Drift Direction Research Articles

Experiments on plasma detachment in a V-shaped slot divertor in the DIII-D tokamak

Experiments in DIII-D demonstrate that the upstream plasma density to detach an un-pumped slot divertor is similar for a V-shaped and a flat-end slot, despite significantly higher neutral pressure in the V-shaped slot and in contrast to SOLPS-ITER predictions. The detachment threshold can be reduced by using in-slot instead of main-chamber gas fuelling or by placing the strike point on the inner slanted slot baffle instead of the slot end, as described by simulations with full drift physics. When increasing the plasma line-averaged density (without extrinsic impurities), the transition to detachment in DIII-D slot divertor is sharp and requires a high value of plasma density with the ion B→×∇B drift into the slot, whereas it is smooth and requires a lower value of plasma density with the opposite drift direction, in accord with detachment experiments in the DIII-D open lower divertor. Unique experiments on DIII-D and comparison to advanced simulations expand the scientific understanding of slot-shaped divertors, considered highly desirable for next step fusion devices.

High sensitivity distributed dynamic pressure sensor based on dual-linear frequency modulated optical frequency domain reflectometry.

In this Letter, we propose and experimentally demonstrate a highly sensitive distributed dynamic pressure sensor based on a dual-linear frequency modulated optical frequency domain reflectometry (OFDR) and a coating thickness-enhanced single-mode fiber (SMF). A dual-sideband linear frequency modulation (LFM) signal is used to interrogate the sensing fiber, which allows us to obtain a dual-sideband Rayleigh backscattering signal. Due to the opposite slopes of the two LFM sidebands, the Rayleigh backscattering spectra of the two sidebands drift in opposite directions when the fiber is disturbed. By subtracting the frequency shifts of the two spectra, we can double the system's sensitivity. We further enhance the sensitivity by using an SMF with a coating thickness of 200 μm. This results in a pressure sensitivity of 3979 MHz/MPa, a measurement accuracy of 0.76 kPa, and a spatial resolution of 35 cm over a 500 m optical fiber. Our system successfully detected a dynamic pressure change at a sampling rate of 1.25 kHz, demonstrating the sensor's excellent dynamic measuring capabilities.

Experimental evidence for the drift wave nature of the weakly coherent mode in ASDEX Upgrade I-mode plasmas

The improved energy confinement mode (I-mode) is a potential candidate for future fusion power plants, as it combines ELM-free operation with good confinement. The unusual edge transport and turbulence in this regime is still not fully understood. This study analyzes the turbulent structure of the weakly coherent mode (WCM) in ASDEX Upgrade. Measurements from Doppler back-scattering and a thermal helium beam diagnostic are used to determine velocities of the background plasma and the WCM over multiple discharges. A phase velocity of the WCM of the order of 2–5 km s−1 in the electron diamagnetic drift direction is found, quantitatively close to a drift wave assuming negligible temperature fluctuations. A good agreement with a previously proposed mechanism behind the I-mode regime is observed. This marks the first experimental verification of a specific understanding of the WCM and the I-mode regime.

Dynamical reconstruction of the upper-ocean state in the central Arctic during the winter period of the MOSAiC expedition

