samples very close to the tip (down to only 1 nm) so that the projected ion maps are interpretable as distinct threads. Projecting distinct shadows is not supported by the scattering physics.     

Mapping of ion beam induced current changes in FinFETs

We report on progress in ion placement into silicon devices with scanning probe alignment. The device is imaged with a scanning force microscope (SFM) and an aligned argon beam (20 keV, 36 keV) is scanned over the transistor surface. Holes in the lever of the SFM tip collimate the argon beam to sizes of 1.6 μm and 100 nm in diameter. Ion impacts upset the channel current due to formation of positive charges in the oxide areas. The induced changes in the source–drain current are recorded in dependence of the ion beam position with respect to the FinFET. Maps of local areas responding to the ion beam are obtained.     

Applications to cultural heritage diagnostics at the new nuclear microprobe beam line at CEDAD

A nuclear microprobe beam line has been installed at CEDAD (Centre for Dating and Diagnostics), University of Salento, Lecce, Italy. The beam line is connected to the ?30° port of the high energy switching magnet of a 3 MV HVEE 4130HC Tandetron accelerator. It is based on an Oxford Microbeam magnetic quadrupole triplet and its general features are presented. The results of functional tests are presented showing how a lateral spatial resolution as low as ～2 μm has been achieved in vacuum by analysing standard reference material. The results obtained in the analysis of ancient radiocarbon dated biological tissues are presented for the identification and distribution of toxic elements such as Pb.     

Biological studies using mammalian cell lines and the current status of the microbeam irradiation system,SPICE

The development of SPICE (single-particle irradiation system to cell), a microbeam irradiation system, has been completed at the National Institute of Radiological Sciences (NIRS). The beam size has been improved to approximately 5 μm in diameter, and the cell targeting system can irradiate up to 400–500 cells per minute. Two cell dishes have been specially designed: one a Si₃N₄ plate (2.5 mm × 2.5 mm area with 1 μm thickness) supported by a 7.5 mm × 7.5 mm frame of 200 μm thickness, and the other a Mylar film stretched by pressing with a metal ring. Both dish types may be placed on a voice coil stage equipped on the cell targeting system, which includes a fluorescent microscope and a CCD camera for capturing cell images. This microscope system captures images of dyed cell nuclei, computes the location coordinates of individual cells, and synchronizes this with the voice coil motor stage and single-particle irradiation system consisting of a scintillation counter and a beam deflector. Irradiation of selected cells with a programmable number of protons is now automatable. We employed the simultaneous detection method for visualizing the position of mammalian cells and proton traversal through CR-39 to determine whether the targeted cells are actually irradiated. An immuno-assay was also performed against γ-H2AX, to confirm the induction of DNA double-strand breaks in the target cells.     

Experimental set-up for time resolved small angle X-ray scattering studies of nanoparticles formation using a free-jet micromixer

Recently, we have designed, fabricated and tested a free-jet micromixer for time resolved small angle X-ray scattering (SAXS) studies of nanoparticles formation in the <100 μs time range. The microjet has a diameter of 25 μm and a time of first accessible measurement of 75 μs has been obtained. This result can still be improved. In this communication, we present a method to estimate whether a given chemical or biological reaction can be investigated with the micromixer, and to optimize the beam size for the measurement at the chosen SAXS beamline. Moreover, we describe a system based on stereoscopic imaging which allows the alignment of the jet with the X-ray beam with a precision of 20 μm. The proposed experimental procedures have been successfully employed to observe the formation of calcium carbonate (CaCO₃) nanoparticles from the reaction of sodium carbonate (Na₂CO₃) and calcium chloride (CaCl₂). The induction time has been estimated in the order of 200 μs and the determined radius of the particles is about 14 nm.     

Determination of the local gold contact morphology on a photoactive polymer film using nanobeam GISAXS

Grazing incidence small-angle X-ray scattering is performed with a nanometer sized X-ray beam (nGISAXS) to probe the local gold contact morphology on a photoactive polymer film. By evaporation a 50 nm thick gold contact is installed on a diblock copolymer film, which consists of a non-conducting poly(styrene) (PS) and a semi-conducting poly(paraphenylene) (PPP) block. The region around the edge of the gold contact of 200 μm is probed with nGISAXS by scanning the sample position in steps of 1 μm with respect to the X-ray beam. The diblock copolymer film has a densely packed micellar structure with a characteristic distance between adjacent micelles of 19 nm which is unaffected by the gold deposition. The gold contact exhibits a tail region which extends its lateral dimension. For the full extended surface area of the gold contact with its tails an interdiffusion of gold into the diblock copolymer film is observed. For comparison imaging ellipsometry, atomic force microscopy and optical microscopy measurements are performed.     

