Methods of Power Balance Analysis and Estimation of Current Density Profile for LHCD and IBW Discharges in HT-7 Tokamak

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.

LHCD Properties with a New Lower Hybrid Wave Antenna on HT-7 Tokamak

The structure and the characteristic power spectrum of a new lower hybrid wave antenna on the HT-7 tokamak are briefly described in this paper. The main experimental properties with the new antenna have been demonstrated by showing the dependence of current drive efficiency and particle confinement time on phase difference between adjacent waveguides of the antenna. A few preliminary analyses about the experimental results are also discussed in the paper.

Nonlinear Dependence of the Synergetic Current by the Combined Effect of ECCD and LHCD on the Power Ratio on HL-2A Tokamak

Nonlinear dependence of the synergetic current by the combined effect of electron-cyclotron current drive(ECCD)and lower-hybrid current drive(LHCD)on the power ratio is shown through the recent simulation research based on common parameters on HL-2A tokamak.Corresponding experiments have been demonstrated on HL-2A tokamak and these experimental results verify qualitatively the simulated ones.

Edge Structure of Reynolds Stress and Poloidal Flow on the HL-1M Tokamak

The measurement on radial profile of electrostatic Reynolds stress, plasma poloidal rotations, radial and poloidal electric field have been performed in the plasma boundary region of the HL-IM Tokamak using a multi-array of Mach/Langmuir probes. In the experiments of Lower Hybrid Current Drive (LHCD), Supersonic Molecular Beam injection (SMBI), Multi-shot Pellet Injection (MPI) and Neutral Beam injection (NBI), the correlation between the Reynolds stress and poloidal flow in the edge plasma is presented. The results indicate that a sheared poloidal flow can be generated in Tokamak plasma due to radially varying Reynolds stress.

Hard X-Ray PHA System on the HT-7 Tokamak

A new hard X-ray pulse-height analysis （PHA） system has been established on HT-7 tokamak for long pulse steady-state operation. This PHA system consists of hard X-ray diagnostics and multi-channel analysers （MCA）. The hard X-ray diagnostics consists of a vertical X-ray detector array （CdTe） and a horizontal X-ray detector array （NaI）. The hard X-ray diagnostics can provide the profile of power deposition and the distribution function of fast electron during radio frequency （RF） current drive. The MCA system is the electronic part of the PHA system, which has been modularized and linked to PC through LAN. Each module of MCA can connect with 8 X-ray detectors. The embedded Ethernet adapter in the MCA module makes the data communication between PC and MCA very convenient. A computer can control several modules of MCA through certain software and a hub. The RAM in MCA can store 1024 or more spectra for each detector and therefore the PHA system can be applied in the long pulse discharge of several minutes.

The Present Status of HT-7U Superconducting Tokamak Project

The first Chinese superconducting tokamak HT-7 was reconstructed on the basis of a Russian tokamak T-7.The main purpose of reconstruction is to improve the accessibility of the device and to provide a possibility of long pulse operation with high performance. The reconstruction has been done successfully. The HT-7U project has been approved and funded as a National Project, the engineering design and R & D are under way.

Sawtooth Activity in Ohmically Heated Plasma on HT-7 Tokamak

Sawtooth activity on HT-7 tokamak has been investigated experimentally mainly by using soft x-ray diode array and magnetic probes. Their behaviors and occurrences are correlated closely to the discharge conditions: the electron density Ne, the electron temperature Te, the safety factor qa on plasma boundary and wall condition etc. When central line-averaged electron density Ne(0) is over 2.0×1013cm-3 , major sawtooth activity emerges with a period of up to 6.5 ms and a fluctuation amplitude of up to 2-30 % of SXR radiation signal. In some cases such as the safety factor between 4.2-4.7 and Zeff=3.0-6.0, a monster sawtooth activity often emerges without apparent deterioration of plasma confinement and without major disruption. During these events, abundant MHD phenomena are observed including partial sawtooth oscillations. In this paper, the observed sawtooth behaviors and their dependence on the and their dependence density Ne and wall condition in ohmically heated plasma are introduced, the results are discussed and presented.