Abstract. This paper presents a methodological tool for dynamic reconstruction of the state of the ocean, based, as an example, on observations from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) experiment. The data used in this study were collected in the Amundsen Basin between October 2019 and January 2020. Analysing observational data to assess tracer field and upper-ocean dynamics is highly challenging when measurement platforms drift with the ice pack due to continuous drift speed and direction changes. We have equipped the new version of the coastal branch of the global Finite-volumE sea ice–Ocean Model (FESOM-C) with a nudging method. Model nudging was carried out assuming a quasi-steady state. Overall, the model can reproduce the lateral and vertical structure of the temperature, salinity, and density fields, which allows for projecting dynamically consistent features of these fields onto a regular grid. We identify two separate depth ranges of enhanced eddy kinetic energy located around two maxima in buoyancy frequency: the depth of the upper halocline and the depth of the warm (modified) Atlantic Water. Simulations reveal a notable decrease in surface layer salinity and density in the Amundsen Basin towards the north but no significant gradient from east to west. However, we find a mixed-layer deepening from east to west, with a 0.084 m km−1 gradient at 0.6 m km−1 standard deviation, compared to a weak deepening from south to north. The model resolves several stationary eddies in the warm Atlantic Water and provides insights into the associated dynamics. The model output can be used to further analyse the thermohaline structure and related dynamics associated with mesoscale and submesoscale processes in the central Arctic, such as estimates of heat fluxes or mass transport. The developed nudging method can be utilized to incorporate observational data from a diverse set of instruments and for further analysis of data from the MOSAiC expedition.

Investigating the Unique Drift Behavior of PSR B2110+27 with FAST

Careful scrutiny of the single pulse emissions from PSR B2110+27 has been conducted through highly sensitive observations using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) at a central frequency of 1250 MHz. Our investigation revealed significant subpulse drift behavior and nulling in this pulsar. Moreover, we observed that the nulling events tend to be of short duration, with an estimated overall nulling fraction of approximately 27% ± 3%. It is noteworthy that the drift direction of the subpulses exhibits abrupt changes, occasionally transitioning into a steady state or displaying a low drift rate. Analysis using longitude resolved fluctuation spectra indicates the presence of two distinct repetition periods for the pulsar: P 3 = (10.8 ± 2.5)P and P 3 = (31.6 ± 4.2)P, where P denotes the pulsar period. Our investigation revealed that the subpulse separation remains consistent across different drift patterns, with P 2 = 2.°3 ± 0.°2. A more comprehensive analysis indicates that the unique drift behavior observed can be explained by a carousel model of the dipole field. Minor changes in P 2 and drift rate caused significant variations in the apparent P 3 and abrupt shifts in the drift direction, while the true repetition period (assuming first-order aliasing) changed by only ∼10%. We observe a drift band memory and apparent phase memory across the null state in this pulsar, as well as variations in the drift rate and drift direction across the null state, though we have not detected significant periodicity of the nulling itself. This suggests that these phenomena may arise from random null pulses intersecting with the frequently aliased drift bands.

Demonstration of event position reconstruction based on diffusion in the NEXT-white detector

Noble element time projection chambers are a leading technology for rare event detection in physics, such as for dark matter and neutrinoless double beta decay searches. Time projection chambers typically assign event position in the drift direction using the relative timing of prompt scintillation and delayed charge collection signals, allowing for reconstruction of an absolute position in the drift direction. In this paper, alternate methods for assigning event drift distance via quantification of electron diffusion in a pure high pressure xenon gas time projection chamber are explored. Data from the NEXT-White detector demonstrate the ability to achieve good position assignment accuracy for both high- and low-energy events. Using point-like energy deposits from 83m\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{83\ extrm{m}}$$\\end{document}Kr calibration electron captures (E∼45\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E\\sim 45$$\\end{document} keV), the position of origin of low-energy events is determined to 2 cm precision with bias <1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$< 1~$$\\end{document}mm. A convolutional neural network approach is then used to quantify diffusion for longer tracks (E≥1.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E\\ge ~1.5$$\\end{document} MeV), from radiogenic electrons, yielding a precision of 3 cm on the event barycenter. The precision achieved with these methods indicates the feasibility energy calibrations of better than 1% FWHM at Qββ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{\\beta \\beta }$$\\end{document} in pure xenon, as well as the potential for event fiducialization in large future detectors using an alternate method that does not rely on primary scintillation.

