共查询到20条相似文献,搜索用时 69 毫秒
1.
An electron Penning-Malmberg trap,which can confine an electron column and provide a good platform to investigate the cross-filed transportation of strongly magnetized electron plasma ,has been set up.With the device,an electron plasma with a density of 10^7 cm^-3 can be confined for a relatively long time.The structure of the trap,electron source,as well as the way how th measure electron plasma density profile and velocity distrbustion are introduced in detail. 相似文献
2.
Based on the single biasing electrode experiments to optimize the confinement of plasma in the device of KT-5C tokamak, dual-biasing electrodes were inserted into the KT5C plasma for the first time to explore the enhancing effects of biasing and the mechanisms of the biasing. By means of applying different combinations of biasing voltages onto the dual electrodes, the changes of Er, which are the key factor for boosting up the Er × B flow shear, were observed. The time evolution showed that the inner electrode played a major role in dual-biasing, which drew larger current than the outer one. The outer electrode produced little influence. It turned out that the dual-biasing electrodes were as effective as a single one in improving the plasma confinement, for the mechanism of biasing was essentially an edge effect. 相似文献
3.
Ramp-up experiments by means of lower hydrid wave on HT-7 superconducting tokamak have been performed and analyzed.A ramp-up rate of over 300kA/s is obtained and a conversion efficiency of over 10% has been achieved during the ramp-up phases.The study of the dependence of conversion efficiency on plasma density shows that the conversion efficiency is affected by the driven current,which is mainly dominated by the competition of impurity concentration with wave accessibility condition.In addition,the effect of current profile may play an important role in determining the conversion efficiency. 相似文献
4.
In this paper, the calculated results about the propagation properties of electromag-netic wave in a plasma slab are described. The relationship of the propagation properties with frequencies of electromagnetic wave, and parameters of plasma (electron temperature, electron density, dimensionless collision frequency and the size of the plasma slab) is analyzed. 相似文献
5.
武玉 《等离子体科学和技术》2002,4(4):1395-1398
Under the condition of steady,the pressure drop of coolant is mainly caused by friction along the cable.in the CICC(cable-in-conduit-conductor).helium flow within the conductor consists of two parallel interconnected tubes.The velocity distribution has some differece between the central channel and conductor space.The region of Reynolds number is from 10^3 to 10^6.This paper describes the calculation of pressure drop of HT-7U CICC at various mass flows.It is assumed that the coolant flows in two parallel,rough tudes during the caclulation. 相似文献
6.
The effect of the charge fluctuation of dust particles on ion acoustic wave(IAW) excited through ionization instability was investigated.The hydrodynamic equations and linear time-dependent perturbation theory served as the starting point of theory,by which the dispersion relatioin and growth rate of the IAW were given.By comparing the results with the case of constant dust charges,it was found that the charge fluctuation of dust particles reduces the instability of the wave mode. 相似文献
7.
During initial studies of ECRH in the HL-1M tokamak,non-standard central MHD activities,such as saturated wawtooth,partially saturated sawtooth,double sawtooth,and the strong m=1 bursts have been observed while changing the heating location,the ECRH power.the plasma density,Complete suppression of sawtooth is achieved for the duration of the ECRH.when the heating power is applied on the high-fiedl side of low-density plasma,and exceeds a threshold value of power .The m=1 bursts riding on the ramp phase of sawtooth can only be excited when the ECRH locaxation activities are produced or suppressed are described.Experimental results imply that the energetic electrons generated during ECRH are responsible for the modification/or stabilization/or excitation of the instability.Near the q=1 surface,the passing electrons play the role of reducing the shear and tending to stabilize the sawtooth activity,while the barely-trapped electrons play the role of enhancing or driving an internal kink instability. 相似文献
8.
K. NAKAMURA罗家融 王华忠季振山 王华王枫 齐娜 K. N. SATO K. HANADA M. SAKAMOTO H. IDEI M. HASEGAWA S. KAWASAKI H. NAKASHIMA A. HIGASHIJIMA 《等离子体科学和技术》2006,8(1):80-83
Magnetic sensorless sensing and control experiments with the plasma horizontal position have been carried out in the superconducting tokamak HT-7. The sensing is made to focus on the ripple frequency component of the power supply with thyristor and directly from them without time integration. There is no drift problem with the integrator of wagnetic sensors. Two kinds of control experiments have been carried out: to keep the position constant and swing the position in a triangular waveform, And magnetic sensorless sensing of plasma shape is discussed. 相似文献
9.
Construction of a 2kW/4K Helium Refrigerator for HT—7U 总被引:2,自引:0,他引:2
Superconducting magnets of toroidal field (TF) and poloidal field(PF) of HT-7U tokamak are all made of NbTi/Cu Cable-in-Conduit Conductor (ClCC),and cooled with a forced flow supercritical helium of 3.8K.A helium refrigerator with an equivalent capacity of 2kW/r K will be constructed.This paper presents the design of the helium refrigerator process.The thermodynamics of the refrigeration cycle and the refrigerator equipments. 相似文献
10.
The two-dimensional energy balance in a coaxial plasma opening switch (POS) is studied based on the single-fluid magnetohydrodynarnic (MHD) equations coupled with the generalized Ohm's law. The energy transfers between the plasma and the magnetic field are considered during the penetration of the magnetic field as the Ohmic heating is included in the energy-balance equation. The focus is on the energy partition between the magnetic-field energy and the dissipated magnetic-field energy in a high-density POS with different rise-in-time electric currents at the generator boundary. The simulation code is tested in two cases: the constant-in-time current case and the linear rise-in-time current case. For the sinusoidally rise-in-time current similar to that of the experiments, it is shown that at the end of the conduction phase the dissipated magnetic-field energy is 36.5% of the input electromagnetic energy, which is consistent with the experimental results. 相似文献
11.
