Low-energy Particles Research Articles

Influence of Material Properties on the Effectiveness of Glidants Used to Improve the Flowability of Cohesive Pharmaceutical Powders.

This study investigated the effect of material properties, primarily particle size and surface energy, on the effectiveness of glidants used for the purpose of flowability enhancement. Three pharmaceutical grade glidants (Aerosil 200, Aerosil R972, and Cab-O-Sil M5P) were evaluated and blended with various pharmaceutical actives as well as cohesive excipients common to capsule and tablet formulation. Flowability enhancement was characterized by the flow function coefficient (ff c ). An industry-relevant mixer (Turbula mixer) and a highly efficient and effective mixer (LabRAM vibratory mixer) were used to further understand the effect of material properties on glidant effectiveness. While concepts of inter-particle cohesion and interaction strength were applied to evaluate their usefulness in understanding and predicting flowability enhancement, theoretical expectations did not fully explain the behavior of all three glidants. However, the study suggests that the low surface energy and optimal particle size of Aerosil R972 relative to the other glidants results in lower inter-particle force and consequently better flowability. Aerosil R972 was also shown to be more effectively utilized in the Turbula mixing process particularly for larger (d50 > 40μm) and less cohesive (ff c > 3) materials. This may be due to its lower surface energy and hydrophobic surface which allows it to disperse easily. Overall, this study provides useful insight into the material properties which influence the effectiveness of glidants used in formulation development.

Water-based acrylate copolymer/silica hybrids for facile preparation of robust and durable superhydrophobic coatings

Resin based superhydrophobic coatings are effective to construct robust superhydrophobic surfaces on large scale without limitation of substrates. However, for most of the common resin based superhydrophobic coatings, it is inevitable to deteriorate environmental or health problems due to release of a large amount volatile solvents. In this work, a kind of water-based organic/inorganic hybrid consisted of acrylate copolymers and superhydrophobic silica nanoparticles were synthesized. The highly water-repellent silica nanoparticles were successfully involved into the aqueous dispersion of acrylate copolymers without additional surfactants. The as-synthesized hybrids simultaneously retain the excellent film-forming property of acrylate resins and amplify the contributions of low surface energy nanoparticles to the superhydrophobicity. Robust superhydrophobic coatings (CA > 160°, CA < 7°) with high adhesion strength, good scratch-resistance and excellent abrasion-resistance were constructed using the synthesized hybrids with significantly reduced content of low surface energy particles and organic solvent. The hybrid coating can stand abrasion up to 300 cycles with a fine sand paper and up to 1200 cycles under rough sand paper abrasion. Benefited from its good water-repellence property, the hybrid coating with a water-based formula not only showed improved water-resistance in comparison with commercial products; but also displayed attractive performances in self-cleaning and oil/water separation processes.

Interaction of cosmic rays with molecular clouds

We analyze interaction of fast charged particles with Galactic molecular clouds. As a results of energy losses inside the clouds, a particle flux, converging to the cloud, is formed in the cloud vicinity. This flux, in its turn, excites there an MHD-turbulence by the streaming instability, which scatter the primary particles. Therefore the CR/cloud interaction is a complex problem described by a system of non-linear equations. We suggested a model of CR penetration into the dense cloud interior through their diffuse outer envelope. Three different regimes of CR propagation are realized in the envelope depending of CR energy: 1) Low energy particles with energies of tens of MeV are almost frozen into the MHD waves and propagate by convection with Alfven velocity. These particle do not reach the dense interior because of energy losses; 2) High energy particles with energies above ten GeV do not experience any scattering and propagate freely with luminal velocities. 3) In the intermediate energy range a ”mirroring shield” is formed between the diffuse envelope and the dense interior which prevents free CR penetration into the interior from outside. This effect is a function of the hydrogen density in the diffuse envelope and the spectrum of CRs in the intracloud medium.

Do Shock Accelerated Cosmic Rays Reach Feedback Levels?

Evidence is reviewed that shock-accelerated cosmic rays (CRs) are typically produced in sufficient quantity as to modify the flow into the shock and thereby regulate the acceleration of lower energy particles.

