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1.
More than 70% of the total plasma current is sustained by the bootstrap current and current drive during the synergy of lower hybrid current driving (LHCD) and ion Berstein wave (IBW) heating on the HT-7 tokamak.The lower hybrid non-inductive current source is off-axis and well localized, and more than 35% bootstrap current plasma has been obtained. The IBW in controlling electron pressure profile can be integrated into the LHCD target plasma. The largest steep gradient of the electron pressure profile in the region ρ - 0.5-0.7 mostly comes from the electron temperature profile, which may induce the large fraction bootstrap current. The large off-axis bootstrap current can help to create negative magnetic shear, and the good plasma confinement is achieved. 相似文献
2.
Ohmic Radio-Frequency Synergy Current Drive and Transformer Recharging Experiments in the HT-7 Tokamak 下载免费PDF全文
Lower hybrid current drive (LHCD) experiments for investigating the interaction between lower hybrid (LH) wave and residual dc electric field were performed in extensive plasma parameter ranges in the HT-7 superconducting tokamak. The experimental results are well fitted to the Karney-Fisch theory on the efficiency of LH waves energy converted to poloidal magnetic field energy. The fraction of absorbed LH power is about 0.75 for the HT-7 machine, and the upshift of the LH-wave parallel refraction index during LHCD experiments have been derived by the optimizing fitting parameters. The LH wave is also used for the transformer recharging when the plasma current is maintained unchanged. The highest efficiency about 7% has been achieved in HT-7 machine. 相似文献
3.
SONGMei WANBao-Nian XUGuo-Sheng LINGBi-Li 《中国物理快报》2003,20(6):865-868
Measurements of boundary fluctuations and fluctuation driven electron fluxes have been performed in ohmic and lower hybrid current drive enhanced confinement plasma using a graphite Langmuir probe array on HT-7 tokamak. The fluctuations are significantly suppressed and the turbulent fluxes are remarkably depressed in the enhanced plasma. We characterized the statistical properties of fluctuations and the particle flux and found a non-Gaussian character in the whole scrape-off layer with minimum deviations from Gaussian in the proximity of the velocity shear layer in ohmic plasma. In the enhanced plasma the deviations in the boundary region are all reduces obviously. The fluctuations and induced electron fluxes show sporadic bursts asymmetric in time and the asymmetry is remarkably weakened in the lower hybrid current driving (LHCD) phase. The results suggest a coupling between the statistical behaviour of fluctuations and the turbulent flow. 相似文献
4.
Operation of HT-7 tokamak in a multicycle alternating
square wave plasma current regime is reported. A set of AC operation
experiments, including LHW heating to enhance plasma ionization
during the current transition and current sustainment, is described.
The behaviour of runaway electrons is analysed by four HXR detectors
tangentially viewing the plasma in the equatorial plane, within
energy ranges 0.3--1.2~MeV and 0.3--7~MeV, separately. High energy
runaway electrons (\sim MeV) are found to circulate predominantly
in the opposite direction to the plasma current, while the number of
low energy runaway electrons (\sim tens to hundreds of keV)
circulating along the plasma current is comparable to that in the
direction opposite to the plasma current. AC operation with lower
hybrid current drive (LHCD) is observed to have an additional
benefit of suppressing the runaway electrons if the drop of the loop
voltage is large enough. 相似文献
5.
SHIBingren 《核工业西南物理研究院年报(英文版)》2001,(1):72-76
Recently, to save the current drive power and to obtain more favorable confinement merit for a tokamak reactor, large fraction of bootstrap current sustained equilibrium has attracted great interests both theoretically and experimentally. We use an powerful expanding technique and the tokamak ordering to expand the GSh-E to obtain a series of ordinary differential equations which allow for different sets of input profiles. The fully bootstrap current sustained tokamak equilibria are then solved analytically. 相似文献
6.
Based on the principle of profile consistency and ηi-mode induced anomalous transport model, the enery confinement in tokamak plasmas is studied with inclusion of the bootstrap curreut in which the poloidal magnetic field is consistently deter-mined. The results show that bootstrap current has a significant effect on plasma confinement. If the bootstrap current is (15-30)% of the total current, global energy confinement time may increase by (20-45)%, and the maximum of related energy store is almost as much as twice the value without bootstrap current. Variation of the energy confinement time with the plasma parameters is of similar trend with Kaye-Goldston scaling. In addition, it can be seen that the radius of q=l surface decreases with bootstrap current, which may be one of the possible mechanisms for some experimental results where sawtooth oscillation disappears because of auxiliary heating. 相似文献
7.
