Image Intensifier Unit Research Articles

Linear plasma device GyM for plasma-material interaction studies

GyM is a linear plasma device operating at Istituto per la Scienza e Tecnologia dei Plasmi, Consiglio Nazionale delle Ricerche, Milan, with the original aim of studying basic plasma physics, such as turbulent processes. Since 2014, GyM experimental program has been mainly focused on the issue of plasma-material interaction (PMI) for magnetic confinement nuclear fusion applications. GyM consists of a stainless steel vacuum chamber (radius and length of 0.125 m and 2.11 m), a pumping system, a gas injection system, 10 magnetic field coils and two magnetron sources at 2.45 GHz, capable of delivering a total microwave power up to 4.5 kW. Highly reproducible steady-state plasmas of different gas species, at a maximum working pressure of ∼10−1 Pa, can be obtained by electron cyclotron resonance heating in the resonance layer at 87.5 mT. Plasmas of GyM have electron and ion temperature ≤15 eV and ∼0.1 eV, respectively. The electron density is in the range of 1015–1017 m−3 and the ion flux is ≤5 × 1020 ions⋅m−2s−1. Main plasma diagnostics of GyM comprise Langmuir probes, an optical emission spectrometer, a mass spectrometer and a fast camera system equipped with an image intensifier unit. For the purpose of investigating the topic of PMI, GyM is provided with two sample exposure systems. Both are biasable at a negative bias voltage down to −400 V, to tune the energy of the impinging ions. One of them is also equipped with a heating lamp and can reach and sustain a temperature of 990 K for several hours, thus allowing to study the role of sample temperature during the plasma-material interaction. This contribution presents the layout of GyM, the diagnostics, the sample exposure systems and the typical plasma parameters. A brief overview of the main PMI activities carried out so far and a description of future machine upgrades are also given.

Experimental study on electrostatic discharges from a metal protrusion inside a silo during continuous loading of polypropylene powder

In this study, the electrostatic discharges from a metal protrusion existing inside a conical-cylindrical silo during continuous loading of polypropylene powders (PP, 3 to 4 mm) were experimentally investigated. A pilot-scale silo connected to a pneumatic powder transport facility was used while all parts were electrically grounded. The metal protrusion used in this study had a diameter of 4 cm. The silo was continuously loaded with PP powders at a mass flow rate of 0.68 kg/s to a total mass of approximately 800 kg. An image intensifier unit was used to observe the electrostatic discharges generated from the metal protrusion, and a current probe attached to an oscilloscope was used to measure the discharge amount (Q [nC]). As for the results, a multiplicity of small electrostatic discharges (brush discharges) from the protrusion was observed. The electrostatic discharge from the protrusion during PP powder loading clearly developed at the 391 s mark, when approximately 270 kg of the powder had been loaded. In addition, a difference was observed in the electrostatic discharges before and after the protrusion was embedded in the accumulated powder. That is to say, after the metal protrusion was embedded in the accumulated powder, the electrostatic discharges were stronger than when the protrusion was not embedded. As well, the Q after the immersion of the metal protrusion in the accumulated powder was several times larger than that when the protrusion was out. Strong broad bulk surface discharges clearly appeared after the protrusion was fully immersed in the powder.

Experimental study on the effect of metal protrusions inside silos on electrostatic discharges