Operating point control method for the Mach-Zehnder modulator in a phase-shift laser range finder

An operating point control method is proposed for the Mach-Zehnder modulator (MZM) based on a dual-cascaded MZM structure. Unlike traditional methods with dither signals, the proposed method is advantageous because the components monitored in the control process are not masked by the spectrum noise floor and the drift direction is clearly determined at the quadrature point, thus imparting greater control stability. Additionally, the proposed control method is suitable for phase-shift laser range finders (PSLRFs). Compared with traditional methods, experimental results reveal that the proposed method increases the operating point stability of MZM from ±0.59° to ±0.36° within 2 h, resulting in better ranging stability than 17 μm in 1 min and 39 μm in 1 h in a PSLRF with a 200 MHz modulation frequency.

The effect of avian eggshell membrane structure on microbial penetration: A simulation study

Avian eggshells exhibit excellent antimicrobial properties. In this study, we conducted simulation experiments to explore the defense mechanisms of eggshell membranes with regards to their physical features. We developed a mathematical model for the movement of microorganisms and estimated their penetration ratio into eggshell membranes based on several factors, including membrane thickness, microbial size, directional drift, and attachment probability to membrane fibers. These results not only suggest that an eggshell membrane with multiple layers and low porosity indicates high antimicrobial performance, but also imply that the fibrous network structure of the membrane might contribute to effective defense. Our simulation results aligned with experimental findings, specifically in measuring the penetration time of Escherichia coli through the eggshell membrane. We briefly discuss the significance and limitations of this pilot study, as well as the potential for these results, to serve as a foundation for the development of antimicrobial materials.

Boosting Bidirectional Photoresponse with Wavelength Selectivity through Ambipolar Transport Modulation

AbstractNegative photoconductive phototransistors, referring to transistors that exhibit a decrease in photocurrent under illumination, have the potential to revolutionize optoelectronic applications involving light, such as optoelectronic logic circuits and visual neural simulation. Currently, achieving negative photoconductivity (NPC) requires complex material design or interface structure construction. However, achieving precise control over NPC behaviors poses a significant challenge. Herein, a simple yet effective strategy is demonstrated for realizing controllable NPC responses in organic phototransistors through ambipolar transport modulation. Due to the controversy between the preferred exciton dissociation/charge separation direction and the gate electric field driven charge drift direction, the main semiconductor channel (n‐ or p‐channel) exhibits NPC behavior under illumination. The validity of this mechanism has been confirmed through intensive studies by varying the component and combination of the p‐n heterostructure. Moreover, devices utilizing ambipolar transport exhibit a wavelength‐selectivity NPC response due to the absorption characteristics of the combined semiconductor materials. Most encouragingly, by incorporating both negative and positve photoconductivity along with wavelength‐selective responses, high‐contrast image sensing, information encryption and decryption, as well as optoelectronic logic circuit design is successfully achieved. This work promotes the design and development of bidirectional optoelectronic devices and offers a new route for developing attractive multifunctional optoelectronic devices.

Efficacy of repeated low-level red-light therapy in the prevention and control of myopia in children

ObjectiveIn this study, we aimed to determine how different factors influence the effectiveness of repeated low-level red-light (RLRL) therapy in preventing and treating myopia in children. MethodsBetween June 2022 and April 2023, 336 children who visited our hospital due to myopia or significant decreases in hyperopia reserve were enrolled. The children were treated twice daily for three minutes with a head-mounted low-level red-light (single wavelength of 650 nm) therapeutic device. Each of the two treatment sessions was separated by at least four hours. The axial lengths and diopters of the children's eyes were compared before and three months after treatment, and the effects of gender, age, and baseline diopter on the efficacy of RLRL therapy were analyzed. ResultsFollowing three months of treatment, the average axial length of the eyes decreased by 0.031 mm. The condition was better for the boys than for girls, but the difference was not statistically significant. As age increased (F = 8.112, P = 0.000) or as the absolute value of baseline myopia degree increased (F = 10.51, P = 0.000), axial lengths of the eyes tended to decrease. The spherical equivalent refraction (SER) of children decreased by an average of 0.012 ± 0.355D. The condition was better for the boys than for girls, but the difference was not statistically significant. SER increased in the direction of hyperopic drift as age increased (F = 2.48, P = 0.031), or as the absolute value of baseline myopia degrees increased (F = 6.835, P = 0.000). There were no obvious side effects following the treatment. ConclusionThis study showed that RLRL therapy is a potential efficient, easily operable, and practically feasible method for the prevention and control of myopia.

