Hard x-radiation accompanying a discharge in a gas

In this paper it is shown that a powerful gas discharge at low pressure is accompanied by the emission of hard X-ray quanta. The radiation is observed in the discharge in various gases. The main properties of the radiation are studied, and consideration is given to a possible mechanism of origin of the effect observed.The authors regard it as their pleasant duty to express their gratitude to L. A. Artsimovich for valuable discussions, and also to S. A. Chuvatin for aid in carrying out the experiments.     

Theoretical model and experimental investigation of optically triggered hollow cathode discharge formation

In order to investigate the process of optically triggered discharge formation,a model of ion space-charge formation based on classical plane electrodes and revised for a characteristic hollow-cathode discharge(HCD)configuration is proposed in this paper.The primary modified factor in our model is the penetrating electric-field parameter,which influences the ionization of trigger electrons and is calculated via particle simulation.Optical-trigger experiments are carried out using different voltages and under different seed-electron conditions,provided by two different photocathodes,Cu and Mg.The ion-accumulation rates calculated by our model are compared to the discharge-formation time,which is deduced from optical-trigger experiments.The results demonstrate that the process of positive space-charge formation is dominant in the HCD formation process or trigger delay,which is highly dependent on the seeding-electron density and applied voltage,and can therefore be quantitatively described by our model.Additionally,electron-beam generation is investigated by optically triggered HCD experiments on Mg-and Cu-photocathode-based devices.The results show that a more efficient trigger device is capable of generating an electron beam with higher amplitude and density.     

气体放电中子的诊断

用气体放电方法研究温核聚变现象。测到了强度为１×１０＾４ｎ／ｓ的中子，中子的产生稳定可控，重复性１００％。使用ＢＦ３中子探测器，６Ｌｉ热释光中子探测器，ＮＥ－２１３有机液体闪烁中子谱仪和ｎ－γ分辨技术对气体放电中子进行了诊断测量，证实了气体放电中子的存在。     

Amplification process of a gas electron multiplier simulated by PIC-MCC model

The performance of a single gas electron multiplier(GEM) in pure Xe at an atmospheric pressure is investigated by Particle in Cell-Monte Carlo Collision(PIC-MCC) model.The micro development processes with electrons and ions distributions in space have been revealed.Based on the micro development processes,the macroscopic parameters such as GEM gain and the effective efficiency have also been obtained.The simulation results indicate that after tens of nanoseconds,electrons are collected by the readout electrode while the ions still exist in the gas space for several microseconds.The main signal current is formed by the electrons arriving at the readout electrode,but electrons and ions are also collected by the copper electrodes near the GEM hole and the thin Kapton film boundary.The simulated gain of GEM exponentially increases with the applied GEM voltage.With the PIC-MCC simulations,both the physical amplification and charging mechanisms in the GEM device can be well understood,which is beneficial to the device design.     

The transient flow in a centrifugal pump during the discharge valve rapid opening process

During the rapid opening period of the discharge valve in the pump system commonly used in nuclear reactor operation, the flow-rate of the pump increases impulsively. In this paper, we report on experiment and numerical simulations which were implemented to investigate the external transient hydrodynamic performance and the internal flow mechanism of the pump during this transient process. External and internal characteristics under different flow-rates were measured with an experimental system. The simulation for steady conditions was based on detached eddy simulation (DES) and sliding mesh was verified by comparing the simulation with test results. More importantly, the transient characteristics during the valve's rapid opening process were simulated using a similar method. Results show that the Q–H curve deviates from the steady-state value. The external characteristics are further explained by analyzing the relative velocity on the middle stream surfaces S_1 m and S_2 m between blades. The pump performance during the valve's rapid opening process is influenced both by the fluid acceleration and instantaneous evolutions of the vortex structure.     

Buoyantly-driven two-phase countercurrent flow in liquid discharge from a vessel with an unvented gas space

This paper details experiments and analyses regarding the phenomenon of liquid discharge into a gaseous atmosphere from the bottom of a vessel with an unvented, upper gas space. The primary goal is the development of a simple model that predicts the rate of liquid discharge under the prevailing unvented condition. A literature survey of previous work on this phenomenon yielded only simple experiments and analyses that were limited in scope. Experiments were subsequently undertaken with an air-water system, using a larger volume and a wide range of drain line diameters. In addition to flowrate data, visual information was acquired regarding the physical mechanism possibly governing the prevalent flow regimes. The governing physical mechanism is identified as the stability of a gas-liquid interface, perturbed by buoyancy, at the drain line entrance. G.I. Taylor's fundamental analysis of interfacial stability lead to the determination of criteria for flow regime transition among the three prevalent flow regimes, corresponding to so-called small, medium, and large diameters. Also, analysis of the growth of interfacial instabilities lead to the application of flooding models for drainage rates within each regime. The models for moderate and large diameters were then compared against data, which confirmed their success in predicting discharge rates under the unvented condition.The motivation for this effort, besides the basic scientific significance of studying such a fundamental phenomenon, was its numerous applications, one of which is commercial nuclear reactor systems. Specifically, the phenomenon prevails in liquid coolant discharge from a PWR pressurizer, with an unvented steam volume, into a steam atmosphere existing in the adjoining hot coolant leg. Such a phenomenon could occur as part of a transient, or severe accident, scenario, entailing saturated conditions and steam production in the normally subcooled primary heat transport loop. The developed model was implemented in the Modular Accident Analysis Program (MAAP), a computer code designed to predict reactor system behavior in response to postulated off-normal conditions, including severe accident scenarios.     

