Superconducting magnet development in Japan

The present state of R & D works on the superconducting magnet and its applications in Japan are presented. On electrical rotating machines, 30 MVA superconducting synchronous rotary condenser (Mitsubishi and Fuji) and 50 MVA generator are under construction. Two ways of ship propulsion by superconducting magnets are developing. A superconducting magnetically levitated and linear motor propelled train "MAGLEV" has developed by the Japan National Railways (JNR). A large scale test track of 7 Km was constructed in Kyushu and the test vehicle reached its target speed of 517 Km/hr. The first manned test running was made by three-vehicles train on new U-shaped guideway. The superconducting magnet development for fusion is the most active field in Japan. The Cluster Test program has beer demonstrated on a 10 T Nb3Sn coil and the first coil of Large Coil Task in IEA collaboration has been constructed and the domestic test was completed in JAERI. These works are for the development of toroidal coils of the next generation tokamak machine. R & D works on superconducting ohmic heating coil are in progress in JAERI and ETL. The latter group has constructed 3.8 MJ pulsed coil. A high ramp rate of changing field in pulsed magnet, 200 T/s, has been tested successfully, for burning tokamak device project in IPP, by joint work of Nihon University, ETL, Mitsubishi and IPP. High Energy Physics Laboratory (KEK) are conducting active works. The superconducting μ meson channel and π meson channel have been constructed and are operating successfully. KEK has also a project of big accelerator named "TRISTAN", which is similar to ISABELLE project of BNL. Superconducting synchrotron magnets are developed for this project. The development of superconducting three thin wall solenoid has been started. One of them, CDF, is progressing under USA-Japan collaboration.     

Field-emission characteristics of chemical vapor deposition-diamond films

Discontinuous and continuous diamond films with different morphologies and qualities were deposited on n²⁺-type Si(100) substrates, using the hot-filament chemical vapor deposition (CVD) technique from CH₄–H₂ gas mixtures. The field-emission characteristics of these diamond films were investigated. The turn-on fields at a 0.01mA/cm² current density were recorded for all the tested CVD-diamond films. It was found that discontinuous diamond films showed a much lower turn-on field (1.2 V/μm) than continuous ones (20 V/μm). The effective working function of continuous diamond films was around 0.1 eV, while that for discontinuous diamond films is about 0.03 eV. O₂ plasma post-deposition sharpening of thick diamond films indicated that the geometrical-field enhancement, caused by the surface topographic changes, has no significant influence on the turn-on field.     

Nb3Al AND Nb3(Al,Ge) SUPERCONDUCTING TAPES BY LASER BEAM ANNEALING

Nb₃Al AND Nb₃(Al,Ge) tapes with excellent superconducting properties have been fabricated using high energy density laser beam irradiation, irradiations were carried out continuously on Nb-25at%AI and Nb-20at%Al -5at%Ge tapes prepared by powder metallurgical processing. With the high power density and short irradiation time, the tape could be heated and cooled much faster than a tape heat treated by conventional methods. The results were fine structure and large critical current density J_c values at high magnetic fields. J_c at 23 Tesla was over 10⁴ A/cm². This value was much greater than that obtained from a commercial Nb₃Sn superconductor. New continuous irradiation systems have been developed for scale-up development. Nb₃Al tapes 10 m in length were successfully fabricated. There was some scatter in J_c along the tape length. Small coil tests in magnetic fields indicated that the tape had excellent stability against a flux jump and mechanical strain.     

Preparation and Characterization of the Ferroelectric Potassium Nitrate: Poly(vinyl alcohol) Composite Films

The composite films of ferroelectric potassium nitrate (KNO₃):poly(vinyl alcohol) (PVA) with different weight percentages of KNO₃ have been prepared at 200°C using the spray-deposition technique. The remanent polarization (P_r) and peak current density for all composite films was estimated by tracing the polarization-electric field (P-E) hysteresis loop and current density-electric field (J-E) loop, respectively, using a modified Sawyer-Tower circuit. Pure KNO₃ is known not to exhibit any ferroelectricity under ambient conditions, but the X-ray diffraction (XRD) studies of PVA:KNO₃ composite films reveal the presence of a ferroelectric phase III of KNO₃ in the composite films at room temperature. The composite film containing KNO₃:PVA in equal proportions shows maximum Pr and peak intensity ratio of approximately 20.10 μC/ cm² and 2.67, respectively, at room temperature. The J-E and capacitance voltage (C-V) characteristics exhibit butterfly features that supports the presence of a ferroelectric phase in the composite films. The field emission scanning electron microscopy (FE-SEM) image of the composite film containing equal proportions of KNO₃ and PVA shows the homogenous distribution of spherical grains of KNO3 of size ~225 nm.     

