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The depletion of a quasi-two-dimensional (quasi-2D) dipolar Bose condensed gas in the presence of both contact and long-range 1/r interactions is investigated in the framework of Hartree–Fock–Bogoliubov (HFB) approximation. When the characteristic wavelength of a mode is much larger than the trap size, the dipole-dipole (DD) interaction can be treated as a contact interaction and in the low momentum limit the long-range nature of the 1/r interaction has the dominant contribution and leads to the nonlinear (nonphononic) dispersion relation. We will show that quantum depletion is temperature independent and is determined by the contact, DD and longrange 1/r coupling constants (ɛdd = gd/g and C). The the quantum depletion is affected by long-range 1/r interaction and at large momentum limits the momentum dependence of quantum depletion unaffected by 1/r interaction.The depletion of a quasi-two-dimensional (quasi-2D) dipolar Bose condensed gas in the presence of both contact and long-range 1/r interactions is investigated in the framework of Hartree–Fock–Bogoliubov (HFB) approximation. When the characteristic wavelength of a mode is much larger than the trap size, the dipole-dipole (DD) interaction can be treated as a contact interaction and in the low momentum limit the long-range nature of the 1/r interaction has the dominant contribution and leads to the nonlinear (nonphononic) dispersion relation. We will show that quantum depletion is temperature independent and is determined by the contact, DD and longrange 1/r coupling constants (ɛdd = gd/g and C). The the quantum depletion is affected by long-range 1/r interaction and at large momentum limits the momentum dependence of quantum depletion unaffected by 1/r interaction.

Droplets and bubbles are thought to be two sides of the same coin; this work determines how true this is at the molecular scale. Stable cylindrical nanodroplets and nanobubbles are obtained in Molecular Dynamics (MD) simulations with three-phase contact lines pinned by alternate hydrophobic and hydrophilic patterns. The surface tension and Tolman length for both types of curved interfaces are obtained with the Kirkwood–Buff method, based on the difference between normal and tangential pressure components. Both bubble and droplet cases are compared to the flat interface case for reference. Results show that the surface tension decreases linearly while the Tolman length increases linearly with the gas/liquid density ratio. By running a careful parameter study of the flat interface over a range of densities, the effect of the density ratio can be corrected isolating the effects of curvature on the surface tension and Tolman length. It is found that such effects start to be seen when the equimolar curvature radius goes down to 20 reduced Lennard–Jones (LJ) units. They have the same magnitude but act with opposite signs for nanodroplet and nanobubble interfaces. Considering effects of the density ratio and curvature, a fitted Tolman equation was obtained, which predicts the surface tension of a curved interface. Results obtained by the fitted Tolman equation agree well with those obtained by the MD simulations except at very small curvature radius (

By creating exotic atoms containing an ever-broadening range of particles, researchers can extend the tools of atomic physics to new realms.

A new method to determine the arbitrary electron energy distribution function (EEDF) from the optical emission spectroscopic measurement in atmospheric-pressure plasma is introduced. The optical emission spectroscopy (OES) continuum emission spectrum, dominated by electron-neutral bremsstrahlung radiation, is analyzed to inspect the usefulness of the conventional OES measurement range for EEDF determination. The EEDF is reconstructed from the OES continuum radiation spectrum by applying machine learning to solve the bremsstrahlung emissivity equation inversely. Through iterative statistical analysis, the presented genetic algorithm can locate the EEDF reliably. Verification of the algorithm shows that theoretical Maxwellian and Druyvesteynian EEDFs can be partially reconstructed from a realistic OES measurement range. Furthermore, preliminary experimental EEDF results of an argon dielectric barrier discharge (DBD) OES measurement are given. The electron energy range and resolution of the determined EEDF are discussed. The results in this paper show potential for accurate determination of the arbitrary EEDF in atmospheric-pressure plasma using simple OES equipment.

The dynamical cluster decay model is applied to understand the decay of 16O+203,205Tl→219,221Ac* reactions by including the deformation effects upto β2i within the hot optimum orientation approach. The evaporation residues of 219,221Ac* nuclei are fitted in the excitation energy range ECN* = 33.1 to 62.4 MeV, by optimizing the only parameter of the model, called neck-length parameter. The DCM calculated cross-sections find nice agreement with the experimental data. The spherical fragmentation of the interacting nuclei is also applied at lowest and highest excitation energies to look for the change in the decay profile while going from the β2i to spherical distribution of fragments. In addition to this, the effect of deformations is also investigated to analyze interaction/ scattering potential.

We have conducted theoretical study on a production reaction 16O(K−,p)K−15C which populates kaonic nuclei CK−15 (=15N-K− bound system). The main purpose of this study is to deduce the kaon-nucleus interaction from the present existing and future experimental observations of kaon-nuclear production through (K−, p) reaction with different targets. Our analysis using 16O target is the first step for our upcoming systematic study by employing wide range of targets. We have considered two models, namely K−pp and Λ*p models in our analysis to determine the formation mechanism of kaonic nucleus and find out the differences between the two models. We have investigated the missing mass spectrum for the above (K−, p) reaction by using Green's function method. The interaction between K− and nucleus is taken to be Woods-Saxon potential. We have analyzed the characteristic of the spectrum by varying the potential strengths as well as scattering angles by using the above two models. It is observed that a large component of quasi free K− is compatible with the Λ*p model.

