Acceleration Of Microparticles Research Articles

Micro-particle injection experiments in ADITYA-U tokamak using an inductively driven pellet injector

A first-of-its-kind, inductively driven micro-particle (Pellet) accelerator and injector have been developed and operated successfully in ADITYA-U circular plasma operations, which may ably address the critical need for a suitable disruption control mechanism in ITER and future tokamak. The device combines the principles of electromagnetic induction, pulse power technology, impact, and fracture dynamics. It is designed to operate in a variety of environments, including atmospheric pressure and ultra-high vacuum. It can also accommodate a wide range of pellet quantities, sizes, and materials and can adjust the pellets’ velocities over a coarse and fine range. The device has a modular design such that the maximum velocity can be increased by increasing the number of modules. A cluster of lithium titanate/carbonate (Li2TiO3/Li2CO3) impurity particles with variable particle sizes, weighing ∼50–200 mg are injected with velocities of the order of ∼200 m s−1 during the current plateau in ADITYA-U tokamak. This leads to a complete collapse of the plasma current within ∼5–6 ms of triggering the injector. The current quench time is dependent on the amount of impurity injected as well as the compound, with Li2TiO3 injection causing a faster current quench than Li2CO3 injection, as more power is radiated in the case of Li2TiO3. The increase in radiation due to the macro-particle injection starts in the plasma core, while the soft x-ray emission indicates that the entire plasma core collapses at once.

Electrical microparticle acceleration by high-speed membrane deformation

In this study, we conducted experiments to explore the potential of a low-power exploding foil initiator for accelerating microparticles through high-speed membrane deformation. This involved the use of a conductive layer with a conversion section known as a “bridge,” which was positioned between the substrate and the cover layer. The application of pulsed electrical energy led to Joule heating at the bridge, while the vaporized gas generated impulsive loading, resulting in the deformation of the cover layer. According to the principles of energy conservation, 8.7% of the electrical input energy was converted into kinetic energy for the membrane. This deformation process achieved a velocity of 800 m/s, with a corresponding strain rate of 1.6 × 107 s−1. The applied impulse predominantly induced extension stresses in the cover layer rather than bending stresses. Under these conditions, a 17.5-µm radius polylactic acid bead was propelled and subsequently captured by a silicone gel layer, resembling human dermic skin. Considering factors such as particle clustering and deceleration due to air resistance during supersonic flight, assuming a normal incident angle, it was estimated that approximately half of the ejected particles could reach the human dermic layer, located 200 µm beneath the skin surface. These findings suggest that pulse discharge is a promising method for inducing high-speed membrane deformation, and the electrical microparticle accelerator holds potential for applications in needle-free drug delivery.

Design of an explosive micro-particle accelerator to simulate micrometeoroid impacts in space

Design of an explosive micro-particle accelerator to simulate micrometeoroid impacts in space

Design of an Explosive Micro-particle Accelerator to Simulate Micrometeoroid Impacts in Space

Design of an Explosive Micro-particle Accelerator to Simulate Micrometeoroid Impacts in Space

Velocity distributions in a gas-gun microparticle accelerator.

Here, we build and characterize a single-stage gas-gun microparticle accelerator, where a pressurized gas expands and launches particles on a target. The microparticles in the range of 60-250 μm are accelerated by the expansion of pressurized nitrogen. By using a high-speed camera, we study how the velocity distribution of accelerated particles is modified by particle size, pressure in the gas reservoir, valve's opening time, and diaphragm's thickness and composition. We employ this microparticle accelerator to study the impact of glass particles with diameters of (69 ± 6) μm accelerated at moderate velocities ∼ (10-25) m/s, using films of poly-dimethylsiloxane as targets.

