Compact Scanning Research Articles

Focus on test, measurement, and materials

Focus on test, measurement, and materials

Atomic resolution scanning tunneling microscope imaging up to 27 T in a water-cooled magnet

We report the first atomically resolved scanning tunneling microscope (STM) imaging in a water-cooled magnet (WM), for which extremely harsh vibrations and noise have been the major challenge. This custom WM-STM features an ultra-rigid and compact scan head in which the coarse approach is driven by our newly designed TunaDrive piezoelectric motor. A three-level spring hanging system is used for vibration isolation. Room-temperature raw-data images of graphite with quality atomic resolution were acquired in the presence of very strong magnetic fields, with a field strength up to 27 T, in a 32-mm-diameter bore WM with a maximum field strength of 27.5 T at a power rating of 10 MW, calibrated by nuclear magnetic resonance (NMR). This record field strength of 27 T exceeds the maximal field strength achieved by the conventional superconducting magnets. Besides, our WM-STM has paved the way to STM imaging using a 45 T, 32-mm-diameter bore hybrid magnet, which is the world’s flagship magnet, producing the strongest steady magnetic field.

X線顕微鏡（cSTXM）を用いたアエンデ隕石マトリクス中の有機物分析

X線顕微鏡（cSTXM）を用いたアエンデ隕石マトリクス中の有機物分析

Compact low temperature scanning tunneling microscope with in-situ sample preparation capability.

We report on the design of a compact low temperature scanning tunneling microscope (STM) having in-situ sample preparation capability. The in-situ sample preparation chamber was designed to be compact allowing quick transfer of samples to the STM stage, which is ideal for preparing temperature sensitive samples such as ultra-thin metal films on semiconductor substrates. Conventional spring suspensions on the STM head often cause mechanical issues. To address this problem, we developed a simple vibration damper consisting of welded metal bellows and rubber pads. In addition, we developed a novel technique to ensure an ultra-high-vacuum (UHV) seal between the copper and stainless steel, which provides excellent reliability for cryostats operating in UHV. The performance of the STM was tested from 2 K to 77 K by using epitaxial thin Pb films on Si. Very high mechanical stability was achieved with clear atomic resolution even when using cryostats operating at 77 K. At 2 K, a clean superconducting gap was observed, and the spectrum was easily fit using the BCS density of states with negligible broadening.

In situ study of modern synthetic materials and pigments in contemporary paintings by laser-induced fluorescence scanning

Laser-induced fluorescence (LIF) has found, in the recent years, widespread application to the field of material study and characterization. In particular, LIF has been applied to the assessment of damage, biological growth, and the analysis of specific materials on various surfaces in cultural heritages. Only a few papers deal with the application of LIF to the study of modern synthetic materials (mostly plastics) and pigments, and the analysis of contemporary works of art. Preliminary laboratory measurements on a wide range of plastic and cellulose-based materials, solvents, resins, and varnishes have been performed for rapid material characterization during in situ measurement campaigns in cultural heritage, security, and forensic contexts. Four paintings by Gastone Novelli, in the National Gallery of Modern and Contemporary Art, Rome, have been investigated by a compact LIDAR fluorosensor scanning system developed at the Laboratory of Diagnostic and Metrology in the ENEA Centre of Frascati (UTAPRAD-DIM Laboratory) for LIF measurements. Results and the relative data processing have provided fluorescence images, false color images, and punctual spectral information. The comparison with data and spectra from purpose-built reference databases has enabled recognition of materials on the paintings, and provided information on their production.

Cell depth imaging by point laser scanning fluorescence microscopy with an optical disk pickup head

A compact, cost-effective, and position-addressable digital laser scanning microscopy (DLSM) instrument is made using a commercially available Blu-ray disc read-only memory (BD-ROM) pickup head. Fluorescent cell images captured by DLSM have resolutions of 0.38 µm. Because of the position-addressable function, multispectral fluorescence cell images are captured using the same sample slide with different excitation laser sources. Specially designed objective lenses with the same working distance as the image-capturing beam are used for the different excitation laser sources. By accurately controlling the tilting angles of the sample slide or by moving the collimator lens of the image-capturing beam, the fluorescence cell images along different depth positions of the sample are obtained. Thus, z-section images with micrometer-depth resolutions are achievable.