This paper experimentally introduces the electrostatic discharges generated from metal protrusions inside a silo during the loading of powders. An industrial-scale pneumatic powder transport facility including a silo and approximately 400 kg of polypropylene powder (PP, 2–3 mm in size) were used for this test. The PP powder loading speed was approximately 0.38 kg/s. Six different diameters (D: 1 cm to 6.3 cm) of metal protrusions were used. The metal protrusions were attached to the silo wall using a 30 cm support rod that was electrically grounded. The height from the accumulated PP powder to the protrusion in the silo varied from 10 cm to 50 cm. An image-intensifier unit was used in order to observe the electrostatic discharges generated from the metal protrusions and a current probe attached to an oscilloscope was used in order to measure the current of the discharges. As for the results, electrostatic discharges (such as brush discharges) from protrusions during the loading of PP powders were clearly observed. Specifically, the electrostatic discharge was the strongest in this paper when the diameter of the protrusion was 4 cm and the height from the accumulated powder was 30 cm. As an important finding, the value of the discharge amount was affected to a greater extent by the maximum discharge current. The maximum charge amount of electrostatic discharges generating from the metal protrusions in all of the test conditions was −122 nC, which is twice as high as the threshold for electrostatic risk assessment in the liquid painting process. These results suggest that, in the chemical process, sensitive powders with MIEs of less than 4 mJ, powders wetted with solvents, and the solvents themselves must be carefully handled, as these kinds of powders may be ignited by brush discharges. In order to prevent and reduce electrostatic accidents, it is important to make sure that no external material enters the silo.

Staff knowledge of radiation protection in endovascular surgery

Image intensification exposes the endovascular surgery staff to ionizing radiation. The aim of this study was to determine awareness of ionizing radiation risks among personnel working in the endovascular surgery environment and the availability of radiation protection clothes and to propose appropriate corrective measures. This descriptive study was performed in the endovascular operating theatre equipped with a mobile image intensifier unit in La Rabta vascular department in September 2017. We visited the endovascular theatre to identify the availability of radiation protection clothes. We used a questionnaire to identify personnel knowledge about ionizing radiation. We established a global score of knowledge to classify our population. We identified 85 professionals exposed to ionizing radiation. Sixty-four of them (75%) responded to our questionnaire; 65% were male; median age was 34 years (range: 25-61). Endovascular theatre personnel were surgeons (35%), nurses (34%), qualified technicians (18%) and other department employees (13%). The mean global score of knowledge was 8.15/20 (2-18). This score increased significantly with grade and seniority (Kruskal-Wallis test). In the present study, the results indicate insufficiency knowledge about radiation exposure among the endovascular staff and in radioprotection tools availability. In order to minimize all unnecessary radiation, attempts should be made to increase vascular theatre staff knowledge about radiation protection. Safety culture is a referral method to reduce radiation exposure as low as possible.

Experimental study on electrostatic charges and discharges inside storage silo during loading of polypropylene powders

As polymer powders have high resistivity, they can easily be charged due to the repeated collision and separation of particles along with particle-wall friction in a pneumatic conveying system. This study experimentally investigated the electrostatic charges and discharges inside a conical-cylindrical silo during the loading of polypropylene (PP, 2–3 mm) powders. The silo was continuously loaded with PP powders at 0.68 kg/s to a total mass of approximately 800 kg. To measure electrostatic charges of the PP powder being loaded into the silo, a Faraday cage with a cover was set at a distance of 50 mm from the center of the loading pipe inside the silo. To observe electrostatic discharges inside the silo, an image-intensifier unit was set on the windowpane of the silo roof. The results show that the charge-to-mass ratio of the loading PP powder remained at a constant value of approximately −12 μC/kg. The ring-shaped light, which is the electrostatic discharge, appeared clearly at the center of the silo approximately 7 s after initial loading. The diameter of the ring-shaped light grew larger as time passed after loading. This was because the diameter of the accumulated PP powders increased in the silo during the running time, meaning that electrostatic discharge occurred between settled PP powders and the grounded metal silo wall. Additionally, the electrostatic discharges during the loading of powder in this study were clearly observed and classified into three kinds of discharges: brush, linear, or broad bulk surface discharges.

Avoiding Complications and Technical Variability During Arthroscopically Assisted Transtibial ACL Reconstructions by Using a C-Arm With Image Intensifier.