The influence of plasma-surface interaction on the performance of tungsten at the ITER divertor vertical targets

The tungsten (W) material in the high heat flux regions of the ITER divertor will be exposed to high fluxes of low-energy particles (e.g. H, D, T, He, Ne and/or N). Combined with long-pulse operations, this implies fluences well in excess of the highest values reached in today’s tokamak experiments. Shaping of the individual monoblock top surface and tilting of the vertical targets for leading-edge protection lead to an increased surface heat flux, and thus increased surface temperature and a reduced margin to remain below the temperature at which recrystallization and grain growth begin. Significant morphology changes are known to occur on W after exposure to high fluences of low-energy particles, be it H or He. An analysis of the formation conditions of these morphology changes is made in relation to the conditions expected at the vertical targets during different phases of operations. It is concluded that both H and He-related effects can occur in ITER. In particular, the case of He-induced nanostructure (also known as ‘fuzz’) is reviewed. Fuzz formation appears possible over a limited region of the outer vertical target, the inner target being generally a net Be deposition area. A simple analysis of the fuzz growth rate including the effect of edge-localized modes (ELMs) and the reduced thermal conductivity of fuzz shows that the fuzz thickness is likely to be limited by the occurrence of annealing during ELM-induced thermal excursions. Not only the morphology, but the material mechanical and thermal properties can be modified by plasma exposure. A review of the existing literature is made, but the existing data are insufficient to conclude quantitatively on the importance and extent of these effects for ITER. As a consequence of the high surface temperatures in ITER, W recrystallization is an important effect to consider, since it leads to a decrease in material strength. An approach is proposed here to develop an operational budget for the W material, i.e. the time the divertor material can be operated at a given temperature before a significant fraction of the material is recrystallized. In general, while it is clear that significant surface damage can occur during ITER operations, the tolerable level of damage in terms of plasma operations currently remains unknown.

Paradigm shifts about dust on the Moon: From Apollo 11 to Chang'e-4

Strategic purposes of this DAP-2017 report are to update our DAP-2010 report on movements of inescapable fine lunar dust, to summarise key new measurements and to assist rigorous focus.Lunar dust is defined here in two sciences, Apollo dust and Ejecta dust, to end several confusions. The Kuhn Cycle is introduced to stimulate progression of a science about movements of Apollo dust which lacks an agreed paradigm to supply puzzles for scientists to solve and tools for their solution. We populate the cycle with two paradigm shifts. The first was serendipitous invention in 1966 of the Apollo Dust Detector Experiment (DDE), 3 orthogonal solar cells each with a thermometer, which on Apollo 12 measured cause and effect, collective movements of billions to trillions of low-energy Apollo dust particles and changes in temperature they cause. In contrast, Apollo 17 LEAM and LADEE LDEX experiments follow traditions to measure impacts of high-velocity Ejecta dust particles, one by one.In 2015, Apollo 12 DDE discoveries of sunrise-driven storms of Apollo dust stimulated a measurement-based 5-step model of dust transport at astronaut waist height. The discoveries solve (i) 50-year-old mysteries of Horizon Glow, (ii) 30-year-old uncertainties about levitated dust, (iii) processes leading to lunar surfaces being smooth and (iv) immobilisation of the Chang'e-3 lunar rover Yutu in 2014 after its first sunrise. The IAC-2017 Website Abstract of a withdrawn Chang'e-3 presentation may support our views that sunrise-mobilised dust caused immobilisation of Yutu.A precursor to a second paradigm shift was May 2016 announced revision of Chang'e-4 scientific priorities. Using Kuhn terminology of scientific progress, a second shift would follow our “revolution” in 2015 that sunrise-driven dust storms caused the 2014 ″crisis” of immobilisation of Chang'e-3 lunar rover Yutu. No such sequence occurred previously with lunar dust. Measurement-based evidence from Apollo 11 to Chang'e-3 confirms that Apollo dust is the major surface problem for risk management plans of lunar expeditions.As of 1 February 2018, a second paradigm change awaits transparent authoritative Ground truth measurements by Chang'e-4 or other relevant dust detectors to compare with Apollo 12 DDE measurements. Re-examination of risk management of effects of Apollo dust is essential for international expeditions including a Moon Village and Google Lunar XMedal competitors.Future DAPs could refine a third paradigm shift for Moon, moving from the past and present Earth-centric cultures of an inert Moon to cultures with visions of Moon as an active and close Extraterrestrial neighbour, because its outermost sunlit two cm of dusty plasmas are a variable soup of lunar and Extraterrestrial plasmas. An emphasis on its research seems a neat fit with the Directive of President Trump on 11 December 2017 to “Lead an innovative and sustainable program of exploration with commercial and international partners” to “lead the return of humans to the Moon for long-term exploration and utilization”. It would also be measurement-based now thus less costly, more safe and quicker than any human visit to Mars.