The paper investigates the effect of Hubbard U (DFT+U) addition on structural and electronic properties of YBa2Cu3O7-δ superconductor. The calculation applies first principles calculation within Generalized Gradient Approximation for Perdew-Burke-Erzenhof for solids (GGA-PBEsol) functional using Density Functional Theory. Energy convergence was found at 400 eV cut-off and 4×4×1 k-point sampling. The DFT+U correction was applied on Cu 3d states at the range of U = 2, 4, 6 and 8 eV where U=2 eV shows the largest band gap difference. Using the GGA-PBEsol+U method, the structural and electronic properties of YBa2Cu3O7-δ were investigated such as its lattice parameters, band structure, the density of states and atomic population.

Many Lattice dynamic models were developed in the past to study the lattice dynamics of metals and their properties. In this present study force constants of Sodium metal have been calculated with the help of De Launay Angular force model. The number of force constants varies with the nature and range of atomic interactions. In the phenomenological theories the force constant of Sodium are evaluated by making use of the experimental data on elastic constants at selected wave vectors. The basic equation of De Launay Angular force model (DAF) relates three elastic constants, force constants as well as two zone boundary frequencies. In the present study, ion-ion interactions of Sodium are considered by neglecting its electron-ion interaction from the proposed relation of DAF model because sodium is the best example of free electron. The force constants of Sodium are calculated here by restricting the range of interaction up to third nearest neighbor. The third angular force constant is considered as neglected because of weaker interaction due to conduction electrons of Sodium. The purpose of this paper is to calculate force constants of Sodium by De Launay Angular Force Model which can be used further in calculation of phonon frequencies of Sodium.

The role of next nearest neighbor (NNN) hopping (t') and next to NNN hopping (t'') on hole pairing and thermodynamic properties such as specific heat, entropy have been investigated using two dimensional (2D) hole-doped t-t'-t''-J model based on exact diagonalization (ED) method. Standard Periodic boundary conditions are applied to minimize error due to finite size effect as the calculations are made using small sized cluster geometry. The attraction between holes increases with the inclusion of third neighbor hopping term. The maximum probability of hole pairing is at NNN site. The system goes to more disordered and ordered state with the increase of long range hopping terms at temperature T≤0.35t and T>0.35t, respectively. A single peak nature is observed in specific heat graph.

A technique to produce spin orientation in RI beams was developed for measurements of nuclear moments. The present scheme of two-step reaction realized highly spin-aligned RI beams for a wide range of exotic nuclei. Recently the two-step reaction scheme was applied to the magnetic moment measurement of an isomeric state of a neutron-rich nucleus 75Cu, where its magnetic moment was determined for the first time owing to a 30%-spin-aligned beam. A further perspective of the nuclear moment measurements employing the present scheme is expected.

We have studied the photoproduction of Λ(1405) from the CLAS Collaboration with a chiral dynamics model. The reaction γ+p→K+(π∑)0 was conducted for the wide range of photon energies 1.95

Since neutrons especially fast neutron has a high weighting factor in radiation dosimetry, exposing the human’s body to a neutron source in a laboratory or clinic may put body tissues at risk and dangerous situations. In doing so, in this investigation, body tissue together with soft tissues (including adipose and skin) were decomposed into their fundamental elements, and then got emitted by neutrons. This research can be put into operation all tissues about cancer therapy. The amounts of neutron energy because of the collision between neutrons and nuclei of the basic elements got calculated in the tissue Next, some results got concluded. The results imply that the highest transferred energy happens within the energy range 3.5-10.5 MeV and also energy ranges 15-16.5 MeV. As well, the tendencies of the transferred-energy graphs were very in a similar way and are the same as other fundamental elements, and the maximum transferred energy happened for the elements that had a small atomic weight.

We present the analysis of the identified hadrons (π±, K±) produced at mid-rapidity (|η| < 0.5) in collisions of Au-Au ions with energies SNN=4,7,9 and 11 GeV. Particle momentum spectra for charged hadrons (pions, kaons) are measured using data from Monte Carlo generator of Ultrarelativistic Quantum Molecular Dynamics (UrQMD) with particle reconstruction made with the response of Multi-Purpose Detector (MPD) obtained with GEANT3 simulations, on Monte Carlo input. We analyze particle multiplicity dependence on the collision energy. Centrality dependence of transverse momentum spectra was calculated for all particle species. Our goal is to study possible signatures of the phase transition between the hadron state of matter and the quark-gluon plasma (QGP) state.

Hadrontherapy deals with the maximum energy deposition in the form of Bragg peak for energetic charged particles at a particular depth for killing cancerous cells. For planning hadrontherapy treatment accuracy in transport codes are primary demands of radiation oncology. In this work, we studied the dose deposition of the proton beam for the energy range of clinical interest i.e. 70 MeV to 240 MeV in water considering as tissue-equivalent material. The Bragg peak studies for different energy values are executed using Monte Carlo codes-based toolkit- GEANT4. We compared the four physics lists, the QGSP_BERT, the QBBC, the PhysListEmStandardNR (StandardNR), and emstandard_opt0, present in the Geant4 toolkit for avoiding uncertainty in the determination of dose deposition in the living cells which may cause damage of healthy cells. The StandardNR physics list is found suitable to get localized dose deposition in the form of smooth Bragg Curve.

