混合磁体超导线圈低温传输线冷屏的设计与分析

对于低温传输线,冷屏是其重要的结构。文中在低温传输线冷屏结构初步设计的基础上,对冷屏屏体材料进行比选,计算分析了低温传输线在80K温区的漏热量,并采用Solidworks软件,对不同厚度的低温传输线冷屏的温度分布进行模拟分析,完成冷屏的工程设计。     

玄武岩纤维布/铝板组合防护结构的高速撞击防护性能

在弹道段撞击速度范围内,针对玄武岩纤维布/铝板组合防护结构开展了高速撞击实验(实验使用的2017铝球弹丸的直径为3.97 mm,撞击速度为1.49~3.65 km/s),获得了防护结构的弹道极限速度,分析了铝球弹丸高速击穿玄武岩纤维布和铝板后的剩余速度。基于单层铝板发生穿孔失效时的临界撞击动能,研究了玄武岩纤维布/铝板组合防护结构的高速撞击防护性能。结果表明:当弹丸未破碎时,相同直径的铝球弹丸以不同速度击穿相同面密度的玄武岩纤维布后的速度减小量近似为常数;铝球弹丸直径越大,弹丸击穿相同面密度的玄武岩纤维布后的速度减小量越小;在防护结构面密度相同的情况下,铝板前置的玄武岩纤维布/铝板组合防护结构比玄武岩纤维布前置的组合防护结构具有更好的高速撞击防护性能。     

商用飞机撞击核电站屏蔽厂房数值模拟

为研究大型商用飞机撞击核电站屏蔽厂房的毁伤特性,建立了Boeing 767商用飞机和双钢板混凝土屏蔽厂房的有限元模型,模拟两者的相互撞击作用过程,得到飞机不同部位(机身、发动机)对屏蔽厂房的撞击力时程曲线,对每一个作用部分给出简化撞击力曲线和作用面积,确定了撞击力分布形式。结果分析表明:飞机轴向网格尺寸对撞击力影响较大;屏蔽厂房被撞击部位变形明显,其他区域变形较小;撞击速度对撞击作用时间影响较小,而对结构响应位移影响很大,撞击力合力随着撞击速度的降低迅速下降。     

Increasing energy relaxation time of superconducting qubits with nonmagnetic infrared filter and shield

One of the primary origins of the energy relaxation in superconducting qubits is the quasiparticle loss. The quasiparticles can be excited remarkably by infrared radiation. In order to minimize the density of quasiparticle and increase the qubit relaxation time, we design and fabricate the infrared filter and shield for superconducting qubits. In comparison with previous filters and shields, a nonmagnetic dielectric is used as the infrared absorbing material, greatly suppressing the background magnetic fluctuations. The filters can be made to impedance-match with other microwave devices. Using the as-fabricated infrared filter and shield, we increased the relaxation time of a transmon qubit from 519 ns to 1125 ns.     

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在有梯度的静磁场中,对由软磁材料制作的磁屏蔽罩所受的静磁力的量级进行了评估.使用有限元分析和实验测试的方法研究了纯铁方形屏蔽罩在梯度静磁场中的受力情况,结果表明:把内腔尺寸100mm×100mm×150mm、罩体厚度为20mm的方形屏蔽罩放置在强度约为0.2T、梯度为0.03T?m-1的磁场中,其所受的静磁力约为184N,与其自身重力相当;静磁力随磁场强度的升高而增大;有限元分析与实验测试结果的偏差在0.2T背景磁场下约为21%.因此,在考虑一定余量的情况下,使用有限元计算评估屏蔽罩在静磁场中的受力情况是一种有效和比较可靠的方法.     

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对ITER包层屏蔽块进行了热工水力学设计及分析,并给出了两套合理的加热方案.分析结果表明,可以通过分阶段改变入口气体温度的方法实现在高效加热屏蔽块的同时满足工程及部件热应力的技术要求,并通过热应力计算验证了加热过程不会对屏蔽块产生不可预期的结构破坏.     