Fluorescence microendoscopy imaging based on GRIN lenses with one- and two-photon excitation modes

With the rapid development of life sciences, there is an increasing demand for intravital fluorescence imaging of small animals. However, large dimensions and limited working distances of objective lenses in traditional fluorescence microscopes have limited their imaging applications mostly to superficial tissues. To overcome these disadvantages, researchers have developed the graded-index (GRIN) probes with small diameters for imaging internal organs of small animals in a minimally invasive fashion. However, dynamic imaging based on GRIN lens has not been studied extensively. Here, this paper presented a fluorescence endoscopic imaging system based on GRIN lenses using one-photon and two-photon excitation. GRIN lenses with 1.15 mm diameter and 7.65 mm length were used in the system. The images were acquired by a compact laser scanning imaging system with a resonant galvo-mirror system to scan the laser beam and a photomultiplier tube (PMT) to detect fluorescence signals. Experimental results showed that this system using two-photon excitation could implement dynamic fluorescence microendoscopic imaging and monitor the movement of blood flow beneath the skin in anesthetized mice while producing images with higher contrast and signal to noise ratio (SNR) than those using one photon excitation. It would be a useful tool for studying biological processes of small animals or plants in vivo.

High-voltage scanning ion microscope: Beam optics and design

This article is devoted to the conceptual design of a compact high-voltage scanning ion microscope (HVSIM). In an HVSIM design, the ion optical system is based on a high-brightness ion source. Specifically, the ion optical system is divided into two components: an ion injector and a probe-forming system (PFS) that consists of an accelerating tube and a multiplet of quadrupole lenses. The crossover is formed and controlled by the injector, which acts as an object collimator, and is focused on the image plane by the PFS. The ion microprobe has a size of 0.1μm and an energy of 2MeV. When the influence of the chromatic and third-order aberrations is theoretically taken into account, the HVSIM forms an ion microprobe.

Design and experimental investigations of a two-dimensional laser scanner based on piezoelectric actuators

A compact two-dimensional laser scanner based on piezoelectric actuators is presented. The scanner consists of two single-axis laser scanners placed perpendicular to each other, which exhibit the advantages of small size, large angle, high scanning speed, and high linearity. The mechanical structure and principle of the scanner are introduced and the performance of the scanner is experimentally investigated. The result shows that the maximum angle of the scanner is approximately 9.315 deg with a main resonant frequency of 1242 Hz. An open-loop controller based on a hysteresis compensation algorithm and analog notch filter is proposed. Its nonlinearity is reduced to ±0.5% after compensation. High frequency scanning and the step response of the scanner are also studied to demonstrate the performance and effectiveness of the scanner.

Non-Invasive Spectroscopic Determination of the Antioxidative Status of Gravidae and Neonates

Pregnancy and postpartum adaptation cause an increased formation of free radicals. This is associated with various perinatological diseases, e.g. necrotising enterocolitis. The human body has developed a protective system in the form of the antioxidative potential. The present study was the first to investigate the kinetics of the cutaneous antioxidative status in pregnant women and newborns using a non-invasive spectroscopic method. Eighteen pregnant women and their babies took part in the study. A light-emitting diode-based compact scanner system was used for quick non-invasive measurements of carotenoid antioxidants in human skin based on reflection spectroscopy. It could be shown that the antioxidative status of the expectant mothers significantly declined during labour (p < 0.001) and on day 1 after delivery (p < 0.01). Compared to the mothers, the newborns exhibited a significantly higher cutaneous carotenoid concentration on both day 1 (p < 0.01) and 5 (p < 0.01) after delivery. These results suggest that the oxidative stress due to postpartum adaptation is counteracted by an enhanced reservoir of carotenoid antioxidants in the subcutaneous fatty tissue. The peripartum cutaneous carotenoid level of mothers declines continuously, whereas term newborns show very high cutaneous antioxidant values.

A compact two-dimensional laser scanner based on piezoelectric actuators.

A compact two-dimensional (2D) single-mirror laser scanner has been designed and prototyped that is structurally small and has high accuracy. The mirror of the scanner is driven by three piezoelectric actuators aligned in parallel and staggered to form a triangular base to provide structural compactness and close drive axes. The mechanical structure and 2D tilt principle of the scanner were analyzed and the architecture was tested. With an asymmetric structure, the scanner has an optical angle of 2.558° and a principle resonance frequency at 1036.8 Hz in the x-axis and 4.495° at 654.0 Hz in the y-axis. Experimental results suggest that, with hysteresis compensation, the nonlinearity of the scanner is reduced to ±0.25% for the x-axis and ±0.3% for the y-axis. With an open-loop controller, the laser scanner can realize linear scanning at several hundred hertz.

