Design and research of magnetically levitated testbed with composite superconductor bearing for micro thrust measurement

A high temperature superconducting (HTS) magnetically levitated testbed has been developed for the steady thrust measurement of miniature ion electrospray thruster.The structure of the testbed mainly consists of an HTS composite bearing,a magnetic shielding plate,an active electromagnetic brake and a laser displacement sensor.The steady thrust is described as a function of the equilibrium angle displacement of the floating frame.Furthermore,the mechanical behaviors of HTS composite beating were studied via finite element simulation and experiments,which include the load capacity,levitation stiffness and background noise.The results show that the thrust testbed can keep in low noise and have a load capacity up to 4 kg.According to the ignition testing of the electrospray thruster,the thrust force of 25.2 μN was measured by the testbed,which is close to the design value of miniature ion electrospray thruster.     

Impacts of laser pulse width and target thickness on laser micro-propulsion performance

In order to optimize the laser ablation performance of a micro-thruster with 1U dimensions, which employs a micro semiconductor laser, the impacts of pulse width and glycidyl azide polymer (GAP) thickness on thrust performance were researched. The results showed that with a GAP thickness of 200 μm, the single-pulse impulse (I) increased gradually with the increase in the laser pulse width from 50 to 800 μs, while the specific impulse (Isp), impulse coupling coefficient (Cm) and ablation efficiency (η) all reached optimal values with a 200 μs pulse width. It is worth noting that the optimal pulse width is identical to the ignition delay time. Both Cm and η peaked with a pulse width of 200 μs, reaching 242.22 μN W−1 and 35.4%, respectively. With the increase in GAP thickness, I and Cm increased gradually. GAP of different thicknesses corresponded to different optimal laser pulse widths. Under a certain laser pulse width, the optimal GAP thickness should be the most vertical thickness of the ablation pit, and the various propulsion performance parameters at this time were also optimal. With the current laser parameters, the optimal GAP thickness was approximately 150 μm, Isp was approximately 322.22 s, and η was approximately 34.94%.     

激光靶丸全表面检测与功率谱特征评价

本工作基于靶丸全球面测量的经纬迹线法,应用由原子力显微镜、精密回转气浮轴系及辅助转位轴系等组成的靶丸表面形貌测量系统,对直径0.34mm的空心塑料靶丸表面进行了测量实验。实验选择了圆周9条经圆(间隔20°),每个经圆方向上纬圆间隔10μm,最大偏移20μm的方案,获取了靶丸全球面的经纬测量迹线,并对测量结果进行了模数-功率谱特征曲线和表面均方根粗糙度的分析。     

Measurement of the Beam Position in the Extraction System of the ILU-10 Linear Electron Accelerator

A system for measuring beam position for a ILU-10 pulsed linear electron accelerator is described. The accelerator generates an electron beam with energy up to 5 MeV. The rf generator operates at 115 MHz in the pulsed mode with pulse duration of about 500 sec and pulse repetition frequency up to 50 Hz. The average beam power can reach 60 kW. Two electrostatic sensors (pickups) are used to measure the position of the beam. The principle of operation of the measurement apparatus is based on homodyne detection of the signals from the pickups. The second harmonic of the frequency of the accelerating voltage of the accelerator power supply (230 MHz) is chosen as the working frequency. The detected signal is fed from each pickup plate into an integrator and then a ADC. The beam position is calculated on a computer. The resulting error in the beam coordinates is about 0.5 mm with a 110 mm in diameter position sensor.     

星载数模转换器抗辐射性能评估测量系统研制

基于面向仪器系统的外围组件互连扩展(Peripheral Component Interconnection extensions for Instrumentation,PXI)平台,提出并实现了一个高精度、高速、全自动星载数模转换器抗辐照性能评估测量系统。该系统采用开尔文四线法和均值滤波算法对芯片电流与电压进行高精度监测,利用软件配置矩阵开关全自动切换参数测量项,使用PXI总线同步与触发模式控制实现模块化仪器间的高速响应,并使用三次样条算法准确提取单粒子饱和截面与线性能量传输值阈值。基于该系统对一款自主研发的星载数模转换器进行辐照试验,试验结果表明研制的系统能够准确、高效地评估出器件抗辐照性能。系统电压识别精度为0.1?V,最高可支持24位数模转换器监测,单粒子效应电流变化与寄存器翻转监测频率分别为50 Hz与100 Hz,总剂量效应时单次表征参数遍历时间为8 s。     

