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A real-time processing system for the two-color CO2 laser interferometer on the JT-60SA has been developed for density feedback control. The system has a novel feature that can detect fringe jumps due to off-normal events, such as loss detection due to displacement of the beam axis and changes in the laser wavelengths. Because a phase change due to the JT-60SA plasma is smaller than π/2, corresponding to the line-integral electron density NL of ∼ 6 × 1 0 19 m−2 in a short interval of 500 ns, the threshold of the fringe jump detection is decided to be π/2. Hence, off-normal events can be detected from a fringe jump, leading to the abort of the real-time feedback control. In the density feedback control of the JT-60SA plasma, the system is employed as a density monitor, with NL being successfully controlled at 16.8% ± 6.6% lower than the reference. [ABSTRACT FROM AUTHOR]

• Lasers require high power and enough beam quality. • A beam homogenizer providing super-Gaussian can be used for amplifications. • The homogenizer sustains long sustained distance with non-peaked profile. • A deformable mirror improves wavefront surface for enough beam quality. This paper suggests the use of two optical elements for laser transfer in Thomson scattering diagnostics, which are widely used for other laser applications. YAG lasers amplified by flash lamps (repetition frequency of 50–100 Hz having a few Joules output) can sometimes have adverse effects such as peaked beam profiles and wavefront distortion. We used a beam homogenizer, which is a refractive optical element, to change the beam profile from peaked to non-peaked at a designated position. Using a super-Gaussian output profile when amplifying lasers facilitated longer—by a factor of 1.5 (=300 mm/200 mm) compared with top-hat beam profile—sustained distances, i.e. the distance along the laser path having a non-peaked profile. In terms of beam quality, wavefront distortion broke the beam profile in the far field. We used a deformable mirror to correct and flatten the wavefront of the beam. A YAG laser having a wavefront distortion of 0.46 λ peak-to-valley was used to test the application of the deformable mirror, the results of which improved wavefront distortion to a wavelength of 0.1 λ peak-to-valley. [ABSTRACT FROM AUTHOR]

Magnification of a polarization angle with Littrow layout gratings has been developed. High magnification with a factor of 7.7 using two gratings in Littrow layout was experimentally proved. The magnification range was investigated by calculation at a wavelength of 10.6 µm. The method can be applied for a high magnification factor >30. Larger groove numbers and smaller blaze angles are suitable for the large magnification. Statistical fluctuation of the diffracted polarization angle is compared with that of the incident polarization angle. [ABSTRACT FROM AUTHOR]

We report on the design of a compact grism-pair stretcher for a near-infrared noncollinear optical parametric chirped-pulse amplification (OPCPA) system. The grisms are produced by bonding a grating to a prism using a resin. The stretcher is capable of controlling a bandwidth of over 300 nm, which is suitable for parametric amplification of few-cycle pulses. After amplification, pulses can be compressed by the dispersion of optical glass, and the residual group-delay can be compensated with an acousto-optic programmable dispersive filter (AOPDF). [ABSTRACT FROM AUTHOR]

A mechanical arcless dc circuit breaker is proposed and has been constructed. A rectifying device is used to block the reverse current of the breaker, allowing the breaker to open under zero current condition created by the discharge of a commutation circuit. A diode and a saturable reactor are used as the rectifying device, with a leakage current of ∼1 and ∼10 A, respectively. The duration of mechanical motion is about 20 ms, and its jitter is 2 ms, which is too long to make an economical system using a commutation capacitor. In order to avoid the dead time, the commutation circuit is started after the breaker kicks in and the final jitter is reduced to 20 μs. Arcless current interruption is achieved at 10 kA and 9.1 kV. Since a strong arc plasma is not generated between the contacts, a long lifetime of the breaker can be expected and a disconnecting switch can be used instead of a circuit breaker, reducing the size of the switch. These characteristics of the new breaker can be expanded for many applications. [ABSTRACT FROM AUTHOR]

A new method to magnify a small polarization angle with brazed gratings has been developed. In the method, difference in diffraction efficiency for S and P polarization components is used. The magnification dependence on the incident angle can be small by arranging the grating in Littrow layout. A magnification with a factor ~2.7 has been demonstrated for a 10.6 µmCO2 laser beam as expected from a calculation. The method is applicable in many polarimetry fields. [ABSTRACT FROM AUTHOR]

Examines electron and ion currents collected at the metal shield and floating shield to study the behavior of high-current vacuum arcs. Behavior of the arcs with the active anode; Property of vacuum arc on small copper electrodes; Difference between the maximum value and the value at the arc-current crest.

