Particle Flux Research Articles

Abstract This study investigates how resonant magnetic perturbation (RMP) govern neoclassical transport and ambipolar electric field dynamics in tokamak plasmas. By integrating magnetic island geometry with collisionality dependent transport regimes, we develop theoretical models to quantify particle and heat fluxes. Numerical simulations reveal stark collisionality driven contrasts: in low-collisionality regimes (e.g., DIII-D), enhanced neoclassical transport dominates, with effective electron diffusion coefficients reaching D ~ 0.1 m2 s−1, accounting for 6.5% of the total observed electron temperature reduction at the q = 2 surface. In high-collisionality regimes (e.g., J-TEXT), neoclassical contributions are suppressed ( D ~ 10 − 4 m 2 s − 1 ), necessitating turbulence coupling to explain experimental particle losses. RMP induce collisionality dependent bifurcation of ambipolar electric fields, with reversal thresholds significantly lower in low-collisionality plasmas, consistent with DIII-D pedestal suppression observations. Crucially, we derive collisionality dependent critical RMP amplitudes for E r bifurcation, to optimize edge-localized mode suppression while minimizing transport penalties in fusion reactor.

The wastewater from Chemical Mechanical Polishing (CMP) generated in the semiconductor industry contains a significant concentration of suspended particles and necessitates rigorous treatment to meet environmental standards. Ceramic ultrafiltration membranes offer significant advantages in treating such high-solid wastewater, including a high separation efficiency, environmental friendliness, and straightforward cleaning and maintenance. However, the preparation of high-precision ceramic ultrafiltration membranes with a smaller pore size (usually <20 nm) is very complicated, requiring the repeated construction of transition layers, which not only increases the time and economic costs of manufacturing but also leads to an elevated transport resistance. In this work, halloysite nanotubes (HNTs), characterized by their high aspect ratio and lumen structure, were utilized to create a high-porosity transition layer using a spray-coating technique, onto which a γ-Al2O3 ultrafiltration selective layer was subsequently coated. Compared to the conventional α-Al2O3 transition multilayers, the HNTs-derived transition layer not only had an improved porosity but also had a reduced pore size. As such, this strategy tended to simplify the preparation process for the ceramic membranes while reducing the transport resistance. The resulting high-flux γ-Al2O3 ultrafiltration membranes were used for the high-efficiency treatment of CMP wastewater, and the fouling behaviors were investigated. As expected, the HNTs-mediated γ-Al2O3 ultrafiltration membranes exhibited excellent water flux (126 LMH) and high rejection (99.4%) of inorganic particles in different solvent systems. In addition, such membranes demonstrated good operation stability and regeneration performance, showing promise for their application in the high-efficiency treatment of CMP wastewater in the semiconductor industry.

We compare enhancements of mesospheric volume mixing ratios of hydroperoxyl radical HO2 and nitric acid HNO3, as well as ozone depletion in the Northern Hemisphere (NH) polar night regions during energetic particle precipitation (EPP) in January of 2005 and 2012. We utilize mesospheric observations of HO2, HNO3, and ozone from the Microwave Limb Sounder (MLS/Aura). During the second half of January 2005 and 2012, the GOES satellite identified strong solar proton events with virtually the same proton flux parameters. Geomagnetic disturbances in January of 2005 were stronger, with Dst decreasing up to 100 nT compared to January 2012 while the Dst drop did not exceed 70 nT. Comparison of observations made with the MLS/Aura shows the highest change of HO2 and HNO3 concentrations and also the deepest ozone destruction at the latitudinal range from 60∘ NH to 80∘ NH inside the north polar vortex right after the spike in energetic particle flux registered by GOES satellites. MLS/Aura observations show HNO3 maximum enhancements of about 1.90 ppb and 1.66 ppb around 0.5 hPa (about 55 km) in January 2005 and January 2012, respectively. The HOx increases lead to short-term ozone destruction in the mesosphere, which is seen in MLS/Aura ozone data. The maximum HO2 enhancement is about 1.05 ppb and 1.62 ppb around 0.046 hPa (about 70 km) after the onset of EPP in the second half of January 2005 and January 2012, respectively. Ozone maximum depletion is observed around 0.02 hPa (about 75 km). Ozone recovery after EPP was much faster in January 2005 than in January 2012.