Pressure- and Size-Dependent Aerodynamic Drag Effects on Mach 0.3–2.2 Microspheres for High-Precision Micro-Ballistic Characterization

The acceleration of microparticles to supersonic velocities is required for microscopic ballistic testing, a method for understanding material characteristics under extreme dynamic conditions, and for projectile gene and drug delivery, a needle-free administration technique. However, precise aerodynamic effects upon supersonic microsphere motion at sub-300 Reynolds numbers have not been quantified. We derive drag coefficients for microspheres traveling in air at subsonic, transonic, and supersonic velocities from the measured trajectories of microspheres launched by laser-induced projectile acceleration. Moreover, the observed drag effects on microspheres in atmospheric (760 Torr) and reduced pressure (76 Torr) are compared with existing empirical data and drag coefficient models. We find that the existing models adequately predict the drag coefficient for subsonic microspheres, while rarefaction effects cause a discrepancy between the model and empirical data in the supersonic regime. These results will improve microsphere flight modeling for high-precision microscopic ballistic testing and projectile gene and drug delivery.

Influence of accelerator energy parameters and silicon carbide microparticle sizes on the changes in magnetic field induction during their acceleration

This article contains the microparticle accelerator scheme, the methods, and the results of practical study of magnetic field induction and electromagnetic radiation formed during explosion product ionization and energy accumulation during explosive charge detonation, as well as the influence of some process parameters on its change. The purpose of this work is to study the influence of accelerator energy parameters and silicon carbide microparticle sizes on the change in magnetic field induction during their acceleration. The influence of technological parameters on the electrodynamic properties of the ionization process of a complex chemical system, which is condensed EXPLOSIVES, was studied by the developed method based on the Hall effect with the use of the developed semiconductor Hall sensors and a special measuring complex. The average magnetic field induction value is 48 MT. The influence of the energy parameters of the accelerator (explosive charge mass), as well as of the size of microparticles introduced into the explosion products (PV) on the electrodynamic properties of the processes of ionization and acceleration of microparticles was determined by measuring and calculating magnetic field induction. Practical results were obtained and confirmed the particle size influence on the plasma state. With an increase in the particle size from 20 to 100 microns, the induction value increases to 50 MT and decreases sharply with a change in the size from 150 to 300 microns. The obtained dependences are the technological characteristics of the process of processing materials by high-speed flows of microparticles with the use of explosion energy, which can be adjusted to make the process manageable.

A Digital Signal Recording Module for a Dust Hit Mass Spectrometer

The hardware and software parts of the signal registration module for a dust-shock mass spectrometer are described. The module allows one to record the spectrum of an ion pulse with frequencies from 100 to 400 MHz; it uses two 14-bit analog-to-digital converters connected to a programmable logic integrated circuit. In this case, a temporary alternation of analog-to-digital converters is used. The test results of the dustproof mass spectrometer at a microparticle accelerator are given (noise level 0.6% of the amplitude of the measured signal, sampling frequency 200 MHz).

Experimental hypervelocity impacts: Implication for the analysis of material retrieved after exposure to space environment

During the last three decades a wide variety of surfaces have been brought back to Earth after being exposed to the space particulate environment. The impact features found on these surfaces can give clues to the characteristics of the orbital debris and meteoroids that created them. Many investigations have been carried out to derive projectile parameters (size, shape, impact angle, origin) from the morphology of impact features and the analysis of projectile their remnants inside the crater. However, there are still some ambiguities in the interpretation of these results. In this study we have investigated carefully the distinguishing features for craters caused by the impact of high velocity iron particles on thick brittle targets, using a micro-particle accelerator. Up to date instrumentation, SEM and EDX, and in depth results analysis provides an extensive data-set that can be used to improve the scientific return of the investigation of material retrieved after exposure to space.

Investigation of optical glass characteristics under the influence of space factors

The paper describes a DF-OPTICS device that the present authors designed for the experimental study of changes in the optical properties of a glass whose surface is exposed to high-speed flows of micron-sized dust particles. The device allows the scattering indicatrix and the spectral transmittance to be automatically measured at each point of the sample with a 0.5-mm increment. Advantages of the developed device include small dimensions and the ability to work in vacuum, allowing it to be used in an accelerator chamber to simulate outer space factors. Experimental results for the K-8 glass put in a microparticle accelerator and bombarded by an aluminum powder PAP-1 with a characteristic size of 1-3 µm and speeds of 2-8 km / s are presented. The device makes it possible to measure the change of the spectral transmittance of transparent materials in the UV and RGB regions with an accuracy of 0.005%, which exceeds the sensitivity of some known spectrophotometers.

