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在HL-2A装置孔栏位形放电的等离子体实验中,电子回旋辅助加热期间观察到了等离子体约束改善的现象,并对等离子体从低约束模式(L模)向约束改善模式转换时的等离子体线平均电子密度、等离子体储能、分界面内辐射功率、能量约束时间、Hα辐射等进行了研究。同时,分析了电子密度和等离子体辐射功率的空间分布随时间的演化。对改善约束的相关功率(辅助加热、欧姆加热功率和损失功率)进行了分析,并研究了等离子体约束改善转换时的边界净输入功率(阈值)与电子线平均密度和环向磁场的关系。     

HL-2A装置的约束改善和边界净输入功率分析

在HL-2A装置孔栏位形放电的等离子体实验中,电子回旋辅助加热期间观察到了等离子体约束改善的现象,并对等离子体从低约束模式(L模)向约束改善模式转换时的等离子体线平均电子密度、等离子体储能、分界面内辐射功率、能量约束时间、H_α辐射等进行了研究。同时,分析了电子密度和等离子体辐射功率的空间分布随时间的演化。对改善约束的相关功率(辅助加热、欧姆加热功率和损失功率)进行了分析,并研究了等离子体约束改善转换时的边界净输入功率(阈值)与电子线平均密度和环向磁场的关系。     

HL-1M装置边缘参数测量

在HL－1M装置上利用马赫／郎缪尔探针分别在欧姆放电,低杂波注入,中性束注入,离子回旋加热和电子回旋加热等情况下测量下刮离层和等离子体边缘的极向流速度和电场,得到了它们的径向分布,研究了LHW,NBI,ICRH和ECRH对改善等离子体约束性能,边缘粒子的径向传输的影响。     

HL－1装置辅助加热等对能量约束的影响

在ＨＬ－１托卡马克上进行了辅助加热、加料、电流驱动的物理实验研究。在改善等离子体约束方面，某些实验取得了较好的结果。在适当的稳定放电条件下，低杂波电流驱动和弹丸注入辅助加料，均能使等离子体能量约束得到一定程度的改善，与相同密度条件下的欧姆加热放电相比，能量约束时间提高了约３０％。在电子回旋共振加热等离子体实验中，等离子体总能量明显增加，但与相同密度条件下的欧姆加热放电相比，能量约束时间减少了约２０％。     

HL—1装置辅助加热等对能量约束的影响

在ＨＬ－１托卡马克上进行了辅助加热，加料，电流驱动的物理实验研究。在改善等离子约束方面，某些实验取得了较好的结果。在适当的稳定放电条件下，低杂波电流驱动和弹丸注入辅助加料，均能使等离子体能量约束得到一定程度的改善，与相同密度条件下的欧姆加热放电相比，能量约束时间提高了约３０％。在电子回旋共振加热等离子体实验中，等离子体总能量明显增加，但与相同密度条件下的欧姆加热放电相比，能量约束时间减少了约２０％     

HT－6M托卡马克等离子体电子密度分布研究

根据等离子体电子密度诊断原理，建立了七道远红外ＨＣＮ激光干涉仪。用电子密度分布特征参数研究了ＨＴ－６Ｍ托卡马克上的边界欧姆加热（ＥＯＨ）、抽气限制器（ＰｕｍｐｉｎｇＬｉｍｉｔｅｒ）和离子回旋共振加热（ＩＣＲＨ）实验中的密度分布变化规律和约束特性。对于ＨＴ－６Ｍ托卡马克装置欧姆放电，密度分布特征参数ｕ约为１．１～１．３；约束改善的放电模式，ｕ上升到１．８～２．０，电子密度分布展宽；当密度分布特征多数ｕ≤０．９时，密度分布峰化，这是大破裂的先兆。     

HT－6M托卡马克等离子体电子密度分布研究

根据等离子体电子密度诊断原理，建立了七道远红外ＨＣＮ激光干涉仪。用电子密度分布特征参数研究了ＨＴ－６Ｍ托卡马克上的边界欧姆加热（ＥＯＨ）、抽气限制器（ＰｕｍｐｉｎｇＬｉｍｉｔｅｒ）和离子回旋共振加热（ＩＣＲＨ）实验中的密度分布变化规律和约束特性。对于ＨＴ－６Ｍ托卡马克装置欧姆放电，密度分布特征参数ｕ约为１．１～１．３；约束改善的放电模式，ｕ上升到１．８～２．０，电子密度分布展宽；当密度分布特征多数ｕ≤０．９时，密度分布峰化，这是大破裂的先兆。     