Cooling of the fusion blanket first wall remains a significant challenge given the adverse conditions of heat and particle flux encountered near the plasma. Helium emerges as an attractive cooling candidate because of its chemical and neutronic inertness and separability from hydrogenic species (e.g. tritium). Because of the low thermal mass of helium, optimization of these coolant channels is warranted to provide high heat transfer performance at low pumping costs. Increasingly, computational fluid dynamics (CFD) simulations are employed to model and optimize these flow channels, and accompanying experimental data are needed to validate the predictions of these models. To provide the aforementioned experimental data, a high-pressure helium flow visualization upgrade has been designed for the Helium Flow Loop Experiment facility. This apparatus was built to American Society of Mechanical Engineers boiler and pressure vessel standards to withstand operating pressure of 4 MPa and mated to high-pressure glass windows. Seedless flow visualization is performed via high-speed background oriented schlieren (BOS), with image correlation used for time-resolved two-dimensional velocimetry at frequencies in excess of 60 kHz. Rectangular flow channel test articles are additively manufactured via laser powder bed fusion and installed into this visualization apparatus, with one-sided heating supplied by resistive heaters. The chosen test geometries were informed by prior CFD simulations, and the helium flow structures observed via BOS (detachment, recirculation, etc.) will be used for the validation of these accompanying models, in support of the design and optimization of blanket cooling channel configurations.

Abstract The study on scaling the scrape-off layer (SOL) power width (λq) is crucial for deepening the understanding of the SOL particle and heat transports. Due to the sparse distribution of the divertor Langmuir probes (Div-LPs) and the erosion of probe tips during the long-pulse high-performance operations on EAST, the estimation of SOL particle flux width (λjs, used to approximate λq) from the measured ion saturation current density profile (js) usually has relatively large uncertainty. This paper introduces a maximum a posteriori (MAP) estimation method based on the Bayes' theorem to reduce the fitting uncertainty for λjs (the fitting accuracy increases by 33% in terms of mean absolute error compared with the traditional ordinary least squares estimation). With the new estimation method and the FreeGS equilibrium code, the databases in [Liu X et al., Nucl. Fusion 64 (2024) 026002] are updated, which are further used to scale λjs. Compared with the old λjs scalings for the L-mode and H-mode databases in deuterium and helium plasmas, the updated λjs scalings show better regression quality with similar results. The deuterium and helium databases for L-mode and H-mode plasmas can be combined to get a unified scaling, λ_js [mm]= 1.35(L ̅_c [m])^1.07 f_GW^0.46 β_p^(-0.38) (P_SOL/S_LCFS [MW∙m^(-2) ])^0.27 Z^0.23, where L ̅_c is the averaged SOL connection length, f_GW is the fraction of Greenwald density, β_p is the poloidal beta, PSOL is the power crossing the last closed flux surface (LCFS), S_LCFS is the surface area of the LCFS, and Z is the charge number. The unified scaling reveals that: i) λjs has a strong scaling dependence on the SOL connection length suggesting the missing scaling dependence on the machine size for the Eich scaling; ii) the helium λjs is slightly larger than the deuterium λjs. Furthermore, the scalings for integrated particle flux width are also given in this paper.

Abstract The impact of space weather on space mission performance is a subject of extensive study by both scientists and space agencies. In this work, we discuss solar activity, the characterization of the interplanetary medium and the fluxes of solar and galactic particles after 2035, when LISA, the first interferometer for low-frequency gravitational wave detection in space, is expected to be launched. According to the lessons learned with LISA Pathfinder, the precursor mission of LISA, we focus on interplanetary phenomena that have been demonstrated to affect mission performance. The results of the study presented here can be considered in any investigation concerning the internal charging of the LISA spacecraft.

Abstract JOREK 3D non-linear magnetohydrodynamic (MHD) simulations with non-equilibrium impurity treatment of thermal quench (TQ) triggered by a massive neon gas in EAST L-mode disruptions are first presented. Neon impurities are deposited at ΨN ~ 0.7, followed by asymmetrical parallel extension along magnetic lines driven by a parallel self-consistent electrical field induced by plasma cooling process. Both double-stage and single-stage TQ observed in EAST experiments are reproduced through simulations with varying impurity particle fluxes. In double-stage TQ, non-linear interactions among the m/n=3/1, 4/1, and 5/1 modes primarily contribute to edge stochastic. Growth of m/n=2/1 mode initiates core energy loss during the first temperature collapse. Subsequently, the m/n=2/1 mode of comparable large amplitude, along with higher harmonics, couples with the 3/1 mode, resulting in a global stochastic and total energy loss in the second collapse. The transition between double-stage and single-stage TQ is primarily determined by the n=1 mode growth rate. In our simulations, the longer duration of double-stage TQ offers benefits for reducing the peak power of outward energy flux. Additionally, deeper impurity injection enhances radiative power and reduces outward energy flow. Strike point splitting on the upper-outer target, observed experimentally, is also reproduced in the simulations.

