HL-2M装置中心螺线管线圈电源变流器过流保护的仿真研究

利用MATLAB仿真工具,搭建HL-2M中心螺线管(CS)电源系统模型,研究了CS电源变流器过流保护策略。通过仿真研究,为HL-2M CS电源系统中变流器制定了最优的过流保护策略,这为电源安全可靠的运行提供了理论依据。     

HL-2M 装置磁场电源逻辑保护系统

为了保障 HL-2M 装置磁场电源的供电安全，其逻辑保护系统设计了 4 级保护机制，分别在主机线 圈、电源变流器、整流变压器、交流开关柜设置保护检测器件，按保护等级确定逻辑保护策略。通过 HL-2M 装 置放电实验，验证了逻辑保护系统的可行性和稳定性。     

HL-2M 装置供电系统研制

为满足 HL-2M 装置的供电需求,须配套建设相应的供电系统。通过仿真计算 HL-2M 装置的总体供 电需求,考虑到 HL-2A 装置现有的供电系统设备,提出了兼顾 HL-2A 和 HL-2M 装置供电需求的总体配置方案。介绍了国内首台 300MVA 立式交流脉冲发电机组、磁体电源、高压电源和电源控制系统的研制情况。     

MW级中性束注入弧电源系统优化

中性束注入弧电源的性能严重影响弧放电的稳定性和中性束加热的效率。HL-2A装置弧电源采用基于晶闸管相控调压和12脉波不控整流的线性电源技术;HL-2M测试束线弧电源采用基于超级电容和IGBT全控整流的开关电源技术。为了优化电源系统性能、改进弧放电稳定性,研究了采样频率对弧放电稳定性的影响。通过对两套电源控制系统进行建模,利用MATLAB仿真了不同采样频率下HL-2M弧流电源控制系统的阶跃响应性能和HL-2A的控制系统性能,分析了采样频率对系统性能的影响。利用离子源测试平台进行不同采样频率下的弧放电实验对仿真结果进行验证,实验结果与仿真结果一致。实验结果验证:采样频率对弧放电稳定性有很大影响,在频率可调范围内,增大采样频率,可以提高控制系统性能,优化弧放电稳定性;HL-2A弧放电不稳定的原因是晶闸管导通特性和滤波电路引起的。     

磁场电源在 HL-2M 装置初始等离子体放电中的应用

磁场电源是 HL-2M 装置初始等离子体放电的重要组成部分,它关系到 HL-2M 装置零场的建立,等 离子体的击穿和维持及位形控制。为实现初始等离子体放电所需的供电电压和电流,对磁场电源从主回路、控制、 测量和保护分别作了相应的调整。在此基础上进行了大量的工程调试,确保了磁场电源的控制和保护等性能达到 初始等离子体放电的需求。在磁场电源运行中,电源控制性能和输出参数的一致性、纹波质量等都有显著提高。 介绍了磁场电源在调试及 HL-2M 装置初始放电中的应用。     

欧姆电源逻辑无环流仿真分析及其运行

介绍了HL-2A装置欧姆加热电源逻辑无环流运行的基本原理和实现步骤。通过对系统的理论分析和仿真,提出了正组变流器逆变可靠运行的控制方案。对出现环流以后的控制策略进行了探讨,实验结果验证了分析的正确性。     

HL-2A装置与HL-2M装置控制处理研究与发展

2006年，围绕HL-2A装置实验控制、数据采集与处理，开展了高性能计算系统建设，基于EFIT代码的HL-2A等离子体位形重建以及若干大型代码的引进移植；实施了水平场电源部分有环流控制；设计制作了新型抗干扰采集器；开展了基于模拟信号脉冲识别的计数研究，在此基础上通过SDD诊断数据计算获得了等离子体电子温度；对HL-2A数据存储系统与实验网进行了全面升级，围绕HL-2M项目，开展了HL-2M位形和极向场线圈设计，HL-2M等离子体控制系统的预研．     