Soft x-ray Diode-array Diagnostic System for HT-7 Superconducting Tokamak

A diagnostic system of soft x-ray diode-array was set up for HT-7 superconducting tokamak. The system consists of two slot-aperture cameras and is capable of measuring the soft x-ray emission from the plasma on HT-7 device with a high resolution in space and a high response in time. Both cameras, located separately in a horizontal port and a vertical port each with thirty-seven detectors of An-Si surface-barrier diode (SBD) can view the same toroidal cross-section of the plasma from different poloidal chords. In this paper, the structure, principle and performance of the diagnostic system are described and some experimental results observed are presented.

Experiments and Studies of Edge Plasma Radial Transport and Confinement Property on the HL-1M Tokamak

This paper describes a Mach/Langmuir probe array with five pins and six pins, which can measure not only parallel flows and the flow perpendicular to the magnetic field but also the radial and the poloidal electric field E. arid E as well. Experimental measurements of the edge fluctuations, velocities of the toroidal, the poloidal flow and electric field have been carried out on both of SOL and the boundary region of HL-1M for Ohmic, biased H-mode, Lower Hybrid Current Drive (LHCD), Supersonic Molecular Beam Injection (MBI), Multi-shot Pellet Injection (MPI), Neutral Beam Injection (NBI), Ion Cyclotron Resonance Heating (ICRH) and Electric Cyclotron Resonance Heating (ECRH) discharges. The results show that the suppressions of the fluctuations are related to poloidal rotations produced by different discharge modes in the improved particle confinement property, simultaneously the change of the radial and poloidal electric field is generated and becomes more negative at the Tokamak plasma edge, and the sheared poloidal flow is related to the reduction in fluctuation level, and the poloidal velocity is mainly dominated by the E × B drift.

Recent Experimental Progress in the HT-7 Tokamak

Recent experimental campaign in the HT-7 toka-mak was scheduled to be ran from November 2002 toMarch 31, 2003, during which various issues were in-vestigated on getting high electron temperature, longpulse discharges and high performance plasma underquasi-steady-state condition. New systems includ-ing LHCD launcher, cryogenic compressor, real-timepoloidal control, water-cooled toroidal belt limiter,ferretic liner and several diagnostics were installedand operated to satisfy long-pulse operation require-ments. The maximum total injected power was over1 MW and the longest discharge duration was nearto 64 s.

LOWER HYBRID CURRENT DRIVE EXPERIMENTS IN THE HT-6M TOKAMAK

Lower hybrid current drive(LHCD)experiments with a multijunction grill have been performed in the HT-6M tokamak.When the RF power pulse with 15ms risetime is injected into the plasma.the toroidal current amplitude is raised,but the temporal variation of the loop voltage does not have measurable change.The efficiency of current drive is I_(rf)/P_(rf)=0.57kA/kW at n_(e)=3×10^(12)cm^(-3) and B_(t)=8KG.It seems that the multijunction grill has the same efficiency as the ordinary grill on the LHCD experiments.

A Study of Energy Conversion Efficiency Versus Plasma Density by Lower Hybrid Current Drive in HT-7 Tokamak

Ramp-up experiments by means of lower hybrid wave on HT-7 superconducting tokamak have been performed and analyzed. A ramp-up rate of over 300 kA/s is obtained and a conversion efficiency of over 1.0% has been achieved during the ramp-up phase. 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.

Analysis of Charge-Exchange Spectrum during Lower Hybrid Current Drive on HT-7 Tokamak

A perpendicular neutral particle analyzer (NPA) is used on HT-7 tokamak experiment to provide the measurements of neutral particle flux and ion temperature. The measured results were compared with calculated data by Monte-carlo method for ohmic heating. In lower hybrid current drive (LHCD) experiments, the ion heating of LHCD was identified. The chargeexchange neutral particle flux enhanced was observed. The energy spectrum clearly showed a high-energy ions tail. The bulk ion temperature increased by 0.4-0.5 keV after the onset of LHCD. Efficient ion heating of 1 eV. kW-1 was obtained.