Drift instability in plasma generated by electron cyclotron resonance (ECR) in KT- 5D device was investigated by using a fast camera and Langmuir probes. The similarity between the distribution of light intensity from the images and the plasma pressure indicates a nearly linear relationship. The discharge images taken by the camera and the plasma parameters measured by the probes also indicate the existence of low frequency turbulent events with a time scale less than a few mini-seconds. 相似文献
12.
Arc voltage fluctuations in a direct current (DC) non-transferred arc plasma generator are experimentally studied, in generating a jet in the laminar, transitional and turbulent regimes. The study is with a view toward elucidating the mechanism of the fluctuations and their relationship with the generating parameters, arc root movement and flow regimes. Results indicate that the existence of a 300 Hz alternating current (AC) component in the power supply ripples does not cause the transition of the laminar plasma jet into a turbulent state. There exists a high frequency fluctuation at 4 kHz in the turbulent jet regime. It may be related to the rapid movement of the anode attachment point of the arc. 相似文献
13.
Edge profiles in Ohmic and lower hybrid (LH) wave heated discharges in EAST are presented. A comparison of the measured profiles is made with those from the the... 相似文献
14.
The formation of SiC through the interface reaction between C60 and Si in a plasmaassisted chemical vapour deposition system (PACVD) is investigated with a C60 film previously deposited on Si wafers. The composition and structure of the deposited samples were characterized by micro-Raman spectroscopy and X-ray diffraction (XRD). The results showed that SiC film was formed successfully in hydrogen plasma at a substrate temperature of 800℃ . The hydrogen atoms in plasma were found to enhance the production of SiC. Furthermore, the effects of the added CH4 on the formation of film were studied. Introduction of CH4 simultaneously with H2 at the beginning would suppress the formation of the initial layer of SiC due to a carbon-rich environment on the substrate, which would be disadvantageous to the further growth of the SiC film. 相似文献
15.
ZANG Linge 《等离子体科学和技术》2013,15(3):213-216
fast video camera is verifi to be a powerful tool for observation of fiments/blobs near the last closed °ux surface (LCFS). In order to extract the fltuation component from the raw data of the fast camera, a pre-processing technique, sliding time window averaging subtraction (STWAS) has been developed to remove the background of slowly varying emission from the bulk plasma. By using this pre-processing technique, the fast camera data are analyzed. A method to identify the fiments in the pre-processed image is also discussed. 相似文献
16.
《等离子体科学和技术》2016,18(11):1076-1080
Plasmas containing ion beams have various applications both in plasma technology and in fundamental research. The ion beam energy and flux are the two factors characterizing the beam properties. Previous studies have not achieved the independent adjustment of these two parameters. In this paper, an ion-beam-background-plasma system was produced with hotcathode discharge in a double plasma device separated by two adjacent grids, with which the beam energy and flux ratio(the ratio between the beam flux and total ion flux) can be controlled independently. It is shown that the discharge voltage(i.e., voltage across the hot-cathode and anode) and the voltage drop between the two separation grids can be used to effectively control the beam energy while the flux ratio is not affected by these voltages. The flux ratio depends sensitively on hot-filaments heating current whose influence on the beam energy is relatively weak,and thus enabling approximate control of the flux ratio 相似文献
17.
《等离子体科学和技术》2015,17(8):638-643
Recently,a laser-induced breakdown spectroscopic(LIBS) system has been developed for in situ measurements of the chemical compositions of plasma facing materials(PFMs)in the Experimental Advanced Superconducting Tokamak(EAST).In this study,a LIBS system,which was used in a similar optical configuration to the in situ LIBS system in EAST,has been developed to investigate the spatial distribution of PFM elements at 1CP4 Pa.The aim of this study was to understand the nature of the spatial distribution of atoms or ions of different elements in the plasma plume and optimize the signal to background ratio for the in situ LIBS diagnosis in EAST.The spatial profiles of the LIBS signals of C,Si,Mo and the continuous background were measured.Moreover,the influence of laser spot size and laser energy density on the LIBS signals of C,Si,Mo and H was also investigated.The results show that the distribution of the C,Si and Mo peaks' intensities first increased and then decreased from the center to the edge of the plasma plume.There was a maximum value at R≈1.5 mm from the center of the plasma plume.This work aims to improve the understanding of ablating plasma dynamics in very low pressure environments and give guidance to optimize the LIBS system in the EAST device. 相似文献
18.
High time resolution measurements of the electrostatic fluctuations and the turbulent particle and energy fluxes have been performed with a Langmuir probe array in the edge plasma in HT-7 tokamak. Bursty behaviour was observed in the time resolved turbulent fluxes with positive skewness and large kurtosis. The contribution of the large sporadic bursts to the transport losses were estimated. The analysis shows that the turbulent fluxes have different behaviour in different frequency domains and the probability distribution functions (PDFs) of the particle and energy fluxes present two distinct scaling ranges. All these are essentially consistent with the predictions of the self-organized criticality (SOC) model, though further studies are needed. 相似文献
19.
In this paper a simple code has been developed to analyze power balance and qualitatively evaluate current profiles for discharges with lower hybrid current drive (LHCD) and ion Bernstein wave (IBW) heating in the HT-7 tokamak. Electron and ion thermal diffusivity, profiles of the bootstrap current density and total plasma current density can be estimated by this code using the experimental data. This code offers an easy and reasonable means to understand plasma transport in HT-7. 相似文献