Applications of microstructures fabricated by proton beam writing to electric-micro filters

Fabrication of high-aspect-ratio microstructures was performed by proton beam writing (PBW) using a microbeam line at Takasaki Ion Accelerators for Advanced Radiation Application (TIARA), JAEA Takasaki, JAPAN. As one of the applications of the high-aspect-ratio structures micro-machined by PBW, we utilized the high-aspect pillars for electric-micro filters of microbes such as Escherichia coli and Yeast based on the dielectrophoretic force. The filter is equipped with high-aspect pillars with a height of ～20 μm and a diameter of ～1 μm on a glass plate. Evaluation of the dielectrophoresis (DEP) device for capturing E. coli and Yeast was made using either observation by optical microscope or photoluminescence (PL) measurements.     

Development of a real-time beam current monitoring system for microbeam scanning-PIXE analysis using a ceramic channel electron multiplier

Microbeam scanning-PIXE (micro-PIXE) analysis is a useful method for obtaining information of multi-elemental distribution in samples by two-dimensional images of sample surfaces such as mammalian cells, tissues, and other environmental monitoring species. In addition to elemental distribution information, quantitative analysis is in demand for further investigations of environmental and biomedical studies concerning heavy metals accumulated in terms of cells and sub-cellular organelles. To make quantitative analysis possible, a real-time beam monitoring system that gives a precise number of ions, and an output independent from a sample that enables one to keep a beam resolution of micrometer size is required. In this paper, we report on the development of beam current monitoring. The beam current was monitored using a ceramic channel electron multiplier (CEM) to detect secondary electrons induced from a 50 nm thick carbon film (10 μg/cm²). This carbon film was attached to a sample holder, which was set at the targeted sample position. The output value of the CEM was proportional to the Faraday cup installed just after the sample position. The beam resolution was measured using off-axis STIM by scanning a copper grid, and was estimated at 1.79 and 1.72 μm for the horizontal and vertical directions, respectively, sufficient for routine micro-PIXE analysis.     

Micro-ERDA,micro-RBS and micro-PIXE techniques in the investigation of fish otoliths

Elemental distribution in the otolith of the fresh water fish burbot (Lota lota L.) collected in Hungary was measured with Elastic Recoil Detection Analysis (ERDA), Rutherford Backscattering Spectrometry (RBS) and as a complementary technique, Particle-Induced X-ray Emission (PIXE) with a focussed ion beam of 1.5 × 1.5 μm² spot size. The organic- and inorganic-rich regions of the otolith are distinguished and they are presented as hydrogen and calcium maps at depth regions of 0–70, 70–140 and 140–210 nm. The textured surface of the sample and its porosity were characterized from the effect on the RBS spectra. The oxygen and carbon PIXE elemental maps can also be used to identify the organic- and inorganic-rich regions of the otolith. The calcium map was found to be more homogeneous because the otolith structure is averaged in a larger depth. The trace elements Fe, Zn and Sr were detected only in very low concentration by micro-PIXE.     

The impact of thermal fatigue and carbidization on the W coatings deposited on CFC tiles for the ITER-like Wall project at JET

Since August 2011 JET operates with the ITER-like wall comprising bulk Be tiles, bulk W tiles and W coated CFC tiles with a thickness of 10–15 μm and 20–25 μm. In order to evaluate behavior of the W coatings to a cyclic thermal loading relevant to JET operation, high heat flux (HHF) tests have been carried out up to 5100 pulses with an electron beam facility at peak temperatures of 1000 °C, 1250 °C and 1450 °C. The pulse duration was 24 s. Optical inspections of the W layer performed periodically by interrupting the test revealed small delaminations with the size of 50–500 μm. The dependence of the delamination percentage on the number of pulses can be seen as a degradation curve for each particular W coating. In this way the thermo-mechanical properties of the W coatings can be characterized quantitatively. Thermal fatigue and carbidization of the tungsten due to the diffusion of the carbon from the substrate have been recognized as mechanisms for degradation of the coatings. Tungsten carbides have been identified by using TEM (transmission electron microscopy) diffraction analysis on FIB (focused ion beam) prepared cross-section samples subjected to HHF tests. Nano-pores developed at the CFC–Mo and Mo–W interfaces during the tests might be also responsible for the degradation of the coating.     

An advance process of aluminum rich coating as tritium permeation barrier on 321 steel workpiece

We have proposed an advance three-step process, Al-electroplating in ionic liquid followed by heat treating and selectively oxidation, preparing aluminum rich coating as tritium permeation barrier (TPB). In present work, the advance process was applied to 321 steel workpieces. In the Al-electroplating, pieces were coated by galvanostatic electrodeposition at 20 mA/cm² in aluminum chloride (AlCl₃)–1-ethyl-3-methylimidazolium chloride (EMIC) ionic liquid. The Al coating on those pieces all displayed attractive brightness and well adhered to surface of pieces. Within the aluminizing time from 1 to 30 h, a series of experiments were carried out to aluminize 321 steel pieces with Al 20 μm coating at 700 °C. After heat treated for 8 h, a 30 μm thick aluminized coating on piece appeared homogeneous, free of porosity, and mainly consisted of (Fe, Cr, Ni)Al₂, and then was selectively oxidized in argon gas at 700 °C for 50 h to form Al₂O₃ scale. The finally fabricated aluminum rich coating, without any visible defects, had a double-layered structure consisting of an outer γ-Al₂O₃ layer with thickness of 0.2 μm and inner (Fe, Cr, Ni)Al/(Fe, Cr, Ni)₃Al layer of 50 μm thickness. The deuterium permeation reduction factor, PRF, of piece (Φ 80 × 2, L 150 mm) with such coating increased by 2 orders of magnitude at 600–727 °C. The reproducibility of the process was also showed.     