Dynamic Stabilization by Modulated Toroidal Current on the HT—7 Superconducting Tokamak 总被引:2,自引:0,他引:2 下载免费PDF全文
The technique of toroidal current modulation has been successfully used in suppressing magnetohydrodynamic (MHD) perturbations effectively on the HT-7 superconducting tokamak.When the ratio of amplitude of plasma modulated current ΔIp versus the equilibrium plasma current Ipo is about 12-30%,the resonance surface is moved outside the island width,and the suppression of MHD perturbations is observed.The disruption induced by tearing mode intability is delayed or avoided.Different formats of frequency modulated are compared. 相似文献
8.
Analytic description of tokamak equilibrium sustained by high fraction bootstrap current 总被引:1,自引:0,他引:1 下载免费PDF全文
By using an expansion technique based on the tokamak ordering, the Grad-Shafranov equation is analytically solved for tokamak equilibrium sustained by a full bootstrap current. This approximate approach is suitable for equilibria with non-circular cross-sections of modest ellipse and triangular deformations. As an input parameter set, the plasma pressure profile and the electron and the ion temperature profiles can be selected as arbitrary functions of the averaged minor radius. Equilibrium properties of this plasma are discussed. 相似文献
9.
XUZengyu JointResearchGroup 《核工业西南物理研究院年报(英文版)》2001,(1):45-47
Carbon-base materials is one of candidate plasma facing materials and have been widely used in current tokamak facilities in the world. But some defect properties are presented on high yield of chemical sputtering, high yield of radiation enhancement sublimate (RES), cracking after heat flux in divertor and so on. These characteris are related to the interstitial carbon atom producing and mobile, so it can be improved by doped some little other elements into the carbon-base materials, such as boron, silicon, titanium and so on. 相似文献
10.
SONGMei WANBao-Nian XUGuo-Sheng LINGBi-Li 《中国物理快报》2003,20(6):869-872
The statistical properties of plasma fluctuations are characterized in the boundary region of HT-7 tokamak. A non-Gaussian feature is observed in fluctuations of ion saturation current and floating potential in most of the scrape-off layer regions. The statistical properties of fluctuations have a clear radial dependence, showing a near-Gaussian character in the proximity of the velocity shear layer location and another region where the poloidal velocity has a trend to zero. Fluctuations show a bursty character with pulses asymmetric in time and the time asymmetry reaches the minimum around the shear layer. From the results, we can see an obvious coupling of the pulses and the poloidal flow. 相似文献
11.
SHI Zhongbing DING Xuantong LIU Zetian 《核工业西南物理研究院年报(英文版)》2005,(1):11-12
As an ordinary mainly auxiliary heating on tokamak plasma, electron cyclotron resonance heating ( ECRH ) is an useful method to the study of electron heat transport and confinement performance. In this work, primary results of ECRH experiments on the HL-2A tokamak are presented. The features of confinement and electron heat transport during ECRH are analyzed. 相似文献
12.
13.
Tomographic analysis of the central magnetohydrodynamic oscillations on the HT-7 tokamak 总被引:1,自引:0,他引:1 下载免费PDF全文
Multi-channel soft x-ray (SX) detectors are applied to generate images of
magnetohydrodynamic (MHD) oscillation on the HT-7 tokamak, and the data
from SX cameras are analysed by using the
Fourier--Bessel harmonic reconstruction method and the singular value
decomposition. The image
reconstruction of SX emissivity is obtained on the assumption of plasma
rigid rotation. One of the important phenomena in the HT-7 discharge is the
transition from the sawtooth oscillations to the MHD oscillations when the
plasma density grows higher. The MHD structure
observed in the SX tomography is featured as follows: the magnetic surface of MHD
structure is made up of the crescent-shaped ``hot core' and the circular
``cold bubble'. The structure of the magnetic surface is relatively stable.
It rotates in the direction of the electron diamagnetic drift at a
frequency being the oscillation frequency of the MHD oscillations. 相似文献
14.
Measurement and analyses of the mean effective ion charge in the centre of tokamak discharges 下载免费PDF全文
There are two different definitions for specifying the mean
effective ion charge Zeff in plasmas: a) from the Spizer
electrical resistivity of the plasma and b) from bremsstrahlung
radiation losses of the plasma.
In this paper Zeff in
the centre of tokamak ohmic discharges has been determined from
information on sawtooth-relaxations of the steady state plasma, based
on the analysis for the power balance of the plasma electrons in the
plasma centre during the period of recovery after the sawtooth
crashes. This method is found to supply reliable results for tokamak
parameters. While its application requires some efforts in data
analysis, it can provide a reliable determination of Zeff,
independent of the information from bremsstrahlung radiation losses
of the plasma. 相似文献
15.
