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Lower Hybrid Wave Current Drive Efficiency on the HT-7 Tokamak

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Chinese Physics Letters 2005年第4期22卷 900-903页

作者：陈忠勇万宝年石跃江胡立群徐旵东李国超 instituteofplasmaphysics ChineseAcademyofSciencesHefei230031

Lower hybrid (LH) wave current drive efficiency on our HT-7 tokamak has been investigated based on the hot electrical conductivity theory. The interaction of the residual toroidal electric field with fast electrons has been included in the determination of current drive efficiency. The LH wave power scan was performed in the plasma parameter ranges of Ip = 50–156kA, e = 0.5×1019–1.6×1019m−3, PLH = 50–350kW. The current drive efficiency is derived to be about 0.1×1019–0.4×1019Am−2W−1 on the HT-7 tokamak, which depends on the electron density and the LH wave phase velocity. At the electron density of about 1.5×1019m−3, with the LH wave parallel refraction index peaked at 1.8, the highest current drive efficiency was obtained. A more generally normalized method is introduced to analyse the experimental data, which combines all the data in one curve. The normalized parameters are independent of the plasma parameters.

关键词： HT-7托卡马克热电导体混合波电流驱动效率相速度

Improved Edge Confinement due to Ion Cyclotron Radio Frequency boronization in the HT—7 Tokamak

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Chinese Physics Letters 2003年第6期20卷 881-884页

作者： XUGuo-Sheng WANBao-Nian SONGMei LINGBi-Li instituteofplasmaphysics ChineseAcademyofSciencesHefei230031

The phenomena of improved edge confinement due to ion cyclotron radio frequency boronization were observed with a fast reciprocating Langmuir probe in the HT-7 tokamak. A strong shear layer of radial electric field was produced in the plasma edge region, which resulted in the formation of an edge transport barrier. Consequently, the edge profiles of electron density were steepened, and both the absolute and relative fluctuation levels were suppressed by the shearing E×B flows. Concomitant reduction of the coherence between electron density and poloidal electric field fluctuations and the change of their cross-phase resulted in turbulent particle flux dropping by more than a half at the plasma edge. This demonstrates the de-correlation effect of turbulence and its contribution to edge transport. The results presented here suggest a link between wall conditions and boundary plasma physics, especially an interaction between atomic processes and turbulence through the formation of radial electric field shear at the plasma edge.

关键词： Carrier concentration

Naturally Occurring Velocity Shear Layer at the Plasma Edge of HT-7 Tokamak

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Chinese Physics Letters 2004年第1期21卷 137-139页

作者：徐国盛万宝年宋梅 instituteofplasmaphysics ChineseAcademyofSciencesHefei230031

A naturally occurring velocity shear layer was observed at the plasma edge of HT-7 tokamak in regular ohmic heated discharges. One fast reciprocating Langmuir probe was used to measure all quantities in the radial force balance equation for main ion, which enables us to present the first report about the radial force balance in the boundary region of the HT-7 tokamak. The sharp gradient of radial electric field and the reduced fluctuation correlation and turbulent particle flux characterized the edge velocity shear layer. It was found that the shear of turbulence poloidal velocity was dominated by the E×B flow shear and the poloidal rotation determined the structure of radial electric field profile and as a result the E×B flows.

关键词： Tokamak devices

Optimum Nanoporous TiO2 Film and Its Application to Dye—sensitized Solar Cells

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Chinese Physics Letters 2003年第6期20卷 953-955页

作者： DAISong-Yuan WANGKong-Jia instituteofplasmaphysics ChineseAcademyofSciencesHeFei230031

Properties of TiO2 nanoporous films, which are one of the crucial technologies in dye-sensitized solar cell, are investigated. The nanocrystalline TiO2 films were prepared with the sol-gel method at different pH in precursor and treatment temperature in autoclave for their application to dye-sensitized solar cells. The thickness of the TiO2 film is very important to the transfer of photoelectron as well as adsorption of dye, it is also known as one of the source to the dark current. The results show that the TiO2 films, such as different particle sizes of TiO2, different pH in precursor and treatment temperature in autoclave, have a strong influence on the photoelectrochemical properties of the dye-sensitized solar cells. We give the optimum TiO2 film thickness and morphology for the application to dye-sensitized solar cells.