Numerical analysis of the static performance of an annular aerostatic gas thrust bearing applied in the cryogenic turbo-expander of the EAST subsystem

The EAST superconducting tokamak,an advanced steady-state plasma physics experimental device,has been built at the Institute of Plasma Physics,Chinese Academy of Sciences.All the toroidal field magnets and poloidal field magnets,made of NbTi/Cu cable-in-conduit conductor,are cooled with forced flow supercritical helium at 3.8 K.The cryogenic system of EAST consists of a 2 kW/4 K helium refrigerator and a helium distribution system for the cooling of coils,structures,thermal shields,bus-lines,etc.The high-speed turbo-expander is an important refrigerating component of the EAST cryogenic system.In the turbo-expander,the axial supporting technology is critical for the smooth operation of the rotor bearing system.In this paper,hydrostatic thrust bearings are designed based on the axial load of the turbo-expander.Thereafter,a computational fluid dynamics-based numerical model of the aerostatic thrust bearing is set up to evaluate the bearing performance.Tilting effect on the pressure distribution and bearing load is analyzed for the thrust bearing.Bearing load and stiffness are compared with different static supply pressures.The net force from the thrust bearings can be calculated for different combinations of bearing clearance and supply pressure.     

传热管与支撑件随机碰撞实验研究

针对蒸汽发生器中传热管与支撑件的碰撞行为,对悬臂梁固定的传热管在不同支撑条件下开展了激振实验,获得了传热管均方根位移与接触率,分析了传热管与支撑件磨损功率的变化规律,并探究了传热管固有频率对振动特性的影响。结果表明,防振条支撑与波纹带支撑时传热管的法向均方根位移均随激振力增加逐渐放缓,而防振条支撑对应的切向位移呈线性增长。防振条支撑与波纹带支撑时的接触率均表现为随激振力增大趋于稳定,其中间隙对防振条支撑的接触率影响更明显。在以冲击为主导的激励方式下,激振力与磨损功率表现为明显的正相关。支撑间隙对磨损功率的影响相对复杂,防振条支撑下磨损功率在0.1 mm和0.25 mm间隙存在极值,而波纹带支撑磨损功率仅在0.2 mm间隙存在极值。传热管固有频率对振动响应结果的影响很小。     

Development of hovering control system for an underwater vehicle to perform core internal inspections

In this paper, a hovering control system for an underwater vehicle is proposed to support core internal inspections. The system adopted a localization part and a thruster control part. The former utilizes a map-matching method, referring cross-sectional shape data cut from a three-dimensional computer aided design (CAD) and structural shapes measured by a laser range system for horizontal positioning. A pressure sensor provides vertical positioning. The latter utilizes the thrust vector control, or reference thrust vectors are converted to each propeller thrust based on the vehicle's geometric structure. Experiments to evaluate performance of the proposed system were implemented at a mock-up of the reactor bottom part. As a result, it was confirmed that the position was detected with an accuracy of 48 mm, and for a flow velocity of 200 mm/s, it was verified that the vehicle hovered within 77 mm of a target point. Therefore, core internal inspections can be stably carried out even where there is external force caused by water convection flow.     

丝扫描快速信号处理测量系统设计

为了提高同步辐射丝扫描探测器的测量分辨率与缩短数据处理时间,设计了丝扫描快速信号处理测量系统。该系统采用了电子学高速连续采样与平均降采样相结合的方法,自动确定拟合区间,调整关键点拟合权重,可有效提高信噪比,滤除光斑边缘毛刺噪声,降低拟合误差,提高测量分辨率与缩短测量用时;其光束位置测量分辨率可达48.3μm,光斑大小测量分辨率可达38.5μm,数据处理时间约150 ms。     