Влияние электронного дрейфа в графене на преобразование поляризации нормально падающей волны

The polarization conversion of an electromagnetic wave normally incident on graphene with a direct electric current is investigated in the hydrodynamic approach. It is shown that the dynamic conductivity of graphene depends on the direction of electron drift even in the absence of spatial dispersion (i.e., for long electromagnetic waves). This changes the polarization of electromagnetic radiation at terahertz frequencies. The real part of the dynamic conductivity of graphene with electron drift can be negative, which leads to amplification of terahertz wave.

Characterization of ECRH plasmas in TOMAS

To improve the plasma performance and control the density and plasma quality during the flat top phase, wall conditioning techniques are used in large fusion devices like W7-X and in JT60-SA. To study the performance of electron cyclotron wall conditioning, numerous experiments were performed on the TOroidally MAgnetized System, which is operated by LPP-ERM/KMS at the FZ-Jülich. It is a facility designed to study plasma production, wall conditioning, and plasma–surface interactions. The produced electron cyclotron resonance heating plasmas are characterized in various conditions by density and temperature measurements using a movable triple Langmuir probe in the horizontal and the vertical direction, complemented by video and spectroscopic data, to obtain a 2D extrapolation of the plasma parameters in the machine. A way to calibrate the triple Langmuir probe measurements is also investigated. These data can be used to determine the direction of the plasma drift in the vessel and identify the power absorption mechanisms. This will give more insight in the plasma behavior and improve the efficiency of wall conditioning and sample exposure experiments.

Extraction and analysis of the sea ice parameter dataset of the Bohai Sea from 2011 to 2021 based on GOCI

The Bohai Sea and its surrounding areas are rich in oil and natural gas and play an important role in industry, agriculture and the economy. However, the Bohai Sea suffers severely from sea ice in the winter. While previous research has predominantly focused on methods for retrieving sea ice parameters in the Bohai Sea, analyses of their long-term statistical patterns have been limited. The Geostationary Ocean Color Imager (GOCI) is the first geostationary satellite for ocean color remote sensing, offering high spatial and temporal resolution, which greatly facilitates the extraction of Bohai Sea ice parameters. Utilizing GOCI data, we systematically extracted relevant sea ice parameters for the Bohai Sea region from 2011 to 2021. These parameters include sea ice concentration, sea ice thickness, and sea ice drift. We conducted a comprehensive statistical analysis of the long-term sea ice changes in the Bohai Sea and found that the development process of winter sea ice area is different from the sea ice thickness, and the direction of sea ice drift is basically unchanged. Then we developed statistical models linking sea ice parameters with ocean dynamic factors such as temperature, wind, and drift currents. Among them, the correlation coefficient between the predicted value and the measured value of the sea ice area model is the highest, reaching 0.8382. Furthermore, we examined the previously unexplored relationship between daily sea ice area, sea ice thickness, and accumulated temperature with their respective starting temperatures and accumulation periods. This study provides critical data to support Bohai Sea ice monitoring and marine environmental research. The results of this study contribute to a better understanding of sea ice change trends in the Bohai Sea and inform the development of disaster prevention and mitigation measures.