Micro-scale characterization of a CMOS-based neutron detector for in-phantom measurements in radiation therapy

The CMOS sensor AlphaRad has been designed at the IPHC Strasbourg for real-time monitoring of fast and thermal neutrons over a full energy spectrum. Completely integrated, highly transparent to photons and optimized for low power consumption, this sensor offers very interesting characteristics for the study of internal neutrons in radiation therapy with anthropomorphic phantoms. However, specific effects related to the CMOS metal substructure and to the charge collection process of low energy particles must be carefully estimated before being used for medical applications. We present a detailed characterization of the AlphaRad chip in the MeV energy range using proton and alpha micro-beam experiments performed at the AIFIRA facility (CENBG, Bordeaux). Two-dimensional maps of the charge collection were carried out on a micro-metric scale to be integrated into a Geant4 Monte Carlo simulation of the system. The gamma rejection, as well as the fast and thermal neutrons separation, were studied using both simulation and experimental data. The results highlight the potential of a future system based on CMOS sensor for in-phantom neutron detection in radiation therapies.

Superhydrophobic Melamine-formaldehyde Foam Prepared by In-situ Coprecipitation

A superhydrophobic melamine-formaldehyde (MF) foam was prepared by a simple method, in which the hydrophobic SA@Fe3O4 (SA = stearic acid) micro-nanoparticles were fabricated on the surface of MF foam skeleton by in-situ coprecipitation. The modified MF foam showed outstanding superhydrophobic, oleophilic, and magnetic response due to its low surface energy, high porosity, and magnetic particles.

Steel surface TiCrN, TiMoNcoatings structural phase state change features after low-energy alpha particles irradiation

.The low-energy alpha particles irradiation impact on structural phase composition and 321S31 steel surface TiCrN and TiMoN coatings morphology have been summarized. The samples irradiation has been carried out in the DTs-60 (the Dubna cyclotron) heavy-ion accelerator by the4He+2 low-energy ions (40 keV) into a 1.0·1017 ion/cm2 fluence. It has been established thatthe 321S31 steel alpha particles implantation having energy of 40 keV results in the austenite initial γ-structurepartial transfer, stimulated by the irradiation, to the martensiteα-structure. The low-energy alpha particles irradiation within the fluencies range from 1016 to 1017 ion/cm2 for the TiCrN and TiMoN coatings formed by the ionic bombardment condensation method doesn’t result in the phase transfers with a coating crystal lattice type change.

Test of Einstein's Mass-Energy Relation

The Einstein's mass-energy relation E = mc^2 is one of the most fundamental formulae in physics, but it has not been seriously tested by an elaborated experiment, and only some indirect evidences in nuclear reaction suggested that it holds to high precision. Manifestly, for a particle, different self potential leads to different energy-speed relation, which can be used as the fingerprints of them. In this letter, we propose an experiment to test this relation. The experiment only involves low energy of particles and measurement of speed, which can be easily realized. The experiment may shed lights on a number of fundamental puzzles in physics.

Measurement of neutron and charged particle fluxes toward earthquake prediction

In this paper, we describe a possible method for predicting the earthquakes, which is based on simultaneous recording of the intensity of fluxes of neutrons and charged particles by detectors, commonly used in nuclear physics. These low-energy particles originate from radioactive nuclear processes in the Earth’s crust. The variations in the particle flux intensity can be the precursor of the earthquake. A description is given of an electronic installation that records the fluxes of charged particles in the radial direction, which are a possible response to the accumulated tectonic stresses in the Earth’s crust. The obtained results showed an increase in the intensity of the fluxes for 10 or more hours before the occurrence of the earthquake. The previous version of the installation was able to indicate for the possibility of an earthquake (Maksudov et al. in Instrum Exp Tech 58:130–131, 2015), but did not give information about the direction of the epicenter location. In this regard, the installation was modified by adding eight directional detectors. With the upgraded setup, we have received both the predictive signals, and signals determining the directions of the location of the forthcoming earthquake, starting 2–3 days before its origin.

