Simulation of ion cyclotron wave heating in the EXL-50U spherical tokamak based on dispersion relations

This study investigates the single-pass absorption(SPA) of ion cyclotron range of frequency(ICRF) heating in hydrogen plasma of the EXL-50U spherical tokamak,which is an upgraded EXL-50 device with a central solenoid and a stronger magnetic field.The reliability of the kinetic dispersion equation is confirmed by the one-dimensional full-wave code,and the applicability of Porkolab's simplified theoretical SPA model is discussed based on the kinetic dispersion equation.Simulations are conducted to investigate the heating effects of the fundamental and second harmonic frequencies.The results indicate that with the design parameters of the EXL-50U device,the SPA for second harmonic heating is 63%,while the SPA for fundamental heating is 13%.Additionally,the optimal injection frequencies are 23 MHz at 0.9 T and 31 MHz at 1.2 T.The wave vector of the antenna parallel to the magnetic field,with a value of k_‖=7.5 m^(-1),falls within the optimal heating region.Simulations reveal that the ICRF heating system can play an important role in the ion heating of the EXL-50U.

Ion heat transport in electron cyclotron resonance heated L-mode plasma on the T-10 tokamak

Anomalous ion heat transport is analyzed in the T-10 tokamak plasma heated with electron cyclotron resonance heating(ECRH) in second-harmonic extra-ordinary mode. Predictive modeling with empirical scaling for Ohmical heat conductivity shows that in ECRH plasmas the calculated ion temperature could be overestimated, so an increase of anomalous ion heat transport is required. To study this effect two scans are presented: over the EC resonance position and over the ECRH power. The EC resonance position varies from the high-field side to the low-field side by variation of the toroidal magnetic field. The scan over the heating power is presented with on-axis and mixed ECRH regimes. Discharges with high anomalous ion heat transport are obtained in all considered regimes. In these discharges the power balance ion heat conductivity exceeds the neoclassical level by up to 10 times. The high ion heat transport regimes are distinguished by three parameters: the ratio Te/Ti, the normalized electron density gradient R/■, and the ion–ion collisionality νii~*. The combination of high Te/Ti, high νii~*, and R/■=6-10 results in values of normalized anomalous ion heat fluxes up to 10 times higher than in the low transport scenario.

Numerical study of plasmas start-up by electron cyclotron waves in NCST spherical tokamak and CN-H1 stellarator

According to the physics of tokamak start-up,this study constructs a zero-dimensional(0D)model applicable to electron cyclotron(EC)wave assisted start-up in NCST spherical torus(spherical tokamak)and CN-H1 stellarators.Using the constructed 0D model,the results obtained in this study under the same conditions are compared and validated against reference results for pure hydrogen plasma start-up in tokamak.The results are in good agreement,especially regarding electron temperature,ion temperature and plasma current.In the presence of finite Ohmic electric field in the spherical tokamak,a study on the EC wave assisted start-up of the NCST plasma at frequency of 28 GHz is conducted.The impact of the vertical magnetic field B_(v)on EC wave assisted start-up,the relationship between EC wave injection power P_(inj),Ohmic electric field E,and initial hydrogen atom density n_(H0)are explored separately.It is found that under conditions of Ohmic electric field lower than ITER(~0.3 V m^(-1)),EC wave can expand the operational space to achieve better plasma parameters.Simulating the process of28 GHz EC wave start-up in the CN-H1 stellarator plasma,the plasma current in the zerodimensional model is replaced with the current in the poloidal coil of the stellarator.Plasma startup can be successfully achieved at injection powers in the hundreds of kilowatts range,resulting in electron densities on the order of 10^(17)-10^(18)m^(-3).

Effects of counter-current driven by electron cyclotron waves on neoclassical tearing mode suppression

Through theoretical analysis,we construct a physical model that includes the influence of counter-external driven current opposite to the plasma current direction in the neoclassical tearing mode(NTM).The equation is used with this model to obtain the modified Rutherford equation with co-current and counter-current contributions.Consistent with the reported experimental results,numerical simulations have shown that the localized counter external current can only partially suppress NTM when it is far from the resonant magnetic surface.Under some circumstances,the Ohkawa mechanism dominated current drive(OKCD)by electron cyclotron waves can concurrently create both co-current and counter-current.In this instance,the minimal electron cyclotron wave power that suppresses a particular NTM was calculated by the Rutherford equation.The result is marginally less than when taking co-current alone into consideration.As a result,to suppress NTM using OKCD,one only needs to align the co-current with a greater OKCD peak well with the resonant magnetic surface.The effect of its lower counter-current does not need to be considered because the location of the counter-current deviates greatly from the resonant magnetic surface.