Background:Surgical reconstruction of the anterior cruciate ligament (ACL) can be complicated by incorrect and variable tunnel placement, graft tunnel mismatch, cortical breaches, and inadequate fixation due to screw divergence. This is the first report describing the use of a C-arm with image intensifier employed for the sole purpose of eliminating those complications during transtibial ACL reconstruction.Purpose:To determine if the use of a C-arm with image intensifier during arthroscopically assisted transtibial ACL reconstruction (IIAA-TACLR) eliminated common complications associated with bone–patellar tendon–bone ACL reconstruction, including screw divergence, cortical breaches, graft-tunnel mismatch, and improper positioning of the femoral and tibial tunnels.Study Design:Case series; Level of evidence, 4.Methods:A total of 110 consecutive patients (112 reconstructed knees) underwent identical IIAA-TACLR using a bone–patellar tendon–bone autograft performed by a single surgeon. Intra- and postoperative radiographic images and operative reports were evaluated for each patient looking for evidence of cortical breeching and screw divergence. Precision of femoral tunnel placement was evaluated using a sector map modified from Bernard et al. Graft recession distance and tibial α angles were recorded.Results:There were no femoral or tibial cortical breaches noted intraoperatively or on postoperative images. There were no instances of loss of fixation screw major thread engagement. There were no instances of graft-tunnel mismatch. The positions of the femoral tunnels were accurate and precise, falling into the desired sector of our location map (sector 1). Tibial α angles and graft recession distances varied widely.Conclusion:The use of the C-arm with image intensifier enabled accurate and precise tunnel placement and completely eliminated cortical breach, graft-tunnel mismatch, and screw divergence during IIAA-TACLR by allowing incremental adjustment of the tibial tunnel and knee flexion angle. Incremental adjustment was essential to accomplish this. Importantly, a C-arm with image intensifier can be used with any ACL reconstruction that incorporates tunnels in the technique, with the expectation of increase in accuracy and precision and the elimination of common complications.Clinical Relevance:The use of an image intensifier during transtibial ACL reconstruction will substantially reduce the common complications associated with the procedure and improve both accuracy and precision of tibial and femoral tunnel placement. Use of an image intensifier unit is generalizable to an individual surgeon’s preferences for graft choices and drilling techniques and will be especially valuable when the intercondylar architecture is altered from injury, time, or prior surgery.

Imaging of Turbulent Structures and Tomographic Reconstruction of GyM Plasma Emissivity

In GyM, a linear magnetized plasma device, low-frequency electrostatic fluctuations are measured by means of Langmuir probes. To complement electrostatic probe measurements of plasma turbulence and the study of plasma structures, a nonperturbative direct imaging system has been used on GyM, including a fast-framing Photron APX-RS camera and an image intensifier unit. From the line-integrated camera images, we compute time-resolved emissivity profiles of the plasma by applying a tomographic reconstruction technique using a pixel method and solving an overdetermined set of equations by singular value decomposition. The validity and robustness of the tomographic reconstruction technique are examined with respect to noise and wall reflection effects.The tomographic reconstruction is applied to fast camera movies acquired with a frame rate of 75 kHz and 4 μs of exposure time to obtain the temporal evolution of the emissivity fluctuations. Plasma structures can be detected and tracked in the reconstructed emissivity movies with a finest spatial resolution of 2 cm. Conditional average sampling is used to determine the size and speed of turbulent structures.

Time-resolved photoluminescence imaging with electronic shuttering using an image intensifier unit

In contrast to traditional steady-state photoluminescence imaging (PLI), time-resolved photoluminescence imaging (TR-PLI) allows for a calibration-free measurement of the effective transient minority charge carrier lifetime τeff in a silicon sample. For transient photoluminescence measurements, the illumination source as well as the camera signal have to be modulated on a time-scale in the order of τeff. Different approaches for camera signal modulation have been presented, including the use of a complementary metal-oxide-semiconductor (CMOS) camera or a rotating shutter wheel. In this work, the use of an InGaAs-based image intensifier unit as a fast optical shutter for TR-PLI was evaluated. Due to the fast switching times of the image intensifier, effective lifetimes down to 1/50 of the modulation period could be resolved reliably. Measurements under different illumination conditions allow for an injection-dependant analysis of τeff and comparison to photoconductance decay measurements.

P-002 Radiation exposure reduction in biplane fluoroscopic flat panel detectors

PurposeFollowing installation of a fluoroscopic digital flat panel detector (FPD) in the neuroangiography suite, three patients who underwent repeated angiographic studies for subarachnoid hemorrhage had complications with epilation, with one...