MINDORO OIL SPILL PROGRESS MONITORING USING SATELLITE IMAGERY

Abstract. Oil spills in the sea pose a significant threat to marine and coastal ecosystems including corals, sea grasses, and mangroves. Responding to oil spills in the high seas can be challenging and costly, as it is difficult to survey the area using ships or planes. Timely monitoring of extents and direction of drift is costly especially when large area is involved. This study used satellite imagery to monitor the progression of an oil spill in a timely manner. Images captured by various types of sensors was used to provide an almost daily oil extent map. Combining opensource satellite imagery, contributed imagery by commercial providers, and imagery from various national space agencies enabled situational awareness during the oil spill incident. Optical and SAR images were processed by using unsupervised K-means classification, for images that undergone image segmentation, and supervised support vector machine classification. The process was used to produce 46 oil extent maps from 196 satellite images from various sources through Sentinel Asia and The International Charter Space and Major Disasters.

Morphological and sedimentary characteristics of raked linear dunes in the southeastern Taklimakan Desert, China

Raked linear dunes were rarely reported, except in the Kumtagh Desert, leaving little known about the dynamic process. However, numerous raked linear dunes have formed in the Kat Kum dunefield of the southeastern Taklimakan Desert, which provides a new case to study the morphodynamics of these dunes. We conducted a comprehensive analysis on the dune morphometry, wind regime, sedimentary characteristics, and sand availability of these dunes. We found that grain size variation is an essential factor affecting the formation of raked linear dunes in addition to wind regime and limited sand availability. These dunes in the Kat Kum present small scale and easily reshaped with fast migration rate compared with these in the Kumtagh Desert, and distributed in areas with low sand cover. The primary ridge extended obliquely to the resultant drift direction, whereas the subsidiary ridge extend is nearly parallel to this direction. The grain size of the primary ridge is noticeably coarser than that of the subsidiary ridge. These dunes seem to have evolved from barchans. Under a north-northeast wind, barchans reshaped to asymmetrical barchans by extending their southeast limbs and eroding their northwest limbs, causing the ridge to be oblique to the resultant drift direction. The strong east-northeast wind erodes and reshapes the primary ridge, transporting fine sand to the northwest and resulting in the formation of proto-subsidiary ridges. With the elongation and lateral movement of primary ridge, a continuous subsidiary ridge with regular dune spacing forms on the northwest flank.

Spontaneously Sliding Multipole Spin Density Waves in Cold Atoms.

We report on the observation of spontaneously drifting coupled spin and quadrupolar density waves in the ground state of laser driven Rubidium atoms. These laser-cooled atomic ensembles exhibit spontaneous magnetism via light mediated interactions when submitted to optical feedback by a retroreflecting mirror. Drift direction and chirality of the waves arise from spontaneous symmetry breaking. The observations demonstrate a novel transport process in out-of-equilibrium magnetic systems.

Characterization of SOL profiles and turbulence in ICRF-heated plasmas in EAST

Scrape-off layer (SOL) profiles and turbulence in ion cyclotron range of frequency (ICRF)-heated plasmas are investigated by the reciprocating probe diagnostic system (FRPs) and gas puff imaging (GPI) diagnostic in EAST. A radio-frequency (RF) sheath potential reaching up to 100 V is identified proximate to the ICRF antennas. Notably, the amplitude of this RF sheath potential escalates in response to rising ICRF power and inversely with plasma density. When a RF sheath is present in the far SOL, a pronounced density ‘shoulder’ forms in front of the ICRF antennas, while the ‘shoulder’ fade away as the antenna and associated RF sheath shift outwards. A strong E r shear is revealed by measurements from both FRPs and GPI. Analysis of the poloidal wave number-frequency spectrum reveals suppression of high-frequency turbulence in the far SOL due to the RF sheath. This effect is manifested in the reduced autocorrelation time τ c and reduced average blob size δ blob of the SOL plasma. Intriguingly, the poloidal propagation direction of the low-frequency turbulence reverses from the electron to the ion diamagnetic drift direction at the RF sheath location. A surge of tungsten impurity is potentially attributed to the heightened interaction between the SOL plasmas and the wall material. Shifting the ICRF antennas outward, to alleviate heat spots, results in the relocation of the RF sheath to the shaded region of the main limiter. This shift amplifies the radial velocity of blobs in the far SOL and concurrently diminishes the SOL density when compared to conditions without ICRF injection. The properties of ion saturation current fluctuations are consistent with the stochastic model predictions.

