Particle Flux Research Articles

In this research, the diagnostic imaging and therapy of the environment of selected human tissues by the produced protons from fusion reactions have been simulated by using the Geant4 tool. As a result, the stopping power and range of protons with different energies in these tissues have been obtained. As an example, Bragg peaks caused by protons with energies of 60 to 150 MeV have been shown in breast tissue. Further, the penetration depth of protons, proton flux, and the secondary particle flux of neutrons and gamma with energies of 20 to 70 MeV (in the therapeutic energy range) have been investigated in the breast tissue. Finally, a comparison of the residual dose in breast tissue without a tumour and with a tumour at 60 MeV energy has been done. Therefore, with such simulations, calculations, and creative approaches, effective measures can be taken in the fields of proton imaging and proton therapy because proton radiography is a method that can be used to extract the maximum required information from different human tissues. Also, tumours located in different human tissues can be targeted and destroyed by using different energies of protons.

Abstract We investigated isotope effects during the tokamak à configuration variable (TCV) ohmic discharge of a diverted positive triangular shape configuration of deuterium (D) and hydrogen (H) plasmas. The transition from the linear ohmic confinement (LOC) regime to the saturated ohmic confinement (SOC) regime was clearly identified from the shot-by-shot density scan experiments. The transport characteristics were almost identical in the H and D plasmas in the LOC regime, and clear improvements were observed in the heat and particle transports in the D plasma compared with the H plasma in the SOC regime. In the SOC regime, the global energy confinement was higher in the D plasma than in the H plasma. Improvements in the SOC regime were evident in the ion channel of the heat transport and the diffusion term of the particle transport. Intrinsic toroidal rotation was found. Its profiles were identical in the H and D plasma in the LOC regime. However, the steeper gradient of toroidal rotation was found in the D plasma than in the H plasma in the SOC regime. The gyrokinetic modeling of switching ion species and keeping identical input profiles showed no difference of the heat flux in the LOC regime and a clear reduction in the D plasma heat flux in the SOC regime. Additionally, collisionality is shown to play an important role in in the heat flux reduction in D plasmas relative to H plasmas. The gyrokinetic validation of the heat transport against the experimental profiles showed a qualitative agreement regarding the heat and particle fluxes. Quantitative agreement was better for the ion heat channel than for the other transport channels.

ABSTRACTThe unclear links between macroscopic input parameters and microscopic active particle motions in DBD plasma impeded controllable plasma processing. This paper investigates effects of O₂/CF₄ content on Ar‐DBD characteristics and active particle distributions using a flat‐plate reactor and fluid model of 10–50 kHz. Results suggest adding CF4 promotes filament discharge, while O2 favors uniform glow discharge. Near‐equal O₂/CF4 content yields mixed mode. Higher O₂/CF4 content reduces most active particle densities (except O⁺) but increases all particle fluxes to material surface. Elevated frequency boosts total density and flux of O, O⁺, O⁻, F, F⁻ particles. Spatially, F/F⁻/O⁺ particles concentrate centrally, O/O⁻ distribute peripherally‐increased frequency shifts O enrichment area inward and expands F/F⁻ enrichment area outward.

Abstract In-situ measurements of the near surface lunar plasma environment are made using the RAMBHA-LP (Radio Anatomy of the Moon Bound Hypersensitive ionosphere and Atmosphere -Langmuir Probe) payload onboard India’s Chandrayaan-3 Lander during lunar day time (24-08-2023 to 02-09-2023). These observations provide estimates of near surface ( 2 meters above the surface) lunar electron density and electron temperature from the south polar region, ‘for the first time'. The estimations reveal the daytime lunar plasma to have mean electron density (Ne) in the range of 380-600/cc and mean electron temperature (Te) in the range of 3000-8000 K. The critical roles of solar wind and the Earth’s magnetospheric particle flux in modulating the lunar dayside ionosphere outside and inside the Earth’s geomagnetic tail respectively are unraveled using RAMBHA-LP observations and Lunar Ionospheric Model (LIM) simulations. The study also highlights the role of molecular species in the genesis of lunar near surface plasma environment.