Recent status of the Kiev nuclear probe

The modified Van de Graaff accelerator with proton beam energy W ? 3 MeV has been installed and put into operation at the TMM laboratory in Kiev. The laboratory incorporates the nuclear probe (NP) beam line, coupled to this accelerator. A short version of an optimized probe-forming system (PFS) has been developed for the Kiev NP. The system is based on divided triplet of the magnetic quadrupole lenses (MQLs). This PFS has two working regimes for the probe operations. The results of numerical calculations of the geometrical and ion-optical parameters of the PFS are presented. It is shown that this versatile PFS is a promising design for a modern nuclear nano-probe. A new precision adjustable MQL has been designed. Three lenses, the slit systems and target chamber are manufactured and installed at the Kiev probe beam line. Also a new data acquisition system for the Kiev NP is being developed.     

Design and fabrication of a CH/Al dual-layer perturbation target for hydrodynamic instability experiments in ICF

A polystyrene (CH)/aluminum (Al) dual-layer perturbation target for hydrodynamic instability experiments in inertial confinement fusion (ICF) was designed and fabricated. The target was composed of a perturbed 40 μm Al foil and a CH layer. The detailed fabrication method consisted of four steps. The 40 μm Al foil was first prepared by roll and polish process; the perturbation patterns were then introduced on the surface of the Al foil by the single-point diamond turning (SPDT) technology; the CH layer was prepared via a simple method which called spin-coating process; finally, the CH layer was directly coated on the perturbation surface of Al foil by a hot-press process to avoid the use of a sticker and to eliminate the gaps between the CH layer and the Al foil. The parameters of the target, such as the perturbation wavelength (T) and perturbation amplitude (A), were characterized by a QC-5000 tool microscope, an alpha-step 500 surface profiler and a NT1100 white light interferometer. The results showed that T and A of the target were about 52 μm and 7.34 μm, respectively. Thickness of the Al foil (H1), thickness of the CH layer (H2), and cross-section of the dual-layer target were characterized by a QC-5000 tool microscope and a scanning electron microscope (SEM). H1 and H2 were about 40 μm and 15 μm, respectively, the cross-sectional photographs of the target showed that the CH layer and the Al foil adhered perfectly with each other.     

Mechanical design for modification of a neutral beam for off-axis injection

DIII-D is planning to implement off-axis neutral beam current drive by neutral beam injection through a midplane port at angles up to 15° from horizontal. To accommodate the beam-line tilting, the following modifications are planned: (1) move the beam line away from the tokamak by 0.39 m to allow for a 0.68 m inside diameter welded bellows of necessary length to provide 15° of vertical motion between the vessel port and the beam line; (2) reduce the vertical height of the injected beam from 0.48 m to 0.43 m to provide clearance for the inclined beam as it passes through the length of the vessel port; (3) add a linkage system between the front of the beam line and the tokamak to restrain the NB against the vacuum loading from the bellows while maintaining zero roll about the axis of the beam line as it is moved about a virtual pivot axis; (4) add a forward and two rear vertical actuators for raising and lowering the beam line (These actuators require coordinated position control to rotate the NB about a virtual pivot axis.); (5) incorporate lateral restraint to comply with seismic requirements.     

A bulk tungsten tile for JET: Heat flux tests in the MARION facility on the power-handling performance and validation of the thermal model

In the frame of the ITER-like Wall (ILW) for the JET tokamak, a divertor row made of bulk tungsten material has been developed for the position where the outer strike point is located in most of the foreseen plasma configurations. In the absence of active cooling, this represents a formidable challenge when one considers the temperature reached by tungsten (T_W,surf > 2000 °C) and the vertical gradient ?T/?z = 5 × 10⁴ K/m.As the development is drawing to an end and most components are in production, actual 1:1 prototypes are exposed to an ion beam with a power density around 7 MW/m² on the plasma-facing surface. Advantage is taken of the flexibility of the Marion facility to bombard the tungsten stack under shallow angles of incidence (～6°) with a powerful beam of ions and neutrals (>70 MW/m² on axis). The shallow angles are important, with respect to the toroidal wetted surface, for properly simulating the expected performance under actual tokamak conditions. The Marion tests have been used to validate for a few typical cases the thermal calculations that were steadily developed along with the tungsten tile and, at the same time, to gather information on the actual temperatures of individual components. The latter is an important factor to a finer estimation of the power handling capabilities.