High gradient magnetic separation with involved Basset history force: Configuration with single axial wire

High gradient magnetic separation (HGMS) is an efficient and useful technique for the recovery of weakly magnetized microparticles. Usually the process of magnetic particle capture is considered to be governed by competition between the magnetic attraction of the particles to the magnetized wires, the Stokes viscous drag, and gravitational force on the particle. For the complete description of the motion of magnetic microparticles we have used the Maxey-Riley integro-differential equation containing also additional forces. We have therefore analysed the importance of these forces, especially the Basset history force and the added mass force, using an axial single wire HGMS filter with a bounded flow field. As has been found, magnitude of the Basset history force is largest in the close proximity to ferromagnetic wire, when the acceleration of microparticles is highest due to the large value of magnetic force. Including the Basset history force term into the description of the movement of a spherical magnetic particle in the moving fluid under the influence of the external magnetic force causes an expected deceleration of its movement. For example, relative capturing delay reaches values up to 10% (in absolute values few hundreds of microseconds). The obtained results clearly demonstrate the importance of these, usually neglected forces for the correct description of capture dynamics.

Measurement of incandescent microparticle acceleration using stereoscopic imaging.

Microparticles ranging from sub-microns to millimeter in size are a common form of matter in magnetic fusion environment, and they are highly mobile due to their small mass. Different forces in addition to gravity can affect their motion both inside and outside the plasmas. Several recent advances open up new diagnostic possibilities to characterize the particles' motion and their forces: high-speed imaging camera technology, microparticle injection techniques developed for fusion, and image processing software. Extending our earlier work on high-temperature 4D microparticle tracking using exploding wires [Z. Wang et al. Rev. Sci. Instrum. 87, 11D601 (2016)], we report here the latest results on time-resolved microparticle acceleration measurement. New particle tracking algorithm is found to be effective in particle tracking even when there are a large number of particles close to each other. Epipolar constraint is used for track-pairing from two-camera views. The error field based on an epi-geometry model is characterized on the basis of a large set of 2D track data and 3D track reconstructions. Accelerations based on individual reconstructed 3D tracks are obtained. Force sensitivity in the order of ten gravitational acceleration has been achieved. High-speed imaging is a useful diagnostic tool for microparticle physics, computer model validation, and mass injection technology development for magnetic fusion.

Gasdynamic acceleration of microparticles and their interaction with a solid body

Based on the physicomathematical model developed before, verified by comparison results of calculations with experimental data, parameters of a gas-dispersed jet, interacting with a solid body, are numerically investigated. In a wide range of temperature and pressure values in a mixing chamber, material density, the size and mass fraction of particles, the nozzle geometry and the streamlined body form, ratio of specific heat capacities, and the Mach number of carrier gas, calculations are made, which allows one to determine the impact of specified factors on the boundary of a perfectly inelastic collision of particles with the body, accompanied by different physical processes (erosion, cold deposition, ultradeep penetration). Since temperature falls below the Debye value at high expansion of flow, the impact of a significant change of the heat capacity and thermal conductivity of particles are taken into account. Radial distributions of density and velocity of the dispersed mass are plotted, which characterize the “quality” of two-phase flow as a tool for the ground modelling of interaction of a flying vehicle with a dust-laden atmosphere (containing, for example, particles of volcanic outbursts or ice crystals) as well as in technologies of surface treatment.

Experimental hypervelocity impacts: Implication for the analysis of material retrieved after exposure to space environment: Part I. Impacts on aluminium targets

During the last three decades a wide variety of surfaces have been brought back to Earth after being exposed to space environment. The impact features found on these surfaces are used to evaluate the damages caused to spacecraft and can give clues to the characteristics of the orbital debris and meteoroids that created them. In order to derive more precisely the particle parameters and to improve the analysis of projectile remnants, we have performed an extensive analysis of craters caused by the impact of high velocity particles on thick ductile targets, using a micro-particle accelerator. We show that from the geometry of the craters and from the analysis of the remnants it is possible to derive the main characteristics of the projectiles. In particular, using up-to-date instrumentation, scanning electron microscope (SEM) and Energy Dispersive X-ray (EDX) spectrometer, we found that even small residues inside craters can be identified. However, this study shows that a velocity resolution better than 1km/s would be appropriate to obtain a fair calibration of the impact processes on a ductile target. This would allow to decipher with precision impact features on ductile surfaces exposed to space environment.