HL-2M托卡马克装置低温控制系统初步设计

首先介绍HL-2M托卡马克装置低温系统的组成。根据低温系统的特点和控制功能的要求,初步设计了HL-2M托卡马克低温控制系统的硬件结构以及软件应用。基于西门子S7-300/400 PLC(可编程控制器)的DCS(集散控制系统)构成HL-2M托卡马克低温控制系统的主体。同时对整个报警联锁保护系统进行了初步设计,使得系统具有很强的可靠性、准确性和安全性。     

欧姆电源整流变压器改造方案及分析计算

根据HL-2A装置电源主回路实施方案，为尽量利用原有设备、节约投资，原HL-1M装置欧姆电源的两台5．6MVA脉冲整流变压器经改造后将作为HL-2A装置多极场E2，E3，E4电源。改造方案及分析计算如下。     

HL-2A装置低杂波保护系统研制

1995年以来在HL-1M装置上成功地进行了LHCD实验，取得了丰硕的成果。2004年的LHCD实验是在HL-1M装置基础上改进的HL-2A装置上进行的。保护系统的优化是LHCD系统提高与完善的重要内容之一。LHCD微波功率传输系统的波导天线内部拉弧打火探测及其保护系统，微波功率输出系统速调管的管体电流定量测量及其保护系统都是本年度实验的重要项目。     

The stability of SiC coating and SiO2/SiC multilayer on the surface of graphite for HTGRs at normal service condition

The stability of SiC coating in helium with a low concentration of O₂, CO₂, and H₂O is a key factor for their application in improvement of oxidation resistance of graphite for high temperature gas-cooled reactors (HTGRs). Through thermodynamic analysis, it is found that the influence factor controlling the critical temperature of passive oxidation for SiC is partial pressure of active gas in helium; the critical temperature of passive oxidation for SiC increases with the partial pressure of O₂, CO₂, and H₂O, SiC is prone to undergo active oxidation in He–CO₂ and He–H₂O system. SiO₂/SiC multilayer coating can improve the oxidation resistance of graphite at higher temperature than SiC coating does under normal operation condition for HTGRs.     

High-performance InGaN/GaN MQW LEDs with Al-doped ZnO transparent conductive layers grown by MOCVD using H_2O as an oxidizer

In this study,the high performance of InGaN/GaN multiple quantum well light-emitting diodes(LEDs) with Aldoped ZnO(AZO) transparent conductive layers(TCLs) has been demonstrated.The AZO-TCLs were fabricated on the n~+-InGaN contact layer by metal organic chemical vapor deposition(MOCVD) using H_2O as an oxidizer at temperatures as low as 400 ℃ without any post-deposition annealing.It shows a high transparency(98%),low resistivity(510 ~4 Ω·cm),and an epitaxial-like excellent interface on p-GaN with an n+-InGaN contact layer.A forward voltage of 2.82 V @ 20 mA was obtained.Most importantly,the power efficiencies can be markedly improved by 53.8%@20 mA current injection and 39.6%@350 mA current injection compared with conventional LEDs with indium tin oxide TCL(LED-Ⅲ),and by28.8%@20 mA current injection and 4.92%@350 mA current injection compared with LEDs with AZO-TCL prepared by MOCVD using O_2 as an oxidizer(LED-Ⅱ),respectively.The results indicate that the AZO-TCL grown by MOCVD using H_2O as an oxidizer is a promising TCL for a low-cost and high-efficiency GaN-based LED application.     