Suppression of the m/n=2/1 tearing mode by electron cyclotron resonance heating on J-TEXT

Stabilization of tearing modes and neoclassical tearing modes is of great importance for tokamak operation.Electron cyclotron waves(ECWs)have been extensively used to stabilize the tearing modes with the virtue of highly localized power deposition.Complete suppression of the m/n=2/1 tearing mode(TM)by electron cyclotron resonance heating(ECRH)has been achieved successfully on the J-TEXT tokamak.The effects of ECW deposition location and power amplitude on the 2/1 TM suppression have been investigated.It is found that the suppression is more effective when the ECW power is deposited closer to the rational surface.As the ECW power increases to approximately 230 k W,the 2/1 TM can be completely suppressed.The island rotation frequency is increased when the island width is reduced.The experimental results show that the local heating inside the magnetic island and the resulting temperature perturbation increase at the O-point of the island play dominant roles in TM suppression.As the ECW power increases,the 2/1 island is suppressed to smaller island width,and the flow shear also plays a stabilizing effect on small magnetic islands.With the stabilizing contribution of heating and flow shear,the 2/1 TM can be completely suppressed.

Design of the electron cyclotron emission diagnostic on EXL-50 spherical torus

The electron cyclotron emission(ECE)diagnostic system has been developed on the ENN spherical torus(EXL-50).The ECE system is designed to detect radiation emitted by energetic electrons,rather than conventional 1D electron temperature profile measurement,in the frequency range of 4-40 GHz.The system is composed of five subsystems,each covering a different frequency band,including the C-band(4-8 GHz),X-band(8-12 GHz),Ku-band(12-18 GHz),K-band(18-26.5 GHz)and Kα-band(26.4-40 GHz).The system uses heterodyne detection to analyze the received signals.The K-band and Kα-band subsystems are located horizontally in the equatorial plane of the EXL-50,while the C-band,X-band and Ku-band subsystems are located under the vacuum vessel of the EXL-50.To direct the microwaves from the plasma to the antennas for the horizontal detection subsystems,a quasi-optical system has been developed.For the vertical detection subsystems,the antennas are directly attached to the port located beneath the torus at R=700 mm,which is also the magnetic axis of the torus.The system integration,bench testing and initial experimental results will be thoroughly discussed,providing a comprehensive understanding of the ECE system s performance and capabilities.

Investigating the occurrence and predictability of pitch angle scattering events at ADITYA-Upgrade tokamak with the electron cyclotron emission radiometer

This paper describes the experimental analysis and preliminary investigation of the predictability of pitch angle scattering(PAS) events through the electron cyclotron emission(ECE)radiometer signals at the ADITYA-Upgrade(ADITYA-U) tokamak. For low-density discharges at ADITYA-U, a sudden abnormal rise is observed in the ECE signature while other plasma parameters are unchanged. Investigations are done to understand this abrupt rise that is expected to occur due to PAS. The rise time is as fast as 100 μs with a single step and/or multiple step rise in ECE radiometer measurements. This event is known to limit the on-axis energy of runaway electrons. Being a repetitive event, the conditions of its repetitive occurrence can be investigated, thereby exploring the possibility of it being triggered and surveyed as an alternate runaway electron mitigation plan. Functional parameterization of such events with other discharge parameters is obtained and the possibility to trigger these events is discussed.PREDICT code is used to investigate the possible interpretations for the PAS occurrence through modeling and supporting the ECE observations. The trigger values so obtained experimentally are set as input criteria for PAS occurrence. Preliminary modeling investigations provide reliable consistency with the findings.

Numerical Simulation of High-Current Vacuum Arc with Consideration of Anode Vapor

A high-current vacuum arc （HCVA） with the consideration of anode vapor is modeled and simulated. First, from the HCVA column model, the heat flux density to the anode is obtained, which is put into the anode activity model, and the parameter distributions （such as the vapor temperature and velocity） of anode vapor are obtained from the simulation results of the anode activity model. Then, by iterating and calculating the HCVA column model and anode activity model, the interaction between the HCVA column and the anode vapor is simulated and analyzed. In the simulation, the distribution of the axial magnetic field （AMF） generated by the electrode system is calculated by software ANSYS. The simulation results show that the influence of anode vapor on the parameter distributions in the arc column is significant. The simulation results are also compared with the vacuum arc photograph.