X-ray micro-CT scanner for small animal imaging based on Timepix detector technology

We describe a newly developed compact micro-CT scanner with rotating gantry equipped with a Timepix Quad hybrid pixel semiconductor detector and a micro-focus X-ray tube providing spatial resolution down to 30µm. The resolving power of the device in relation to soft tissue sensitivity is demonstrated using a tissue-equivalent phantom and different types of biological samples. The results demonstrate that the use of noiseless particle counting detectors is a promising way to achieve sufficient soft tissue contrast even without any contrast agents.

Compact Low-cost Scanner for 3D-Reconstruction of Body Parts with Structured Light Illumination

This paper describes a low-cost miniaturized 3D reconstruction approach using structured light. By projecting known patterns onto a surface, shape and structure of the surface can be measured and characteristic parameters of deformation can be determined. Existing approaches use large geometries and complex optical components. Here we present our system with the size of a cigarette pack and a working distance of only 6 cm. The theoretical depth resolution of the system is determined by the resolution of the camera and the projector as well as the system geometry and was found to be about 100 µm.

Magnetic spring characteristic of an oscillatory actuator with silicone rubber torsion springs for optical scanner applications

A compact electro-magnetic oscillatory actuator was proposed based on a pair of torsion springs for optical scanners operating at low oscillating frequencies, such as 50 Hz for a portable barcode scanner. Each torsion spring in the actuator is made of silicone rubber and is dually supported at both ends. A yoke is coupled with the driven coil to enhance the driving torque of the actuator. In this study, we analyzed the effect of the yoke on the resonant frequency of the actuator, as well as the torsion moment. We also experimentally determined the relationship between the resonant frequency and the magnetic gap of the yoke. Compared with the mechanical resonant frequency in the experiments, which was designed to be 50 Hz, the frequency was modified to 57.4 Hz, 54.7 Hz and 52.9 Hz when the gap between the yoke and the permanent magnet was 1.5 mm, 1.7 mm and 1.9 mm, respectively. The proposed actuator, which combines a yoke with flexible torsion springs, is potentially useful as a compact optical scanner, taking advantages of both low power consumption and high reliability.

Scanning force microscope for in situ nanofocused X-ray diffraction studies.

A compact scanning force microscope has been developed for in situ combination with nanofocused X-ray diffraction techniques at third-generation synchrotron beamlines. Its capabilities are demonstrated on Au nano-islands grown on a sapphire substrate. The new in situ device allows for in situ imaging the sample topography and the crystallinity by recording simultaneously an atomic force microscope (AFM) image and a scanning X-ray diffraction map of the same area. Moreover, a selected Au island can be mechanically deformed using the AFM tip while monitoring the deformation of the atomic lattice by nanofocused X-ray diffraction. This in situ approach gives access to the mechanical behavior of nanomaterials.

The ReactorSTM: atomically resolved scanning tunneling microscopy under high-pressure, high-temperature catalytic reaction conditions.

To enable atomic-scale observations of model catalysts under conditions approaching those used by the chemical industry, we have developed a second generation, high-pressure, high-temperature scanning tunneling microscope (STM): the ReactorSTM. It consists of a compact STM scanner, of which the tip extends into a 0.5 ml reactor flow-cell, that is housed in a ultra-high vacuum (UHV) system. The STM can be operated from UHV to 6 bars and from room temperature up to 600 K. A gas mixing and analysis system optimized for fast response times allows us to directly correlate the surface structure observed by STM with reactivity measurements from a mass spectrometer. The in situ STM experiments can be combined with ex situ UHV sample preparation and analysis techniques, including ion bombardment, thin film deposition, low-energy electron diffraction and x-ray photoelectron spectroscopy. The performance of the instrument is demonstrated by atomically resolved images of Au(111) and atom-row resolution on Pt(110), both under high-pressure and high-temperature conditions.

Practical design for compact image scanner with large depth of field by compound eye system.

We designed a new image scanner using the reflective optics of a compound eye system that can easily assemble plural imaging optical units (called imaging cells) and is compact with a large depth of field (DOF). Our image scanner is constructed from 32 reflective imaging cells, each of which takes an image of approximately a 10-mm field of view (FOV) that slightly overlap the adjacent imaging cells. The total image is rebuilt by combining the 32 images in post processing. We studied how to fold the optical path in the imaging cells and simplified the structure, resulting in the following three advances of our previous work: 1) greater compactness (50 × 31 mm2 in the cross section), 2) less variable optical characteristics among the imaging cells, and 3) easy assembly thanks to small number of optical components constructing the imaging cell.