EAST等离子体电子温度涨落特征的初步实验研究

在EAST上使用相关电子回旋辐射(CECE)诊断系统观测到不同等离子体参数下的电子温度涨落特征,介绍了欧姆放电、L模放电及无ELM的H模放电的三种现象。在欧姆密度爬升等离子体中,电子温度涨落与电子密度之间表现出很强的相关性,即存在电子温度涨落处于较高水平的电子密度的窗口。初步分析表明,电子温度涨落变化是电子密度梯度和电子温度梯度共同影响的结果。不同辅助加热下的L模等离子体中,电子温度涨落的频谱表现出不同的行为。由于电子回旋共振加热(ECRH)的功率有限,其对电子温度的改变很小,而中性束注入(NBI)有较高的注入功率,能够明显提升电子温度,加热方式及加热功率大小引起的电子温度变化与电子温度涨落变化相关。在没有边缘局域模(ELM)的H模期间,可以观测到频率为18kHz的准相干模,其存在于归一化半径ρ=0.71～0.87较宽的径向范围内。     

HL－1托卡马克杂质注入实验及杂质输运特性的研究

本文给出了ＨＬ－１托卡马克在通常欧姆放电和偏压诱发Ｈ模放电条件下，脉冲注入杂质气体的实验结果以及对杂质在通常欧姆等离子体和偏压诱发Ｈ模等离子体中的输运研究结果。实验结果表明，在ＨＬ－１上偏压诱发Ｈ模等离子体中对杂质的约束性能明显优于在通常欧姆等离子体中对杂质的约束性能。杂质输运的数值模拟结果说明，无论在通常欧姆等离子体中，还是在偏压诱发Ｈ模等离子体中，杂质的输运系数都比新经典理论预计的要大得多，输运是反常的。在偏压诱发的Ｈ模等离子体中引入杂质输运“位阱”概念，能够对杂质离子约束时间长的实验现象进行很好的描述。合理地解释了在偏压杂质注入实验中杂质辐射上升时间长、衰减慢的现象。     

托卡马克实验与工程——HL-2A装置上芯部弹丸加料中的电子热输运研究

从80年代中期开始，在许多聚变装置上观察到了用弹丸注入改善的等离子体能量约束。在JET和一些大型托卡马克上实现了弹丸增强约束模（PEP）。PEP模的机制也已在理论上做了分析。分析表明，有多种机制在减小反常输运中起作用，而这些机制的作用依赖于实验的条件。本文将报道在HL-2A装置上无辅助加热条件下的弹丸加料实验结果。该工作的着重点是研究在中心加料欧姆放电中的电子热输运。     

Investigation of lower hybrid current drive during H-mode in EAST tokamak

H-mode discharges with lower hybrid current drive (LHCD) alone are achieved in EAST divertor plasma over a wide parameter range. These H-mode discharges are characterized by a sudden drop in D_α emission and a spontaneous rise in main plasma density. Good lower hybrid (LH) coupling during H-mode is obtained by putting the plasma close to the antenna and by injecting D₂ gas from a pipe near the grill mouse. The analysis of lower hybrid current drive properties shows that the LH deposition profile shifts off axis during H-mode, and current drive (CD) efficiency decreases due to the increase in density. Modeling results of H-mode discharges with a general ray tracing code GENRAY are reported.     

低杂波驱动电流改善等离子体约束的光谱测量

在ＨＴ－６Ｂ托卡马克低杂波驱动电流（ＬＨＣＤ）的同时，等离子体的粒子及能量约束也随之发生改善。我们从空间多道Ｈα线的测量推算出ＬＨＣＤ可将等离子体粒子约束时间提高１－５倍，介绍了我们的分析过程，ＨＴ－６Ｂ上的Ｈα线测量还表明粒子约束的改善程度与低杂波（ＬＨＷ）的注入功率无明显依赖关系；改善粒子约束的发生与超热电子的产生相对应，通过观察边界层ＯＩＩ两条不同激发电位的谱线强度比的变化，发现等离子体在约束改善的同时，具有边界电子温度梯度增大的类Ｈ模现象。 关键词：     

Profile evolution of edge parameters during L/H and H/L mode transitions on compass-D

On COMPASS-D the profile evolution of electron density, electron temperature, perpendicular electric field, poloidal impurity velocity, and neutral density at the outboard mid-plane has been investigated during ohmic single null diverted (SND) discharges undergoing an L/H, H/L, and another L/H transition. This was achieved using a novel combined diagnostic consisting of thermal helium beam and Doppler spectrometry, sharing the same lines of sight. To generate the transitions first an ELM-free H-mode phase was produced by terminating the gas fuelling. Within this H-mode a stepped gas puff was applied triggering an intermediate L-mode phase followed by a second ELM-free phase. It was found that on COMPASS-D the L/H transition is not preceded by a change in velocity or electric field shear. The maximum electric field shear of ∇ ▽E _ψ ≈2×10³kV/m² develops after the L/H transition around the 95% flux surface. Although the neutral density at the separatrix is of the ordern _D ≈ 10¹⁷m⁻³ no indication of a local influence could be concluded. However, a correlation between the decay of the shear and the gas puff was observed. Presented at the Workshop on Role of Electric Fields in Plasma Confinement and Exhaust, Budapest, 18–19 June 2000. This work was jointly funded by the UK Department of Trade and Industry and EURATOM. The author H. Meyer is funded by a Marie Curie Research Training Grant.     