Motivated by complex bidirectional transport processes that occur in various biological and physical systems, we examine a one-dimensional closed system comprising two parallel lanes under limited resources. One lane is characterized by driven diffusive transport, while the other supports solely unidirectional motion in the opposite direction, mutually coupled through strong coupling. The total number of particles in the system, quantified by the filling factor, regulates the inflow of particles onto the lanes. The stationary properties of the system are analyzed through both simple and vertical cluster mean-field approaches, complemented by boundary layer analysis to elucidate its detailed behavior. Our theoretical results demonstrate that, for any set of parameters, one of the lanes invariably resides in a phase of zero net particle flux, manifesting either in a completely empty or fully jammed state. Two distinct types of phase transitions are identified and characterized: bulk transitions and surface transitions. Notably, phases emerge that exhibit boundary layers in their density profiles near both boundaries. A distinctive feature of the interplay between lane coupling and bidirectional transport is the appearance of kink and dip in the boundary layers, which is scrutinized by using the residence time method and fixed point analysis. Furthermore, we investigate the dynamics of phases involving shock and its sensitivity to system parameters. All theoretical outcomes are corroborated through stochastic simulations based on the Gillespie algorithm and numerical technique.

In this article, we claim that axionlike particles (ALPs) with MeV masses can be produced with semirelativistic velocities in core-collapse supernovae (SNe), generating a diffuse galactic flux. We show that these ALPs can be detected in neutrino water Cherenkov detectors via ap→pγ interactions. Using Super-Kamiokande data, we derive new constraints on the ALP parameter space, excluding a region spanning more than one order of magnitude in the ALP-proton coupling above cooling bounds for ALP masses in the range of 1–80 MeV and ALP-proton couplings between 8×10−6–2×10−4. We show that the future Hyper-Kamiokande will be able to probe couplings as small as 2.5×10−6, fully closing the allowed region above SN 1987A cooling bounds.

Abstract The effects of transport barriers on impurity transport, specifically helium (He) and tungsten (W), are investigated using the global, flux-driven, full-F, 5D gyrokinetic code GYSELA. The transport barrier is induced by triggering E × B shear via an external poloidal momentum source, thereby stabilizing ITG turbulence and reducing outward heat fluxes. These reductions in particle and heat fluxes due to the transport barrier lead to enhanced confinement, thereby steepening the ion temperature profiles and reducing the heat diffusivity of the main ion species (i.e. deuterium). Impurity transport in both turbulent and neoclassical regimes is investigated under various conditions, with and without the transport barrier, along with a reversed density profile for tungsten. The transport barrier is found to reduce outward impurity transport and enhance neoclassical thermal screening due to the steepened temperature profile. However, it also prevents helium from being flushed out, due to an increased inward Banana-Plateau flux, caused by the poloidal asymmetry of the source. Overall, a transport barrier induced by an E × B shear proves to be an effective mechanism not only for reducing heat fluxes but also for controlling impurity transport.

Abstract Pedestal turbulence spreading into SOL could be used to explain experimentally observed strong pedestal-SOL coupling and expected to be important for the broadening of divertor deposition profile in future device (Xu X Q et al 2019 Nucl. Fusion 59 126039). On EAST tokamak, it is found that an electromagnetic mode in pedestal region can spread into SOL and broaden divertor particle flux width. A multi-channel fluctuation reflectometry is used to measure the density fluctuations in the plasma edge. The electromagnetic mode rotates in the electron diamagnetic drift direction in the lab frame with a frequency range of [40-90] kHz, toroidal mode number n=12-13 and poloidal wavenumber kθ=0.41 cm-1. The mode amplitude peaks around the maximum of pedestal density gradient. As the mode amplitude increases, the reflectometry channel in SOL can clearly capture the mode. This result suggests that the EM mode is excited in pedestal gradient region and spreads into SOL. It is further found that the particle flux deposition profile in divertor is broadened as the EM mode appears.