The first synchrotron light source in Thailand was established in 1996, Siam Photon Source is operated and developed the capability of the facility to increase the energy up to 1.2 GeV by Synchrotron Light Research Institute (SLRI). Many users from both inside and outside the country come to use the synchrotron light which is increasing steadily. As a result, Siam Photon Source II at 3 GeV project is taken place in 2019. The Hard X-ray absorption spectroscopy has been planned to support which two consideration designs of the X-ray energy range are 2.4 – 40 keV at the first and 4 – 35 keV at the second. The scattering synchrotron radiation can occur from the optical components in the beamline. The radiation must be controlled to be safe for the utilization of synchrotron radiation in which the radiation shielding design is taken into account. This work aimed to compare the first and second HXAS beamline shielding designs to evaluate the dose distribution to prevent the radiation scattering. The dose calculation was performed by STAC 8 program, therefore, estimate the radiation dose level at the surface outside of the beamline both optic hutch and experimental hutch. The results of the two design indicated that dose distributions with the scattering angle were below the design criteria at 0.1 µSv/h. The optic hutch shielding wall for the first design is below the second design while the experimental hutch shielding wall for the first design is higher than the second design.

Introduction. Due to the air density correction in the operation of secondary standards with no equivalent air walls, there is a fail of the kPT correction factor in order of 1% to 2.5% in the realization of air kerma rate at the atmospheric conditions of the Mexican highlands (3000 meters above sea level). For this reason, the SSDL-ININ-MEXICO has elected to design and build the Free Air Chamber (FAC), for medium energy X-ray dosimetry. Methods. The air kerma primary standard for X-ray photons is based on parallel-plate FAC for ionometric measurements, which must be operated and designed to fulfill the Charged Particle Equilibrium (CPE) conditions; where the main correction factors is the attenuation factor (katt); therefore, the attenuation length (lat) must be enough to comply with the CPE, where this lat is obtained by Monte Carlo (MC) simulation. Results and discussion. The distribution of the average imparted energy of 300 keV monoenergetic photons as a function of the distance from the reference plane is simulated by the PENELOPE 2008 code, where the plateau corresponds to the CPE region. Therefore, according to the MC simulation, the value of attenuation length lat must be calculated for the point: 44.0 ± 0.5 cm, where the width of the collector electrode is elected 20 cm, within the CPE region of 34 to 54 cm. Conclusions. In this first stage of the design of a FAC, the MC simulation determines that the range to achieve the CPE condition is from 34 to 54 cm, with a collector electrode length of 20 cm and considering an atmospheric pressure P ≈ 710 hPa for a height of 3000 m above sea level.

Within the framework of the Nuclotron–based Ion Collider fAcility (NICA) project an Innovation Block is being constructed. It includes an applied research station for microchips with a package for radiation resistance testing. The ions up to Au with the energy range of 150-350 MeV/n are available for researches. The detailed overview of a technical station for irradiation by long-range ions is presented. A concept for reconstruction of the capsulated microchip structure at it’s interaction with high-energy ions was proposed.

To study the dependence of incomplete fusion on entrance channel parameters, the excitation functions of evaporation residues populated through complete and/or incomplete fusion in 19F + 154Sm system were measured at projectile energy range ≈ 4–6 MeV/nucleon The measured excitation functions were compared with theoretical model PACE-4 predictions. Analysis of measured data suggests the production of xn/pxn-channels via complete fusion, as these were satisfactorily reproduced by PACE-4 cross-sections, while, a significant enhancement in the cross-sections of α-emitting channels was found, which was attributed due to the incomplete fusion process. A systematic study suggests that the incomplete fusion contribution increases with the entrance channel mass asymmetry and coulomb factor. Further, a study on the breakup threshold suggests that the incomplete fusion contribution increases with decrease in the α-Q value of the projectile. These present results clearly show the effect of projectile structure on ICF dynamics along with other entrance channel parameters.

In this paper, the double-Λ hypernuclei, HΛΛ6e, HΛΛ5e and HΛΛ5e have been theoretically investigated to determine effective Λ-Λ interaction energies in double-Λ hypernuclei which is closely related to hyperon superfluidity in neutron stars. These double-Λ hypernuclei were considered as three-body cluster model; Λ-Λ-core nucleus. We constructed the free-space single-channel Λ-Λ interaction from Shinmura's multi-channel S=-2 potentials which are phase shift equivalent to Nijmegen soft core potentials. The interaction strength and range parameter are fitted with the most updated experimental data of Nagara event from E373 experiment. By using NSC97e potential, the effective Λ-Λ interaction energies are found to be 0.67 MeV, 0.88 MeV and 0.64 MeV for HΛΛ6e, HΛΛ5e and HΛΛ5e respectively. The medium effects are not negligible in these double-Λ hypernuclei.