东方超环托卡马克高约束模式边界等离子体输运数值模拟研究

利用SOLPS5.0模拟研究东方超环托卡马克（EAST）高约束模式时的刮削层等离子体. 在高约束模式放电实验参数（第36291炮）的限制下,通过调整上游区径向反常输运系数来实现高约束模式模拟,在上游电子密度和温度与实验符合的条件下能够很好地进行下游区模拟. 在实现高约束模拟的基础上又分别研究了漂移项对偏滤器靶板能流不对称性的影响和上游能流衰减宽度对靶板能流密度峰值的影响. 通过模拟发现,漂移是导致EAST放电内外靶板不对称性的主要原因,增大上游能流衰减宽度可以明显降低入射到靶板的峰值热流,并且偏滤器区辐射以及与中性粒子的相互作用减小了能流的衰减宽度对达到靶板能流的影响. 关键词： 托卡马克 高约束模式 SOLPS5.0 漂移     

First Results of Biasing Experiments on the T-10 Tokamak

The first results of the electrode biasing experiments performed on the T-10 tokamak are presented. Positive voltage applied to an electrode inserted inside the tokamak limiter results in the H-mode transition characterised by a decrease of D emission intensity, a rise of line-average plasma density and an increase in energy lifetime. Growth of core electron and ion temperatures during the electrode biasing implies the formation of the thermal barrier in addition to the particle transport barrier.     

Mixing Properties for Mechanical Motion¶of a Charged Particle in a Random Medium

We study a one-dimensional semi-infinite system of particles driven by a constant positive force F which acts only on the leftmost particle of mass M, called the heavy particle (the h.p.), and all other particles are mechanically identical and have the same mass m < M. Particles interact through elastic collisions. At initial time all neutral particles are at rest, and the initial measure is such that the interparticle distances ξ _i are i.i.d. r.v. Under conditions on the distribution of ξ which imply that the minimal velocity obtained by each neutral particle after the first interaction with the h.p. is bigger than the drift of an associated Markovian dynamics (in which each neutral particle is annihilated after the first collision) we prove that the dynamics has a strong cluster property, and as a consequence, we prove existence of the discrete time limit distribution for the system as seen from the first particle, a ψ-mixing property, a drift velocity, as well as the central limit theorem for the tracer particle. Received: 22 March 2000 / Accepted: 8 December 2000     

H-mode in tokamaks attributed to absence of trapped ions in poloidally rotating plasma

It is proposed that the suppression of transport in the H-mode in tokamaks is caused by the absence of trapped ions in the transport barrier. If the poloidal Mach number M=v _θ B/(v _TiB_θ) is large there are exponentially few trapped ions. This criterion agrees with experimental observations of H-mode plasmas. The recently observed transport suppression by reversed shear also points to the dominant role of trapped particles in turbulent transport. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 6, 427–430 (25 March 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Strange particle production at the intersection of soft and hard processes at RHIC

Nuclear suppression factor and u ₂ measurements as a function of transverse momentum for neutral strange particles are shown and compared to particle identified spectra from PHENIX and WA98 and to models that attempt to describe the suppression of particles at moderate pt in central RHIC Au?Au collisions. It is shown that identified spectra carry additional information to the published charged particle spectra. In particular, dependencies of the R _AA and u ₂ values on the measured particle species will be discussed in the context of several models.     

Measurement of neutral gas temperature in inductively coupled plasmas

Dependence of the neutral gas temperature on the gas pressure and discharge power in an inductively coupled plasma source has been investigated using optical emission spectroscopy. Both nitrogen and argon plasmas have been studied separately. In the case of argon plasma, about 5% nitrogen was added to the total gas flow as an actinometer. The maximum temperature was found to be as high as 1850 K at 1 Torr working pressure and 600 W radiofrequency power. The temperature increases almost linearly with the logarithm of the gas pressure, but changes only slightly with the discharge power in the range of 100–600 W. In a nitrogen plasma, a sudden increase in the neutral gas temperature occurs when the gas pressure is increased at a given discharge power. This suggests a discharge-mode transition from the H-mode (high plasma density) to the E-mode (low plasma density). In the H-mode, the gas temperature is proportional to the logarithm of the gas pressure, as in the argon plasma. However, the gas temperature increases almost linearly with the discharge power, which is in contrast to the case of argon plasma. The electron density in the nitrogen plasma is about 10% of that in the argon plasma. This may explain the observation that the nitrogen neutral temperature is always lower than the argon neutral temperature under the same discharge power and gas pressure.     

Electro-optic holography fringe control using diode laser current modulation

Electro-optic holography (EOH) is a whole field, laser-based, vibration measurement technique. Highly dense, unresolvable fringe patterns often limit the EOH measurement range. This paper presents a technique for increasing the measurement range of an EOH system using diode laser current modulation. This technique is known as frequency translated electro-optic holography (FTEOH). Using diode laser current modulation, the fringe patterns are based on higher-order Bessel functions and the sensitivity of the EOH system can either be increased or decreased. The amount of sensitivity reduction is limited only by the frequency limit of the signal generator that modulates the current supplied to the diode laser. EOH and FTEOH experimental results are presented and shown to closely compare.