We propose to search for millicharged particles produced in high-intensity electron beam dumps using small ultralow-threshold sensors. As a concrete example, we consider a Skipper-CCD placed behind the beam dump in Hall A at Jefferson Lab. We compute the millicharged particle flux, including both electromagnetic cascade and meson productions emanating from an aluminum target. We find that the sensitivity of a modest 2 × 14 array of Skipper-CCDs can exceed the sensitivity of all existing searches for millicharged particle masses below 1.5 GeV, and is either competitive or world leading when compared to other proposed experiments. Our results demonstrate that small-scale ultralow threshold silicon devices can enhance the reach of accelerator-based experiments, while fitting comfortably within existing experimental halls.

Abstract Recent studies underscore the critical role of heterotrophy in enhancing the resilience of symbiotic corals to global stressors, such as ocean warming. However, much remains unknown about the role of heterotrophy on coral reproduction, despite its key role in the persistence of coral populations and connectivity. In this study, we experimentally investigated how the trophic regime of parental colonies of the symbiotic gorgonian Eunicella singularis during gametogenesis may affect larval release, survival and settlement rates under both optimal and simulated marine heatwave temperatures. Eunicella singularis is widespread and abundant species in the Mediterranean Sea, being tolerant to a wide range of environmental conditions, and it has been proposed as a potential “winner” under future climatic conditions in the Mediterranean. Our results, however, suggest that predicted declines in marine primary production, zooplankton abundance, and particle flux could undermine their resilience. Notably, we observed a 1 week delay in larval release in absence of heterotrophic inputs, emphasizing heterotrophy’s significant contribution to gametogenesis. Moreover, heterotrophy also plays a crucial role in sustaining larval survival, since the absence of heterotrophic inputs lead to significantly higher mortality of the resulting larvae, regardless of temperature exposure. Overall, this study contributes to increase our understanding of the broader consequences of global change on coral populations under the globally forecasted reduction of primary production and zooplankton abundance.

Influence of austral summer sea ice melting timing on particle fluxes and composition in Prydz Bay, East Antarctica

The physics studies at heavy-ion nucleus-nucleus collision experiments demand reliable detectors at high particle flux. Therefore, Gas Electron Multipliers (GEM) detectors, which show resilience to extreme radiation, are one of the prime choices for the upcoming Compressed Baryonic Matter (CBM) experiment at the Facility of Antiproton and Ion Research, Germany. However, operating them under these demanding conditions requires a systemic study at the highest incident particle flux. To this end, we have conducted extensive tests on a real-size triple GEM detector module with the high-intensity gamma flux using the Cs-137 source at the upgraded Gamma Irradiation Facility (GIF++) at Conseil Européen pour la Recherche Nucléaire (CERN). The detector response, particularly regarding the gain and efficiency of muon detection, was studied extensively with and without a gamma source in a free-streaming mode using self-triggered electronics. This configuration will be necessary for the CBM experiment since it will observe unprecedented event rates of about 10 MHz for Au-Au collisions. The analysis reveals an alignment between the expected and observed value of gain and efficiency with an increasing intensity of gamma flux at the operating voltage. The test results demonstrate that the large-size GEM detector prototype can handle elevated gamma rates of approximately 17.25 MHz/cm2 without significantly impacting its performance or suffering irreversible damage.

Primordial black holes (PBH), while still constituting a viable dark matter component, are expected to evaporate through Hawking radiation. Assuming the semi-classical approximation holds up to near the Planck scale, PBHs are expected to evaporate by the present time, emitting a significant flux of particles in their final moments, if produced in the early Universe with an initial mass of ∼ 1015 g. These “exploding” black holes will release a burst of Standard Model particles alongside any additional degrees of freedom, should they exist. We explore the possibility that heavy neutral leptons (HNL), mixing with active neutrinos, are emitted in the final evaporation stages. We perform a multimessenger analysis. We calculate the expected number of active neutrinos from such an event, including contributions due to the HNL decay for different assumptions on the mixings, that could be visible in IceCube. We also estimate the number of gamma-ray events expected at HAWC. By combining the two signals, we infer sensitivities on the active-sterile neutrino mixing and on the sterile neutrino mass. We find that, for instance, for the scenario where U τ 4 ≠ 0, IceCube and HAWC could improve current constraints by a few orders of magnitude, for HNLs masses between 0.1–1 GeV, and a PBH explosion occurring at a distance of ∼ 10-4 pc from Earth.