Abstract. The Arctic is experiencing a warming much faster than the global average and aerosol–cloud–sea–ice interactions are considered to be one of the key features of the Arctic climate system. It is therefore crucial to identify particle sources and sinks to study their impact on cloud formation and cloud properties in the Arctic. Near-surface particle and sensible heat fluxes were measured using the gradient method during the ARTofMELT Arctic Ocean Expedition 2023. A gradient system was deployed to calculate sensible heat and particle fluxes over three different surface conditions: wide lead, narrow lead, and closed ice. To evaluate the gradient measurements, sensible heat fluxes and friction velocities were compared with eddy covariance data. The strongest mean sensible heat fluxes, ranging from 16 to 51 W m−2, were observed over wide lead surfaces, aligning with measurements from the icebreaker. In contrast, closed ice surfaces had weak, often negative, sensible heat fluxes. Wide leads acted as a particle source, with median net particle emission fluxes of 0.09 × 106 m−2 s−1. Narrow lead surfaces exhibited both net emission and net deposition, though the particle fluxes were weaker. Closed ice surfaces acted as a particle sink, with normalized fluxes around 0.06 cm s−1. The gradient method was found to be effective for measuring both sensible heat and particle fluxes, allowing flexible deployment over different surface types. This study addresses the critical need for improved quantification of turbulent vertical particle fluxes and related processes that influence the local particle number budget in the high Arctic.

Abstract Charged particle therapy, including proton, helium-ion, and carbon-ion modalities, is increasingly utilized for brain tumor treatment due to their superior dose distribution. This study compares the flux and equivalent dose of primary and secondary particles delivered to tumors and healthy tissues using Monte Carlo simulations (MCNP code) with a Snyder head phantom. The equivalent dose delivered to the tumor by carbon-ion therapy was found to be 8.1 times higher than that of helium-ion therapy and 41.8 times higher than that of proton therapy. The equivalent dose to surrounding brain tissues ranged from 15–22 Sv for proton, 100–125 Sv for helium-ion, and 1000–1220 Sv for carbon-ion therapy. The flux of carbon particles in the head and tumor was 0.0068 #/cm2 and 0.0001 #/cm2, respectively, which is negligible compared to proton and helium-ion fluxes. Secondary neutron flux was highest in carbon-ion and helium-ion therapies, raising concerns about secondary cancer risk, while proton therapy showed the lowest secondary particle flux. Lateral dose analysis indicated broader peaks for carbon-ion therapy. In conclusion, although carbon-ion therapy achieves greater tumor dose coverage, proton therapy offers better sparing of healthy tissues and reduced secondary particle production, making it a more precise option for brain tumor radiotherapy.

Abstract Shifts in the phytoplankton assemblage induced by environmental changes have significant implications for carbon cycling and marine food webs, but remain poorly constrained across spatiotemporal scales. Here, we investigate the effects of rising sea surface temperatures and increased stratification on the phytoplankton composition and size in the northwestern Mediterranean Sea (2010–2019) using two sediment trap series: one in the oligotrophic Ligurian Sea and the other in the deep convection zone of the Gulf of Lion. We apply deep learning image analysis to quantify phytoplankton particle fluxes, size distributions, and relative assemblages, focusing on coccolithophores, diatoms, and silicoflagellates. Our results show a general decline of phytoplankton fluxes to the seafloor, mirroring the decrease in vertical mixing in the water column. Both sites show a shift toward phytoplankton species adapted to stratified and nutrient‐depleted conditions, although with contrasting patterns. In the Ligurian Sea, deep‐dwelling coccolithophore species become dominant, while in the Gulf of Lion, summer‐associated siliceous species, including large diatoms and silicoflagellates, show an increase. These contrasted trends, which likely result from differences in nutrient inputs and pH changes in the surface between the two sites, have implications for the efficiency of carbon export pathways at depth. Specifically, the increasing dominance of smaller phytoplankton in the Ligurian Sea leads to a reduction in carbon burial efficiency, while in the Gulf of Lion, the enhanced contribution of larger diatoms may sustain higher export and burial rates in the future.

Abstract Global gyrokinetic simulations find a strongly unstable trapped electron mode excited by a density gradient in a quasi-isodynamic stellarator. The eigenmode structure localizes on the inner side of the torus with an unfavorable magnetic curvature and weak magnetic field, where there is a large fraction of trapped electrons. The instability saturates by nonlinear processes of turbulence spreading in the real space and spectral transfer from unstable to damped regions. The steady state turbulence drives a large particle flux that may have significant implications for the confinement of fusion fuel and removal of fusion ash in the optimized stellarator reactor.