关键词： Dye-sensitized solar cells

First Measurement of the Magnetic Turbulence Induced Reynolds Stress in a Tokamak

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Chinese Physics Letters 2003年第12期20卷 2210-2213页

作者：徐国盛万宝年宋梅 instituteofplasmaphysics ChineseAcademyofSciencesHefei230031

Reynolds stress component due to magnetic turbulence was first measured in the plasma edge region of the HT-7 superconducting tokamak using an insertable magnetic probe. A radial gradient of magnetic Reynolds stress was observed to be close to the velocity shear layer location; however, in this experiment its contribution to driving the poloidal flows is small compared to the electrostatic component. The electron heat transport driven by magnetic turbulence is quite small and cannot account for the total energy transport at the plasma edge.

关键词： First Measurement Magnetic Turbulence Induced Reynolds Stress Tokamak

Observation of Magnetohydrodynamics Instabilities in Ion Berstein Wave and Lower-Hybrid-Current Driving Synergetic Discharges on HT-7 Tokamak

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Chinese Physics Letters 2004年第7期21卷 1310-1313页

作者： MAOJian-Shan LUOJia-Rong SHENBiao ZHAOJun-Yu HULi-Qun ZHUYu-Bao XUGuo-Sheng M.Asif GAOXiang WANBao-Nian instituteofplasmaphysics ChineseAcademyofSciencesHefei230031

The normalized performance indicated by the product of βNH89>2 was achieved by a combination of the lower hybrid current driving (LHCD) and the ion Berstein wave (IBW) heating in the HT-7 tokamak. More than 80% of the plasma current was sustained by the LHCD and the bootstrap current. Large edge pressure gradients were observed. The magnetohydrodynamic (MHD) instabilities were often driven to terminate the discharge or reduce the discharge performance, when the IBW resonant layer was near the rational surface. The resonant layer of the safety factor q = 2 is located at 0.6a with a = 27cm being the minor radius. The width of magnetic island (the poloidal mode number m = 2) was about 2cm. The plasma energy was reduced quickly by 30% by MHD instabilities. The behaviour of MHD instabilities is reported. A large sawtooth activity (m = 1) was observed before inducing MHD (m = 2).

关键词： Safety factor

Observation of Lower Hybrid Current Drive Improved Confinement With a Graphite Probe at the Last Closed Flux Surface of the HT—7 Tokamak

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Chinese Physics Letters 2002年第9期19卷 1316-1318页

作者：徐国盛万宝年等 instituteofplasmaphysics ChineseAcademyofSciencesHefei230031

High time resolution measurements of the electrostatic fluctuations, radial electric field Er and turbulence-induced electron flux Γe have been performed across the transition of lower hybrid current drive improved confinement with a graphite Langmuir probe array at the last closed flux surface of the HT-7 tokamak. The decrease of Γe is dominated by the suppression of fluctuation levels, which follows the change of Er. A reversal of the poloidal propagation direction of turbulence demonstrates that the poloidal propagation is dominated by Er×B drift. The enhancement of poloidal coherence accompanies the fluctuation suppression, which suggests the subtle variation of turbulence features.

关键词： Turbulence

Ohmic Radio-Frequency Synergy Current Drive and Transformer Recharging Experiments in the HT-7 Tokamak

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Chinese Physics Letters 2005年第7期22卷 1721-1724页

作者：陈忠勇万宝年石跃江胡立群徐(han)东 instituteofplasmaphysics ChineseAcademyofSciencesHefei230031

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.

关键词： LH MHD LHCD

Preliminary Observation on Coordination of Pellet Injection and Ion Bernstein Wave on a HT—7 Tokamak

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Chinese Physics Letters 2002年第5期19卷 701-703页

作者：杨愚赵燕平等 instituteofplasmaphysics ChineseAcademyofSciencesHefei230031

A pellet injection (PI) experiment was performed during the application of the ion Bernstein wave on a HT-7 tokamak. A preliminary coordination effect was observed. With a lower wave power, shortly after PI, the coupling of the wave was enhanced, and the particle confinement was improved. With higher power, off-axis heating for 15% at about a/3 in the low field side was observed.

关键词： Wave power