The Realization of Low Loop Voltage Start-up of HT-7 Tokamak Discharge with the Assistance of Lower Hybrid Wave

Low voltage start-up was realized in HT-7 discharges under the assistance of lower hybrid (LH) waves. The use of a strong LH wavet which can Change its N// spectrum in a large range of several milliseconds, made the loop voltage for start-up reduce from around 20 V to less than 5 V. It means that the electric field for HT-7 start-up decreases from 2.5-3 V/m to 0.6 V/m. Some physical phenomena such as the consumption of magnetic flux in start-up phase and the radiation from the initial plasma were observed in this kind of low voltage start-up discharges.

用于HL-1M装置LHCD的多结发射天线阵

采用对天线阵主要物理参数优化设计的方法，研制出了用于ＨＬ－１Ｍ装置ＬＨＣＤ实验的兆瓦级多结发射天线阵。研制出的天线阵为双层密封窗２×１２多结型天线阵，投入使用后经受住了大功率微波的考验，已成功地用于ＨＬ－１Ｍ装置的ＬＨＣＤ实验。

LHCD期间HL-1M装置等离子体中心区域的MHD行为

本文叙述低杂波电流驱动（ＬＨＣＤ）对ＨＬ－１Ｍ等离子体中心ＭＨＤ不稳定性［锯齿振荡（ｍ＝０），ｍ＝１模］的影响。不稳定性的振荡幅度是进入等离子体的低杂波功率的函数。当功率超过某阈值时，不稳定性被抑制，而且存在一个最佳抑制功率范围。在一定条件下，低杂波功率脉冲会激发ＭＨＤ不稳定性。

HL-2A装置LHCD系统灯丝电源远程控制的一种新方法

为解决HL-2A装置低杂波电流驱动(LHCD)系统灯丝电源无法远程控制的问题,介绍了基于西门子WinCC监测系统的HL-2A装置LHCD系统灯丝电源MSComm串行通信系统的设计与实现。在WinCC图形编辑器中直接调用MSComm控件,编写VBS全局脚本实现对串口的访问,解决了硬件组态过程中串行通讯操作被WinCC所限制的问题。采用了虚拟串口技术、工业以太网通讯技术、光纤隔离技术等,提高了WinCC组态串口设备的灵活性。HL-2A装置LHCD实验证明,在HL-2A装置放电的复杂电磁环境下,LHCD灯丝电源MSComm串行通信系统运行稳定、功能完善。

Improvement of plasma confinement with lower hybrid current drive on HT-6B tokamak

Using lower hybrid current drive (LHCD), improved confinement has been achieved on HT-6B tokamak. The particle confinement time was increased by 2- 6 times and the plasma-stored energy was doubled. Only obtainable in an electron density window of 0.3×1013- 1.5× 1013cm-3, the improvement was accompanied by suppression of the fast fluctuations and increment of the gradient of edge electron temperature with very low power threshold. An analysis shows that the improvement might be possibly caused by certain energetic electrons produced by LHCD.

托卡马克LHCD系统的等离子体电流熄灭保护技术

根据实际HT - 7托卡马克的实验需要 ,提出并实现了等离子体电流熄灭保护装置 ,杜绝了等离子体电流熄灭或在低等离子体电流下 ,强功率。

HL-2A装置LHCD新天线热分析和电磁力分析

用有限元方法对LHCD天线实际工况条件下的受热情况进行了模拟分析,结果表明无氧铜可满足热对材料的要求。给出了托卡马克环向磁场和等离子体电流变化时天线所受电磁力的解析与数值结果,论证了对天线起破坏作用的是等离子体破裂时由一对扭力所产生的扭矩,不锈钢更满足扭力对材料的要求。实际加工过程中使用无氧铜和不锈钢相结合的方式是比较合理的。该工作为天线的研制提供了理论指导。