Mass transport of the Knudsen gas in a porous medium is investigated on the basis of the kinetic theory of gases. First, the mass flow conductance is computed numerically for various porosities and solid grain sizes by stochastic particle simulations (SPS). Then, a kinetic model with a homogeneous scatterer is introduced, which contains the reference Knudsen number as the sole parameter that characterizes the collision frequency of gas molecules with the micro-structural solid surface. With the aid of the standard asymptotic analyses for small and large Knudsen numbers combined with the percolation theory, the effective reference Knudsen number is identified to reproduce the SPS results for a wide range of porosities., This paper is part of the Special Topic, Advances in Micro/Nano Fluid Flows: In Memory of Prof. Jason Reese.

We measured current–voltage and optical emission for self-sustained discharges obtained using two forms of cylindrical wire grid cathodes, having either an enclosed or an open end. Enclosure of the open end extended the low-pressure range for a “cathode-confined” or CC mode, from around 12.5 Pa to below 3.5 Pa, conditions at which a “beam” mode discharge otherwise occurs. The modification also caused a dark space to envelop the glow within the cathode, bridged by a bright emission resembling plume for the CC mode, and an electron beam for the beam mode. We explain these results by treating the CC mode as a hollow cathode discharge, for which only γ-electrons that suffer inelastic loss before escaping the cathode grid are significant. For the two cathodes, respective degrees of electron confinement possible for the different sheath configurations predict the low-pressure ranges, and the calculated values of cathode fall for self-sustenance by the hollow cathode effect agree approximately with the experimental voltages across a range of pressures. Plume- and beam-like forms of emission indicate inherently different electron energies, consistent with bulk transport across potential distributions characteristic to the mode. Where these features bridge the enclosed cathode boundary, this shows existence of an otherwise closed potential surface within the cathode, confirmed by the geometry of the plume-CC mode configuration, where the relationship between the main glow and plume interface surfaces indicates the arrangement to self-organize in a state of non-ambipolar current flow. Similarities in the mode structure reported elsewhere for related discharges indicates the findings to be relevant for these also.

High-power plasma waves in the lower hybrid range of frequencies (LHRF) are being used for non-inductive current drive in experiments around the world. In this range, plasmas can support waves with two different polarizations, a quasi-electrostatic wave known as the “slow wave” or simply the lower hybrid wave, and a quasi-electromagnetic wave referred to variously as the “fast wave in the LHRF”, “whistler”, or “helicon”. An improved qualitative understanding of how fast and slow waves in the LHRF propagate can be gained by studying the “inverse wave normal surface” or IWNS. It is shown that the two branches propagate in a qualitatively similar way, with, however, important quantitative differences.

The law states that energy and time want to be or remain in equilibrium. At the time of the big bang, this time was constricted so much, and singularity was present. The whole universe came and expanded from that singularity, the energy was produced and cosmic inflation of the time limit of 10−36 s happened. However, why did this happen? Why did energy at that time expanded and evolved into the universe as we know it to be present? Also, why the only universe as we know it as it is and not something else, why did the energy did not evolve into something else? These are some questions which we will explain and answer using the law of energy time equilibrium. We have discussed the properties of time correlation with energy for several systems that are simple enough to illustrate the extraction of energy through fluctuation and distortion of equilibrium. We develop a succinct theory of extraction of electrical energy from a classical system subjected to cyclic change between electric and magnetic energy via virtue of fluctuation of energy-time-equilibrium. We show the range inside of which energy-time-equilibrium is established, outside of which it gets distort or disturbed. To sustain the system and extracting the electrical energy, we introduce an engineering machine named Eklavya, which periodically comes out and goes inside of the energy density (with respect of time) sphere of range of equilibrium. In this paper we will not give detailed information about Eklavya.

Lower hybrid (LH) wave has been widely used for non-inductive current drive in modern tokamak experiments with high power injection. LH parametric instability (PI) has been observed in many LH experiments and considered as the most likely candidate which causes the decrease of LH current drive efficiency. Traditional LH PI theories are mostly based on the electrostatic model given the fact that the slow wave branch in LH frequency range is a quasi-electrostatic wave. However, electrostatic description is not accurate for the plasma parameters of scraped-off layer(SOL) region where LH PIs are observed in current fusion experiments. Thus, in this work, we include the electromagnetic correction for slow wave and build up the corresponding nonlinear dispersion relation of PI. The electromagnetic effects on two major decay channels, i.e., ion sound quasi-mode (ISQM) and ion cyclotron quasi-mode (ICQM) are discussed.

We have numerically calculated the free correlation energy fc of an electron quantum wire for two completely different electronic spin-states i.e. the unpolarized and fully polarized states. The dynamics of electron (spin) correlations is included through the dynamic/quantum version of Singwi, Tosi, Land and Sjolander (the so called qSTLS) mean-field approximation. The results for fc are reported for both the electron spin-states over a wide range of temperature and linear electron number density. Ata fixed temperature, the magnitude of fcin unpolarized state is found to be always more thanthat of the fully-polarized spin-state. To highlight the effect of dynamics of electron correlations, our results of fc are compared withthe (static) STLS theory. We note that the magnitude of the STLS fc is small in comparison to the qSTLS results and the difference between them is quite significant at low electronnumber density.