基于原子力显微术的DNA折纸弹性模量的研究

原子力显微术(Atomic force microscopy,AFM)的力学成像模式可在高分辨成像的同时,定量测量材料的力学性质。然而,对尺度小、质地薄而软的生物分子的弹性模量的测量仍然是一个挑战。本文以脱氧核糖核酸(Deoxyribonucleic acid,DNA)折纸为检测样品,将峰值力定量纳米力学模式(Peak Force Quantitative Nanomechanical Mapping,PF-QNM)作为测量手段研究了DNA分子的力学性质,探索不同作用力对DNA折纸弹性模量的影响。结果表明,当峰值力控制在80-100 p N时,峰值力成像稳定,获得的杨氏模量维持在约10 MPa。与传统力曲线阵列模式(Force volume mapping,FV)相比较,在小力区(100 p N),两种方法符合性较好。这种峰值力定量纳米力学模式为DNA分子定量力学性质研究提供了一种简便而有效的研究方法。     

Interpretation of Müller-Klemm's Semi-Empirical Formula by Mason-Monchick Approximation for Thermal Diffusion Factor of Hydrogen Isotope Molecules

Comprehensive analysis on core support barrel (CSB) movements in the ULJIN Nuclear Plant is performed through noise and structural analysis techniques. Noise signals are taken from the lower channel outputs of ex-core instrumentation system during the full power reactor operation period. Then they are converted into auto-power spectral densities (APSDs) and coherence functions in the frequency range of 0–50 Hz to obtain the vibratory information of CSB movements.

From APSDs, the three different vibration peaks of CSB are detected around the frequencies of 8, 15 and 20 Hz, distinctly. These results are also agreed well with those obtained from the structural analysis by ANSYS version 4.3 computer program, which is the finite element method (FEM). Three different vibration mechanisms of CSB at each resonant peaks are identified as two types of the beam mode vibrations (vig., pendulum motion and torsional motion) and the shell mode vibration, respectively.     

多用途低温核供热堆运行目标的开环优化研究

为满足海边的工业开发小区在远离淡水网、热网时,由一座低温核供热堆动力厂提供小区全部淡化海水、供热、工业蒸汽和部分用电的需要,目标是在保证安全性的前提下,使低温核供热堆取得最佳的经济效益,达到运行经济性最优。本文采用开环优化的方法,研究低温核供热堆在负荷跟踪运行方式下的稳态运行目标,并为低温核供热堆负荷跟踪控制系统的分析设计提供负荷需求的输入参数。     

Characterization of an ionic liquid electrospray thruster with a porous ceramic emitter

An ionic liquid(IL) electrospray thruster was developed for application in micro-nano satellites or gravitational wave detectors. The thruster employed a porous ceramic emitter with seven emitter strips located on its emission surface. Without any liquid-supply device, IL was delivered through porous media to emitter strips via capillary effect. Multiple emission sites then formed at the tip of each strip. A charged beam of up to 350 μA(with a current density of 540 μA cm~(-2))was stably produced in the negative mode. However, in the positive mode, a corona was observed which could prevent the thruster from emitting larger current. A time-of-flight mass spectrometer with significantly improved signal-to-noise ratio was built, which was used to obtain the mass distribution of the beam of the thruster. A retarding potential analysis was also performed. The test results showed that the thruster worked in the pure-ion regime, and delivered a maximum thrust of 67.1 μN with specific impulses of 3952 s and 3117 s in the positive and negative modes, respectively.     

恒流模式直流流强检测系统的优化

介绍了上海光源恒流模式下直流流强检测系统的软硬件结构。Matlab仿真比对两种束流流强算法性能,结果表明,使用整数周期算术平均算法时,2 Hz系统带宽下系统直流流强测量分辨率可望好于0.38μA。由于Top-up模式束流的特性,对束流寿命算法进行优化,进行两点曲线拟合。介绍了Top-up模式下直流流强检测系统的置信度算法,并用实测数据进行了验证,数据预测准确,收敛速度快,性能较好。对DCCT系统的软件实现给出了软件流程图,指导软件代码的实现。     

Characterization and comprehension of corona partial discharge in air under power frequency to very low frequency voltage