Fast Imaging of Blob Motion in TORPEX Plasmas

To complement electrostatic probe measurements of plasma turbulence and study plasma structures with high spatial resolution, a nonperturbative direct imaging system has been developed on TORPEX. This system includes a fast framing Photron-APX-RS camera and a fast gated image intensifier unit. Fast camera movies are acquired at a 150 thousand frames/s frame rate and 2 μs of exposure time. The plasma emissivity profile is tomographically reconstructed from the tangentially viewed image. Conditional average sampling is then applied to visualize and measure the size of structures associated with interchange modes as well as blobs in TORPEX plasmas.

Imaging of turbulent structures and tomographic reconstruction of TORPEX plasma emissivity

In the TORPEX [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)], a simple magnetized plasma device, low frequency electrostatic fluctuations associated with interchange waves, are routinely measured by means of extensive sets of Langmuir probes. To complement the electrostatic probe measurements of plasma turbulence and study of plasma structures smaller than the spatial resolution of probes array, a nonperturbative direct imaging system has been developed on TORPEX, including a fast framing Photron-APX-RS camera and an image intensifier unit. From the line-integrated camera images, we compute the poloidal emissivity profile of the plasma by applying a tomographic reconstruction technique using a pixel method and solving an overdetermined set of equations by singular value decomposition. This allows comparing statistical, spectral, and spatial properties of visible light radiation with electrostatic fluctuations. The shape and position of the time-averaged reconstructed plasma emissivity are observed to be similar to those of the ion saturation current profile. In the core plasma, excluding the electron cyclotron and upper hybrid resonant layers, the mean value of the plasma emissivity is observed to vary with (Te)α(ne)β, in which α=0.25–0.7 and β=0.8–1.4, in agreement with collisional radiative model. The tomographic reconstruction is applied to the fast camera movie acquired with 50 kframes/s rate and 2 μs of exposure time to obtain the temporal evolutions of the emissivity fluctuations. Conditional average sampling is also applied to visualize and measure sizes of structures associated with the interchange mode. The ω-time and the two-dimensional k-space Fourier analysis of the reconstructed emissivity fluctuations show the same interchange mode that is detected in the ω and k spectra of the ion saturation current fluctuations measured by probes. Small scale turbulent plasma structures can be detected and tracked in the reconstructed emissivity movies with the spatial resolution down to 2 cm, well beyond the spatial resolution of the probe array.

Time-Resolved Long-Lived Luminescence Imaging Method Employing Luminescent Lanthanide Probes with a New Microscopy System

Superior fluorescence imaging methods are needed for detailed studies on biological phenomena, and one approach that permits precise analyses is time-resolved fluorescence measurement, which offers a high signal-to-noise ratio. Herein, we describe a new fluorescence imaging system to visualize biomolecules within living biological samples by means of time-resolved, long-lived luminescence microscopy (TRLLM). In TRLLM, short-lived background fluorescence and scattered light are gated out, allowing the long-lived luminescence to be selectively imaged. Usual time-resolved fluorescence microscopy provides fluorescence images with nanosecond resolution and has been used to image interactions between proteins, protein phosphorylation, the local pH, the refractive index, ion or oxygen concentrations, etc. Luminescent lanthanide complexes (especially europium and terbium trivalent ions (Eu3+ and Tb3+)), in contrast, have long luminescence lifetimes on the order of milliseconds. We have designed and synthesized new luminescent Eu3+ complexes for TRLLM and also developed a new TRLLM system using a conventional fluorescence microscope with an image intensifier unit for gated signal acquisition and a xenon flash lamp as the excitation source. When the newly developed luminescent Eu3+ complexes were applied to living cells, clear fluorescence images were acquired with the TRLLM system, and short-lived fluorescence was completely excluded. By using Eu3+ and Tb3+ luminescent complexes in combination, time-resolved dual-color imaging was also possible. Furthermore, we monitored changes of intracellular ionic zinc (Zn2+) concentration by using a Zn2+-selective luminescent Eu3+ chemosensor, [Eu-7]. This new imaging technique should facilitate investigations of biological functions with fluorescence microscopy, complementing other fluorescence imaging methodologies.