Abstract In the Experimental Advanced Superconducting Tokamak (EAST), a transition from electromagnetic to electrostatic turbulence is observed in the pedestal region as plasma density ramps up. This transition is manifested by the suppression of magnetic fluctuations and the presence of broadband electrostatic turbulence. The frequency domain of the electrostatic turbulence is typically beyond 300kHz. It leads to a rapid build-up of density gradient and a sharp degradation of energy confinement. By reducing the gas puffing rate, a prolonged intermediate transition phase is observed, and the confinement improved with increasing density in this phase. The emergence of broad electrostatic turbulence is associated with the enhanced turbulence control parameter αt, together with a weaken edge radial electric field. Furthermore, the impact of the turbulence transition to scrape-off layer (SOL) transport is evaluated. Measurements suggested that radial particle flux and intermittent structures are strengthened after the transition. Moreover, the profiles in the far SOL are broaden with increase of αt. The properties of the magnetic fluctuations are consistent with the nature of the magnetic coherent mode (MCM) previously observed in EAST, while the broad electrostatic turbulence is proposed to be an ion temperature gradient (ITG) mode by the Gyrokinetic Electromagnetic Numerical Experiment (GENE) simulation. It is clarified that the energy confinement degradation in high-density regimes is primarily driven by the broadband turbulence rather than divertor detachment. These findings advance our understanding of high-density H-mode plasmas and provides additional insights into the interplay between edge turbulence and global confinement properties.

Abstract Simultaneous measurements of electrostatic and electromagnetic turbulence have been conducted in low-beta ( β N ∼ 0.65 ) HL-2A plasmas using a reciprocating multi-probe array. Electrostatic fluctuation-driven particle flux exceeds electromagnetic-induced transport by 3–4 orders of magnitude. Electromagnetic turbulence in the 20–80 kHz range dominates particle transport while higher frequency electromagnetic fluctuations (80–200 kHz) show reduced impact, which contrasts with edge electrostatic turbulence. Time-resolved analysis of particle flux components reveals that phase coherence plays a dominant role in determining cross-field transport dynamics. Electromagnetic fluctuations demonstrate complex behavior as δ B r increases, with counteracting transport components Γ n e − B r and Γ v t − B r of comparable magnitude in opposing directions, which could necessitate adjustments to existing electromagnetic turbulence theories. Strong nonlinear interaction between electrostatic and electromagnetic turbulence is observed and experimental identification of Geodesic Acoustic Mode (GAM) signatures in both turbulence spectra. Concurrent coupling of magnetohydrodynamic activity and GAM with electrostatic fluctuations is confirmed, suggesting potential energy transfer mechanisms between these modes.

Abstract In this work, gyrokinetic simulations are performed with the CGYRO code (Candy et al 2016 J. Comput. Phys. 324 73–93) for a negative triangularity H-mode plasma in ASDEX Upgrade, and compared with experimental measurements. The PORTALS framework (Rodriguez-Fernandez et al 2024 Nucl. Fusion 64 076034) is used to accelerate the prediction of kinetic profiles for this plasma, using surrogate modeling and Bayesian optimization. Ion heat flux, electron heat flux, and electron particle flux are simultaneously matched across the simulated radial regime of the plasma (normalized radius r / a = 0.35 − 0.90 ), and the resulting ion temperature, electron temperature, and electron density profiles match well with the experimental profile data within this radial range. A synthetic Correlation Electron Cyclotron Emission diagnostic is applied to find well-matched electron temperature fluctuation properties between simulation and experiment. The flux-matched profiles provide a basis for investigation of the turbulence nature across the plasma radius, revealing the dominance of Trapped Electron Mode turbulence at r / a = 0.35 , the dominance of Ion Temperature Gradient turbulence at r / a = 0.55 , 0.75, and 0.83, and an instability boundary at r / a = 0.90 .

Linear plasma devices have been a vital tool to sharpen our understanding of plasma wall interactions in fusion devices. Aiming at mimicking divertor plasmas in next-generation fusion devices, our institute has been constructing a high-flux linear plasma device named SWORD. Here, we report its first milestone result—a continuous helium plasma discharge with a particle flux greater than 1024 m−2 s−1 and a duration greater than 1000 s, which is confirmed by both the Langmuir probe and optical emission spectroscopy. This marks an important step towards the realization of fusion energy in China.