The GlueX experiment is a photoproduction experiment located at Thomas Jefferson National Lab in Newport News, Virginia. GlueX is capable of making beam asymmetry (Σ) measurements using a tagged, linearly-polarized 9 GeV photon beam incident on a hydrogen target. Measurements of the beam asymmetry for the exclusive reactions γp → π0 p, γp → ηp and γp → η′p will provide insight into the meson production mechanisms. GlueX measurements are the first beam asymmetry results for the η and η′ in this energy range and are expected to further constrain Regge theory models for photoproduced pseudoscalar mesons. This talk will present preliminary results of the photon beam asymmetries as a function of the Mandelstam variable, t, for multiple η decay modes and the η′ → π+π− η decay mode.

Tuning electric and magnetic response of dielectric structures at the nanoscale is a very important task nowadays. Multipole decomposition is a useful instrument to analyze and then control an opical response. Here we show the way to excite magnetic octupole moment by nanostructuring dielectric scatterer in near-IR spectral range. This response leads to magnetic hot-spots generations and a eresonant peak in scattering cross-section. Our results can be widely used to design novel metasurfaces avoiding diffraction limit, for particle trapping and imaging applications.

In the present work we explore a new prescription of getting pure spin current through a nanojunction with the help of a spin battery, circumventing the use of conventional charged based batteries. The main advantage of this prescription is that we do not need to consider ferromagnetic materials, as normally used, or systems with spin-orbit couplings. Employing a tight-binding prescription, we investigate transport characteristics within the Green’s functional formalism. Several interesting features are obtained depending on the conductor-to-electrode coupling and system temperatures. All the results are valid for a wide range of physical parameters, and thus, we strongly believe that the present analysis can be examined in a suitable laboratory set up.

We present measurements of the photon beam asymmetry Σ for the reaction γp → K+Σ0(1193) using the GlueX experiment in Jefferson Lab's Hall D. Data were collected using a linearly polarized photon beam with energy range 8.2-8.8 GeV incident on a liquid hydrogen target. Asymmetries are measured as functions of Mandelstam variables −t and −u. These are the first fully exclusive measurements of the photon beam asymmetry Σ in this reaction at high energies with detection of all final state particles. In the t-channel, results show that the reaction is dominated by the natural-parity exchange of presumably the K*(892) meson, as predicted by theoretical models. Results obtained for the u-channel are consistent with an intermediate baryon exchange mechanism predicted by theoretical models.

Many research studies the loss of ion energy in chemicals and materials, because this subject has a great interest for multiple applications in material science and atomic physics. Proton loses its energy when interacting with oxides such as Al2O3 and ZrO2. In the current work under the formalities of insulation, the calculations were performed by combination of Durde energy loss functions with a generalized oscillator to describe the electrons in the outer and inner cascades sequentially. Provides a realistic description of the electronic properties of each goal of this method. Comparable cross sections are compared fairly well with a wide range of proton energies with experimental data available. The non-free average path parameter (IMFP) is calculated because the most important in surface-sensitive quantitative spectral analysis (IMFP) can be determined as a average distance between an electron and a given energy between successive non-elastic collisions. Another parameter describes the angular distribution of the extruded electron. This parameter is known as the differential cross-section, thus obtaining the energy distribution of the electrons produced by each proton from the corresponding cross-section.

Extended-magnetohydrodynamics (MHD) transports magnetic flux and electron energy in high-energy-density experiments, but individual transport effects remain unobserved experimentally. Two factors are responsible in defining the transport: electron temperature and electron current. Each electron energy transport term has a direct analog in magnetic flux transport. To measure the thermally driven transport of magnetic flux and electron energy, a simple experimental configuration is explored computationally using a laser-heated pre-magnetized under-dense plasma. Changes to the laser heating profile precipitate clear diagnostic signatures from the Nernst, cross-gradient-Nernst, anisotropic conduction, and Righi-Leduc heat-flow. With a wide operating parameter range, this configuration can be used in both small and large scale facilities to benchmark MHD and kinetic transport in collisional/semi-collisional, local/non-local, and magnetized/unmagnetized regimes.

The Novosibirsk FEL facility includes three FELs operating in the terahertz, far-, and mid- infrared spectral ranges. It has rather long history, but its potential has not been fully revealed so far. The first FEL of this facility has been operating for users of terahertz radiation since 2004. It remains the world's most powerful sources of coherent narrow- band radiation in its wavelength range (90 – 340 µm). The second FEL was commissioned in 2009. Now it operates in the range of 35 – 80 µm, but we plan to replace its undulator soon with a new one, and its short wavelength boundary will be shifted down to 15 µm. The third FEL was commissioned in 2015 to cover the wavelength range of 5 – 20 µm. Its undulator comprises three separate sections. Such lattice is suited very well to demonstrate the new off-mirror way of radiation outcoupling in an FEL oscillator (so called electron outcoupling), which we also plan for near future. We also intend to improve the accelerator injection system. As a result, the average electron beam current and consequently the radiation power of all the three FELs will increase. In this paper, we present an overview of the facility and discuss our recent achievements and future plans.