Superconducting magnets for toroidal fusion reactors

Fusion reactors will soon be employing superconducting magnets to confine plasma in which deuterium and tritium (D-T) are fused to produce usable energy. At present there is one small confinement experiment with superconducting toroidal field (TF) coils: Tokamak 7 (T-7), in the USSR, which operates at 4 T. By 1983, six different 2.5 × 3.5-m D-shaped coils from six manufacturers in four countries will be assembled in a toroidal array in the Large Coil Test Facility (LCTF) at Oak Ridge National Laboratory (ORNL) for testing at fields up to 8 T. Soon afterwards ELMO Bumpy Torus (EBT-P) will begin operation at Oak Ridge with superconducting TF coils. At the same time there will be tokamaks with superconducting TF coils 2 to 3 m in diameter in the USSR and France. Toroidal field strength in these machines will range from 6-9 T. NbTi and Nb3Sn, bath cooling and forced flow, cryostable and metastable - various designs are being tried in this period when this new application of superconductivity is growing and maturing.     

A 17.5 Tesla superconducting concentric Nb3Sn and V3Ga magnet system

A superconducting magnet system has been designed and constructed; it now operates to a field of 17.5 Tesla. The system consists of an outer Nb3Sn solenoid with a 160 mm bore producing 13.5 T, and an inner V3Ga solenoid with a 31 mm bore producing an incremental 4 T. Electrical transients were monitored in the outer magnet during normal transition and compared with predictions. The inner magnet operates close to the critical current of the V3Ga as measured in small coil tests. The magnet system was driven normal several times at a stored energy level of approximately 1.8 Megajoules, activating protective circuitry, designed to safely dissipate the energy released.     

Characteristics of the radiation damage seen in the silicon microstrip detector of Fermilab experiment E771

The central region of the silicon microstrip detector used in Fermilab experiment E771 was subjected to a peak fluence of 9.5 × 10¹³ p/cm² induced by 800 GeV protons over a two-month period. Fourteen 300 μm thick planes manufactured by Micron Semiconductor were operated at bias voltages ranging from 84 to 109 V. Analysis of data from low intensity beam triggers taken near the end of the run shows that the mean pulse height from our amplifiers began to decline at a fluence of approximately 2 × 10¹³ p/cm² and fell to near zero by 6 × 10¹³ p/cm². We show that the use of fast amplifiers contributed to this early loss of signal.     

原位负载Pt-Co高指数晶面催化剂的制备及其电催化性能

直接乙醇燃料电池(DEFC)具有燃料易得、绿色高效的优点,得到了广泛的研究,但是DEFC催化剂存在催化效率低、稳定性差的问题,制约了其快速发展。本研究采用液相水热合成法,以聚乙烯吡咯烷酮(PVP k-25)为分散剂和还原剂、甘氨酸为表面控制剂和共还原剂,通过调控Pt-Co金属前驱体的摩尔比,一步制备了XC-72R炭黑负载的Pt₁Co_x/C高指数晶面纳米催化剂,实现了催化剂晶粒在碳载体上的原位生长。Pt₁Co_1/3/C纳米催化剂暴露的高指数晶面主要包括(410)、(510)和(610)晶面。在晶体生长过程中, Pt₁Co_1/3/C纳米催化剂晶粒由“类球体”转变立方块,最终得到具有高指数晶面取向的内凹形貌。Pt₁Co_1/3/C高指数晶面纳米催化剂的电催化活性最高,其电化学活性表面积为18.46 m²/g,对乙醇氧化峰电流密度为48.70 mA/cm²,稳态电流密度为8.29...     

电催化金属辅助化学刻蚀法制备硅纳米线/多孔硅复合结构

量子限制效应使硅纳米线具有良好的场致发射特性,结合多孔硅的准弹道电子漂移模型可提高场发射器件的性能.传统的金属辅助化学刻蚀法制备硅纳米线的效率较低,本研究在传统方法的基础上引入恒流源,提出电催化金属辅助化学刻蚀法,高效制备了硅纳米线/多孔硅复合结构.在外加30 mA恒定电流的条件下,硅纳米线的平均制备速率可达308 n...     

Physics and applications of Si/SiGe/Si resonant interband tunneling diodes

Room temperature (RT) current–voltage characteristics of Si/Si_1−xGe_x/Si p⁺-i-n⁺ interband tunneling diodes are presented. The variation of the structural properties results in a more detailed picture of the tunneling process in these diodes, which allows further improvement of the relevant parameter. Special attention is paid to the peak current density (PCD) and the peak-to-valley current ratio (PVCR) of the devices. For an optimized structure with a 3-nm thick Si_0.54Ge_0.46 layer in the intrinsic zone a record PVCR of 6.0 at a PCD of approximately 1.5 kA/cm² was achieved. By reducing the layer thickness to 2.6 nm and simultaneously increasing the Ge content to 54%, the PCD increases to 30 kA/cm² at a high PVCR of 4.8.     