Real-time imaging of radioisotope labeled compounds in a living plant

We developed a quantitative, real-time imaging system of labeled compounds in a living plant. The system was composed of CsI scintillator to convert β-rays to visible light and an image intensifier unit (composed of GaAsP semiconductor and MCP; micro channel plate) to detect extremely weak light. When the sensitivity and resolution of the image of our system was compared with that of an imaging plate (IP), the sensitivity of our system (with 20 minutes) was higher than that of an IP, with similar quality to that of an IP. Using this system, the translocation of 32P in a soybean plant tissue was shown in successive images.

Non-invasive visualisation of the development of peritoneal carcinomatosis and tumour regression after 213Bi-radioimmunotherapy using bioluminescence imaging

Non-invasive imaging of tumour development remains a challenge, especially for tumours in the intraperitoneal cavity. Therefore, the aim of this study was the visualisation of both the development of peritoneal carcinomatosis and tumour regression after radioimmunotherapy with tumour-specific 213Bi-Immunoconjugates, via in vivo bioluminescence imaging of firefly luciferase-transfected cells. Human diffuse-type gastric cancer cells expressing mutant d9-E-cadherin were stably transfected with firefly luciferase (HSC45-M2-luc). For bioluminescence imaging, nude mice were inoculated intraperitoneally with 1x10(7) HSC45-M2-luc cells. On days 4 and 8 after tumour cell inoculation, imaging was performed following D-luciferin injection using a cooled CCD camera with an image intensifier unit. For therapy, mice were injected with 2.7 MBq 213Bi-d9MAb targeting d9-E-cadherin on day 8 after tumour cell inoculation. Bioluminescence images were taken every 4 days to monitor tumour development. After i.p. inoculation of HSC45-M2-luc cells into nude mice, development as well as localisation of peritoneal carcinomatosis could be visualised using bioluminescence imaging. Following 213Bi-d9MAb therapy on day 8 after intraperitoneal inoculation of HSC45-M2-luc cells, small tumour nodules were totally eliminated and larger nodules showed a clear reduction in size on day 12 after tumour cell inoculation. Subsequently a recurrence of tumour mass was observed, starting from the remaining tumour spots. By measuring the mean grey level intensity, tumour development over time could be demonstrated. Non-invasive bioluminescence imaging permits visualisation of the development of peritoneal carcinomatosis, localisation of tumour in the intraperitoneal cavity and evaluation of therapeutic success after 213Bi-d9MAb treatment.

3023 フェンス状ナノ構造配列を用いたDNA分離用マイクロ流路における分子の運動解析(J21 マイクロナノ理工学,J21 マイクロナノ理工学)

We have analyzed motion of DNA molecules in the microchannel with nanofences in order to clarify the mechanism of size-based separation. The traces of DNA molecules were obtained from video images taken by a CCD camera with an image intensifier unit. We developed a program to trace DNA molecules in the microchannel during electrophoresis. It was found that smaller DNA molecules had longer detours around nanofences and the detour had nearly inverse relationship with applied voltage.

A computer model of an image intensifier system working under automatic brightness control.

A computer model of a fluoroscopy unit operating under automatic brightness control has been developed. The model has been validated by simulating one particular unit but is very general in nature and can easily be applied to other fluoroscopy systems. The model was developed by breaking the operation of a fluoroscopy unit down into its constituent parts then implementing each part in a module of code. It is controlled using the input air kerma to the intensifier face. Discrepancies from the situation when the model is controlled by the energy deposited in the input phosphor have been investigated and shown to be negligible over the operating range. To calculate entrance surface dose rates (ESDRs) to water and polymethylmethacrylate (PMMA) phantoms, Monte Carlo techniques were used to generate backscatter factors for these materials using the beam geometry and range of possible tube potentials and field sizes of a typical mobile image intensifier unit. The model was validated by calculating ESDRs to different thicknesses of water and PMMA phantoms. The predictions generated by the model were in good agreement with experimental measurements. Potential uses of the model include evaluation of dose reduction techniques, investigation of the balance between patient dose and image quality, and assessment of scatter dose.

