托卡马克实验装置的实验大厅移动辐射监测机器人设计

托卡马克实验装置(experimental advanced superconducting tokamak, EAST)在进行聚变等离子体放电实验时,随着中性束注入、低杂波电流驱动、电子回旋波共振加热等大功率辅助加热系统投入运行,等离子体中子出射强度可达10¹⁴ n/s,这导致大厅及窗口区域的中子光子剂量率明显增加。为了保证工作人员及维护人员的安全,需要及时了解不同位置处的辐射剂量。本研究基于六轮移动救援机器人底盘,研制EAST实验大厅移动辐射监测机器人,并搭载X、γ辐射在线监测仪,通过同步定位与建图技术（SLAM）构建环境地图自主移动或通过高清图像远程控制及数据传输系统,将大厅内不同位置的辐射剂量值传递给上位机。通过巡测路径上的剂量率异常,可向周围的工作人员及时发出警示,以此确保实验人员的辐射安全和判断现场维护人员的滞留时间。     

EAST中性束注入下快离子输运行为的研究

利用等离子体输运分析程序TRANSP和粒子导心轨道模拟程序ORBIT,结合聚变中子和等离子体储能诊断数据,对EAST(Experimental Advanced Superconducting Tokamak)托卡马克中性束注入加热时不同等离子体电流和纵场强度下的快离子输运行为进行了研究。实验和模拟结果表明:中性束反向束注入时的快离子初始轨道损失功率大于中性束同向束;中性束4条束线产生快离子初始轨道损失区域主要集中在装置中平面以下第一壁以及偏滤器区域;在EAST目前的运行参数范围内,提高等离子体电流和纵场强度,可以使等离子体中快离子的漂移轨道宽度和拉莫尔回旋半径缩小,更有利于快离子的约束,从而提高中性束的加热效率,增加聚变中子产额和等离子体储能。     

兰州大学的中子发生器研制及应用展望

1988年兰州大学成功研制了3×10¹² s^-1的ZF-300强流中子发生器,主要用于核数据测量、材料辐照损伤等研究。为进一步开展活化法中子核数据测量、裂变物理等研究,兰州大学启动了基于倍压加速器的ZF-400强流中子发生器研制工程,该中子发生器的设计指标为D束流能量400 keV、D束流强度大于30 mA、D-D中子产额大于5×10¹⁰ s^-1,D-T中子产额大于5×10¹² s^-1。在裂变物理研究方面,已成功发展了描述裂变核断点裂变势的势驱动模型（potential-driving model）,并开展了中子诱发典型锕系核素裂变发射中子前裂变产物的质量分布计算研究;将potential-driving model植入Geant4程序,发展了用于裂变发射中子后裂变产物质量分布、动能分布、裂变中子能谱等模拟的蒙特卡罗方法,并开展了可靠性评估研究;研制了一套用于裂变产物实验测量的双屏栅电离室（TFGIC）,并完成了初步实验测试。在中子应用技术方面,为满足小型化中子应用技术系统的研发需求,兰州大学成功研制了长度984 mm、直径234 mm的紧凑型中子发生器,通过在引出加速电极和靶之间加电阻的方式产生偏置电场,实现对靶上二次电子的抑制。在自注入靶条件和150 keV氘束流能量下,D-D中子产额可大于5×10⁸ s^-1,该中子发生器已具备产生D-T中子产额大于10¹⁰ s^-1量级的潜力。完成了基于紧凑型D-T中子发生器的快中子准直屏蔽体的设计,并研发了基于微通道板的快中子成像探测器,初步D-T快中成像测试显示,图像空间分辨率约为500 μm。开展了基于紧凑型D-D中子发生器的核燃料棒²³⁵U富集度及均匀性检测系统研发,仿真研究表明,在D-D中子产额5×10⁸ s^-1条件下,对核燃料棒中10%范围内的²³⁵U富集度相对变化的检测置信度可达到99%。     