氩、氢混合等离子体处理对GaAs表面性质及发光特性的影响

介绍了一种氩、氢混合等离子体清洗GaAs基片的实验工艺,深入研究了氩、氢等离子体清洗GaAs表面污染物和氧化层,并活化表面性能的基本原理,同时讨论了气体流量、溅射功率和清洗时间等不同溅射参数对等离子体清洗效果的影响。结果表明,在氩气和氢气流量分别为10 cm³/min和30 cm³/min,溅射功率为20 W,清洗时间为15 min的条件下,GaAs样品的光致发光强度提高达139.12%,样品表面的As-O键和Ga-O键基本消失。     

Synthesis of ternary compound in H-S-Se system at high pressures

The chemical reaction products of elemental sulfur (S), selenium (Se), and molecular hydrogen (H₂) at high pressures and room temperature are probed by Raman spectroscopy. Two known compounds H₂S and H₂Se can be synthesized after laser heating at pressures lower than 1 GPa. Under further compression at room temperature, an H₂S-H₂Se and an H₂S-H₂Se-H₂ van der Waals compounds are synthesized at 4 GPa and 6 GPa, respectively. The later is of guest-host structure and can be identified as (H₂S)_x(H₂Se)_(2-x)H₂. It can be maintained up to 37 GPa at least, and the stability of its H₂Se molecules is extended:the H-Se stretching mode can be detected at least to 36 GPa but disappears at 22 GPa in (H₂Se)₂H₂. The pressure dependence of S-H and Se-H stretching modes of this ternary compound is in line with that of (H₂S)₂H₂ and (H₂Se)₂H₂, respectively. However, its hydrogen subsystem only shows the relevance to (H₂S)₂H₂, indicating that this ternary compound can be viewed as H₂Se-replaced partial H₂S of (H₂S)₂H₂.     

Polyhedral silver clusters as single molecule ammonia sensor based on charge transfer-induced plasmon enhancement

The unique plasmon resonance characteristics of nanostructures based on metal clusters have always been the focus of various plasmon devices and different applications. In this work, the plasmon resonance phenomena of polyhedral silver clusters under the adsorption of NH₃, N₂, H₂, and CH₄ molecules are studied by using time-dependent density functional theory. Under the adsorption of NH₃, the tunneling current of silver clusters changes significantly due to the charge transfer from NH₃ to silver clusters. However, the effects of N₂, H₂, and CH₄ adsorption on the tunneling current of silver clusters are negligible. Our results indicate that these silver clusters exhibit excellent selectivities and sensitivities for NH₃ detection. These findings confirm that the silver cluster is a promising NH₃ sensor and provide a new method for designing high-performance sensors in the future.     

Role of graphene in improving catalytic behaviors of AuNPs/MoS2/Gr/Ni-F structure in hydrogen evolution reaction

The efficient production of hydrogen through electrocatalytic decomposition of water has broad prospects in modern energy equipment. However, the catalytic efficiency and durability of hydrogen evolution catalyst are still very deficient, which need to be further explored. Here in this work, we prove that introducing a graphene layer (Gr) between the molybdenum disulfide and nickel foam (Ni-F) substrate can greatly improve the catalytic performance of the hybrid. Owing to the excitation of local surface plasmon resonance (LSPR) of gold nanoparticles (NPs), the electrocatalytic hydrogen releasing activity of the MoS₂/Gr/Ni-F heterostructure is greatly improved. This results in a significant increase in the current density of AuNPs/MoS₂/Gr/Ni-F composite material under light irradiation and in the dark at 0.2 V (versus reversible hydrogen electrode (RHE)), which is much better than in MoS₂/Gr/Ni-F composite materials. The enhancement of hydrogen release can be attributed to the injection of hot electrons into MoS₂/Gr/Ni-F by AuNPs, which will improve the electron density of MoS₂/Gr/Ni-F, promote the reduction of H₂O, and further reduce the activation energy of the electrocatalyst hydrogen evolution reaction (HER). We also prove that the introduction of graphene can improve its stability in acidic catalytic environments. This work provides a new way of designing efficient water splitting system.     