Modeling of a DC glow discharge in a neon–xenon gas mixture at low pressure and with metastable atom densities

The physical properties of Ne–Xe DC glow discharges at low pressure are reported for a gap length of 1 cm for the first time in the literature. The model deals specifically with the first three moments of Boltzmann's equation and includes the radiation processes and metastable atom densities. The spatio-temporal distributions of the electron and neon and xenon ion densities, the neon and xenon metastable atom densities, the electric potential and the electric field as well as the mean electron energy are presented at 1.5 Torr and 250 V. The current–voltage characteristic is shown at 3 Torr, and it is compared with previous work for pure neon gas. The model is validated theoretically and experimentally in the case of pure gas.     

A model for calculation of pressure in the duct due to discharge of gas from a failed fuel pin

In this paper an anlytical model for the calculation of the pressure pulse in hexagonal ducts due to discharge of gas from a failed fuel pin is developed. The analysis yields the time history of the pressure pulse which can be used in the calculation of permanent deformation of the duct or in the assessment of the susceptibility of the duct to fracture. In this model the analysis is divided into two stages. In the first stage the gas expands as a spherical bubble, but the influence of duct wall is taken into account. At the end of the first stage the spherical shape of the bubble is assumed to be lost and the gas is assumed to expand axially as a column. The end conditions of stage 1 are the initial conditions for stage 2. The analysis involves solving the continuity and momentum equations for the liquid along with the energy balance equation for the gas. In the analysis the liquid is assumed to be incompressible.     

Intermittent increase of electron current on a probe during a discharge in a magnetic field

An account is given of preliminary results in a study of the influence of a magnetic field on electron diffusion in a plasma. An intermittent increase was observed in the ratio of the electron current in the probe to the ion current at some critical value of the magnetic field intensity. According to the preliminary data, the critical magnetic field changes proportionally to the gas pressure. These facts evidently indicate the existence of two qualitatively different mechanisms for the transverse movement of the electrons, one of which is diffusion by collision.In conclusion, I wish to thank P. M. Morozov for his assistance and interest in this work, and also S. Sinotov, for taking part in the measurements.     

Effect of a transverse magnetic field on a toroidal discharge in a strong longitudinal magnetic field

The effect of a transverse magnetic field on a toroidal discharge in a strong longitudinal magnetic field was studied. It was found that, for a definite value of the pinch displacement caused by the 1/c [I,B], force, the oscillations on the oscillograms of the electrical characteristics of the discharge had minimum amplitude, while the mean plasma conductivity reached a maximum. It was shown that the effect of the transverse component of the magnetic field could, in general, be explained from the concept of the equilibrium of the plasma pinch inside the conducting sheath.Translated from Atomnaya Énergiya, Vol. 17, No. 3, pp. 177–184, September, 1964.     

Investigation of a high-current gaseous discharge in a longitudinal magnetic field

A gaseous discharge in deuterium at currents reaching 700 kiloamps in longitudinal magnetic fields up to 12,000 gauss has been investigated. The effect of the field on the development of the discharge has been studied and it is shown that there is an increase in the magnetic field within the discharge column. An estimate is made of the conductivity of the plasma and the ionization coefficient.Presented at a conference at the Karolinska Technical Institutet, Stockholm, September 2, 1956.     

Investigation of electromagnetic radiation from a straight high-current discharge

In this work we investigate the formation of runaway electrons in the electric field of a gas discharge. It is shown that the interaction of the runaway beam with the plasma results in the production of intense coherent electromagnetic radiation at frequencies in the region of the plasma frequency. The power of this radiation is much greater than the thermal noise power.Translated from Atomnaya Énergiya, Vol. 14, No. 4, pp. 349–352, April, 1963     

Effect of an electron gas on a neutron-rich nuclear pasta

We studied the role that electron gas has on the formation of nuclear structures at subsaturation densities and low temperatures(T1 Me V).Using a classical molecular dynamics model we studied isospin symmetric and asymmetric matter at subsaturation densities and low temperatures varying the Coulomb interaction strength.The effect of such variation was quantified on the fragment size multiplicity,the inter-particle distance,the isospin content of the clusters,the nucleon mobility and cluster persistence,and on the nuclear structure shapes.We found that the presence of an electron gas distributes matter more evenly,disrupts the formation of larger objects,reduces the isospin content,and modifies the nucleon average displacement,but does not affect the inter-nucleon distance in clusters.The nuclear structures are also found to change shapes by different degrees depending on their isospin content,temperature and density.