EAST在不同加热模式下的辐射响应研究

利用EAST(Experimental Advanced Superconducting Tokamak)上的在线辐射剂量监测系统,对氘氘等离子体实验期间各种加热模式下装置主机厅内中子、γ剂量进行测量。对比分析了欧姆加热、低杂波加热、中性束注入加热,以及中性束与射频波协同加热实验时的中子、γ辐射强度随时间演化的规律。结果显示:在纯欧姆加热模式,辐射剂量主要来源于逃逸电子轫致辐射产生的高能γ(X)射线和光中子;低杂波辅助加热时,通常会出现环电压下降的现象,离子温度和聚变反应率提高有限,而逃逸电子产生的韧致辐射却被有效抑制,使得总体辐射剂量水平反而低于纯欧姆加热模式;中性束注入加热时,束靶反应使得中子产额提高2～3个数量级,聚变中子以及中子与周围物质核反应产生的γ射线成为辐射剂量的主要来源。通过统计归纳得到在中性束注入加热时,中子周围剂量当量与γ周围剂量当量存在近似的线性关系。该线性关系对于中性束与各种射频波协同加热实验时,中子、γ射线来源于多种途径的情形并不完全适用。     

EAST中性束注入器研制进展

EAST(Experimental Advanced Superconducting Tokamak)作为世界上第一个全超导非圆截面托克马克,其目标是研究1 000 s的长脉冲稳态运行的前沿性物理问题,要达成这一目标,必须有高功率电流驱动和辅助加热系统以实现EAST装置的高参数稳态运行。中性束注入(Neutral Beam Injection,NBI)加热是等离子体辅助加热和维持最有效的手段之一,为此一套注入功率4–8 MW、脉冲宽度10–100 s的中性束注入系统于2010年开工建设,并于2014年实现了对等离子体的加热和驱动。本文主要展示了EAST中性束注入器的最新进展,从长脉冲束引出和高功率束引出两个方面介绍了EAST中性束注入器综合测试台的最新实验结果,结果表明在束功率和脉冲宽度方面已经达到或超过设计指标。     

同位素中子源参考辐射能谱测量及模拟中子谱分析

不同成分中子参考辐射场是对中子防护材料性能测试的基本条件。为获得较理想的测试中子防护材料的中子参考辐射场，构建基于³He正比计数管的多球中子能谱测量系统，对基于²⁴¹Am-Be和²⁵²Cf中子源的中子辐射场慢化情况进行MCNP模拟和能谱实验测量。为准确判断实验室校准参考位置的中子散射情况，基于多球中子能谱测量系统，开展了中子散射成分测量。采用ICRP推荐的注量-剂量转换系数对能谱进行了剂量率转化，与使用长计数器的测量结果进行比较，发现在校准参考位置的剂量率相对偏差≤20%。开展了聚乙烯慢化同位素中子源获得特定能谱的实验研究，进行了慢化谱的模拟计算和实验测量，两者结果符合较好。该工作为后续的中子计量测试和中子防护材料测试提供了可用的中子参考辐射场。     

反冲释放对反应堆活化腐蚀产物源项的影响研究

中子与靶核碰撞时引起的靶核反冲释放，对于反应堆活化腐蚀产物源项分析有非常重要的影响。对于使用水冷方式的反应堆，在辐照区反冲释放可使活化腐蚀产物离开壁面进入到冷却剂中，并随冷却剂迁移到非辐照区，使非辐照区的设备也带有放射性。本文研究了反冲释放在反应堆内的作用方式，建立了反冲释放的计算模型和程序模块，并集成到活化腐蚀产物源项分析程序CATE中，利用改进后的CATE程序，计算分析了堆芯与蒸汽发生器中主要的活化腐蚀产物核素⁵⁸Co与⁶⁰Co在考虑反冲释放前后的数值，明确了反冲释放效应的影响程度。计算结果表明：考虑反冲释放前后堆芯处⁵⁸Co与⁶⁰Co活度的比值有所下降，而在蒸汽发生器中的比值则有所上升；反冲释放的总作用概率与腐蚀产物层厚度相关，会随着反应堆的运行而逐渐降低，反应堆运行初期作用概率的数量级在10^-1，对活化腐蚀产物的迁移有显著影响，100 d后作用概率的数量级下降到10^-3，对活化腐蚀产物源项的影响较小。     