Local variations of the cross-field transversal anisotropy orientation and drift direction in the F-region of the mid-latitude ionosphere

Analysis of fluctuations of the satellite radio-signals scattered on small-scale irregularities in F-region of the ionosphere and obtained recorded by a terrestrial ground-based receiver in Moscow showed has shown that often two or three maxima are present in the latitudinal profile of amplitude dispersion variance. The orientation of the cross-field transverse or transversal anisotropy of the irregularities was determined and compared with the drift direction obtained by the ionosonde DPS-4 using the LocalDrift program.

Nonstoichiometric Protic Ionic Liquids: The Role of Excess Acid in Charge Transport Mechanisms.

A study of charge transport mechanisms in an electric field was conducted on nonstoichiometric protic ionic liquids (PIL) based on triethylamine (TEA), in combination with an excess of either trifluoroacetic acid (TFA) or trifluoromethanesulfonic acid (TfO). The addition of excess precursor acid adds proton-donor sites to the system to support potential structural proton transport, which could, for example, enable the use in fuel cells. Transport measurements by pulsed field gradient (PFG) NMR diffusion and, in particular, electrophoretic NMR (eNMR) are supported by NMR chemical shifts and Raman spectroscopy, where the latter techniques elucidate the local solvation structures. Migration of the acidic proton of the excess acid in the electric field occurs toward the cathode with a velocity larger than that of the anions. This intriguing feature of a rapid drift of a neutral molecule is explained by the interplay of strong correlations between anion and cation as well as between anion and acid. The neutral acid is subject to vehicular transport with the anion, while the anion is partitioning between anion-acid and anion-cation clusters, resulting in a lower average drift velocity. The negative drift direction of the neutral acid and its proton is superimposed to and thus counteracts the vehicular transport of protons with the cation. The study sheds light on the role of excess acid in PIL and reveals the versatile interactions between anion, cation, and excess acid within a PIL determining its charge transport properties.

Evaluating Strategies to Enhance Li Transference in Salt-in-Ionic Liquid Electrolytes: Mixed Anions, Coordinating Cations, and High Salt Concentration.

The increased safety of salt-in-ionic liquid electrolytes compared with established carbonate-based systems has promoted intense research in this field, but low conductivities, slow lithium transport, and unfavorable lithium anion correlations still prevent a mass market application. In particular, strong Li-anion correlations lead to dominant vehicular Li transport with the same drift direction for anions and lithium in the electric field. Here, three different strategies and their mutual interplay are evaluated, which could reduce Li-anion coordination, i.e., high salt concentration, a mixed-anion composition, as well as an ether functionalization of the organic cation. To this end, two series of highly concentrated IL-based electrolytes, based on either ethylmethylimidazolium (EMIM) or the ether-functionalized 1-methoxyethyl-1-methylpyrrolidinium (Pyr12O1) organic cation, and employing mixed bis(fluorosulfonyl)imide/bis(trifluoromethylsulfonyl)imide (FSI/TFSI) anions are investigated. Measurements of conductivities, diffusion coefficients, and electrophoretic mobilities reveal no beneficial effect due to the increased heterogeneity of the FSI/TFSI-based electrolyte matrix, generally showing improved transport properties with increasing FSI share. However, a combination of both the ether-functionalized cation and high FSI content is proven successful, as lithium mobilities are positive, and vehicular transport is overcome by structural Li transport. Our study demonstrates the decisive role of synergy of the different approaches: While the single effect of a high salt concentration, weakly lithium-coordinating anions, or organic cations with lithium-affine functional groups is too weak to prevent vehicular transport, their joint effect can overcome vehicular Li transport, leading to improved Li conduction in ionic liquids.