基于一维TiO_2纳米管阵列薄膜的β伏特效应研究

介绍了一种采用宽禁带半导体二氧化钛纳米管阵列薄膜材料制备β伏特效应同位素电池的方法.通过对金属钛片的电化学阳极氧化制备了垂直定向、有序排列的二氧化钛纳米管阵列薄膜,研究了退火条件对二氧化钛纳米管阵列薄膜半导体光电性能的影响.通过与镍-63辐射源的集成封装,形成三明治结构镍-63/二氧化钛纳米管阵列薄膜/钛片的β伏特同位素电池.实验结果表明,基于氩气氛围下450?C退火的黑色二氧化钛纳米管阵列薄膜具有高的氧空位缺陷浓度和宽的可见-紫外吸收光谱.在使用β辐射总能量为10 m Ci的镍-63辐射源时,同位素电池的开路电压为1.02 V,短路电流75.52 n A,最大有效转换效率为22.48%.     

Electrical conductivity and defect structure of Mg-doped Cr2O3

The electrical conductivity of Cr₂O₃ nominally doped with 2 mol% MgO has been studied by the four point a.c. technique as a function of the oxygen activity (O₂ + Ar, CO + CO₂ and H₂ + H₂O) in the temperature range 400–1200 °C. It is concluded that Cr₂O₃ doped with MgO is an extrinsic conductor and that the dissolved Mg-dopant is compensated by the formation of electron holes at near atmospheric oxygen pressures and by oxygen vacancies (or possibly interstitial chromium ions) at highly reduced oxygen activities (in CO + CO₂ and H₂ + H₂O gas mixtures). In H₂ + H₂O mixtures Mg-doped chromia also dissolves hydrogen as protons and significantly affects the defect structure and electrical conductivity. The defect structure of the oxide under various conditions is discussed.     

Evidence for bicarbonate formation on vacuum annealed TiO2(110) resulting from a precursor-mediated interaction between CO2 and H2O

The reaction of CO₂ and H₂O to form bicarbonate (HCO⁻₃) was examined on the nearly perfect and vacuum annealed surfaces of TiO₂(110) with temperature programmed desorption (TPD), static secondary ion mass spectrometry (SSIMS) and high resolution electron energy loss spectrometry (HREELS). The vacuum annealed TiO₂(110) surface possesses oxygen vacancy sites that are manifested in electronic EELS by a loss feature at 0.75 V. These oxygen vacancy sites bind CO₂ only slightly more strongly (TPD peak at 166 K) than do the five-coordinated Ti⁴⁺ sites (TPD peak at 137 K) typical of the nearly perfect TiO₂(110) surface. Vibrational HREELS indicates that CO₂ is linearly bound at the latter sites with a ν_a(OCO) frequency similar to the gas phase value. In contrast, oxygen vacancies dissociate H₂O to bridging OH groups which recombine to liberate H₂O in TPD at 490 K. No evidence for a reaction between CO₂ and H₂O is detected on the nearly perfect surface. In sequentially dosed experiments on the vacuum annealed surface at 110 K, CO₂ adsorption is blocked by the presence of preadsorbed H₂O, adsorbed CO₂ is displaced by postdosed H₂O, and there is little or no evidence for bicarbonate formation in either case. However, when CO₂ and H₂O are simultaneously dosed, a new CO₂ TPD state is observed at 213 K, and the 166 K state associated with CO₂ at the vacancies is absent. SSIMS was used to tentatively assign the 213 K CO₂ TPD state to a bicarbonate species. The 213 K CO₂ TPD state is not formed if the vacancy sites are filled with OH groups prior to simultaneous CO₂+H₂O exposure. Sticking coefficient measurements suggest that CO₂ adsorption at 110 K is precursor-mediated, as is known to be the case for H₂O adsorption on TiO₂(110). A model explaining the circumstances under which the proposed bicarbonate species is formed involves the surface catalyzed conversion of a precursor-bound H₂O–CO₂ van der Waals complex to carbonic acid, which then reacts at unoccupied oxygen vacancies to generate bicarbonate, but falls apart to CO₂ and H₂O in the absence of these sites. This model is consistent with the conditions under which bicarbonate is formed on powdered TiO₂, and is similar to the mechanism by which water catalyzes carbonic acid formation in aqueous solution.