Irradiation-induced microstructure damage in He-irradiated 3C-SiC at 1000℃

The effect of the high-temperature helium irradiation on microstructural evolution of 3C-SiC was investigated by the combination of Raman spectroscopy, conventional transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). 3C-SiC wafers were irradiated with 130 keV He⁺ ions at fluences of 2 × 10¹⁶ He⁺/cm², 4 × 10¹⁶ He⁺/cm² and 2 × 10¹⁷ He⁺/cm² at 1000℃. Helium bubbles, dislocation loops, and their interaction with the stacking faults were focused on and characterized by TEM. Helium bubbles preferentially nucleate and grow on stacking faults. Bubble links on the (100) plane in 3C-SiC are formed. In addition, stacking faults can effectively trap irradiation-induced lattice defects to enhance their recovery. The type of irradiation-induced lattice defects and elemental distribution are also investigated. The research results are valuable for the 3C-SiC used in the advanced nuclear energy systems.     

An iterative method for suboptimal control of linear time-delayed systems

This article presents a new approach for solving the Optimal Control Problem (OCP) of linear time-delay systems with a quadratic cost functional. The proposed method can also be used for designing optimal control time-delay systems with disturbance. In this study, the Variational Iteration Method (VIM) is employed to convert the original Time-Delay Optimal Control Problem (TDOCP) into a sequence of nonhomogeneous linear two-point boundary value problems (TPBVPs). The optimal control law obtained consists of an accurate linear feedback term and a nonlinear compensation term which is the limit of an adjoint vector sequence. The feedback term is determined by solving Riccati matrix differential equation. By using the finite-step iteration of a nonlinear compensation sequence, we can obtain a suboptimal control law. Finally, Illustrative examples are included to demonstrate the validity and applicability of the technique.     

引入激光回馈的双光束干涉效应的研究

提出了一种引入He-Ne激光回馈的双光束干涉系统,并在理论和实验两方面进行了研究。实验中对系统中的干涉信号及激光器尾光功率变化同时进行探测。发现当干涉仪的主回馈镜移动时,激光器尾光信号是正弦形波形,而干涉仪输出的是以双峰为一个周期的信号,双峰中一峰总是高于另一峰,并且当主回馈镜移动方向改变时,同一周期中两峰出现的顺序也随之改变。对实验现象进行了理论分析,并模拟出干涉信号及激光自身功率的变化曲线。理论分析及模拟结果与实验结果完全吻合。讨论了利用发现的现象进行测量的可行性,所提出的测量方法易于实现。     

Comparative studies on Ar and He closed-cycle MHD power plants combined with fossil fuel

Comparative studies on Ar and He closed-cycle MHD power plants combined with fossil fuel are performed. The sizes of a regenerative heat exchanger and a boiler are expected to be smaller for He than for Ar. The pressure loss of a working gas in a regenerative heat exchanger is reduced for He. The purification subsystem for He is expected to be more compact and economical than that for Ar; but a larger compressor is required for He than for Ar.     

Heat transfer and flow of He II in narrow channels

Heat transfer and fluid flow of He II in a long, narrow channel connected to a bath that supplies a constant supply of heat have been investigated by numerical simulations by using the simplified model of Kitamura et al. [Cryogenics 37 (1) (1997) 1]. Such channels are used to cool compact, stable, low-temperature magnets. The fluid flow is driven by natural convection and the mutual friction between the normal fluid and the superfluid.In this model, the thermomechanical effect and the Goter-Mellink mutual friction balance each other. A consequence of this balance is that the velocity and temperature distributions of He II can be characterized by a dimensionless, dependent parameter equal to the ratio of the fluid speeds of internal convection to the total fluid flow. After a sudden application of heat flux, the internal convection dominates over the total fluid flow until the establishment of steady-state temperature gradients. This predicts that the time required to set up the steady-state total fluid flow is proportional to the total heat capacity in the channel.     

Experimental results of the erosion of molybdenum due to blistering by He+ bombardment

We report some preliminary measurement of the erosion rate of plasma dumps when bombarded with 100 keV He⁺ ions at high power density ( 1 MW/m²). The expected erosion rates, based on measurements of He blistering that were made at lower power density ( 0.3 MW/m²), indicate a potentially serious problem for fusion reactors. Our tests use a reactorlike power density and produce He blisters at a rate that is slower than predicted by 2 to 4 orders of magnitude, depending on the temperature of the molybdenum target.     

靖边气田盒8段钻井液封堵性能提高方法研究

高桥地区靖边气田石盒子组盒8段砂岩储层井径扩大严重,引起测井信息失真、地质储量评价不准确等一系列问题.通过优化CaCO3酸溶性封堵剂的复配比例和添加成膜剂及润湿反转剂降低砂岩自吸两种途径提高钻井液的封堵性能,从而实现井壁稳定.改进后钻井液对盒8段的封堵率提高至95.6%,砂岩自吸量降低85%.     

金属氚化物的时效和时效效应

结合贮氚材料在核技术中的应用，简要介绍了目前关于^3He在氚化物中的存在和演化行为、延缓。^3He从材料中析出的可能途径以及氚时效对氚化物性能影响的研究进展，并对几种单质氚化物的固He性能进行了比较．为了对照理解，也简要介绍了高能辐照产生的He在材料中的存在行为．     

Design study of a 120-keV,3He neutral beam injector

We describe a design for a 120-keV, 2.3-MW,³He neutral beam injector for use on a D-³He fusion reactor. The constraint that limits operating life when injecting He is its high sputtering rate. The sputtering is partly controlled by using an extra grid to prevent ion flow from the neutralizer duct to the electron suppressor grid, but a tradeoff between beam current and operating life is still required. Hollow grid wires functioning as mercury heat pipes cool the grid and enable steady state operation. Voltage holding and radiation effects on the acceleration grid structure are discussed. We also briefly describe the vacuum system and analyze use of a direct energy converter to recapture energy from unneutralized ions exiting the neutralizer. Of crucial importance to the technical feasibility of the³He-burning reactor are the injector efficiency and cost; these are 53% and $5.5 million, respectively, when power supplies are included.The beam is composed of 91 separate, parallel currents that flow in the gaps between the elements or wires of a grid. Each such flow is referred to as a beamlet. The current densities in Figs. 5, 8, and 9 are values within a beamlet, as measured at the beam-forming grid. They are not values averaged over the entire beam cross-section.