Study on the Nonlinear Tension-Torsion Coupled Stiffness of the High-Current Composite Umbilical Considering the Thermal Effect

The gradual advances of offshore oil and gas exploitation and the development tendency of equipment integration have prompted the design of a new type of the high-current composite umbilical to meet development needs.In order to study the mechanical behavior of the high-current composite umbilical(HCCU)and provide design suggestions,a theoretical analysis framework of the tension-torsion coupled behavior of the spirally wound structure is proposed,which focuses more on the radial mechanical behavior.Then,by considering the mechanical and thermal conditions during the operation of HCCU,a semi-analytical method of the tension and torsion stiffness of the high-current composite umbilical considering the temperature effect is established.Furthermore,a practical case of HCCU is given,and the thermal effect on the radial and axial mechanical behaviors are analyzed.It is found that the thermal effect has a significant influence on the radial stiffness,and shows non-linear variation characteristics.Finally,the sensitivity analysis is carried out to study the influence of the design parameter on the stiffness of tension and torsion.The results indicated that the equivalent radial stiffness and helical angle have obvious effect on the tension-torsion coupled stiffness,which can provide reasonable reference for the design of HCCU.

HIGH-CURRENT PULSED ELECTRON BEAM: RAPID SURFACE ALLOYING AND WEAR RESISTANCE IMPROVEMENT

The present paper reports the rapid surface alloying induced by the bombardment of high-current pulsed electron beam. Two kinds of substrate materials were examined to show this effect. The first sample was a pure Al metal pre-coated with fine carbon powders prior to the bombardment, and the second alloy is the D2-Crl2MolVl mould steel pre-coated with Cr, Ti, and TiN powders. The surface elements diffuse about several micrometers into the substrate materials only after several bombardments. Tribological behaviors of these samples were characterized and significant improvement in wear resistance was found. Finally, a TEM analysis reveals the presence of stress waves generated by coupled thermal and stress fields, which was considered as the main cause of the enhanced properties.

Initial testing of ohmic heating through double flux swing during electron cyclotron start-up in the QUEST spherical tokamak

A power-supply system was developed for Ohmic heating(OH)to double×10^(18)the amount of change magnetic flux in the primary central solenoid(CS)on the QUEST spherical tokamak.Two power supplies are connected with stacks of insulated-gate bipolar transistors,and sequentially operated to generate positive and negative CS currents.This bipolar power-supply system is controlled via a field-programmable gate array,which guarantees the safety of the entire system operation.The new OH system,assisted by electron cyclotron heating,enables the stable generation of plasma currents exceeding 100 k A.Moreover,the achieved electron density over the wide range in the major radial direction exceeds the cut-off density for one of the highpower microwave sources in QUEST.This strategy yields target plasmas for future experiments with the electron Bernstein wave.

中国原子能科学研究院紧凑型强流质子回旋加速器的发展和应用

中国原子能科学研究院(简称原子能院)自1958年建成我国第1台回旋加速器以来,已经研发出了一系列强流回旋加速器装置,为我国核学科和核技术应用等发展发挥了极其重要的作用。原子能院在1996年建成了我国第一台专用于医用同位素生产的30 MeV/350μA强流质子回旋加速器,在2014年建成了国际上最大的紧凑型强流质子回旋加速器大科学装置(100 MeV/520μA)。在2021年,原子能院自主研发出了国内首台引出流强1 mA以上的14 MeV强流质子回旋加速器。该加速器的建成,为我国基于小型化强流质子回旋加速器的中子源应用奠定了基础。基于14 MeV强流质子回旋加速装置,先后建成了国内首台用于硼中子俘获治疗(BNCT)的治疗装置样机和用于中子成像无损检测的实验验证样机,并开展了相关实验研究。目前,原子能院正在研制用于BNCT临床等应用的18 MeV/1 mA强流质子回旋加速器,并且正在开展流强达到3~5 mA的基于H_(2)^(+)的新型强流回旋加速器的研发。原子能院的强流回旋加速器,在基于加速器中子源的BNCT和中子成像、加速器生产医用放射性同位素等应用方面将发挥重要的作用。