DigiPET: sub-millimeter spatial resolution small-animal PET imaging using thin monolithic scintillators

A new preclinical PET system based on dSiPMs, called DigiPET, is presented. The system is based on thin monolithic scintillation crystals and exhibits superior spatial resolution at low-cost compared to systems based on pixelated crystals. Current dedicated small-rodent PET scanners have a spatial resolution in the order of 1 mm. Most of them have a large footprint, requiring considerable laboratory space. For rodent brain imaging, a PET scanner with sub-millimeter resolution is desired. To achieve this, crystals with a pixel pitch down to 0.5 mm have been used. However, fine pixels are difficult to produce and will render systems expensive. In this work, we present the first results with a high-resolution preclinical PET scanner based on thin monolithic scintillators and a large solid angle. The design is dedicated to rat-brain imaging and therefore has a very compact geometry. Four detectors were placed in a square arrangement with a distance of 34.5 mm between two opposing detector modules, defining a field of view (FOV) of 32 × 32 × 32 mm3. Each detector consists of a thin monolithic LYSO crystal of 32 × 32 × 2 mm3 optically coupled to a digital silicon photomultiplier (dSiPM). Event positioning within each detector was obtained using the maximum likelihood estimation (MLE) method. To evaluate the system performance, we measured the energy resolution, coincidence resolving time (CRT), sensitivity and spatial resolution. The image quality was evaluated by acquiring a hot-rod phantom filled with 18F-FDG and a rat head one hour after an 18F-FDG injection. The MLE yielded an average intrinsic spatial resolution on the detector of 0.54 mm FWHM. We obtained a CRT of 680 ps and an energy resolution of 18% FWHM at 511 keV. The sensitivity and spatial resolution obtained at the center of the FOV were 6.0 cps kBq−1 and 0.7 mm, respectively. In the reconstructed images of the hot-rod phantom, hot rods down to 0.7 mm can be discriminated. In conclusion, a compact PET scanner was built using dSiPM technology and thin monolithic LYSO crystals. Excellent spatial resolution and acceptable sensitivity were demonstrated. Promising results were also obtained in a hot-rod phantom and in rat-brain imaging.

Development of a Compact Scanning Transmission X-Ray Microscope

We report a compact scanning transmission X-ray microscope newly designed and developed at the Photon Factory. The microscope has very compact size and is equipped with fully digitized control electronics to realize high stability, precise positioning and fast data acquisition. The hardware design of the microscope is described in detail. Results of measurement using test samples are also presented.

2.12. A moot point! A case report on potential projectile movement on postmortem MR

Objective This homicide case we investigate potential projectile movement on postmortem MR (PMMR) in a lodged ricochet projectile in the skull. The purpose of this case report is to evaluate the different aspects of PMMR-related properties of projectiles in gunshot wounds. Material and method The case underwent whole body postmortem computed tomography (Somatom Definition Flash Dual Source, Siemens Medical Solutions, Forchheim, Germany) in supine position, 3D-suface scanning (Atos Compact Scan 5 m, GOM mbH, Braunschweig, Germany) with reposition of the corpse to prone position and PMMR (Achieva 3.0 TX MR scanner, Philips Medical System, Best, The Netherlands). For validation purposes a later head CT-scan in supine position and subsequent autopsy was performed. Ferromagnetic properties of the projectile were tested. Results Imaging revealed projectile movement between PMCT and PMMR. The ricochet projectile showed bullet migration along the wound channel on PMMR from midbrain position to a frontal location of the bullet. The bullet did not produce susceptibility artifacts on PMMR. Autopsy revealed no heating effects of the adjacent tissue indicating no thermal effects by the PMMR scanning. The bullet showed no ferromagnetic properties after being tested by a magnet and literature review of the metallic compounding of this specific projectile. Therefore, the bullet migration was caused by repositioning of the corpse from supine to prone position along the ricochet wound channel. Conclusion Presence of susceptibility artifacts on PMMR images depend on the material compounds of the projectile. PMMR allows for better anatomical detail of bullet path within the soft tissue and may be performed in the vast majority of projectiles.