Abstract In this paper, the 1D physics-based dynamic scrape-off-layer (SOL) model DIV1D is extended to include molecular interactions and the effects of finite atomic flow velocity parallel to the magnetic field lines. The addition of molecular interactions, atomic flow, and geometric settings in DIV1D leads to qualitative agreement with stationary 1D profiles obtained by mapping 2D SOLPS-ITER simulations for the parallel heat flux, electron temperature, electron density, plasma flow velocity, atomic density, atomic flow velocity and molecular density. Steady-state simulations of DIV1D show higher levels of particle, momentum and heat losses through collisional-radiative interactions between ions and molecules, compared to ions and atoms, in the divertor. Density ramp simulations show that DIV1D is now capable of dynamically transitioning between different SOLPS-ITER equilibria for MAST-U, capturing behaviour throughout the target particle flux rollover into deeply detached regimes.

Abstract Observations from the Juno spacecraft near the M‐shells of the Galilean moons have identified alternating enhancements and reductions of particle fluxes at discrete energies. These banded structures were previously attributed to bounce resonance between particles and standing Alfvén waves generated by moon‐magnetospheric interactions. Here, we show that this explanation is inconsistent with key observational features, and propose an alternative interpretation: the bands are remote signatures of particle absorption at the moons. In this scenario, whether a particle encounters the moon before reaching Juno depends on the number of bounce cycles it undergoes within a fixed drift segment determined by the moon‐spacecraft separation. Therefore, the absorption bands are expected to appear at discrete, equally‐spaced velocities. This is largely consistent with the observations, though discrepancies remain, possibly due to spacecraft charging and/or finite data resolution. This finding improves our understanding of moon‐plasma interactions and may help constrain Jovian magnetospheric models.

The linear stability of a thermally stratified fluid layer between horizontal walls, where non-Brownian thermal particles are injected continuously at one boundary and extracted at the other – a system known as particulate Rayleigh–Bénard (pRB) – is studied. For a fixed volumetric particle flux and minimal thermal coupling, reducing the injection velocity stabilises the system when heavy particles are introduced from above, but destabilises it when light particles are injected from below. For very light particles (bubbles), low injection velocities can shift the onset of convection to negative Rayleigh numbers, i.e. heating from above. Particles accumulate non-uniformly near the extraction wall and in regions of strong vertical flow, aligning with either wall-impinging or wall-detaching zones depending on whether injection is at sub- or super-terminal velocity. The increase of the volumetric particle flux always enhances these effects.

Abstract The multiple plasma simulation linear device (MPS-LD) device aims to experimentally simulate tokamak divertor plasma and its interactions with plasma-facing materials. To achieve this objective, improving target plasma parameters by understanding plasma transport characteristics is essential. In this work, both experimental and simulation studies of argon (Ar) plasma transport are carried out, with a focus on investigating the physical methods and mechanisms for increasing target electron density ( n et ). In the experiments, Langmuir triple probes and optical emission spectroscopy are employed to diagnose plasma parameters. SOLPS-ITER is utilized to conduct corresponding numerical simulations. First, SOLPS-ITER simulations are compared with experimental results to demonstrate the accuracy of the physical model. After the simulation validation, subsequently, by moving the target axially, the effects of target positions (Z) on n et and particle flux density (Γt ) are investigated through the combination of experimental and numerical approaches. The results demonstrate that both n et and Γt show a nearly linear increase as Z decreases. This phenomenon is explained by the reduction in radial particle transport losses, as revealed by particle balance analysis. Based on the analysis, a method is proposed to further increase n et by enhancing plasma confinement via adjusting the target magnetic field strength (Btar ) to establish different magnetic field configurations. The corresponding experimental and simulation results show that increasing Btar effectively enhances n et , particularly in the axis region, accompanied by an increased radial density gradient. This improvement is because the enhanced Btar leads to a significant reduction of radial particle losses. Meanwhile, the intensified Btar induces convergence of magnetic field lines toward the axis, promoting plasma transport into the axis region. By optimizing the target positions (Z shortened from 3 m to 1.68 m) and magnetic field configurations (Btar increased from 0.1 T to 0.25 T), n et is significantly increased by more than fivefold. This work deepens the comprehension of Ar plasma transport mechanisms and provides feasible solutions for achieving higher n et .