Introducing a biased grid between an asymmetrical electrode system significantly influences plasma dynamics by controlling charged particle flux in the presence of an ambient magnetic field. Selective biasing facilitates the axial transport of energetic electrons through the grid, evidently supported by the rise in discharge current along with the emergence of negative differential resistance (NDR). The trapping of low energetic electrons near the biased grid and subsequent diffusion of nonthermal electrons toward the anode momentarily characterize the NDR formation and generate burst oscillations. The presence of NDR and its resilience to withstand associated instabilities demands further investigation of discharge transition to chaos using the empirical mode decomposition technique. The power spectrum analysis and the estimation of the largest Lyapunov exponent are concurrently used to verify the presence of complexity and the transition of periodicity into chaos. Multiple coherent modes, represented by the intrinsic mode function, carry most of the energies during the discharge in the presence of sheath–plasma instability, confirming the transition of multiple dominant modes from periodic to chaotic discharge regimes due to the intermittent behavior of the burst oscillations in the system.

Abstract The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) aboard the Lunar Reconnaissance Orbiter spacecraft has been operating in lunar orbit since 2009. CRaTER data provide a long‐term record of the near‐Moon radiation environment that is relevant to human exploration. In considering requirements for operational instruments on crewed lunar missions that are anticipated in the next several years, the question arises whether real‐time measurements by existing assets such as Geostationary Operational Environment Satellite (GOES) are adequate for providing radiation warnings for the safety of astronauts on or near the Moon during Energetic Solar Particle Events (ESPEs). ESPEs are distinguished from more typical Solar Particle Events (SPEs) by their large fluxes of higher‐energy particles. Here we show direct comparisons of contemporaneous ESPE measurements made in the two locations to establish that the radiation environments in lunar space and in geostationary orbit (GEO) are sufficiently similar to allow the use of GOES as a warning system for crew on or near the Moon. The conclusion is based primarily on data from six ESPEs in the October 2021–October 2024 time frame in which the integral flux of protons with energies greater than 100 MeV exceeded 1 at the event's peak as measured by operational GOES satellites, and to a lesser extent on data from two earlier ground‐level events (GLEs) that are of particular interest. We report new methods for analyzing CRaTER data under high‐flux conditions and find good agreement with data reported by GOES‐16 and later satellites.

A network of spectroscopic cameras was installed and successfully operated during the entire operation phase 1 of the optimized stellarator, Wendelstein 7-X. This diagnostic system enabled spatially resolved measurements of photon fluxes at specific wavelengths. Narrow band pass filters in the optical path allowed for targeted photon flux measurements of various spectral lines, specifically for the main ion species, hydrogen, and the primary impurity, carbon.The cameras were arranged in a stellarator-symmetric configuration, with one camera assembly per half-module. Each camera was equipped with a 135 ° ultra-wide field-of-view lens centered on the divertor, enabling comprehensive observation of the entire divertor unit, including the baffle and most of the surrounding heat shield. This configuration achieved coverage of 56 % of all plasma-facing surfaces at W7-X, providing a spatial resolution up to 1.4 pixel/cm at a frame rate of 25 Hz.This diagnostic system supports a wide range of applications, from studies of ionizing particle fluxes and wall recycling to investigations of plasma radiation and detachment, edge impurity sources, and their distribution. This paper details the diagnostic system's observation geometry, measurement principles, calibration processes, inter-diagnostic comparisons, synthetic diagnostic modeling, and plans for further development.

Abstract Earth suffered the attack of the strongest geomagnetic storm in the last 20 years (Kp = 9, Dst −400 nT) occurred on 11 May 2024. Taking advantage of the LEO multi‐parameter CSES satellite (launched in 2018) with a large inclination angle , with the joint observations of NOAA and GOES, we present a comprehensive near‐earth space responses on this super geomagnetic storm and report the precise high energy particle flux enhancements, electric and magnetic field disturbances and plasma density changes. A new proton belt with fluxes exceeding with energy 2.5–14 MeV at L = 1.5 ∼ 2 was formed, which was likely caused by the inward proton penetration from solar proton events(SPEs) and possible energization under the condition of compressed magnetopause in the southward interplanetary magnetic field of subsequent storm sudden commencement(SSC). During this super storm, many kinds of excited electromagnetic (EM) waves, such as ULF waves at several Hz, left‐hand polarized quasi‐periodic waves and magnetosonic waves, were observed in the ionosphere. Simultaneously, the electron and ion density, temperature and the total electron content (TEC) show significantly complicated changes after the storm occurrence. We also investigated the ground influence in western region of China and an obvious Forbush decrease of muon detection by 5 was caused by the storm effect.