Magnetic bubble device scaling and density limits

Scaling of magnetic bubble devices to smaller bubble sizes and higher density is considered. Drive field requirements, materials requirements, fabrication requirements, current requirements, and detector signal-to-noise ratio are all calculated as a function of bubble size and related to practical limits imposed by bubble materials, fabrication techniques, and electromigration limits. It is concluded that "conventional" bubble devices using Permalloy bars can be made practical with 1-μm bubble domains (storage densitysim6 times 10^{6}bits/cm²). Although it may be possible to extend these Permalloy bar devices to even smaller bubbles, it seems more likely that other bubble devices such as contiguous disk devices or bubble lattice devices will in fact be used for densities greater than 6 × 10⁶bits/cm².     

CL-20基压装型温压炸药的设计及性能研究

为了提高六硝基六氮杂异伍兹烷（CL-20）基温压炸药的能量水平和安全性能,通过分析温压炸药爆炸反应历程,开展了CL-20基压装型温压炸药的设计及性能研究。结果表明:CL-20基压装型温压炸药装药密度2.015 g/cm³、爆热8 361 kJ/kg、爆速7 815 m/s,30 kg炸药爆炸时在远场12 m处的冲击波超压可对人员达到中度以上的毁伤;且其撞击感度8%,摩擦感度24%;在慢速烤燃、快速烤燃、12.7 mm子弹撞击试验中,炸药响应等级均为燃烧反应,爆轰性能和安全性能优异。     

Nb5+掺杂对低氟MOD法制备的YBCO薄膜性能的影响

本研究通过低氟MOD法成功地制备了Nb⁵⁺掺杂的YBa₂Cu₃O_7-x(YBCO)薄膜, Nb⁵⁺在薄膜中生成了大小在20~30 nm之间的纳米颗粒; 纳米颗粒的生成不会对 YBCO薄膜的织构和临界温度(T_c)构成明显的影响。由于纳米颗粒的引入, 掺杂后薄膜的临界电流密度(J_c)在整个磁场范围内都要高于纯的YBCO, 自场下的Jc更是达到了3.4 MA/cm²。掺杂薄膜的钉扎力(F_p)也远远大于纯YBCO, 最大钉扎力达到了3.25 GN/m³, 有效地提高了YBCO在外加磁下的超导性能。     

含稻壳粉可燃剂的膨化硝铵炸药性能研究

通过分析稻壳粉与木粉的理化特性，用稻壳粉代替木粉设计试验方案，进行对比试验研究，结合生产企业降本增效的需求，得出稻壳粉作为可燃剂的最优试验方案。该试验方案中，膨化硝铵炸药的药卷密度从0.85 g/cm³提高至0.94 g/cm³;有毒气体含量从68 L/kg降低至59 L/kg；爆速从3 400 m/s提高至3 480 m/s；殉爆距离从5 cm提高至7 cm。     

An eight coil superconducting torus for elastic buckling studies

Elastic structural analysis of proposed fusion reactors suggests that without sufficient lateral constraints the toroidal magnets could suffer a buckling deformation. To model such effects a small, flexible, 32 kA, eight coil superconducting torus has been built and tested. Test results show the predicted buckling behaviour at current below the normal-superconducting transition.     

A comparative study of low dielectric constant barrier layer, etch stop and hardmask films of hydrogenated amorphous Si-(C, O, N)

New barrier layer, etch stop and hardmask films, including hydrogenated amorphous a-SiC_x:H (SiC), a-SiC_xO_y:H (SiCO), and a-SiC_xN_y:H (SiCN) films with a dielectric constant (k) approximately 4.3, are produced using the plasma-enhanced chemical vapor deposition technique. The chemical and structural nature, and mechanical properties of these films are characterized using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and nano-indentation. The leakage current density and breakdown electric field are investigated by a mercury probe on a metal-insulator-semiconductor structure. The properties of the studied films indicate that they are potential candidates as barrier layer, etch stop and hardmask films for the advanced interconnect technology. The SiC film shows a high leakage current density (1.3×10⁻⁷ A/cm² at 1.0 MV/cm) and low breakdown field (1.2 MV/cm at 1.0×10⁻⁶ A/cm²). Considering the mechanical and electrical properties requirements of the interconnect process, SiCN might be a good choice, but the N content may result in via poison problem. The low leakage current (1.2×10⁻⁹ A/cm² at 1.0 MV/cm), high breakdown field (3.1 MV/cm at 1.0×10⁻⁶ A/cm²), and relative high hardness (5.7 GPa) of the SiCO film indicates a good candidate as a barrier layer, etch stop, or hardmask.     