We report on the results of an experimental campaign to measure time-varying velocity distributions in the near-field of a low power Hall thruster. We employ a sample-hold technique, enhanced by parallelizing the measurement hardware into several signal processing channels that vastly increases the data acquisition rate. The measurements are applied to study flow field dynamics in a commercial BHT-600 Hall thruster undergoing unforced breathing mode oscillations in the 44–49 kHz range. A very detailed experimental picture of the near-field emerges from these studies. The results indicate that velocity fluctuations lessen further downstream of the exit plane. Along the thruster axis where there is a general appearance of a central jet, there is evidence of a low velocity ion population in between the periodic bursts of high velocity ions, indicative of local ionization of neutrals outside of the thruster. One possible source of this residual ionization may be background chamber gas, which is not unexpected with the limited pumping capacity of ground test facilities.

Optical trapping has become an important tool in a wide range of fields. While these traps are most commonly realized using optical tweezers, dual-beam optical traps offer specific advantages for certain experiments. It is commonly assumed that a particle will become trapped midway between the focal points of the two beams. However, this is not always the case. We perform a theoretical and experimental investigation of trapping positions of weakly absorbing, spherical particles in a dual-beam optical trap. We evaluate the effect of offsetting the beams in the direction of propagation and identify four regimes with distinct trapping behavior. The effect of an offset perpendicular to the propagation direction and an imbalance in power between the two beams is also considered. Experiments utilize an aqueous aerosol particle whose size can be readily controlled and monitored over hundreds of nanometers. As such, it serves as an excellent probe of the optical trap. We demonstrate that it is possible to fit the evolution of the particle trapping position in order to determine the position of the particle relative to the focal point of each beam. The results presented here provide key insights into the workings of dual-beam optical traps, elucidating more complex behaviors than previously known.

We present the results of calculations of the ion microfield distribution function of a two-component fully ionized classical Coulomb plasma having ion charge numbers from two to three, performed by the molecular dynamics method. The model of ultracold plasma is used, where particles interact according to the Coulomb law without any restrictions at large or small distances. The calculations are carried out in a wide range of the strong coupling parameter. A comparison with the results of calculations for other plasma models is given. The results obtained can be used for any classical non-degenerate strongly coupled plasma.

Harvesting multi-frequency sound energy from environmental noise is a meaningful topic to supply energy for potential devices. In this work, we constructed an array of Helmholtz resonators (HRs) with cross-linked polypropylene (IXPP) ferroelectret films on the inner walls of HR cavities, whose resonant frequencies range from 300 to 800 Hz and quasi-static piezoelectric coefficient d33 is 230 pC/N. The energy harvesting performance of IXPP films is investigated, both theoretically and experimentally, in a single HR with various sizes, showing the high energy conversion capability close to the resonant frequencies of HRs, e.g., 337, 375, 445, 522, 588, 661, 739, 782, and 795 Hz, in the experiment. By putting one, two, three, and four samples of nine different sized HRs in series connection in order, we measured the average output power of 3.16, 5.31, 7.36, and 8.66 nW at the resonant frequencies. It shows that the output power of IXPP films has been significantly improved at multiple frequencies by series connection of IXPP films. In parallel, the optimal electrical resistance increases in a quasilinear way compared to the number of HRs. These results are helpful for designing efficient sound energy harvesters in the broadband frequency range.

The dimer under study is a dielectric structure formed of two identical sub-units. Dimer interactions with electromagnetic waves are widely studied in connection with electromagnetic properties of complex systems. The dimer in the form of two closely spaced grapes is also a subject of high public interest because its gap region sparks curiously in a household microwave oven. A recent paper presented the first scientific interpretation of this long-standing puzzle. It attributed the sparking phenomenon to an electromagnetic hotspot in the gap created by electromagnetic resonances in the dimer. This study has opened up a fertile ground for further research as well as motivating the current study on an independent mechanism. Our simulation and experimental results consistently point to an electrical origin for the sparks. The triggering mechanism is a two to three orders-of-magnitude buildup of localized electric field in the narrow gap, which results from the mutual enhancement of polarization charges on opposite sides of the gap. Consequently, sparks are observed at the frequency of 27 MHz, at which no electromagnetic resonance in the dimer is possible. Results also indicate a broad frequency range of the electrical mechanism, which persists even when the dimer is in strong electromagnetic resonance with the first few higher-order modes. These quantitative characterizations of basic dimer properties, in particular the broad frequency range of the polarization-charge enhancement effect, may be helpful for the understanding of collective behavior of multi-particle systems under electromagnetic radiations.

A numerical tool for analysing spatially anisotropic electron populations in electron cyclotron resonance (ECR) plasmas has been developed, using a trial-and-error electron energy distribution function (EEDF) fitting method. The method has been tested on space-resolved warm electrons in the energy range $2-20\,\mathrm{keV}$, obtained from self-consistent simulations modelling only electron dynamics in ECR devices, but lacked real-world validation. For experimentally benchmarking the method, we attempted to numerically reproduce the experimental X-ray emission spectrum measured from an argon plasma. Results of this analysis have provided crucial information about density and temperature of warm electrons, and competing distributions of warm and hot electron components. This information can be fed back to simulation models to generate more realistic data. Subsequent application of the numerical tool as described to the improved simulation data can result in continuous EEDFs that reflect the nature of charge distributions in anisotropic ECR plasmas. These functions can be also applied to electron dependent reactions, in order to reproduce experimental results, like those concerning space-dependent K$\alpha$ emissions.