Aims: This study aimed to investigate the effect of Bacillus subtilis var. natto on the susceptibility of the model host, Caenorhabditis elegans, to bacterial infection. Methods and Results: Caenorhabditiselegans worms were fed with a standard food consisting of Escherichia coli OP50 strain (control) or B. subtilis (natto) during their larval stage. The worms were then infected with pathogenic bacteria. We analyzed their survival time and RNA sequencing‐based transcriptome. Upon infection with Staphylococcus aureus and Enterococcus faecalis, the survival time of B. subtilis (natto)‐fed worms was longer than that of the control. Transcriptome analyses showed upregulation of genes associated with innate immunity and defense response to gram‐positive bacteria in B. subtilis (natto)‐fed worms. Conclusions: Bacillus subtilis (natto) conferred an increased resistance of C. elegans to gram‐positive bacteria. Our findings provided insights into the molecular mechanisms underlying B. subtilis (natto)‐regulated host immunity and emphasized its probiotic properties for preventing and alleviating infections caused by gram‐positive bacteria. Significance and Impact of the Study: To the best of our knowledge, this is the first study to show that B. subtilis (natto) confers specific resistance against gram‐positive bacteria. [ABSTRACT FROM AUTHOR]

Abstract: A demonstration study of focusing geometry small-angle neutron scattering (FSANS) experiment was successfully performed using a superconducting sextupole magnet as a neutron focusing device and a polarized cold neutron beam. The obtained small-angle neutron scattering intensities from monodispersed SiO2 spherical particles were discussed in terms of the scattering function taking into account the -resolution. [Copyright &y& Elsevier]

The neutron focusing effect of a superconducting sextupole magnet has been investigated using unpolarized and polarized cold neutrons. The feasibility on the application of the magnetic lens to small-angle neutron scattering experiments are discussed. [Copyright &y& Elsevier]

An incoherent Thomson scattering diagnostic will be installed in the JT-60SA tokamak to measure electron temperature and electron density profiles. The target radial spatial resolution is 25 mm with 46 spatial channels. The accuracy in electron temperature and density is a few percent at ne = 7.5 × 1019 m−3, which is the expected value in the plasma core. This paper presents the designs of collection optics, fibers with their alignment system, and polychromators. The collection optics overcomes unique issues for superconducting fusion devices, i.e., limited design space, high-temperature measurements, and harsh radiation condition. When in several years the more performing plasma will generate intense nuclear radiation, the lens materials of the optics can be replaced by radiation resistant glasses without major changes in the lens holder. It will prevent transmission degradation and keep stable measurement accuracy. [ABSTRACT FROM AUTHOR]

A tangential viewing phase contrast imaging system is being designed for the JT-60SA tokamak to investigate microturbulence. In order to obtain localized information on the turbulence, a spatialfiltering technique is applied, based on magnetic shearing. The tangential viewing geometry enhances the radial localization. The probing laser beam is injected tangentially and traverses the entire plasma region including both low and high field sides. The spatial resolution for an Internal Transport Barrier discharge is estimated at 30%-70% of the minor radius at k = 5 cm-1, which is the typical expected wave number of ion scale turbulence such as ion temperature gradient/trapped electron mode. [ABSTRACT FROM AUTHOR]

We have constructed a new system which could analyze a position distribution of several elements in a sample with 2 dimensional prompt γ-ray analysis (2D PGA) system using focused neutron beam at JAEA. We aimed that the system could analyze local information in a sample with a good signal γ-ray from interested elements to noise of background γ-ray ratio. As a result, this system could determine the position resolution and spatial resolution within 1 mm. [ABSTRACT FROM AUTHOR]

Neutron optics has a potential to remarkably improve the performance of neutron scattering instruments. A superconducting sextupole magnet was constructed and characterized. The application of the magnetic optics to the small-angle neutron scattering with the focusing geometry is discussed. [Copyright &y& Elsevier]

A 14-channel grating polychromator for the purpose of measuring the electron cyclotron emission (ECE) spectrum has been developed and installed on the large helical device (LHD). The grating polychromator has a Czerny–Turner setup. The main advantage of the grating polychromator is that it has a broad spectral range. Hence, it can be utilized at different magnetic field strengths. Changing the angle or replacing the grating can do this. Gratings with a grid constant of d=2.3, 3, and 5 mm and a blaze angle of 20° can be applied and the scattered spectrum is directed to 14-liquid He cooled InSb detectors. Standard operation is performed with d=3 mm, f[sup range]=148–105 GHz. This is second harmonic ECE for B=2.75 T. Each channel has a spectral resolution of Δf (full width at half maximum)=2.6 GHz or f/Δf=60 at f=150 GHz. The properties of the instrument and first experimental results of LHD ECE will be described in this article. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A pair of conventional permanent magnet quadrupoles is used to focus a 2.4 MeV laser-driven proton beam at a 1 Hz repetition rate. The magnetic field strengths are 55 and 60 T/m for the first and second quadrupoles, respectively. The proton beam is focused to a spot with a size of less than ∼3×8 mm2 at a distance of 650 mm from the source. This result is in good agreement with the Monte Carlo particle trajectory simulation. [ABSTRACT FROM AUTHOR]

Electron cyclotron emission (ECE) can be used to determine the electron temperature profile in magnetized plasmas. The complex structure of the magnetic field configuration in the Large Helical Device (LHD) [M. Fujiwara et al., J. Fusion Energy 15, 7 (1996)] complicates the analysis of the ECE spectrum. The magnetic field is a nonmonotonous function of the radius and has a very large shear. The effects of the magnetic-field shear on the polarization of the ECE spectrum have been numerically and experimentally analyzed. For a high enough density (n[sub e]>1.0x10[sup 19] m[sup -3]) the polarization is found to rotate with the sheared magnetic field, yielding only a negligible mode conversion. Experiments on the polarization have been carried out at LHD. X-mode emission was detected under a specific angle, in agreement with the numerical predictions. The elliptically polarized ECE emission showed a very strong O-mode component (70% of X-mode), that can be attributed to the effect of wall reflections. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]