Low-energy particle experiments\u2013electron analyzer (LEPe) onboard the Arase spacecraft

In this report, we describe the low-energy electron instrument LEPe (low-energy particle experiments–electron analyzer) onboard the Arase (ERG) spacecraft. The instrument measures a three-dimensional distribution function of electrons with energies of sim 19 eV–19 keV. Electrons in this energy range dominate in the inner magnetosphere, and measurement of such electrons is important in terms of understanding the magnetospheric dynamics and wave–particle interaction. The instrument employs a toroidal tophat electrostatic energy analyzer with a passive 6-mm aluminum shield. To minimize background radiation effects, the analyzer has a background channel, which monitors counts produced by background radiation. Background counts are then subtracted from measured counts. Electronic components are radiation tolerant, and 5-mm-thick shielding of the electronics housing ensures that the total dose is less than 100 kRad for the one-year nominal mission lifetime. The first in-space measurement test was done on February 12, 2017, showing that the instrument functions well. On February 27, the first all-instrument run test was done, and the LEPe instrument measured an energy dispersion event probably related to a substorm injection occurring immediately before the instrument turn-on. These initial results indicate that the instrument works fine in space, and the measurement performance is good for science purposes.

Full-Stokes, Multi-Frequency Radio Polarimetry of Fermi Blazars; Monitoring and Modelling

The polarised emission from active galactic nuclei (AGN) jets carries information about the physical conditions at the emitting plasma elements, while its temporal evolution probes the physical processes that introduce variability and dynamically modify the local conditions. Here we present the analysis of multi-frequency radio linear and circular polarisation datasets with the aim of exactly quantifying the conditions in blazar jets. Our analysis includes both the careful treatment of observational datasets and numerical modelling for the reproduction of synthetic polarisation curves that can be compared to the observed ones. In our approach, the variability is attributed to traveling shocks. The emission from the cells of our jet model is computed with radiative transfer of all Stokes parameters. The model also accounts for Faraday effects which map the low-energy particle populations. We present two extreme cases in terms of the significance of Faraday conversion in the production of circular polarisation. As we show, in both regimes the model gives a realistic reproduction of the observed emission.

Low energy tertiary beam line design for the CERN neutrino platform project

In the framework of CERN neutrino platform project at the CERN SPS North Area, two new beam lines have been designed as extensions of the existing secondary beam lines, able to provide low energy particles in the momentum range of 0.4 to $12\text{ }\text{ }\mathrm{GeV}/c$. The layout of these very low energy beam lines, their design parameters as well as outlook on their expected performance, are summarized in this paper.

Analysis of the angular distribution of cosmic-ray-induced particles in the atmosphere based on Monte Carlo simulations including the influence of the Earth's magnetic field

Several applications exist that calculate cosmic-ray-induced particle (CRIP) spectra as a function of the altitude in the atmosphere. In general, the Earth's magnetic field is only used to modulate the primary cosmic radiation that arrives at the top of the atmosphere, but it can also modulate low-energy charged particles at flight altitudes. The effects of the Earth's magnetic field on the angular distributions of CRIP transport in the atmosphere should be quantified, because it furnishes important data for the development of applications for aircrew radiation protection, onboard dosimetry and the simulation of irradiation of sensitive equipment and particle detector systems used at ground level, flight and atmospheric balloon altitudes.In this work we calculate the angular distribution of the cosmic-ray-induced particles (CRIP) for altitudes from ground level up to 80 km using an application based on Geant4 developed in previous works. In order to quantify the effects of the Earth's magnetic field (EMF) on the angular distribution of the CRIP, the calculations were carried out both including the EMF in the South Atlantic Magnetic region and omitting it. A part of these results were compared with analytical calculations of the ratio between the mean free path of the primary particles from the cosmic radiation and the deflection radii at different altitudes in the atmosphere. The albedos of neutrons and protons at 80 km were estimated and compared with the QARM and ATMORAD codes, which ignore the Earth's magnetic field.