自研28 GHz/50 kW回旋管实现长时间连续运行

介绍了中国工程物理研究院应用电子学研究所针对磁约束聚变装置电子回旋共振加热(ECRH)系统、重离子加速器电子回旋共振(ECR)离子源以及前沿科技探索应用研制的28 GHz/50 kW连续波回旋管最新实验结果。研究团队在2019年该回旋管实现50 kW/30 s运行的基础上,通过结构优化和稳定性设计验证,最终实现了在10~50 kW功率范围多个功率水平的稳定长时间连续运行,典型运行结果为16 kW/3000 s、26 kW/900 s、46 kW/1800 s、50 kW/300 s,特别在输出功率32 kW连续稳定工作了400 min。这是国内首次研制出小时级连续工作的中等功率回旋管。

CRAFT-ICRF低电平控制系统的设计和实现

在聚变堆主机关键系统综合研究设施(CRAFT)的实验中,为了稳定控制射频功率和满足复杂的物理实验需求,设计了基于现场可编程门阵列(FPGA)芯片的低电平控制系统。通过上位机输入射频信号功率参数,采用对数检波器AD8307、直接数字频率合成器(DDS)、高精度的模数转换器(ADC)以及模拟衰减器等芯片,完成了射频功率测量与稳定输出、射频功率的反馈控制以及多阶功率调制等功能设计与实现。搭建了一套能够高效开展低电平控制系统的测试平台,通过实验验证该系统的功率反馈控制与多阶调制的有效性的同时,实现±0.3%的幅度稳定度和±0.3°的相位稳定度,且达到长时间稳定运行的要求。

天然气净化厂废水处理过程中溶解性有机物的变化

溶解性有机物(DOM)是废水达标排放标准的重要考虑因素,综合分析废水中DOM的分子组成是对其高效去除的前提。以某天然气净化厂废水为研究对象,采用傅里叶变换离子回旋共振质谱法(FT-ICR MS)和三维荧光光谱(3D-EEMs)从分子层面深入分析氧化过程中DOM的荧光性质、分子组成、质荷比、分子转化。EEM结果表明,废水中主要以类腐殖质物质为主,其次为富里酸类物质。O_(3)/H_(2)O_(2)氧化降低了类腐殖质物质的荧光强度,但DOM降解受限于臭氧与富含电子有机物的反应特性;而O_(3)/H_(2)O_(2)-Fenton联合氧化能大幅降低总荧光强度,有效去除类腐殖质。FT-ICR MS结果表明,O_(3)/H_(2)O_(2)氧化去除了部分CHO类、CHON类DOM,但对CHOS类、CHONS类DOM的去除效果欠佳。多环芳烃和高度不饱和的化合物被臭氧降解为脂肪族类化合物,增加了CHO类DOM含氧量。O_(3)/H_(2)O_(2)-Fenton氧化对CHOS类、CHONS类DOM具有较好的去除效果,去除了大部分多酚化合物,生成具有含氧量更低和饱和度更高的DOM。同时,联合氧化极大地缓解了超滤膜污染,去除了大部分可逆污染和不可逆污染。

HL-3装置上离子回旋波加热对中子产额的影响

离子回旋射频(Ion Cyclotron Range of Frequencies,ICRF)波加热是托卡马克装置上至关重要的辅助加热方式之一。托卡马克装置中国环流三号(HL-3,原名HL-2M)拟安装加热功率为6 MW的ICRF加热系统。本工作利用TRANSP程序,模拟并研究了ICRF加热的频率和功率对聚变中子产额以及快离子分布的影响。研究结果表明:ICRF的频率和功率对中子产额有显著影响,固定ICRF频率时,中子产额与加热功率成正比关系,而在固定ICRF加热功率的情况下,中子产额的增加幅度显著依赖ICRF的频率,在研究参数范围内,30 MHz的ICRF对中子产额的增加具有最显著的增强作用。快离子分布的模拟结果显示,在考虑ICRF加热后,中性束和ICRF的协同加热机制能够将快离子加热至最高1 MeV,有效地提高了中子产额。此外,基于中子相机诊断的概念对中子信号进行了仿真。结果表明,中子相机能够有效地测量到由ICRF加热导致的中子产额高低和分布剖面的变化,这为将来优化中子相机诊断系统设计和测量中子空间分布提供了一定的参考。

