【作者】 张静；

【导师】 黄娟；

【作者基本信息】 中国科学技术大学 ， 材料物理与化学， 2019， 硕士

【摘要】 在托卡马克装置中,快离子主要通过中性束注入,射频加热以及聚变反应产生,它们是装置中等离子体粒子、动量以及能量的主要来源。所以他们决定了加热或电流驱动的效率。同时快离子还会驱动阿尔芬型和声波型的不稳定性,结果,这些不稳定性会导致大量的能量和粒子损失,这将降低等离子体品质。同时损失出去的快离子会使等离子体的约束性能变坏,严重时,甚至会毁坏第一壁。因此,快离子诊断方面的物理研究是不可回避的问题。对于EAST(实验先进超导托卡马克)装置来说,快离子主要产生于辅助加热。由于着眼于实现高功率长脉冲稳态等离子体的运行目标,因此等离子体辅助加热功率在不断地提高,这些辅助加热系统,在实现稳态高性能等离子体的同时,也增加了等离子体中的快离子成分。因此,有必要在EAST上建立快离子诊断,以研究快离子行为,以及其带来的相关物理问题。为了研究快离子在EAST上的行为,最近在EAST上发展并应用了快离子Dα快速测量(f-FIDA)诊断系统。f-FIDA的目标是在足够短的时间尺度上获得波长积分信号,以研究快离子信号的高频宏观波动。该系统主要使用带通滤波器和光电倍增管(PMT),提供651nm到654nm的光谱段积分强度(多普勒频移光谱的蓝移分量)的时间演变信息。基于诊断原理,对主要光学材料—滤光片、PMT、透镜进行理论设计与加工,对相关材料性能进行调研,选取最优材料,最后建立了两套诊断系统。首先发展了多通道阵列PMT的f-FIDA诊断系统,该系统的PMT为4X4多阳极阵列型,每个阳极尺寸为4.2 mm X 4.2 mm,因此要求光纤投射到PMT的光斑大小不能超过4mm,否则将产生交叉干扰。由于PMT对光斑尺寸的限制,以及PMT尺寸对光学设计的要求,难以满足f-FIDA系统对光强的需求,导致信号性能受到限制。为了提高采样率和光利用率,进一步发展了多通道单PMT的f-FIDA诊断系统。该系统优化了系统后端的光电转换部分,设计放大器与PMT等光电材料的集成,充分发挥了光电材料的特性,与阵列型的PMT相比较,多通道单PMT减少了系统的噪声和漏电流,减少寄生电容,达到了高增益、大带宽和低噪声的特点,能够很好的检测预期的FIDA信号。论文中对于已经搭建完成的两套快离子Dα快速测量(f-FIDA)诊断系统进行了对比。由于阵列型PMT系统中PMT材料与型号的不同,导致光路设计受到限制,光束的平行度较差,而单PMT系统的光学器件材料的选择则更灵活,镜头更大,焦距更长,因此单PMT系统的平行度更好。由于单PMT系统更好的光透过率,平行度和电子学带宽,多通道单PMT的f-FIDA的诊断系统是实验的首选。达到了系统改进的目的,同时验证了不同材料元件对系统的差异性。在EAST 2017年度实验中,利用建立的多阵列单PMT的f-FIDA诊断系统,并结合其他相关快离子诊断数据分析了中性束注入下的f-FIDA信号。当诊断束NBI1L注入时,f-FIDA信号均有明显上升,然后当束关闭时,则快速下降。另外,通过积分s-FIDA相应波长区间的净FIDA信号以及体积积分的中子速率来测试FIDA信号的一致性,获得的信息与f-FIDA信号变化趋势也是一致的,进一步验证了装置的可靠性。更多还原

【Abstract】 In the tokamak device,fast ions are produced by neutral beam injection,radio-frequency heating and fusion reactions,and they are the main source of plasma particles,momentum and energy in the device.So they determine the efficiency of heating or current drive.Fast ions also drive the instability,such as the Alfven eigenmodes.As a result,these instability results in a large amount of energy and particle loss,which reduces plasma quality.At the same time,the loss of fast ions will make the constraint properties of the plasma worse,and even destroy the first wall.Therefore,the study of fast ion diagnosis is an unavoidable problem.EAST tokamak is aimed at addressing physics and technology issues facing high power,long-pulse operation in high confinement regimes.Fast ions are mainly produced by auxiliary heating on EAST,As the auxiliary heating systems are being perfected gradually,high performance plasma has been achieved,but problems caused by fast ions get increasingly prominent.Therefore,it is necessary to develop the fast ion diagnostics on EAST to study fast ion behavior and related physical problems.A new filter-based fast ion D-alpha system f-FIDA has been recently developed on EAST to improve temporal resolution ability of the FIDA diagnostic and study relationship between fast-ion transport and plasma instabilities.This system equipped with band pass filters and photomultiplier tube modules measures integrated intensity evolution of the blue-shift part of Doppler shifted Da spectrum in the spectral region of 651-654 nm,and can detect high-frequency oscillations in FIDA signal benefiting from its high temporal resolution.The thesis is focused on design and development of the multi-channel f-FIDA diagnostic on EAST tokamak.An array-PMT is firstly used in the f-FIDA diagnostic.This PMT consists of a 4×4 multi-anode array,each of whose anodes has a size of 4.2×4.2 mm.As a result,diameter of the facula from the end of optical fiber should be limited within 4 mm in order to avoid interference between adjacent light spots,leading to that measured intensity does not satisfy requirements of the f-FIDA diagnostic well.Therefore,the f-FIDA diagnostic has been upgraded with single PMTs measuring independently to achieve high sampling rate and maximize light utilization efficiency.The system now consists of the optical part and the integrated part.While the former has no substantial change compared with the optical system of original f-FIDA diagnostic,the latter,by which the new f-FIDA diagnostic is featured,reduces noise and minimizes parasitic capacitance and leakage current by integrating the photomultiplier tube and current amplifier together.Benefiting from its high gain,broad bandwidth and low noise,good signals from f-FIDA diagnostic have been recorded as expected and experimental purpose has been achieved.Comparison of light parallelism,sampling rate and light utilization efficiency has been made between the two f-FIDA systems.It is observed in discharges that single-PMT f-FIDA has a much better signal-to-noise ratio than array-PMT system.Measurements show that parallelism of single-PMT f-FIDA is almost two times better than that of array-PMT system.The sampling rate of 2 MHz for f-FIDA with single-PMT is much higher than that of 150 kHz for f-FIDA with array-PMT.Moreover,light utilization efficiency of f-FIDA with single-PMT is 90%,while that of f-FIDA with array-PMT is only 60%.Therefore,as a result of its better signal-to-noise ratio,light parallelism,sampling rate and light utilization efficiency,multi-channel f-FIDA diagnostic equipped with single PMTs is preferred in EAST experiments.In EAST 2017 campaign,the f-FIDA diagnostic system with multi-array single PMT has been developed and put into the experiment.The signal of f-FIDA under neutral beam injection was analyzed.The f-FIDA signal under neutral beam injection was analyzed by combining with other fast ion diagnostic data.When the diagnostic beam NBI1L is injected,the f-FIDA signal increases significantly,and then decreases rapidly when the beam is closed.In addition,the consistency of FIDA signal was tested by integrating the net FIDA signal of corresponding wavelength interval of s-fida and the neutron rate of volume integral,and the obtained information was consistent with the variation trend of f-fida signal,further verifying the reliability of the device.更多还原