The first results of divertor discharge and supersonic molecular beam injection on the HL-2A tokamak 总被引:1,自引:0,他引:1 下载免费PDF全文
HL-2A tokamak is the first tokamak with divertors in China. The
plasma boundary and the position of the striking point on the target
plates of the HL-2A closed divertor were simulated by the current
filament code and they were in agreement with the diagnostic results
in the divertor. Supersonic molecular beam injection (SMBI) system
was first installed and tested on the HL-2A tokamak in 2004. In the
present experiment low pressure SMBI fuelling on the HL-2A closed
divertor was carried out. The experimental results indicate that the
divertor was operated in the `linear regime' and during the period of
SMB pulse injection into the HL-2A plasma the power density convected
at the target plate surfaces was 0.4 times of that before or after
the beam injection. It is a useful fuelling method for decreasing the
heat load on the neutralizer plates of the divertor. 相似文献
16.
Discharge simulation and volt-second consumption analysis during ramp-up on the CFETR tokamak 下载免费PDF全文
《中国物理 B》2020,(2)
The plasma current ramp-up is an important process for tokamak discharge,which directly affects the quality of the plasma and the system resources such as volt-second consumption and plasma current profile.The China Fusion Engineering Test Reactor(CFETR) ramp-up discharge is predicted with the tokamak simulation code(TSC).The main plasma parameters,the plasma configuration evolution and coil current evolution are given out.At the same time,the voltsecond consumption during CFETR ramp-up is analyzed for different plasma shaping times and different plasma current ramp rates dIp/dt with/without assisted heating.The results show that the earlier shaping time and the faster plasma current ramp rate with auxiliary heating will enable the volt-second to save 5%-10%.At the same time,the system ability to provide the volt-second is probably 470 V·s.These simulations will give some reference to engineering design for CFETR to some degree. 相似文献
17.
EXPERIMENTAL EVIDENCE OF THE SELF-SIMILARITY AND LONG-RANGE CORRELATIONS OF THE EDGE FLUCTUATIONS IN HT-6M TOKAMAK 下载免费PDF全文
To better understand long-time-scale transport dynamics, the rescaled range analysis techniques, the autocorrelation function (ACF) and the probability distribution function (PDF) are used to investigate long-range dependences in edge plasma fluctuations in HT-6M tokamak. The results reveal the self-similar characters of the electrostatic fluctuations with self-similarity parameters (Hurst exponent) ranging from 0.64 to 0.79, taking into consideration the {\vec E}r×{\vec B} rotation-sheared effect. Fluctuation ACFs of both the ion saturation current and the floating potential, as well as PDF of the turbulence-induced particle flux, have two distinct time scales. One corresponds to the decorrelation time scale of local fluctuations (μs) and the other lasts to the order of the confinement time (ms). All these experimental results suggest that some of the mechanisms of the underlying turbulence are consistent with plasma transport as characterized by self-organized criticality(SOC). 相似文献
18.
Estimation of Charge Exchange Recombination Emission Based on Diagnostic Neutral Beam on the Experimental Advanced Superconducting Tokamak 下载免费PDF全文
Diagnostic neutral beam (DNB) attenuation and charge exchange recombination emission are estimated on EAST tokamak. Approximately 40% of the beam with the energy of 50 keV can reach the plasma centre (r = 0) for the typical parameters of the Experimental Advanced Superconducting Tokamak (EAST) plasma. Emissivities of CVI (n = 8 → 7, 529.0nm) and OVⅢ (n = 10 →9, 607.Ohm) visible charge exchange recombination emissions based on the DNB are estimated. The emissivities of the visible bremsstrahlung emission near this wavelength are also calculated for comparison. The results show that the charge exchange recombination emission is about two orders of magnitude greater than the bremsstrahlung emission. It is theoretically indicated that the ratio of signal of charge exchange recombination spectroscopy to the noise from background bremsstrahlung emission, S/N, is large enough in the EAST tokamak with the typical designed parameters. The present results are helpful for experiment design of charge-exchange recombination spectroscopy based on the DNB in the EAST tokamak. 相似文献
19.
Electron Injection by E—Field Drift and its Application in Starting—up Tokamaks at Low Loop Voltage 下载免费PDF全文
PANYuan YANXiao-Lin LIUBao-Hua 《中国物理快报》2003,20(5):688-691
We propose an innovative method of election injection by E-field drift into a plasma device and discuss its application in starting-up tokamak plasmas at low loop voltage.The experimental results obtained from HT-6M Tokamak are also presented.The breakdown loop voltage is obviously reduced and the discharge performance is improved by using the electron injection method.It could be applied to some other types of plasma device. 相似文献
20.
Dependence of the bootstrap current fraction of spherical torus plasma on the aspect ratio and the triangular deformation is studied by using a simple equilibrium model, the Solov‘ev-type equilibrium. Two bootstrap current models are used: one is the single-ion collisionless regime model, the other is the recently developed arbitrary collisional regime model. It is found that besides the well known favourable effect of the small aspect ratio on the enhancement of the bootstrap current fraction, the triangularity is beneficial for raising the total bootstrap current though it does not change its fraction much. 相似文献