Research on plasma axial velocity generated by small debris accelerator coaxial gun

"Plasma driven micro-particle accelerator" is a ground device for simulating impact effects of small debris in space. The particle velocity is determined mainly by axial velocity of plasma in a coaxial gun. Emission spectrometry is used to study the plasma axial velocity at different voltages and gas pressures. The experimental results indicate that axial velocity increases with the increase of discharging voltage, and doesn't change significantly with the pressure of working gas, which is consistent with the result of numerical simulation. This result is useful to improve the plasma axial velocity further, and provides an experimental basis for optimizing the accelerator.

Mechanism and operation parameters of a plasma-driven micro-particle accelerator

There is a large amount of micro debris ranging between millimeters and micrometers in space, which has significant influence on the reliability and life of spacecrafts through long-duration integrated impacts and has to be considered in designing a vehicle’s suitability to the space environment. In order to simulate the micro-impacts on exposed materials, a plasma-driven micro-particle accelerator was developed. The major processes, including the acceleration, compression and ejection of plasmas, were modeled. By comparing the theoretical simulations with the experimental results, the acceleration mechanism was clarified. Moreover, through a series of experiments, the optimum operation range was investigated, and the acceleration ability was primarily determined.

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Transdermal and topical drug delivery with minimal tissue damage has been an area of vigorous research for years. Our research team has initiated the development of an effective method for delivering drug particles across the skin (transdermal) for systemic circulation, and to localized (topical) areas. The device consists of a laser ablation based micro-particle acceleration system that can be integrated with endoscopic surgical techniques. We have successfully delivered 3㎛ size cobalt particles into gelatin models that represent soft tissue with remarkable penetration depth.

Experimental Demonstration of Plasma-Drag Acceleration of a Dust Cloud to Hypervelocities

Simultaneous acceleration of hundreds of dust particles to hypervelocities by collimated plasma flows ejected from a coaxial gun is demonstrated. Graphite and diamond grains with radii between 5 and 30 microm, and flying at speeds up to 3.7 km/s, have been recorded with a high-speed camera. The observations agree well with a model for plasma-drag acceleration of microparticles much larger than the plasma screening length.

Acceleration of microparticles in a gasdynamic facility with high expansion of flow

In addition to being used for achieving the traditional objective (developing a high-velocity steady flow with uniform transverse distribution of parameters), high-enthalpy aerodynamic facilities may be employed as devices which accelerate microparticles for implementing modern technological processes (for example, treating the surfaces of solids). The acceleration of particles to high velocities is accompanied by a decrease in the density of carrier gas and its deep cooling. In this paper, a physicomathematical model of two-phase flow is constructed, which takes into account the strong temperature dependence of the thermal properties of material of the dispersed phase (thermal conductivity coefficient and specific heat capacity in accordance with the Debye theory), as well as the possibility flow past particles at arbitrary values of Knudsen number (from continuous to free-molecule mode of flow). Numerical investigation results are given for the values of parameters, which are characteristic of a typical high-velocity aerogasdynamic facility and dielectric microparticles accelerated in this facility. Considered by way of example are the cases of two materials with particles of different sizes.

Swirling effects on the performance of the micro-particle acceleration and penetration: parametric studies

A unique biomedical delivery system (biolistics), for micro-sized powder formulation of drugs (typically protein- and/or DNA-based macromolecules) to be effectively and efficiently delivered into human skin or mucosal tissue for the treatment of a scope of diseases, has been proposed. One of the key concerns for designing and evaluating the biolistic system is to warrant that micro-particles are accelerated and penetrated in to the skin with a controllable velocity range and uniform spatial distribution for optimal targeting the cells of interest. In this paper, we numerically interrogate the performance of a prototype biolistic device, designed for a uniform micro-particle acceleration and penetration. Swirling effects on the gas–particle dynamics, the particle acceleration and penetration as well as the device performance are presented and interpreted. Variations of the micro-particle velocity range and spatial distribution with swirl ratios are examined. The ability of the micro-particles penetrating in to a model skin target is demonstrated and discussed.