We study the motion of radially driven fluid-immersed particles in a novel Hele-Shaw cell with open boundaries. The initially uniform suspension forms a striped pattern within a specific range of horizontal oscillation frequencies and for sufficiently large amplitudes. We observe that the initial coarsening dynamics of the stripes gradually slows down and the pattern reaches a steady state after a few minutes. The distance between the stripes in the steady state exhibits an exponentially saturating increase with increased oscillation amplitude or frequency. The width of the stripes decreases as a power-law with the frequency while its amplitude dependence follows a logistic function. We propose a mechanism -- based on the interplay between shear stress, hydrodynamic interactions, and frictional forces -- to link the structural characteristics of the stripes to the properties of the oscillatory external drive., Comment: 7 pages, 4 figures

The equation of states, diffusions, and viscosities of strongly coupled Fe at 80 and 240 eV with densities from 1.6 to 40 g/cm3 are studied by orbital-free molecular dynamics, classical molecular dynamics with a corrected Yukawa potential and compared with the results from average atom model. A new local pseudopotential is generated for orbital free calculations. For low densities, the Yukawa model captures the correct ionic interaction behavior around the first peak of the radial distribution function (RDF), thus it gives correct RDFs and transport coefficients. For higher densities, the scaled transformation of the Yukawa potential or adding a short range repulsion part to the Yukawa potential can give correct RDFs and transport coefficients. The corrected potentials are further validated by the force matching method. Keywords: Transport properties, Orbital-free molecular dynamics, Yukawa model, Force matching, PACS codes: 34.20.Cf, 52.25.Fi, 52.27.Gr, 52.65.Yy

The work is concerned with the modeling of low-current quasi-stationary discharges, including the Townsend and corona discharges. The aim is to develop an integrated approach suitable for the computation of the whole range of existence of a quasi-stationary discharge from its inception to a non-stationary transition to another discharge form, such as a transition from the Townsend discharge to a normal glow discharge or the corona-to-streamer transition. This task includes three steps: (i) modeling of the ignition of a self-sustaining discharge, (ii) modeling of the quasi-stationary evolution of the discharge with increasing current, and (iii) the determination of the current range where the quasi-stationary discharge becomes unstable and the non-stationary transition to another discharge form begins. Each of these three steps is considered in some detail with a number of examples, referring mostly to discharges in high-pressure air.

Binary collision rates are calculated for the permeable particles undergoing (i) Brownian motion, (ii) gravity sedimentation, (iii) uniaxial straining flow, and (iv) shear flow. Darcy's law is used to describe the flow inside the permeable particles, and no-slip boundary conditions are applied at particle surfaces. A leading-order asymptotic solution of the problem is developed for the weak permeability regime K=k/a2≪1, where k=12(k1+k2) is the mean permeability and a=a1a2/(a1+a2) is the reduced radius; ai, ki (i = 1, 2), respectively, is the radius and permeability of each particle. The resulting collision rates are given by the quadrature of the pair mobility functions for permeable particles in the near-contact lubrication region and size-ratio-dependent parameters obtained from standard hard-sphere pair mobility functions. Collision rates in shear flow vanish below a critical value of the permeability parameter K* that increases with diminishing size ratio. The analogous problem of pair collision rates of particles with small-amplitude surface roughness δa is also analyzed. The formulas for the collision rates of rough particles provide accurate analytical approximations for the collision rates of permeable particles for all four aggregation mechanisms and a wide range of size ratios using an equivalent roughness δ=0.72K2/5.

Collision of two vortex rings (VR) initially arranged in axis-offset and orthogonal configurations at Reynolds numbers ( ReΓ) in the range of 5000–200 000 was simulated to investigate turbulent energy cascade associated with their reconnection. Two elliptical VRs are generated by joining each part of the first VR with another part of the second VR for the axis-offset collision, while two VRs associate to form a double U-shaped vortex, and this vortex reconnects itself at two points to form three elliptical VRs linked by the vortex filaments for the orthogonal collision. Many vortex structures in various scales and shapes, including small-scale VRs and horseshoe vortices, are observed in connection regions for both cases. As ReΓ increases, the energy of formed small vortices raises and their wavenumber (k) range enlarges. The flow energy spectrum approaches a k−5/3 slope of the Kolmogorov hypotheses at low wavenumbers. For the axis-offset collision, the energy spectrum at medium wavenumbers continuously changes from k−3.0 at ReΓ= 5000 to k−1.8 at ReΓ= 200 000, and the exponent (α) of the wavenumber is determined by a function as α=0.3304 ln(ReΓ)−5.6538. Meanwhile, the energy spectrum at two medium-wavenumber subranges for the orthogonal collision with ReΓ≥ 20 000 approaches the slopes of k−3.0 and k−2.6. Turbulent mixing performance due to the axis-offset collision of two vortex rings is better than that with the orthogonal one.