For the partial discharge test of electrical equipment with large capacitance, the use of lowfrequency voltage instead of power frequency voltage can effectively reduce the capacity requirements of test power supply. However, the validity of PD test under low frequency voltage needs to be evaluated. In order to investigate the influence of voltage frequency on corona discharge in the air, the discharge test of the tip-plate electrode under the frequency from 50 to 0.1 Hz is carried out based on the impulse current method. The results show that some of the main features of corona under low frequency do not change. The magnitude of discharge in a positive half cycle is obviously larger than that in a negative cycle. The magnitude of discharge and interval in positive cycle are random, while that in negative cycle are regular. With the decrease of frequency, the inception voltage increases. The variation trend of maximum and average magnitude and repetition rate of the discharge in positive and negative half cycle with the variation of voltage frequency and magnitude is demonstrated, with discussion and interpretation from the aspects of space charge transportation, effective discharge time and transition of discharge modes. There is an obvious difference in the phase resolved pattern of partial discharge and characteristic parameters of discharge patterns between power and low frequency. The experimental results can be the reference for mode identification of partial discharge under low frequency tests. The trend of the measured parameters with the variation of frequency provides more information about the insulation defect than traditional measurements under a single frequency (usually 50 Hz). Also it helps to understand the mechanism of corona discharge with an explanation of the characteristics under different frequencies.     

Probe method to measure the electromagnetic field in a plasma by Poynting vector conversion

In this paper,a high-precision electromagnetic measurement system suitable for a high-temperature and high-speed plasma is built to provide a platform for scientific research on the interaction mechanism of the electromagnetic fields and a plasma.This paper presents a method to measure the electromagnetic field inside a plasma by using a probe and Poynting vector conversion,which is a new and completely different method from the traditional method of measuring the electromagnetic field inside plasma.In addition,for this system and method,this work designs a microstrip antenna probe that can suppress multipath effects.This method is confirmed to be valid and usable after closed-loop verification by the CST software.     

Progress and improvement of KSTAR plasma control using model-based control simulators

Superconducting tokamaks like KSTAR, EAST and ITER need elaborate magnetic controls mainly due to either the demanding experiment schedule or tighter hardware limitations caused by the superconducting coils. In order to reduce the operation runtime requirements, two types of plasma simulators for the KSTAR plasma control system (PCS) have been developed for improving axisymmetric magnetic controls. The first one is an open-loop type, which can reproduce the control done in an old shot by loading the corresponding diagnostics data and PCS setup. The other one, a closed-loop simulator based on a linear nonrigid plasma model, is designed to simulate dynamic responses of the plasma equilibrium and plasma current (I_p) due to changes of the axisymmetric poloidal field (PF) coil currents, poloidal beta, and internal inductance. The closed-loop simulator is the one that actually can test and enable alteration of the feedback control setup for the next shot. The simulators have been used routinely in 2012 plasma campaign, and the experimental performances of the axisymmetric shape control algorithm are enhanced. Quality of the real-time EFIT has been enhanced by utilizations of the open-loop type. Using the closed-loop type, the decoupling scheme of the plasma current control and axisymmetric shape controls are verified through both the simulations and experiments. By combining with the relay feedback tuning algorithm, the improved controls helped to maintain the shape suitable for longer H-mode (10–16 s) with the number of required commissioning shots largely reduced.     

宽频带电光式脉冲电场测量系统的研制及应用

介绍了一种宽频带电光式脉冲电场测量系统（ＰＥＭＳ－１）,该系统动态范围约６０ｄＢ,频率响应为０．１Ｈｚ～７００ＭＨｚ,具有抗电磁干扰能力强、探头部分无源化、体积小等优点,可用于传统测试手段难于实现的复杂电磁环境下或小空间内的瞬变电场测量。给出了系统组成及分析,对频率响应与线性测量范围进行了实验研究,提出了一种无标准场时有效进行幅值标定的方法。最后,在两种脉冲电场环境中进行了测试应用。     

BEPCⅡ直线加速器束流能量反馈系统设计

为满足BEPCⅡ储存环对注入束流的要求,BEPCⅡ直线加速器末增设了束流能量反馈系统。该系统由束流能量在线测量单元,图形界面应用软件和相控执行单元构成。束流能量测量单元使用3个BPM对束流能量进行在线非阻拦式测量,测量结果实行人机交互与控制逻辑输出,相控执行单元使用消除回程差的控制方法。该系统束流中心能量调节频率为2 Hz,注入速率波动小于10m A/min,束流中心能量稳定度不大于±0.1%。