Influence Of Charged Particles Research Articles

Cylindrical electrodes for neutralization of insulating flowing particles

This paper is aimed at studying charge neutralization of flowing particles using a DC corona discharge. The efficiency of two electrodes configurations, namely cone-grid and coaxial cylinder, was experimentally studied. The influence of electrode placement in the middle or at the end of a lab-scale canalization installation is highlighted. Surface potential distribution and charge measurements showed that both configurations can lead to excellent neutralization rates, of around 99%, depending on electrode voltage and placement. The performances of the cone-grid configuration were found to vary according to the electrode placement. Conversely, the coaxial configuration is more stable and, practically, placement independent. A theoretical calculation of required corona discharge to perfectly neutralize charges is also presented. The obtained formula was experimentally verified showing a good agreement between calculation and measurement. Furthermore, the influence of charged particles on the corona discharge when crossing the coaxial electrode is highlighted through discharge current measurement and electric field calculation using finite element software. The charged particles were found to alter the electric field distribution and discharge current resulting in the electric field increase near the wire and his decrease near the grounded cylinder. Therefore, the charged particles act as a dielectric barrier that can affect the discharge current.

Monte Carlo track structure simulation in studies of biological effects induced by accelerated charged particles in the central nervous system

Simulating the biological damage induced by charged particles trajectories (tracks) in the central nervous system (CNS) at different levels of its organization (molecular, cellular, and tissue) is a challenge of modern radiobiology studies. According to the recent experimental studies at particle accelerators, the most radiation-sensitive area of the CNS is the hippocampus. In this regards, the development of measurement-based Monte Carlo simulation of radiation-induced alterations in the hippocampus is of great interest to understand the radiobiological effects on the CNS. The present work investigates the influence of charged particles on the hippocampal cells of the rat brain using the Geant4 Monte Carlo radiation transport code. The applied computer simulation provides a method to simulate physics processes and chemical reactions in the developed model of the rat hippocampus, which contains different types of neural cells - pyramidal cells, mature and immature granular cells, mossy cells, and neural stem cells. The distribution of stochastic energy depositions has been obtained and analyzed in critical structures of the hippocampal neurons after irradiation with 600 MeV/u iron particles. The computed energy deposition in irradiated hippocampal neurons following a track of iron ion suggests that most of the energy is accumulated by granular cells. The obtained quantities at the level of molecular targets also assume that NMDA and GABA receptors belong to the most probable targets in the irradiated neural cells.

Effect of charged particles’ flow velocity on THz absorption characteristic of dusty plasma

In this paper, on the basis of considering the influence of charged particles’ (electrons and ions) flow velocity, the absorption characteristic of dusty plasma in THz region is studied. Firstly, based on the model of conductivity which has considered the effect of flow velocity, the absorption coefficient is deduced. And then, the dependence of absorption coefficient on the flow velocity is discussed, which manifests that the absorption coefficient has a turning point (minimum) in the relation. In particular, it is found that the minimal absorption coefficient does not appear when the flow velocity is comparable to the thermal velocity, which is different from that of the complex conductivity. Finally, the condition where the minimal absorption coefficient appears is theoretically deduced.

Influence of particle velocity on the conductivity of dusty plasma

Conductivity is a popular branch of dusty plasma research. In this paper, on the basis of considering the influence of charged particles’ (electrons and ions) flow velocity, the conductivity of dusty plasma is derived and studied. Firstly, the charging currents are deduced on considering the influence of flow velocity, and the theoretical results manifest that it increases with the increase of flow velocity. Secondly, both the real and imaginary parts of the conductivity are derived, based on which, the dependence of conductivity on the flow velocity is discussed. In further, it is found that both the real and imaginary parts have a turning point. Finally, a ratio defined as charged particles’ flow velocity to thermal velocity is proposed to analyze the dependence of the conductivity on the velocities. The involved results reveal that both the real and imaginary parts of the conductivity have a turning point in their dependence on the ratio, but the specific ratio value is different.

Modeling of multi-junction solar cells for estimation of EQE under influence of charged particles using artificial neural networks

Abstract External quantum efficiency (EQE) of a solar cell provides information on the internal operations of the solar cells which can be used in optimization of solar cell design. The EQE of solar cells for space applications is adversely affected by the influence of charged particles in space. Usually numerical model based software, e.g., PC1D, are used to estimate the EQE and fitted with the measured EQE to obtain degradation performance of space solar cells. However, the accuracy of these models may be limited due to complex phenomena and interactions occurring between the junctions of the solar cells and the nonlinear influence of charged particles. In this paper we propose an artificial neural network (ANN)-based model to estimate the EQE performance of triple-junction InGaP/GaAs/Ge solar cells under the influence of a wide range of charged particles. Using the experimental data from Sato et al. [1] , it is shown that the ANN-based models provide a better estimate of the EQE than the PC1D model [1] in terms of mean square error and correlation coefficient.