不同碳氮比下后置反硝化工艺中溶解性有机质的分子特征及其转化机理

污水处理厂后置反硝化工艺中外加碳源的投加量会影响出水溶解性有机质(DOM)的特性,从而影响后置反硝化的处理效率和出水水质.本研究以实际污水中DOM为研究对象,利用傅里叶变换离子回旋共振质谱(FT ICR-MS)开展了不同碳氮比(C/N=3、4、5、6)下后置反硝化工艺中DOM的分子特征及其转化机理研究.结果表明,在4种C/N下,C/N=5的反应器出水芳香性DOM分子(AImod>0.5)和不饱和程度高的分子(DBE≥4)占比最高,分别为24.72%和97.6%,说明C/N=5时,出水难生物降解程度较高.通过分子转化分析可知,C/N=5的反应器产生的DOM分子占比(58.35%)最高且不饱和程度较高,去除的分子占比(2.80%)低且不饱和程度较低,再次证实C/N=5的反应器出水相较于C/N=3、4、6的反应器出水DOM分子惰性高,排放至受纳水体环境风险较低.此外,微生物群落结构及其与DOM的关联分析可知,Proteobacteria在C/N=5的反应器中相对丰度最高,其主导后置反硝化工艺中DOM分子的产生,Planctomycetota、Nitrospirota、Chloroflexi和Gemmatimonadota对DOM分子的去除和产生也具有重要作用.综上所述,推荐C/N比为5作为后置反硝化工艺中外加碳源的适宜C/N比.

磁阵列微波放电中和器的电子引出机制

微波放电中和器作为微波离子推力器系统的重要组成部分,在维持航天器电位平衡、中和羽流方面发挥着重要作用,其电子引出性能直接关系到电推力器系统的工作状态.在磁阵列微波放电中和器的磁场结构定型实验中,发现调转磁阵列朝向后引出电流的伏安特性曲线差异极大.由于磁阵列微波放电中和器的放电室直径仅10 mm,介入式探针诊断对等离子体干扰大,本文采用了一体化粒子模拟方法对中和器的工作过程进行仿真,仿真结果与实验现象相符合.通过对比不同磁场结构、工作电压下的等离子体参数分布,发现引出孔附近的电势分布决定着中和器的电子引出能力;并进一步揭示了离子在中和器电子引出过程中发挥的关键作用,阐明了磁场结构对中和器电子引出能力的影响机制.最后,本文总结了微波放电中和器有效引出电子的两个必要条件:1)磁场梯度指向引出孔,引导等离子体迁移;2)引出孔附近有足够的离子抬升电势,降低或打破电势阱.

磁场对电子回旋共振中和器等离子体与电子引出影响的数值模拟

10 cm电子回旋共振离子推力器(ECRIT)的ECR中和器是关键部件,其内部磁场是影响中和器性能的重要因素.磁场的均匀性和磁阱位置是磁场特征的重要表现,制约等离子体与电势的分布规律、电子引出过程及中和器性能.本文分别建立磁场均匀性低、磁阱位于电子引出孔上游和磁场均匀性高、磁阱位于电子引出孔下游的ECR中和器PIC/MCC模型,在给定参数条件下,开展等离子体和电势分布规律及电子引出过程的数值模拟研究并分析其对中和器性能的影响.结果表明,磁场均匀性高、磁阱位于电子引出孔下游时,中和器内整体电势分布较均匀,电子容易朝磁阱区迁移,低引出电势引出高电子束流,其性能高于磁场均匀性低、磁阱内置的中和器.研究工作将为发展高性能的ECR中和器奠定重要基础.

回旋加速器主磁铁非理想磁场垫补方法研究

回旋加速器主磁场的精密测量和误差垫补技术是回旋加速器技术研究的一个重要方向,也是设备建造的关键环节之一。由于受铁材料内部缺陷、机械加工误差等因素的影响,回旋加速器主磁铁所产生非理想磁场通常会偏离所需要的等时性磁场分布,且含有一定幅值的谐波磁场。因此,在研制回旋加速器的过程中需对非理想磁场进行多次垫补,通过修正实际磁场的分布而最终达到使用要求。与传统磁场垫补算法相比,本文提出了一种基于多元线性回归模型的垫补算法,加入对一次谐波磁场的计算,实现对磁场等时性误差与一次谐波误差同时进行定量化垫补,省去了单独针对一次谐波磁场的垫补过程。为避免增加有限元计算量,本文在新算法中使用了基于1/4磁铁模型获取平均磁场、一次谐波磁场的垫补形状函数。最后使用本文所提垫补方法,将中国原子能科学研究院16 MeV回旋加速器主磁场的等时性误差降低至10-4量级、一次谐波磁场降低至6 Gs以内。实验结果表明,本文提出的算法具有形状函数计算量小、垫补精度高、迭代次数少的特点。