高通量堆NTD硅系统活化剂量计算

根据单晶硅及靶桶材料成分、测量的辐照孔道中子通量谱与辐照时间,采用点燃耗程序ORIGEN与蒙特卡罗程序MCNP耦合计算高通量堆中子嬗变掺杂(NTD)硅辐照系统活化后的外照射剂量当量率及各种活化产物放射性核素衰减变化情况,同时对各种活化核素剂量率贡献及相应衰减时间进行了分析。通过计算结果与堆厅γ电离室剂量率监测对比验证及堆厅屏蔽层厚度的保守估算,表明目前NTD硅系统转运过程屏蔽设计满足辐射防护要求,并提出有益建议。     

EAST中性束注入器大厅内辐射剂量计算与测量

利用解析方法对EAST大功率中性束注入器充氢运行时实验大厅内6个关键点的辐射剂量进行了理论计算,并利用光致光剂量计(OSL)对这些位置点进行了辐射剂量测量。理论计算和OSL测量结果表明:理论计算结果与实验测量结果具有一定吻合度。同时还表明:EAST中性束注入器现有的防护装置满足实验运行时辐射防护要求。     

293,294119与294,295120超重核衰变性质理论预言

熔合蒸发反应²⁴³Am (⁵⁴Cr,xn)^297-x119以及²⁴³ Am (⁵⁵Mn,xn)^298-x120是最近核物理学家提出的合成Z为119及120新元素的可能途径，α衰变是实验上鉴定新元素或新核素合成的有力工具。利用改进的密度依赖结团模型(Improved Density-dependent Cluster Model,DDCM+)，对于熔合蒸发反应²⁴³Am (⁵⁴Cr,xn)^297-x119以及²⁴³Am(⁵⁵Mn,xn)^298-x120蒸发3或4个中子得到的反应产物^293,294119与^294,295120的α衰变半衰期进行了理论预言。在此基础上，进一步分析了^293,294119与^294,295120核素α衰变过程与自发裂变以...     

Numerical Simulation of Non-Inductive Current Driven Scenario in EAST Using Neutral Beam Injection

For achieving the scientific mission of long pulse and high performance operation,experimental advanced superconducting tokamak(EAST) applies fully superconducting magnet technology and is equiped with high power auxiliary heating system.Besides RF(Radio Frequency) wave heating,neutral beam injection(NBI) is an effective heating and current drive method in fusion research.NBCD(Neutral Beam Current Drive) as a viable non-inductive current drive source plays an important role in quasi-steady state operating scenario for tokamak.The non-inductive current driven scenario in EAST only by NBI is predicted using the TSC/NUBEAM code.At the condition of low plasma current and moderate plasma density,neutral beam injection heats the plasma effectively and NBCD plus bootstrap current accounts for a large proportion among the total plasma current for the flattop time.     

Time Dependent DD Neutrons Measurement Using a Single Crystal Chemical Vapor Deposition Diamond Detector on EAST

A single crystal chemical vapor deposition(scCVD) diamond detector has been successfully employed for neutron measurements in the EAST(Experimental Advanced Superconducting Tokamak) plasmas.The scCVD diamond detector coated with a 5 μm ~6LiF(95%~6Li enriched) layer was placed inside a polyethylene moderator to enhance the detection efficiency.The time-dependent neutron emission from deuteron plasmas during neutral beam injection(NBI)heating was obtained.The measured results are compared with that of fission chamber detectors,which always act as standard neutron flux monitors.The scCVD diamond detector exhibits good reliability,stability and the capability to withstand harsh radiation environments despite its low detection efficiency due to the small active volume.     

Predictive Simulations of Plasma Heating and Current Drive by Neutral Beam Injection on EAST

Long pulse and high performance steady-state operation is the main scientific mission of experimental advanced superconducting tokamak (EAST). In order to achieve this objective, high-power auxiliary heating systems are essential. Radio frequency (RF) wave heating and neutral beam injection (NBI) are two principal methods. NBI is an effective method of plasma heating and current drive, and it has been used in many magnetic confinement fusion devices. Based on the plasma equilibrium of EAST (Li et al., Plasma Phys Control Fusion 55:125008, 2013) plus previous EAST experimental data used as initial conditions, the NBI module (Polevoi et al., JAERI-Data, 1997) employed in automated system for transport analysis (ASTRA) code (Pereverzev et al., IPP-Report, 2002) is applied to predict the effects of plasma heating and current drive with different neutral beam injection power levels. At certain levels of plasma densities and plasma current densities, the simulation results show that the NBI heats plasma effectively, also increases the proportions of NB current and bootstrap current among total current significantly.     