Personal neutron dosimetry in the space station MIR and the space shuttle

A passive neutron dosemeter based on nuclear track detectors and TLD's was used in 1995 and 1997 on the MIR station and in Space Shuttle flights to MIR. As it is equipped with neutron converters and shieldings of different types the track detector system allows the neutron dose equivalent to be determined in rough energy intervals. The results of the measurements on the MIR station and in the Space Shuttle flights are presented and the influence of charged particles in the complex mixed radiation field in space is discussed. Improvements are possible by means of a new active neutron dosemeter which is under development at the PTB. First measurements with a prototype in the high-energy reference fields at CERN are presented and discussed.

Influence of charged particles on the fullerene formation process

The influence of charged particles on the process of fullerene formation is determined. Systematic experiments are used to show that the presence of carbon ions in the fullerene formation zone substantially increases the fullerene content in the soot.

Nonlinear vortical structures in the Earth’s ionosphere

The influence of charged particles and the Earth’s magnetic field on the possibility of the formation of solitary dipole vortical structures in the different layers of the Earth’s ionosphere is considered for the first time. It is shown that such influence manifests itself only in the E and F layers and leads to the destruction of the vortical structures. The magnetized Rossby vortices in the E layer are found. The damping decrement due to induction inhibition of the Rossby waves in the F layer is defined. The nonlinear equations describing the vortical formation dynamics in the D, E and F layers are obtained.

Solitary dipole vortices in the Earth's ionosphere

The influence of charged particles and the Earth's magnetic field on the possibility of the formation of solitary vortical structures in the different layers of the Earth's ionosphere is considered for the first time. It is shown that such influence manifests itself only in the E and F layers and leads to the destruction of the vortical dipole structures. Therefore longlived vortices mainly exist in the D layer of the atmosphere in the form of solitary dipole Rossby vortices. The nonlinear equations describing the vortical formation dynamics in the D, E and F layers are obtained.

Particle number density and velocity distributions in laser plumes

A time-of-flight mass spectrometer with electron impact ionization facility was used in investigations of the laser plume structure. Densities and velocity distributions of positively charged and neutral species were measured 12 cm downstream of the target. Velocities of particles in a plume were measured by the retarding potential method. The combination of a skimmer and declining electric field was used to suppress the influence of charged particles during the measurement of the neutral component parameters. In the case of YBaCuO ceramic laser ablation, a strong variation of the laser-induced plume composition was observed from its head to its tail. It seems to be accounted for by the difference of the starting (phase transition) temperatures of various layers of a plume. Ions detected mainly in the head of a plume were followed by atoms, molecules and clusters in inverse succession to their appearance in the plume under the light intensity increase. The characteristic of the number density dependence upon the laser spot diameter make it clear that most of the molecules BaO and YO are the direct product of ablation. In contrast, the detected clusters with masses up to 2000 amu are the product of condensation in the expanding plume under the conditions of the experiments.

On the conductivity of metal films during coalescence and the influence of an electric field on their growth

The influence of an electric field normal to the substrate during film growth on the electrical resistance of thin silver deposits is investigated. For interpretation of the results, the coalescence processes are subdivided into three stages. In the first two stages the resistance of the channels determines the resistance of the film. In the first stage the islands gather after film deposition has been interrupted; in the second stage they form bridges between one another. In the third stage the resistance is determined by that of the tracks. Owing to the interaction of dipoles, an electric field causes repulsive forces between the islands without the influence of charged particles. Accelerated charge carriers in the vapour beam increase the resistance of the channels, decrease the growth rate and the mobility of the islands and change the density of the islands.

Nucleation in bubble chambers

A new approach is presented to the creation of vapour bubbles in superheated liquids by high ebergy charged particles. A compilation is given of the theoretical work done on both spontaneous nucleation and nucleation under the influence of charged particles. The processes are compared with another nucleation process, the condensation of supersaturated vapours. Some striking differences are demonstrated. It is seen to be plausible that nucleation in liquids through the action of charged particles is a thermal process, for which the liquid must be heated locally. The amount of heat necessary to create a bubble that can grow to visible size has been calculated for a number of practical cases. The energies are 8.2 eV for helium, 12.0 eV for hydrogen and 256 eV for propane. It is shown that this amount of heat must be concentrated in an area with a diameter of about 10 nm at the beginning of the nucleation process. The non-occurence of a relativistic increase in the bubble density—velocity curve supports the assumption that, at least in hydrogen, the bubbles are created by δ-electrons. In the case of helium a detailed calculation is given of the way in which a δ-electron transfers its energy to the liquid. It can be shown that direct heating of the liquid by electrons is only a minor effect, but that excitation and ionization can produce the necessary heat for bubble formation by their subsequent processes, deexcitation and recombination. In the presented model the liquid is treated as gas-like, only those effects which are observed in gaseous helium are incorporated in the mechanism. It is made clear that a single deexcitation or recombination event is not sufficient to create a bubble, but that a number of them have to cooperate. A discussion about bubble creation in hydrogen and in more complex liquids is presented. The influence of molecular effects, the possibility of collective excitations and the consequences of complex chemical behaviour are estimated. It is seen to be plausible that the nucleation process takes place more easily in more complex liquids, because of the greater variety of ways in which the charged particles can transfer their energy to the liquid. Mention is made of the possibility that, in complex liquids, bubbles can be created by an excitation of lower atomoc levels rather than by the production of δ-electrons. This may explain the occurence of a relativistic rise in the bubble density—velocity curve in liquids like freon.