（n,xnγ）反应截面测量的实验本底改进研究

瞬发γ射线法测量（n,xnγ）反应截面实验中,在线的实验本底对测量结果影响显著,是影响测量结果的关键因素。为了达到降低在线实验本底一个量级的目标,通过蒙特卡罗模拟程序给出了屏蔽体和准直器的改进方案,最终选取的屏蔽方案:在原有屏蔽体上加厚30 cm（C₂H₄）n+9 cmPb,原屏蔽墙加厚54 cm重混凝土,再在屏蔽体和屏蔽墙上共同加厚2 cm厚的铅（Pb）;准直孔开孔形状在圆柱形、圆锥形和对称双锥形这三种方案中准直效果和能量单一性方面对称双锥形准直孔最好。在屏蔽体改造完成后,利用尺寸为φ5.08cm×5.08 cm型液体闪烁体探测器（BC501）测量了改造后距准直孔右方径向距离70 cm处透射出来的中子和γ射线的相对强度,在扣除无束流天然本底后,有束流的中子本底降低了7.75倍,γ本底降低了38.5倍,改造效果达到了测量要求。In the experiment of measuring (n,xnγ) reaction cross section with prompt γ ray method, the experiment background has a significant influence on the result and is the key factor. In order to achieve the goal of reducing a certain amount of the experiment background, the improvement scheme of shield and collimator was given through Monte Carlo method and the shielding scheme was finally selected: add 30 cm(C₂H₄)n+9 cm Pb on the original shield, 54 cm heavy concrete on the original shield wall and then 2 cm thick lead(Pb) on the shield and shield wall. The collimation effect and energy uniformity of symmetrical double cone collimation hole are the best among cylindrical, conical, and symmetrical double cone. After the completion of the transformation of shield, the relative intensities of the transmitted neutron and γ rays from the 70 cm in right radial of the transformed collimation hole were measured with ?5.08 cm×5.08 cm type liquid scintillator detector(BC501). After deducting the natural background of no beam current, the neutron background of the beam current is reduced by 7.75 times and the γ background is reduced by 38.5 times, which meets the requirement.     

泥水平衡盾构机掘进并行数值模拟方法研究

以某大型越江隧道工程为背景,建立该工程场地土层的大规模三维非线性数值模型。同时基于共享内存式并行计算平台(SMP),利用刚度迁移法,完成了泥水平衡盾构机逐步掘进百米长距离,并穿越大堤这一复杂力学过程的大规模数值模拟。为模拟泥水平衡盾构机掘进各施工阶段,不同施工因素之间的复杂力学作用关系,提出了对各施工因素模拟的简化方法。具体包括:开挖面泥水压力对前方土体的作用、盾构机机头的超挖、盾构机机身对土体的作用、盾尾注浆材料的时空变化特性、盾构机后方百米长拖车对已铺成隧道的作用等施工因素。通过对计算结果与工程试验段实测数据对比验证的基础上,预测了地表沉降在盾构机掘进过程中的变化规律。通过对SMP并行计算平台下盾构法施工数值模型之并行计算效率的对比研究,给出了各并行算法的加速比、计算效率以及接触模型对并行计算效率的影响关系。     

单晶炉导流筒、热屏及炭毡对单晶硅生长影响的优化模拟

在CZ法生长太阳能级单晶硅中,单晶炉的导流筒、热屏和炭毡对晶体生长有很大影响.通过对上述三个部件进行改进优化,并通过数值模拟对优化前后晶体和熔体的热场、热屏外表面与石英坩埚内壁面之间的氩气流场以及晶体中的热应力进行分析,得出以下结论:石墨导流筒的引入减少了炉体上部的氩气流动涡胞,进而减少了SiO在单晶炉上部的沉积;优化后的热屏减少了加热器对晶体的烘烤,使结晶速率加快;优化后的侧壁炭毡阻止了加热器向上部的热损失.优化后在加热器功耗不变时,结晶速率至少可提高35;,而不增加宏观位错的发生概率.     

Stepped side shield writer for perpendicular recording

To increase the track density in hard disk drive (HDD), the write head fringing field should be controlled. The side shield is one of the candidates to reduce the fringing stray field. Although the wrap-around type [K. Nakamoto, et al., IEEE Trans. Magn. 41(10) (2005) 2914] and many other side shield structures [Y. Kanai, et al., IEEE Trans. Magn. 39(4) (2003) 1955; D.T. Wilton, D.J. Mapps, IEEE Trans. Magn. 29 (1993) 4182] were proposed, these side shield structures have a trade-off between the track edge field sharpness and the maximum write field strength on the center track. In this paper, we propose the new side shield writer called the stepped side shield (3S) head. The 3S head satisfies both the on-track write field strength and reduction of the adjacent track stray field. The track edge field sharpness is much improved especially in the high skew angle recording. We studied the 3S head effect by the statistic field simulation.