EAST托卡马克的中性束注入方案

高能中性束注入(Neutral beam injection,NBI)是核聚变装置托卡马克采用的芯部辅助加热和非感应电流驱动主要手段之一.本文介绍了国家大科学工程全超导托卡马克实验装置(Experimental advanced super-conductingtokamak,EAST)上的高能NBI加热方案及注入器的工程要求,并讨论了中性束在EAST等离子体中的传输等相关问题.     

Overview of Development Status for EAST-NBI System

The neutral beam injection(NBI) system was developed on the Experimental Advanced Superconducting Tokamak(EAST) for plasma heating and current driving. This paper presents the brief history, design, development, and the main experimental results of the RD of neutral beam injector on the test bed and on EAST. In particular, it will describe:(1) how the two beamlines with a total beam power of 8 MW were developed;(2) the design of the EAST-NBI system including the high power ion source, main vacuum chamber, inner components, beam diagnostic system and sub-system;(3) the experimental results of beamline-1 on the summer campaign of EAST in 2014 and,(4) the status of beamline-2 and the future plan of EAST-NBIs.     

Achievement of 100 s Long Pulse Neutral Beam Extraction in EAST Neutral Beam Injector

Neutral beam injection (NBI) is recognized as one of the most e®ective means for plasma heating. A 100 s long pulse neutral beam with 30 keV beam energy, 10 A beam current and a 100 s long pulse modulating neutral beam with 50 keV beam energy, 16 A beam current were achieved in the EAST neutral beam injector on the test-stand. The preliminary results suggest that EAST-NBI system initially possess the ability of long pulse beam extraction.     

R&D progress of high power ion source on EAST-NBI

The neutral beam injector(NBI) system was designed and developed mainly for the plasma heating on the Experimental Advanced Superconducting Tokamak(EAST). The high power ion source is the key part of the NBI. A hot cathode ion source was used on the EAST-NBI. The ion source was conditioned on the ion source test bed with hydrogen gas and achieved the designed parameters. The deuterium gas was used when it moved to the EAST-NBI. The main performance of the ion source on EAST is presented in this paper. The highest beam power of 4.5 MW in NBI-1 and 2.75 MW in NBI-2 was achieved. The total neutral beam power is about 4.5 MW. The long pulse beam of 100 s is injected into the EAST plasma too.     

Analysis of Power Distribution on Beamline Components at Different Neutralization Efficiencies on NBI Test Stand

Neutral beam injection is recognized as one of the most effective means for plasma heating. According to the research plan of the EAST physics experiment, two sets of neutral beam injector(4–8 MW, 10–100 s) were built and operated in 2014. Neutralization efficiency is one of the important parameters for neutral beam. High neutralization efficiency can not only improve injection power at the same beam energy, but also decrease the power deposited on the heat-load components in the neutral beam injector(NBI). This research explores the power deposition distribution at different neutralization efficiencies on the beamline components of the NBI device. This work has great significance for guiding the operation of EAST-NBI, especially in long pulse and high power operation, which can reduce the risk of thermal damage of the beamline components and extend the working life of the NBI device.     

Data Server Application Software for Neutral Beam Injection Control System

The neutral beam injection (NBI) heating is one of the mainly auxiliary plasma heating methods for EAST. In this paper, a data server application software is presented for NBI control system. This application software is developed on Centos OS by C programming language with TCP and multithreading technology. It mainly focuses on storing and querying experimental pulse data and engineering data; experimental user’s operation records; experimental configuration information; the collected data after processing; as well as managing and releasing experimental discharge shot number and so on. By using the unified data header structure, the data server software provides universal information exchange interfaces for different service request terminals with different operating platform, such as WinCC, Labview. With the help of data server software, those problems related on the storage, querying and processing of information and data for NBI control system are well solved.