Erratum: Probing a diffuse flux of axionlike particles from Galactic supernovae with neutrino water Cherenkov detectors [Phys. Rev. D <b>111</b> , 083019 (2025)

The aim of this study was to develop and optimize α-arbutin-loaded nanostructured lipid carriers (Ar- NLCs) using the QbD. Additionally, the formulation studies, in-vitro and ex-vivo performance of Ar-NLCs were assessed, along with their cytotoxic efficacy in melanoma cells. The Ar-NLCs were fabricated using the high-speed homogenization-ultrasonication method, incorporating Gelucire 48/16, Castor oil, Capryol 90, and Tween 80. To analyze the impact of factors on Ar-NLCs, the Box-Behnken design (BBD) was utilized. The Ar-NLCs were characterized by particle size, polydispersity index, morphology, zeta potential, release kinetics, permeation, flux and stability. Additionally, Ar-NLCs cytotoxicity was assessed using the A375 cells. The Ar-NLCs demonstrated a particle size of 228.7 ± 44.5 nm, a zeta potential of -14.2 ± 2.64 mV respectively. The entrapment efficiency was 67.62 ± 4.46%. The α- arbutin release from NLCs followed Weibull kinetics. Notably, Ar-NLCs demonstrated a 2.53-fold higher permeability compared to Ar-SOL. Furthermore, Ar-NLCs exhibited significantly stronger cytotoxic effects against melanoma cells than Ar-SOL. This study reports the successful development of Ar-NLCs using a QbD approach. Enhanced transdermal permeability, enhanced cytotoxicity on melanoma cells, and sustained release of α-arbutin from NLCs were achieved. These findings indicate that NLCs offer a viable alternative drug delivery system for transdermal applications.

In the past decade, hundreds of exoplanets have been discovered in extremely short orbits below 10 days. Unlike in the Solar System, planets in these systems orbit their host stars close enough to disturb the stellar magnetic field lines1. The interaction can enhance the magnetic activity of the star, such as its chromospheric2 and radio3 emission or flaring4. So far, the search for magnetic star-planet interactions has remained inconclusive. Here we report the detection of planet-induced flares on HIP 67522, a 17 million-year-old G dwarf star with two known close-in planets5,6. Combining space-borne photometry from the Transiting Exoplanet Survey Satellite and dedicated Characterising Exoplanets Telescope observations over 5 years, we find that the 15 flares in HIP 67522 cluster near the transit phase of the innermost planet, indicating persistent magnetic star-planet interaction in the system. The stability of interaction implies that the innermost planet is continuously self-inflicting a six times higher flare rate than it would experience without interaction. The subsequent flux of energetic radiation and particles bombarding HIP 67522 b may explain the remarkably extended atmosphere of the planet, recently detected with the James Webb Space Telescope7. HIP 67522 is, therefore, an archetype to understand the impact of magnetic star-planet interaction on the atmospheres of nascent exoplanets.

As global energy demands rise, the advancement of new energy technologies increasingly relies on the development of metals that can endure extreme pressures, temperatures, and fluxes of energetic particles and photons, as well as aggressive chemical reactions. One way to assist in the design and manufacturing of metals for the future is by learning from their past. Here we track the progress of metallic materials for extreme environments in the past 35 years using the text mining method, which allows us to discover patterns from a large scale of literature in the field. Specifically, we leverage transfer learning and dynamic word embeddings. Approximately one million relevant abstracts ranging from 1989 to 2023 were collected from the Web of Science. The literature was then mapped to a 200-dimensional vector space, generating time-series word embeddings across six time periods. Subsequent orthogonal Procrustes analysis was employed to align and compare vectors across these periods, overcoming challenges posed by training randomness and the non-uniqueness of singular value decomposition. This enabled the comparison of the semantic evolution of terms related to metals under extreme conditions. The model’s performance was evaluated using inputs categorized into materials, properties, and applications, demonstrating its ability to identify relevant metallic materials to the three input categories. The study also revealed the temporal changes in keyword associations, indicating shifts in research focus or industrial interest towards high-performance alloys for applications in aerospace and biomedical engineering, among others. This showcases the model’s capability to track the progress in metallic materials for extreme environments over time.