7B04铝合金-CFRP300在模拟海洋大气环境下的电偶腐蚀行为

为了有效地从腐蚀防护角度为飞机异种金属选材提供指导,针对飞机特定的服役环境,通过有限元仿真和腐蚀实验研究飞机典型搭接结构的腐蚀行为。对铝合金、复合材料及搭接件进行了实验室的周浸实验,然后通过极化曲线测量实验、宏微观形貌的观察、疲劳测试、XRD等表征手段研究7B04铝合金与CCF300/QY9511复合材料搭接件的电偶腐蚀规律,并以极化曲线测得的电化学参数为边界条件,建立了搭接件的腐蚀仿真模型。结果表明,在周浸实验0周期和10周期后,铝合金的自腐蚀电位和自腐蚀电流密度分别为-802 mV和2.357×10^-7 A/cm²,-872 mV和1.477×10^-6 A/cm²,复合材料则分别为-240 mV和6.217×10^-7 A/cm²,-98 mV和2.286×10^-7 A/cm²,随着腐蚀周期的延长7B04铝合金材料呈现自腐蚀速率加快、自腐蚀电位负移的变化趋势,而复合材料呈现自腐蚀电位正移、自腐蚀速率缓慢增大的变化趋势;搭接件腐蚀产物逐渐增多,腐蚀程度越来越严重;疲劳寿命随着腐蚀周期的延长而降低;随着腐蚀周期延长,腐蚀坑深度逐渐增大;腐蚀的产物包括Al（OH）₃,Al₂O₃,AlCl₃;搭接件仿真结果与加速腐蚀实验后的结果具有良好的一致性。该研究给出了飞机典型搭接结构的易腐蚀部位,揭示了电偶腐蚀规律,为飞机结构的腐蚀防护指明了方向。     

Polycrystalline silicon prepared by metal induced crystallization

Growth of large-grain polycrystalline silicon has been demonstrated using silicide-mediated crystallization of amorphous silicon (a-Si) by a pulsed rapid thermal annealing (RTA). The Ni atoms in concentration of 4.6×10¹²/cm² on the a-Si surface were heated at 700 °C in the RTA system for 10 s, ten times with 60 s intervals between the heat pulses. The Ni atoms on a-Si aggregate together, forming NiSi₂ precipitates. The crystallization proceeds from the NiSi₂ nuclei until the neighboring crystallites collide and forms distinct grain boundaries. It was found that 3.6×10⁷ Ni atoms form a seed for metal induced crystallization and the grain size was 40 μm when the Ni density was 4.6×10¹²/cm² on the a-Si. The grain size increases with decreasing metal density on a-Si.     

镍掺杂四氧化三钴纳米线阵列的制备及其超级电容特性

采用直流电化学沉积与高温氧化相结合的合成方法, 在氧化铝模板的辅助下, 成功制备了一种新颖的Ni掺杂的Co₃O₄纳米线阵列, 利用X射线衍射仪、扫描电镜和高分辨透射电镜等对所制备的纳米线阵列的物相和形貌进行了表征, 结果表明：所制备的Ni掺杂Co₃O₄纳米线形貌和尺寸均匀、垂直于基底排列, 纳米线的平均直径约为80 nm, 长度约为1.4 μm, 整个纳米线由纳米颗粒堆积而成, 其中Co : Ni的比例约为20 : 1。利用循环伏安和恒流充放电技术在2 mol/L的KOH电解液中对材料的电化学性能进行了测试, 结果显示所制备的纳米线阵列具有优异的电化学电容特性, 当电流密度为10 mA/cm²时, 纳米线阵列的面积比电容为173 mF/cm², 经过1000次充放电后, 比电容值仍能保持最初值的98%, 表现出良好的循环稳定性。优异的性能可归因于材料的比表面积较大以及镍掺杂后材料导电特性的提高。     

一种平板状爆炸焊接用炸药

将硝酸铵、硝酸钠、尿素、水、机油和Span80等通过乳化技术制备出乳胶基质。将制备好的乳胶基质和泡沫树脂混合,得到一种平板状炸药。实验表明:该种炸药的密度可低至0.17g/cm³,爆轰的临界厚度为18 mm,在最低临界密度下的爆速为1 678 m/s;随着密度的增加,爆速增加。密度为0.23 g/cm³时,测得爆速为2 149 m/s。初步分析,该炸药可满足某些爆炸焊接工艺的要求。