A new approach to estimate the pitch angle of highly energetic postdisruption runaway electrons is presented by imaging the polarized runaway electron synchrotron emission. The vertical to horizontal polarization ratio is found to range between 3 and 14 in image-average studies looking at repeated shots as well as the polarization in a single discharge. Numerical studies with guiding center and full orbit simulations performed with the SOFT and KORC codes are given and compared to the experiment. The pitch angle evolution analyzed using a 1D impurity diffusion model in combination with kinetic simulations is also presented. These studies find agreement in the magnitude of the pitch angle, but not in the temporal rate of change of pitch angle. The measured pitch angle evolution timescale of order 50 ms falls between a modeled timescale of 20 ms in an equilibrium model and ≫100 ms in a nonequilibrium model.

In saturated Ohmic confinement regime of the experimental advanced superconducting tokamak, significant changes in the relative electron temperature fluctuations T e / T ¯ e, measured by a correlation electron cyclotron emission system, have been observed. It was found that T e / T ¯ e is strongly dependent on the normalized electron temperature and density gradient, R / L T e = R ∇ T e / T e and R / L n e = R ∇ n e / n e. T e / T ¯ e stay at a high level when R / L T e is within the range of 17 − 25 and R / L n e is within the range of 4 − 6. It has been also observed that the energy confinement degradation is correlated with the increase in electron temperature fluctuations. The linear stability analysis results show that the electron temperature fluctuations are mainly attributed to the ion temperature gradient modes.

Proton beams with energies beyond 100 MeV are essential for a wide range of applications, including modern cancer therapies. The generation of high-energetic protons beyond 100 MeV in experiments using PW-level laser pulses normally requires laser energies of 10–200 J. We propose an efficient hybrid scheme using tabletop (tens of TW) dual-laser pulses with laser energy of a few Joules with tandem solid density and near-critical density targets. The results of a 2D particle-in-cell simulation show that the combination acceleration scheme of the radiation pressure acceleration (RPA), laser wakefield acceleration (LWFA), and target normal sheath acceleration (TNSA) with the dual-pulses can considerably enhance the maximum proton energy to ∼220 MeV, which is nearly three times of the proton energy achieved by the RPA or the RPA-LWFA-TNSA using a single laser pulse.

We study Alfven eigenmodes (AEs) in the TJ-II heliac in hydrogen plasmas heated by hydrogen co-field neutral beam injector. Taking advantage of the unique TJ-II flexibility in a varying plasma current, we have observed strong variation of the AE frequency from fAE ∼ 30 to ∼220 kHz for selected modes. An advanced heavy-ion beam probe diagnostic determines the spatial location and internal amplitudes of the modes. The modes satisfy a local AE dispersion relation including the geodesic acoustic frequency that represents the lowest frequency of the mode. Linear MHD modeling with STELLGAP and FAR3D codes shows that the calculated temporal evolution of the mode frequency reproduces the observed maxima and minima at the same time intervals with a similar frequency range, and the radial profile peaks near the outer edge of the observed one.

Electromagnetic ion cyclotron (EMIC) waves have been studied in this manuscript which are triggered by hot proton thermal anisotropy having energy ranging from 7 to 26 keV with a minimum resonant energy of 6.9 keV. However, an opposite effect can be observed for the hot protons for energy less than the minimum resonant energy. When the intensity of EMIC waves is large, the cold protons (ions) having low-energies can be energized by the EMIC waves. The possible reasons for this energization are the phase bunching of low energy ions with EMIC waves and the generation of electric fields at the relaxation time of substorm. As a consequence, these undetectable protons now become detectable, and the number density and temperature anisotropy of the protons also increase within the energy range from 1 to 100 eV. Accordingly, the helium ions are also energized by the EMIC waves.

Edge localized mode (ELM) mitigation accompanied by density pump-out has been achieved during the application of resonant magnetic perturbation (RMP) with a toroidal mode number of n = 4 on EAST recently. The mean ELM frequency increases by a factor of 2.7 from 86 to 235 Hz with a decreased reduction in ELM loss. The evolution of pedestal electron density measured by a profile reflectometer before and after turning on the RMP current is presented. Both the pedestal density and density gradient show a decrease with application of RMP. The density fluctuation in the pedestal region has been measured by an O-mode fluctuation reflectometer. The broadband density fluctuation with a frequency range of 20–115 kHz is enhanced at the later period of the inter-ELM phase during ELM mitigation. This phenomenon is also observed for magnetic fluctuation measured by magnetic probes mounted in the vacuum vessel. A further study shows that the enhanced broadband fluctuations lead to a decrease in the growth rate of the pedestal density and an increase in divert or particle flux. This result implies that these enhanced broadband fluctuations could lead to an enhancement of outward particle transport. The possible roles of the enhanced fluctuations observed in ELM mitigation are also discussed.

Using molecular dynamics, we found that the localized phonon-mode spectrum in SiGe alloys, which was recently discovered by an inelastic x-ray scattering experiment, changes according to the size distribution of compositional clusters in alloys. By varying the spatial distributions of Si and Ge, alloy models with differing compositions of Si and Ge clusters were able to be produced. For a range of alloys comprising 20%–80% Ge, a mixture of small and intermediate sized clusters will give the highest intensities of the local mode. The Si–Ge optical mode intensity increases with the local mode intensity, but the Si–Ge bond alone is not sufficient to produce the local mode. Si rich alloys with small Ge clusters produce the highest local mode intensities, suggesting that this mode is caused by small Ge clusters surrounded by Si pairs.