DHCAL with minimal absorber: measurements with positrons

In special tests, the active layers of the CALICE Digital Hadron Calorimeter prototype, the DHCAL, were exposed to low energy particle beams, without being interleaved by absorber plates. The thickness of each layer corresponded approximately to 0.29 radiation lengths or 0.034 nuclear interaction lengths, defined mostly by the copper and steel skins of the detector cassettes. This paper reports on measurements performed with this device in the Fermilab test beam with positrons in the energy range of 1 to 10 GeV. The measurements are compared to simulations based on GEANT4 and a standalone program to emulate the detailed response of the active elements.

N =1 supergravitational heterotic galileons

Heterotic M -theory consists of a five-dimensional manifold of the form S1/Z2 × M4. It has been shown that one of the two orbifold planes, the “observable” sector, can have a low energy particle spectrum which is precisely the N = 1 super-symmetric standard model with three right-handed neutrino chiral supermultiplets. The other orbifold plane constitutes a “hidden” sector which, since its communication with the observable sector is suppressed, will be ignored in this paper. However, the finite fifth-dimension allows for the existence of three-brane solitons which, in order to render the vacuum anomaly free, must appear. That is, heterotic M -theory provides a natural framework for brane-world cosmological scenarios coupled to realistic particle physics. The complete worldvolume action of such three-branes is unknown. Here, treating these solitons as probe branes, we construct their scalar worldvolume Lagrangian as a derivative expansion of the heterotic DBI action. In analogy with similar calculations in the M5 and AdS5 context, this leads to the construction of “heterotic Galileons”. However, realistic vacua of heterotic M -theory are necessarily N = 1 supersymmetric in four dimensions. Hence, we proceed to supersymmetrize the three-brane worldvolume action, first in flat superspace and then extend the results to N = 1 supergravity. Such a worldvolume action may lead to interesting cosmology, such as “bouncing” universe models, by allowing for the violation of the Null Energy Condition (NEC).

Superbanana transport in the collisional heating of a plasma column forced across a squeeze potential

When weakly collisional plasmas have locally trapped particle populations, perturbations to the plasma equilibrium (such as waves or static field-errors) can induce phase-space discontinuities in the particle distribution function that strongly enhance entropy production, plasma loss, and wave damping via superbanana transport. This paper presents a simple version of this superbanana transport process, wherein a plasma is heated as it is slowly forced back and forth across a squeeze potential (at a frequency ω that is small compared with the particle bounce frequency). The squeeze potential traps low-energy particles on either side of the squeeze, but particles with higher energy can pass through it. Trapped and passing particles have different responses to the forcing, causing a collisionless discontinuity in the distribution function at the separatrix between the trapped and passing particles. Expressions for both the adiabatic and non-adiabatic distribution functions are presented, and the heating rate caused by collisional broadening of the separatrix discontinuity is derived. The heating rate is proportional to νω, provided that ν≪ω, where ν is the collision rate (i.e., the ν regime of superbanana theory).

Jets of Ionospheric Cold Plasma Discovered at the Magnetopause

The lower-energy particles may play a larger role in magnetic reconnection than previously believed, influencing space weather near Earth.

OSCAR: A new modular device for the identification and correlation of low energy particles

A new modular and high versatility hodoscope, OSCAR, has been developed and characterized. The aim of this hodoscope is to work as an ancillary detector of present large acceptance heavy ion detectors in specific angular regions where low thresholds and high granularities are needed. We discuss the capabilities of OSCAR in the ΔE–E identification of very low energy light particles, providing a precise map of the thickness uniformity of the ΔE (SSSSD, 20μm) stage and showing how the thickness gradient affects the identification of particles. Energy spectra of light identified particles produced in Ca+Ca collisions at 35AMeV are used to investigate isospin transport phenomena involving the emission of low energy particles from the quasi-target (QT) source in semi-peripheral nuclear collisions. The possibility to explore particle–particle correlations are also discussed.