Parallel Correlation Studies of Fluctuations and the Impact of Perturbations in the Magnetic Configuration

The plasma turbulence in the boundary of fusion relevant experiments is known to have a quasi two‐dimensional nature: the scale lengths perpendicular to the magnetic field are in the order of mm to cm, but parallel to the magnetic field, the correlation lengths are in the order of several meters. Recent parallel correlation studies with Langmuir probes at the JET tokamak over very long connection lengths (23 m and 66 m probe tip separation along the magnetic field) showed a correlation of less than 50%, in contrast to the finding of 80–90% correlation in other devices at measurements with smaller probe tip separations. However, it was not clear if this is a genuine physical property of the electrostatic turbulence in the scrape‐off layer or whether perturbations in the magnetic configuration had caused an additional decorrelation by a time‐dependent misalignment of the two probe tips along the connecting field line. In this contribution we analyze the effect of such perturbations in the magnetic configuration on the parallel correlation measurements in a simple model and compare the results with those of the measurements at JET.     

The Prevalence of Childhood Dysphonia: A Cross-Sectional Study

There is only very limited information on the prevalence of voice disorders, particularly for the pediatric population. This study examined the prevalence of dysphonia in a large cohort of children (n = 7389) at 8 years of age. Data were collected within a large prospective epidemiological study and included a formal assessment by one of five research speech and language therapists as well as a parental report of their child's voice. Common risk factors that were also analyzed included sex, sibling numbers, asthma, regular conductive hearing loss, and frequent upper respiratory infection. The research clinicians identified a dysphonia prevalence of 6% compared with a parental report of 11%. Both measures suggested a significant risk of dysphonia for children with older siblings. Other measures were not in agreement between clinician and parental reports. The clinician judgments also suggested significant risk factors for sex (male) but not for any common respiratory or otolaryngological conditions that were analyzed. Parental report suggested significant risk factors with respect to asthma and tonsillectomy. These results are discussed in detail.     

Enhancement of the stabilization efficiency of a neoclassical magnetic island by modulated electron cyclotron current drive in the ASDEX upgrade tokamak

The efficiency of generating a helical current in magnetic islands for the purpose of suppression of neoclassical tearing modes (NTMs) by electron cyclotron current drive (ECCD) is studied experimentally in the ASDEX Upgrade tokamak. It is found that the efficiency of generating helical current by continuous current drive in a rotating island drops drastically as the width 2d of the co-ECCD driven current becomes larger than the island width W. However, by modulating the co-ECCD in phase with the rotating islands O point, the efficiency can be recovered. The results are in good agreement with theoretical calculations taking into account the equilibration of the externally driven current on the island flux surfaces. The result is especially important for large next-step fusion devices, such as ITER, where 2d>W is expected to be unavoidable during NTM suppression, suggesting that modulation capability should be foreseen.     

300MVA 脉冲发电机高压变频器调速装置设计及调试

HL-2M 装置 300MVA 脉冲发电机组的调速装置高压变频器主要由输入和输出部分、功率单元、控 制部分组成。对高压变频器进行了调试及试验运行。试验表明其输入谐波含量小,输出波形也是完美正弦波,启 动到工作转速的时间为 16min,再加速时间未超过 5min,能够满足实验放电要求。根据调试情况对空载电流及转 子时间常数进行了优化,在空载电流为 300A、转子时间常数为 1.34s 时,其性能为最优。     

HL-2M 装置主机集成安装工程质量管理

基于 HL-2M 装置主机集成安装实践,以风险控制、过程管理为质量管理工作总体思路,对工程策 划、实施、验收环节进行全面质量管理。通过实施质量管理活动,确保了 HL-2M 装置主机集成安装工程达到质 量目标,并于 2020 年 12 月 4 日首次放电成功。通过本项目的实施积累了大科学工程的质量管理经验。     

HL-2M 装置集成安装进度控制研究

大型托卡马克装置集成安装工程子项多、接口繁多、工作空间狭小、系统复杂、参与人员众多,如 何做好装置集成安装的进度控制至关重要。基于工程进度风险管理思维,详细分析了 HL-2M 装置集成安装进度 控制风险因素,并探索了进度控制体系有效运行方式,为安装进度风险可控且实现进度控制目标提供了保障,也 为我国大型磁约束核聚变装置集成安装标准化和规模化发展积累了经验。     

HL-2M 装置极向场线圈的结构设计与制造

介绍了 HL-2M 装置极向场(PF)线圈的结构设计和制造。16 饼 PF 线圈布置在环向场(TF)线圈空腔之 内、真空室外,沿中平面对称分布。PF 线圈采用中空矩形铜导体绕制,其中 PF1~PF4 线圈为双层螺旋绕制结构, 最大运行电流 14.5kA;PF5~PF8 线圈为多层盘式绕制结构,最大运行电流 38~42kA。      

HL-2M 装置中心螺旋管线圈结构和制造工艺概述

HL-2M 装置中心螺旋管(CS)线圈采用了 AB 两组交替缠绕、内外层轴向反向绕制的结构,AB 两组 引线对称引出。在中心螺旋管线圈制造过程中,开展了中空铜导线焊接工艺、绝缘包扎工艺、绕制工艺、内外层 跳线连接工艺、加热固化工艺等试验。研制的线圈满足对地主绝缘耐压 60kV、A/B 组匝间耐压 1kV 的设计要求。     

Edge operational regimes in tokamaks

Edge operational regimes in tokamaks are described using mostly experimental results of ASDEX Upgrade. Emphasis is put on high confinement mode (H-mode) at medium and high densities up to the density limit. Implications for the physics of H-mode and the density limit are discussed.