A small scintillating fiber camera consisting of 0.25-mm square fibers for space dosimetry

A small scintillating fiber camera for space dosimetry was developed. The camera consists of a scintillating fiber stack bundled with 0.25-mm square fibers, two image intensifier units whose input windows are 40 mm in diameter, and two photomultipliers. Neutron events are distinguished from gamma-ray events by observing three-dimensional track images of recoil protons and electrons. Experimental results show that events caused by recoil protons with energies above 5 MeV can be distinguished from gamma-ray events. The purpose of this camera is to evaluate the LET, of charged particles produced in the interaction of neutrons with the nucleus in scintillating fibers. The camera is expected to measure the dose contribution from higher energy neutron, especially, more than /spl sim/10 MeV, which is the upper limit energy of the present measurement in space.

Scintillating fiber camera for neutron dosimetry in spacecraft

A scintillating fiber camera for three-dimensional imaging was newly developed for radiation dosimetry in spacecraft. The camera consists of a scintillating fiber stack, an image intensifier unit and photomultipliers for triggering events. The scintillating fiber stack has 100 scintillating fiber layers. The layers are alternatively stacked up to be perpendicular to each other. The stack is coupled to a two-stage image intensifier and then coupled to a CCD camera for the track readout. Each fiber layer consists of 100 scintillating fibers and the fiber stack composed of 100 layers leads us to a sensitive volume of 50×50×50 mm 3 . Each fiber has a cross-section of 0.5×0.5 mm 2 . It is found that the camera has the capability to clearly identify charged particles, neutrons and γ-rays by observing individual three-dimensional images of those tracks. The threshold energy for identification of neutrons and γ-rays is 5– 10 MeV for recoil proton energy when the coincidence signals from 2 photomultipliers are used as triggers and is expected to be 2–3 MeV when the triggers from either photomultiplier are used. The whole energy region for neutron dosimetry will be covered by the combination with the Bonner spheres for the energy region lower than ∼10 MeV .

718 衝撃風洞を用いたスクラムジェットエンジン内の流れと超音速燃焼(OS7-6 航空宇宙推進(流体,燃焼))(OS7 北海道における航空宇宙工学研究の進展と未来)

Flow and combustion phenomena in a scramjet engine model were investigated by using a small high enthalpy shock tunnel. At Mach number about 6.5, double wedges were set in the test section as a scramjet engine intake and a combustion chamber model. Schlieren-image visualization and wall static pressure measurements were conducted. The compression process used the oblique shock system, which was generated by vehicle edge (fore-body) and cowl, was observed. H_2 and/or premixed C_2H_2-air mixture was injected normally to the supersonic cross flow in the combustion chamber model. To observe a self-emission from combustion gas, the high-speed video camera (18,000fps) with an image intensifier unit was used. The supersonic combustion in supersonic flowfield in the combustion chamber model was confirmed.

Thermoluminescence (TL) spectra from quartz grains using on-line TL-spectrometric system.

An on-line spectrometric system installed with a small spectrometer and an image intensifier unit has been developed for weak and changeable TL-spectrum measurements with rising temperature for application to natural minerals. The detection sensitivity over visible wavelength regions was corrected using a known spectrum from a standard light source, and the detection sensitivity was also examined by a chemical luminol reaction. In an applied experiment, two quartz grain samples from two pyroclastic flows of the same origin, were subjected to testing with the present measuring system. The original data, consisting of 512 channels for every second at a constant heating rate of 1°C/s, were used to create a contour map or a 3-dimensional expression of TL-spectra after subtraction of background radiation. The artificially irradiated quartz grains clearly showed both red (RTL) and blue TL (BTL) in contrast to RTL alone from naturally accumulated TL. Both spectral expressions and glow curves from the same original data were found to be available to estimate quartz formation temperatures, together with thermoluminescence colour images (TLCIs).